Recyclable 3D-Printed Composite Hydrogel Containing Rice Husk Biochar for Organic Contaminants Adsorption in Tap Water
可回收的 3D 列印複合水凝膠，含有稻殼生物炭，用於自來水中有機污染物的吸附

Emilly C. Silva, Victória R. Soares, Andressa B. Nörnberg, and André R. Fajardo*
艾米莉·C·席爾瓦，維多利亞·R·索阿雷斯，安德蕾莎·B·諾恩貝格，和安德烈·R·法哈多*

Cite This: ACS Appl. Polym. Mater. 2023, 5, 8415-8429
引用來源：ACS Appl. Polym. Mater. 2023, 5, 8415-8429

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Abstract 摘要

Water and wastewater treatment face significant challenges in removing organic contaminants, and the search for efficient processes and materials is crucial to reducing this issue. Herein, the design and manufacturing of 3D-printed composite hydrogels using a combination of alginate and rice husk biochar was proposed. These composite hydrogels were evaluated as adsorbents for removing ibuprofen (IBU) and methylene blue (MB) from tap water. Various characterization techniques, including FTIR, XRD, SEM, and BET analyses, confirmed the successful formation of the composite hydrogels. Also, the properties of the composite hydrogels, such as total porosity, cross-linking density, and swelling, were found to vary with the biochar content in the composite. Batch experiments demonstrated that the hydrogel containing 10% w/w biochar (Alg/Biochar10) has significant adsorption capacities for IBU $(111.4 mg / g)$ and $MB (214.6 mg / g)$ . These values represented substantial increases of $48 %$ (IBU) and $58 %$ (MB) compared to the conventional hydrogel without biochar, highlighting the enhanced performance achieved by incorporating biochar into the composite. The adsorption kinetics of both IBU and MB followed the pseudo-first-order model, while the Freundlich isotherm model provided insights into the adsorption mechanism. Notably, the adsorption of MB on the composite hydrogel was particularly favorable due to electrostatic interactions between the adsorbent and the adsorbate. Furthermore, the composite hydrogel exhibited recyclability and reusability, as demonstrated through 20 reuse cycles, indicating its stability and practical applicability. In summary, the original 3D-printed composite hydrogels manufactured with the alginate/rice husk biochar ink showed great potential as adsorbent materials for organic removal from water and wastewater.
水和廢水處理在去除有機污染物方面面臨重大挑戰，尋找高效的處理過程和材料對於減少這一問題至關重要。在此，提出了使用海藻酸鈉和稻殼生物炭的組合設計和製造 3D 列印複合水凝膠。這些複合水凝膠被評估為去除自來水中布洛芬（IBU）和美藍（MB）的吸附劑。各種表徵技術，包括 FTIR、XRD、SEM 和 BET 分析，確認了複合水凝膠的成功形成。此外，複合水凝膠的性質，如總孔隙率、交聯密度和膨脹性，發現隨著複合材料中生物炭含量的變化而變化。批次實驗表明，含有 10% w/w 生物炭的水凝膠（Alg/Biochar10）對 IBU 的吸附能力顯著。這些值相比於不含生物炭的傳統水凝膠，顯示出對 IBU 和 MB 的吸附能力有顯著提高，突顯了通過將生物炭納入複合材料所實現的性能增強。 IBU 和 MB 的吸附動力學均遵循偽一級模型，而弗倫德利希等溫線模型則提供了吸附機制的見解。值得注意的是，MB 在複合水凝膠上的吸附特別有利，這是由於吸附劑與吸附物之間的靜電相互作用。此外，複合水凝膠顯示出可回收性和可重用性，通過 20 次重複使用循環證明了其穩定性和實際應用性。總之，使用海藻酸鹽/稻殼生物炭墨水製造的原始 3D 列印複合水凝膠顯示出作為水和廢水中有機物去除的吸附材料的巨大潛力。

KEYWORDS: additive manufacturing, waste biochar, polysaccharides, emerging contaminants, water remediation
關鍵詞：增材製造，廢棄生物炭，多醣類，新興污染物，水體修復

INTRODUCTION 引言

Industrial development has brought about significant progress in society, but it has also led to environmental challenges.

^{1}

Among these challenges, anthropogenic contamination resulting from the discharge of industrial sewage into water sources has caused damage to ecosystems.

^{2}

Additionally, the increasing demand for resources like drinking water necessitates the treatment and decontamination of wastewater to remove various contaminants such as metals, dyes, pharmaceuticals, plastics, and oil.

^{3, 4}

Considering the different groups of contaminants detected in water, organic compounds are particularly relevant and harmful due to their toxicity, persistence, and potential for bioaccumulation. Most of these organic contaminants are resistant to degradation through a chemical and biological processes. Even those that are degradable can generate reactive and highly toxic intermediates.

^{5}

Currently, traditional water/wastewater treatment plants are unable to completely remove these contaminants, as indicated by various studies.

^{6}

Therefore, advanced technologies for the removal of organic contaminants from water and wastewater are needed to protect the environment and human
工業發展帶來了社會的重大進步，但也引發了環境挑戰。

^{1}

在這些挑戰中，來自工業污水排放到水源的人工污染對生態系統造成了損害。

^{2}

此外，對飲用水等資源需求的增加使得必須對廢水進行處理和去污，以去除各種污染物，如金屬、染料、藥物、塑料和油。

^{3, 4}

考慮到水中檢測到的不同污染物群體，有機化合物特別相關且有害，因為它們具有毒性、持久性和生物累積的潛力。這些有機污染物大多對化學和生物降解過程具有抗性。即使是可降解的污染物也可能產生反應性和高度毒性的中間產物。

^{5}

目前，傳統的水/廢水處理廠無法完全去除這些污染物，這一點已被多項研究所證實。因此，需要先進技術來去除水和廢水中的有機污染物，以保護環境和人類
health. In this regard, numerous decontamination methods have been studied, including chemical precipitation,

^{7}

membrane separation,

^{8}

electrochemical treatments,

^{9}

and advanced oxidative processes.

^{10}

Among these methods, adsorption stands out primarily because of its attractive characteristics, such as low cost, ease of implementation, and minimal generation of byproducts.

^{11}

The success of the adsorption process is directly linked to the adsorbent, which must possess suitable surface properties and compatibility with the contaminants in the water environment.

^{12}

Furthermore, recyclability is another desirable feature for an ideal adsorbent.
健康。在這方面，已經研究了多種去污方法，包括化學沉澱、膜分離、電化學處理和先進氧化過程。在這些方法中，吸附法因其低成本、易於實施和最小副產物生成等吸引人的特性而脫穎而出。吸附過程的成功與吸附劑直接相關，吸附劑必須具備適當的表面特性和與水環境中污染物的相容性。此外，回收性是理想吸附劑的另一個理想特徵。

Considering the different materials tested as adsorbents, hydrogels are of particular interest due to their physicochemical and morphological properties. Hydrogels are composed of
考慮到不同材料作為吸附劑的測試，水凝膠因其物理化學和形態特性而特別引人注目。水凝膠由...組成。

3D networks of cross-linked polymers that can swell in an aqueous medium.

^{13}

The highly functionalized structure of the hydrogels provides the necessary adsorption sites for various contaminants. Furthermore, water uptake facilitates the access of contaminants to the adsorption sites within the hydrogel network.

^{14}

According to the literature, various methods are available for preparing hydrogels for adsorption purposes. Unfortunately, most of these methods do not allow the production of materials with complex and well-defined structures, which are more efficient for mass transfer processes such as adsorption.

^{15}

三維交聯聚合物網絡，能夠在水性介質中膨脹。

^{13}

水凝膠的高度功能化結構提供了各種污染物所需的吸附位點。此外，水的吸收促進了污染物進入水凝膠網絡內部的吸附位點。

^{14}

根據文獻，已有多種方法可用於製備用於吸附的水凝膠。不幸的是，這些方法大多無法生產具有複雜且明確結構的材料，而這些材料在如吸附等質量轉移過程中更為高效。

^{15}

Over the past decade, additive manufacturing processes, including 3D printing, have emerged as an alternative for obtaining custom-made hydrogels with ordered and intricate structures. Additionally, 3D printing offers several advantages in hydrogel manufacturing, including the potential for mass production, minimal raw material wastage, and the ability to produce hydrogels under controlled conditions independent of humidity and other weather factors.

^{16}

As a result, it becomes possible to produce materials with customized thicknesses and predetermined operational conditions, thereby saving time, costs, and raw materials. These appealing aspects have been extensively explored in the manufacturing of hydrogels for biomedical and pharmaceutical applications. However, there are few studies reporting the use of 3D-printed hydrogels for adsorption processes, with the majority focusing on metal removal.

^{17}

In terms of studies focused on the adsorption of organic contaminants, one example is the work conducted by Yuan et al.,

^{18}

which describes the preparation of 3D-printed porous cellulose/alginate monolithic hydrogels for the removal of methylene blue (MB). Baigorria et al.

^{19}

utilized 3D-printed composite hydrogels of alginate/clay to adsorb the pesticide paraquat. Shojaeiarani et al.

^{20}

investigated the adsorption of cationic and anionic dyes from water using 3D-printed hydrogels of poly(ethylene oxide) (PEO) and cellulose nanocrystals (CNCs). Considering the limited literature on this relevant research topic, there is a clear need for advances and contributions.
在過去十年中，增材製造過程，包括 3D 列印，已成為獲得具有有序和複雜結構的定制水凝膠的替代方案。此外，3D 列印在水凝膠製造中提供了幾個優勢，包括大規模生產的潛力、最小的原材料浪費，以及在不受濕度和其他氣候因素影響的控制條件下生產水凝膠的能力。因此，可以生產具有定制厚度和預定操作條件的材料，從而節省時間、成本和原材料。這些吸引人的特點在生物醫學和製藥應用的水凝膠製造中得到了廣泛探索。然而，報告使用 3D 列印水凝膠進行吸附過程的研究相對較少，大多數集中在金屬去除方面。在專注於有機污染物吸附的研究中，一個例子是 Yuan 等人的工作，該研究描述了製備 3D 列印多孔纖維素/海藻酸鹽單體水凝膠以去除美藍（MB）。Baigorria 等人。

^{19}

利用 3D 列印的複合水凝膠（海藻酸鹽/黏土）來吸附農藥巴拉圭。Shojaeiarani 等人

^{20}

研究了使用 3D 列印的聚乙烯氧化物（PEO）和纖維素奈米晶體（CNCs）從水中吸附陽離子和陰離子染料。考慮到這一相關研究主題的文獻有限，顯然需要進一步的進展和貢獻。
This study proposes the manufacture of composite hydrogels composed of alginate and rice husk (RH) biochar using 3D printing as a strategy to create enhanced adsorbents for the removal of organic contaminants. As evident from the literature, both RH and RH ashes (RHA) have been directly employed as adsorbent materials for various contaminants.

^{21 - 23}

Herein, we hypothesize that combining the alginate matrix with RH biochar can yield a high-performance adsorbent. Additionally, we successfully demonstrated the use of residual biomass to formulate a printable ink for the mass production of adsorbents through additive manufacturing. The 3D-printed composite hydrogels underwent comprehensive characterization, and their adsorption efficiency toward two specific organic contaminants, ibuprofen (IBU) and methylene blue (MB), was assessed via a series of batch adsorption experiments, encompassing kinetic and isothermal analyses. All adsorption experiments were performed using tap water to replicate real operational conditions. Moreover, we evaluated the reusability of this adsorbent through successive adsorption/desorption experiments. Collectively, all of the acquired data affirm the superior performance of the composite hydrogel and its potential for practical adsorption applications.
本研究提出製造由海藻酸鈉和稻殼（RH）生物炭組成的複合水凝膠，利用 3D 列印作為創造增強型吸附劑以去除有機污染物的策略。文獻顯示，RH 及其灰燼（RHA）已被直接用作各種污染物的吸附材料。本文假設將海藻酸鈉基質與 RH 生物炭結合可以產生高性能的吸附劑。此外，我們成功展示了利用殘餘生物質製備可列印墨水，以通過增材製造進行吸附劑的大規模生產。3D 列印的複合水凝膠經過全面表徵，並通過一系列批次吸附實驗評估其對兩種特定有機污染物，即布洛芬（IBU）和美藍（MB）的吸附效率，涵蓋動力學和等溫分析。所有吸附實驗均使用自來水進行，以模擬實際操作條件。此外，我們通過連續的吸附/脫附實驗評估了該吸附劑的重複使用性。綜合所有獲得的數據，證實了複合水凝膠的卓越性能及其在實際吸附應用中的潛力。

MATERIALS AND METHODS 材料與方法

Materials. Alginic acid sodium salt (SA), with a mannuronic acid to guluronic acid ratio of approximately 1.56 and a molecular weight

(M_{w})

ranging from 80 to 120 kDa (

96 %

purity), and Nafion 117 (2.5 wt % in a mixture of lower aliphatic alcohols and water and 65% purity) were acquired from Sigma-Aldrich (USA). Calcium chloride (

{CaCl}_{2}

, P.A.,

99 %

purity) was purchased from LabSynth (Brazil). Rice husk was donated by LabMeQui/UFPel (Pelotas, Brazil). Ibuprofen sodium (IBU) with

99 %

purity was purchased from Birzeit Pharmaceutical Company (Palestine), and methylene blue (MB) with 97% purity was purchased from Fluka (Switzerland).
材料。海藻酸鈉（SA），其甘露酸與古魯酸的比例約為 1.56，分子量

(M_{w})

範圍為 80 至 120 kDa（

96 %

純度），以及 Nafion 117（在低級脂肪醇和水的混合物中 2.5 wt %，純度 65%）均由 Sigma-Aldrich（美國）獲得。氯化鈣（

{CaCl}_{2}

，P.A.，

99 %

純度）由 LabSynth（巴西）購得。稻殼由 LabMeQui/UFPel（巴西佩洛塔斯）捐贈。伊布 uprofen 鈉（IBU）純度為

99 %

，由 Birzeit 製藥公司（巴勒斯坦）購得，亞甲藍（MB）純度為 97%，由 Fluka（瑞士）購得。

Preparation of RH Biochar. The raw rice husk (RH) was thoroughly washed in distilled water and then oven-dried at

60^{\circ} C

for 48 h . Subsequently, it was processed following the protocol described by Tsai et al.

^{24}

with a few modifications. The dried RH was milled using a ball mill (Marconi MA 350, Brazil) and added to a sealed Teflon vessel along with 24 mL of a NaOH solution (

7.5 mol / L)

. The mass ratio of RH to NaOH was set at

1.88 : 1

. The Teflon vessel was placed inside a stainless-steel container for the hydrothermal reactions. The temperature was then increased to

120^{\circ} C

at a heating rate of

10^{\circ} C / \min

and maintained for 5 h . After cooling to room temperature (approximately

25^{\circ} C

), the mixture was filtered by vacuum, and the resulting material (RH biochar) was washed with deionized water until it reached a neutral pH .
RH 生物炭的製備。生稻殼 (RH) 在蒸餾水中徹底清洗後，於

60^{\circ} C

的烘箱中乾燥 48 小時。隨後，根據 Tsai 等人所描述的協議

^{24}

進行處理，並進行了一些修改。乾燥的 RH 使用球磨機 (Marconi MA 350, 巴西) 研磨，並與 24 毫升的氫氧化鈉溶液一起加入密封的特氟龍容器中 (

7.5 mol / L)

)。RH 與氫氧化鈉的質量比設置為

1.88 : 1

。特氟龍容器放置在不銹鋼容器內進行水熱反應。然後，將溫度提高至

120^{\circ} C

，加熱速率為

10^{\circ} C / \min

，並保持 5 小時。冷卻至室溫 (約

25^{\circ} C

) 後，混合物通過真空過濾，得到的材料 (RH 生物炭) 用去離子水洗滌，直到達到中性 pH。

Printing of the Alg and Alg/Biochar Hydrogels. The first step involved preparing the inks for the 3D printing process. Specific amounts of SA were added to distilled water and solubilized at room temperature by using magnetic stirring for 4 h . Next, Nafion was added to the polysaccharide solution and vigorously stirred for 2 h . The resulting solution was used to print the alginate hydrogels (termed Alg). Simultaneously, inks for printing Alg hydrogels containing the RH biochar (termed Alg/Biochar) were prepared with some modifications. Different amounts of biochar (

1 %, 5 %

, or

10 % w / w

relative to the mass of alginate) were added to the alginate/ Nafion solution, which was stirred at 500 rpm for 2 h to achieve homogenization. The composition of each ink and its printability are listed in Table 1.
Alg 和 Alg/Biochar 水凝膠的印刷。第一步是為 3D 印刷過程準備墨水。將特定量的 SA 添加到蒸餾水中，並在室溫下使用磁力攪拌器攪拌 4 小時以使其溶解。接著，將 Nafion 添加到多醣溶液中，並劇烈攪拌 2 小時。所得溶液用於印刷海藻酸鈉水凝膠（稱為 Alg）。同時，為印刷含有 RH 生物炭的 Alg 水凝膠（稱為 Alg/Biochar）準備了墨水，並進行了一些修改。將不同量的生物炭（

1 %, 5 %

或

10 % w / w

相對於海藻酸鈉的質量）添加到海藻酸鈉/Nafion 溶液中，並以 500 rpm 攪拌 2 小時以達到均勻化。每種墨水的組成及其可印刷性列於表 1。

Table 1. Composition of the Prepared Inks, Printability Information, and Sample Coding
表 1. 準備墨水的成分、可印刷性資訊及樣本編碼

\begin{matrix} Alg \\ (mg) \end{matrix}

Biochar (mg) 生物炭 (毫克)

\underset{(μ L)}{{Nafion}^{a}}

vol of water (mL)
水的體積 (毫升)

printability 可印刷性

hydrogel code 水凝膠代碼

2.5

nonprintable 無法列印

2.5

nonprintable 無法列印

2.5

0.25

nonprintable 無法列印

2.5

0.25

nonprintable 無法列印

2.0

printable 可列印的

Alg 算法

2.0

0.02

printable 可列印的

Alg/ 生物炭 1

Alg/

Biochar1

2.0

0.12

printable 可列印的

Alg/ Biochar5 Alg/ 生物炭 5

2.0

0.25

printable 可列印的

Alg/ 算法

^{a} 20 μ L

is equivalent to

42.0 μ g

^{a} 20 μ L

等於

42.0 μ g

。

Before printing, a plastic syringe ( 5 mL ) equipped with a needle (inner diameter of 1.0 mm ) was filled with the prepared inks. The Alg and Alg /Biochar hydrogels were printed using a 3D Genesis II bioprinter (3D Biotechnology Solutions, Brazil) with an extrusion printhead equipped with a syringe and a

0.70 mm \times 20 mm

nozzle. The printing pressure was set at 25 kPa , and the printing velocity was

70 mm / s

. The hydrogels were designed as disc-shaped structures with a diameter of 1.5 cm and a thickness of 5 mm by using Slic3r, an open-source software. The internal architecture was designed in a mesh shape, where interconnected lines were distributed orthogonally and cylindrically in the

x, y

, and

z

directions.

^{25}

After the printing process, all hydrogels were immersed directly in a

{CaCl}_{2}

aqueous
在打印之前，使用一個配有針頭（內徑為 1.0 毫米）的塑料注射器（5 毫升）填充了準備好的墨水。Alg 和 Alg /生物炭水凝膠是使用 3D Genesis II 生物打印機（3D Biotechnology Solutions，巴西）進行打印的，該打印機配備了一個注射器和一個

0.70 mm \times 20 mm

噴嘴的擠出打印頭。打印壓力設置為 25 kPa，打印速度為

70 mm / s

。水凝膠被設計為直徑 1.5 厘米、厚度 5 毫米的圓盤形結構，使用開源軟件 Slic3r 進行設計。內部結構設計為網格形狀，其中互相連接的線條在

x, y

和

z

方向上以正交和圓柱形分佈。

^{25}

打印過程結束後，所有水凝膠直接浸入

{CaCl}_{2}

水溶液中。
solution

(5 % w / v)

to facilitate the ionotropic cross-linking of the alginate chains. It is important to note that conditions requiring larger amounts of reagents and solvents were discarded, and other conditions with lower volumes of reagents did not result in inks with suitable printability (Table 1).
解決方案

(5 % w / v)

以促進海藻酸鹽鏈的離子交聯。值得注意的是，要求使用較大量試劑和溶劑的條件被捨棄，而其他使用較少試劑的條件則未能產生具有適當可印刷性的墨水（表 1）。
Characterization Apparatus and Experiments. Fourier transform infrared (FTIR) spectra were recorded by using a Shimadzu IR spectrometer (model Affinity 1, Japan). Prior to recording the spectra, the samples were powdered using an Anton Parr BM500 ball mill (USA), mixed with KBr , and then pressed. The spectra were recorded in the range of

400 - 4000 {cm}^{- 1}

with a resolution of

4 {cm}^{- 1} (64

scans). X-ray diffraction (XRD) patterns were obtained by using a Siemens diffractometer (model D500, Germany) with a

Cu K α

radiation source. The XRD patterns were scanned in a

2 θ

range of

10^{\circ} - 50^{\circ}

at a scanning speed of

{0.05}^{\circ} / s

. A JEOL scanning electron microscope (model JSM-6610LV, USA) was used to image the samples. Prior to image acquisition, the hydrogels were rapidly frozen in liquid nitrogen, dried through lyophilization at

- 55^{\circ} C

for 48 h and then gold-coated by sputtering. The Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods were employed to determine the specific surface area and porosity of the printed materials.

^{26} N_{2}

sorption-desorption analysis was performed by using a Quantachrome Autosorb-iQ3-MP/Kr BET surface analyzer (USA). The materials were degassed and dried before the analysis.
特徵化設備與實驗。傅立葉變換紅外光譜（FTIR）是使用島津 IR 光譜儀（型號 Affinity 1，日本）記錄的。在記錄光譜之前，樣品使用安東帕 BM500 球磨機（美國）粉碎，與 KBr 混合後再壓制。光譜在

400 - 4000 {cm}^{- 1}

範圍內以

4 {cm}^{- 1} (64

的解析度記錄。X 射線衍射（XRD）圖譜是使用西門子衍射儀（型號 D500，德國）與

Cu K α

輻射源獲得的。XRD 圖譜在

2 θ

範圍內以

10^{\circ} - 50^{\circ}

的掃描速度掃描。使用 JEOL 掃描電子顯微鏡（型號 JSM-6610LV，美國）對樣品進行成像。在圖像獲取之前，水凝膠在液氮中迅速冷凍，然後在

- 55^{\circ} C

下進行 48 小時的冷凍乾燥，並經過濺鍍金屬處理。使用 Brunauer-Emmett-Teller（BET）和 Barrett-Joyner-Halenda（BJH）方法來確定印刷材料的比表面積和孔隙率。

^{26} N_{2}

吸附-脫附分析是使用 Quantachrome Autosorb-iQ3-MP/Kr BET 表面分析儀（美國）進行的。材料在分析之前已進行脫氣和乾燥處理。
The total porosity of the Alg and Alg/Biochar hydrogels was determined using the solvent displacement method described by Chuysinuan et al.

^{27}

Each hydrogel sample was completely immersed in absolute ethanol until saturation, which took approximately 48 h . The samples were weighed before and after immersion in ethanol. The total porosity was calculated using eq 1 :
Alg 和 Alg/Biochar 水凝膠的總孔隙率是使用 Chuysinuan 等人所描述的溶劑置換法來確定的。每個水凝膠樣品完全浸泡在無水乙醇中，直到飽和，這大約需要 48 小時。樣品在浸泡前後的重量被測量。總孔隙率是使用公式 1 計算的：

total porosity (%) = \frac{w_{2} - w_{1}}{ρ V_{sample}} \times 100

where

w_{1}

and

w_{2}

represent the weights of the samples before and after immersion,

V_{sample}

is the hydrogel volume after immersion, and

ρ

is the density of absolute ethanol at

25^{\circ} C

. This analysis was performed in triplicate for each hydrogel sample.
其中

w_{1}

和

w_{2}

代表浸泡前後樣本的權重，

V_{sample}

是浸泡後的水凝膠體積，

ρ

是在

25^{\circ} C

時的無水乙醇密度。此分析對每個水凝膠樣本進行了三次重複。
The pH of the point of zero charge

({pH}_{PZC})

of the printed hydrogels was determined using the solid addition method according to Yadav et al.

^{28} NaCl

solutions (

0.1 mol / L, 50 mL

) with pH values ranging from 2.0 to 10.0 were prepared using

0.1 mol / L HCl

or NaOH , with the assistance of a pH meter (Hanna Instruments model HI2211, USA). These solutions were placed in vials along with the hydrogel samples ( 30 mg ). The vials were stirred on an orbital shaker at 150 rpm for 24 h at room temperature. Subsequently, the final pH of each solution was measured again using a pH meter. The pH variation

(Δ pH = {pH}_{initial} - {pH}_{final})

was plotted against the initial pH values, and the

{pH}_{PZc}

was estimated by identifying the intersection point of the horizontal line at

Δ pH = 0

with the plot.

^{21}

印刷水凝膠的零電荷點 pH 值

({pH}_{PZC})

是根據 Yadav 等人

^{28} NaCl

的固體添加法測定的，所使用的溶液 (

0.1 mol / L, 50 mL

) 的 pH 值範圍從 2.0 到 10.0，這些溶液是使用

0.1 mol / L HCl

或 NaOH 準備的，並借助 pH 計 (Hanna Instruments 型號 HI2211，美國)。這些溶液與水凝膠樣品 (30 mg) 一起放置在小瓶中。小瓶在室溫下以 150 rpm 的速度在 orbital shaker 上攪拌 24 小時。隨後，使用 pH 計再次測量每個溶液的最終 pH 值。pH 變化

(Δ pH = {pH}_{initial} - {pH}_{final})

被繪製成與初始 pH 值的圖表，並通過識別在

Δ pH = 0

的水平線與圖表的交點來估算

{pH}_{PZc}

。

^{21}

Swelling Experiments. Swelling experiments were conducted to investigate the liquid uptake behavior of the printed Alg and

Alg /

Biochar hydrogels. For this purpose, hydrogel samples weighing approximately 30 mg were placed in vials filled with tap water ( 50 mL ). The vials containing the hydrogels were subjected to mild stirring at around 100 rpm and maintained at approximately

25^{\circ} C

. At specific time intervals, the swollen hydrogel samples were removed from the vials, excess water on their surface was removed using a paper towel, and they were reweighed. After this step, the hydrogel samples were returned to their respective vials. The swelling rate at each time point was calculated using eq 2 , where

w_{s}

and

w_{d}

represent the weights of the hydrogel samples at the swollen and dry states, respectively. This experiment was conducted in triplicate for each hydrogel sample.
膨脹實驗。進行膨脹實驗以研究印刷的 Alg 和

Alg /

生物炭水凝膠的液體吸收行為。為此，約 30 毫克的水凝膠樣品被放置在裝有自來水（50 毫升）的瓶子中。含有水凝膠的瓶子在約 100 轉每分鐘的輕微攪拌下進行處理，並保持在約

25^{\circ} C

。在特定的時間間隔內，將膨脹的水凝膠樣品從瓶中取出，使用紙巾去除其表面的多餘水分，然後重新稱重。在這一步驟之後，水凝膠樣品被放回各自的瓶中。每個時間點的膨脹率是使用公式 2 計算的，其中

w_{s}

和

w_{d}

分別代表水凝膠樣品在膨脹和乾燥狀態下的重量。此實驗對每個水凝膠樣品進行了三次重複。

wwelling rate (%) = \frac{w_{s} - w_{d}}{w_{d}} \times 100

Cross-Link Density. The cross-linking density of the printed hydrogels was determined using the method described by Lira et al.,

^{29}

which is based on the Flöry-Rehner equation. Hydrogel samples
交聯密度。印刷水凝膠的交聯密度是使用 Lira 等人所描述的方法來確定的

^{29}

，該方法基於 Flöry-Rehner 方程。水凝膠樣本
weighing 60 mg were placed in vials filled with distilled water

(50 mL)

25^{\circ} C

. After equilibrium was reached (approximately 3 h ), the swollen hydrogels were collected and reweighed. The swelling rate at equilibrium was calculated using eq 2 , as mentioned before.
重 60 毫克的樣品被放置在裝有蒸餾水的瓶中

(50 mL)

於

25^{\circ} C

。在達到平衡後（約 3 小時），收集膨脹的水凝膠並重新稱重。平衡時的膨脹率是使用之前提到的公式 2 計算的。

\begin{aligned} M_{c} = V_{p} + χ {(V_{p})}^{2} + \frac{\ln (1 - V_{p})}{V_{s} d_{B}} [\sqrt[3]{V_{p}} - \frac{V_{p}}{2}] \\ V_{p} = \frac{1}{1 + \frac{S}{100}} \\ χ = \frac{\ln (1 - V_{p}) + V_{p}}{V_{p}^{2}} \\ v_{e} = \frac{1}{M_{c}} \end{aligned}

where

M_{c}

is the average molecular weight between adjacent crosslinking points,

V_{p}

is the volume fraction of the disc in its swollen state,

χ

is the parameter that defines the interaction that occurs between the polymers and the deionized water (

\sim 0.49

V_{s}

is the molar volume of solvent

(18 {cm}^{3} / mol

for

H_{2} O), d_{B}

is the density of the sample used (

1.6 g / {cm}^{3}

determined using a pycnometer),

^{30}

and

S

is the maximum swelling rate calculated at equilibrium.
其中

M_{c}

是相鄰交聯點之間的平均分子量，

V_{p}

是膨脹狀態下圓盤的體積分數，

χ

是定義聚合物與去離子水 (

\sim 0.49

) 之間相互作用的參數，

V_{s}

是溶劑

(18 {cm}^{3} / mol

的摩爾體積，

H_{2} O), d_{B}

是所用樣品的密度 (

1.6 g / {cm}^{3}

由比重計測定)，

^{30}

和

S

是在平衡時計算的最大膨脹速率。

Adsorption Experiments. The adsorption capacity of the printed hydrogels for IBU and MB from tap water was investigated through batch experiments conducted under different conditions. The general experimental procedures were as follows: 250 mL Erlenmeyer flasks were filled with stock solutions of IBU or MB ( 50 mL ) prepared with tap water, with specific initial concentrations

(C_{0})

. Hydrogel samples were placed in the Erlenmeyer flasks, and the flasks were stirred at 150 rpm at room temperature. At specific time intervals, aliquots were collected from the Erlenmeyer flasks by using a syringe equipped with a

0.45 μ m

filter. The aliquots were then transferred to a quartz cuvette and analyzed by using a UV-vis spectrophotometer (PerkinElmer Lambda35, Canada). Absorbance intensities at 220 and 595 nm were measured to identify and quantify IBU and MB, and calibration curves were used to convert the absorbance data into concentration values. It is worth informing the reader that after the UV-vis measurements the aliquots were returned to their respective Erlenmeyer flasks. The removal efficiency (%) and adsorption capacity (

mg / g

) values at each time interval were determined using eqs 7 and 8 :
吸附實驗。通過在不同條件下進行的批次實驗，研究了印刷水凝膠對自來水中布洛芬（IBU）和美藍（MB）的吸附能力。一般實驗程序如下：250 毫升的錐形瓶中裝入用自來水製備的 IBU 或 MB 的儲備溶液（50 毫升），其初始濃度為

(C_{0})

。將水凝膠樣品放入錐形瓶中，並在室溫下以 150 轉/分鐘的速度攪拌。在特定的時間間隔內，使用配有

0.45 μ m

過濾器的注射器從錐形瓶中取出等分試樣。然後將等分試樣轉移到石英比色皿中，並使用紫外-可見分光光度計（PerkinElmer Lambda35，加拿大）進行分析。測量 220 和 595 納米的吸光度強度以識別和定量 IBU 和 MB，並使用標定曲線將吸光度數據轉換為濃度值。值得告知讀者的是，在紫外-可見測量後，等分試樣被返回到各自的錐形瓶中。去除效率 (%) 和吸附容量 (

mg / g

) 在每個時間間隔的值是使用方程式 7 和 8 確定的：

\begin{aligned} removal (%) = \frac{C_{0} - C_{t}}{C_{i}} \times 100 \\ q_{t} = \frac{C_{0} - C_{t}}{m} \times V \end{aligned}

where

C_{0}

is the initial contaminant concentration and

C_{t}

is the concentration at time

t, m

is the mass of the adsorbent, and

V

is the volume of the solution. The parameter

q_{t}

refers to the amount of contaminant adsorbed per gram of hydrogel at a given time

t

. It is worth informing the reader that

C_{t}

is replaced by

C_{e}

in eqs 7 and 8 , and it is replaced by

q_{e}

in eq 8 . The experimental conditions were varied as follows: hydrogel dosage (

30 - 90 mg

), initial contaminant concentration

(1 - 12 mg / L)

, and

pH (5 - 7)

. All experiments described in this section were conducted at room temperature in triplicate.
其中

C_{0}

是初始污染物濃度，

C_{t}

是時間

t, m

的濃度，

V

是吸附劑的質量，

q_{t}

參數指的是在特定時間

t

每克水凝膠吸附的污染物量。值得告知讀者的是，在方程式 7 和 8 中，

C_{t}

被

C_{e}

取代，而在方程式 8 中則被

q_{e}

取代。實驗條件變化如下：水凝膠劑量 (

30 - 90 mg

)、初始污染物濃度

(1 - 12 mg / L)

和

pH (5 - 7)

。本節中描述的所有實驗均在室溫下進行，並重複三次。

Adsorption Selectivity Experiments. Batch experiments were conducted by using a binary solution of IBU and MB in tap water ( 50 mL , with a concentration of

12 mg / L

for each contaminant) to assess the selective adsorption capability of the Alg/Biochar10 hydrogel. The binary solution was placed in a 250 mL Erlenmeyer flask along with the hydrogel sample ( 30 mg ), and the mixture was stirred at 150 rpm for 2 h at

25^{\circ} C

. Subsequently, an aliquot was taken from the Erlenmeyer flask, filtered, and analyzed by using a UV-vis spectrometer. The maximum removal rate for each contaminant was determined, as explained in the previous section. The selectivity parameter was calculated using eq 9:
吸附選擇性實驗。進行了批次實驗，使用自來水中的 IBU 和 MB 二元溶液（50 毫升，每種污染物的濃度為

12 mg / L

）來評估 Alg/Biochar10 水凝膠的選擇性吸附能力。將二元溶液放入 250 毫升的圓底燒瓶中，並加入水凝膠樣品（30 毫克），混合物以 150 轉/分鐘的速度攪拌 2 小時，溫度為

25^{\circ} C

。隨後，從圓底燒瓶中取出一部分，過濾後使用紫外-可見光光譜儀進行分析。每種污染物的最大去除率如前一部分所述進行了確定。選擇性參數使用公式 9 計算。

Figure 1. (a) FTIR spectra of pure SA, biochar, Alg hydrogel, and Alg/Biochar10 hydrogel. (b) XRD patterns of (i) pure SA, (ii) Alg hydrogel, and (iii) Alg/Biochar10 hydrogel.
圖 1. (a) 純 SA、生物炭、Alg 水凝膠及 Alg/Biochar10 水凝膠的 FTIR 光譜。(b) (i) 純 SA、(ii) Alg 水凝膠及(iii) Alg/Biochar10 水凝膠的 XRD 圖譜。

selectivity (%) = \frac{m_{i}}{m_{i} + m_{i i}}

where

m_{i}

and

m_{i i}

are the masses of each adsorbed contaminant.
其中

m_{i}

和

m_{i i}

是每個吸附污染物的質量。
Desorption and Reuse Experiments. The recycling of the postutilized hydrogels was done by desorbing the contaminants (IBU or MB) from postutilized hydrogels. For this, just after the adsorption experiments, the hydrogels were recovered and immersed in a methanol/distilled water solution (

2 : 1

ratio, 15 mL ), which was stirred for 30 min at

\sim 25^{\circ} C

. UV-vis spectroscopy was utilized to measure the absorbance of the desorption media. From these data, the desorption rate was calculated per eq 10:
脫附與重用實驗。後利用水凝膠的回收是通過從後利用的水凝膠中脫附污染物（IBU 或 MB）來進行的。為此，在吸附實驗結束後，水凝膠被回收並浸入一個甲醇/蒸餾水溶液（

2 : 1

比例，15 毫升）中，並在

\sim 25^{\circ} C

下攪拌 30 分鐘。使用紫外-可見光光譜法測量脫附介質的吸光度。根據這些數據，根據公式 10 計算脫附率：

desorption (%) = \frac{q_{des}}{q_{ads}} \times 100

where

q_{des}

and

q_{ads}

are the amount of compound desorbed and adsorbed by the printed hydrogels. For reuse experiments, the recycled hydrogels were used in adsorption/desorption cycles. In total, 20 consecutive cycles were performed using the adsorption and desorption conditions described above.
其中

q_{des}

和

q_{ads}

是印刷水凝膠所脫附和吸附的化合物量。在重複使用實驗中，回收的水凝膠用於吸附/脫附循環。總共進行了 20 次連續循環，使用上述描述的吸附和脫附條件。

RESULTS AND DISCUSSION 結果與討論

Characterization of the Printed Hydrogels. FTIR analysis was used to characterize the chemistry of the printed hydrogels as precursor materials. The FTIR spectrum of SA (Figure 1a) exhibited characteristic broadband centered at

3433 {cm}^{- 1}

attributed to the stretching of

O - H

bonds, bands in the range of

2925 - 2865 {cm}^{- 1}

due to the stretching of

C - H

bonds (aliphatic

{CH}_{x}

groups), bands at 1614 and

1432 {cm}^{- 1}

due to the

C = O

asymmetric and symmetric stretching of

C =

O bonds, and bands in the range of

1100 - 1030 {cm}^{- 1}

attributable to the stretching of

C - O - C, C - C

, and

C - OH

bonds of the pyranose ring.

^{31}

The FTIR spectrum of biochar displayed bands at

3415 {cm}^{- 1}

due to the stretching of the

O -

H bonds, while the band at

2923 {cm}^{- 1}

is assigned to the stretching of the

C - H

bonds in the

{CH}_{2}

groups of cellulose and hemicelluloses. The band observed at

1653 {cm}^{- 1}

refers to the stretching of

C = C

bonds of hemicellulose, and the band at

1118 {cm}^{- 1}

is attributable to the stretching of

C - O

bonds of lignin.

^{32}

Additionally, the band at

1074 {cm}^{- 1}

originates from the combination of the stretching and deformation of the

C - O

and

O - H

bonds, and the band at

896 {cm}^{- 1}

is attributable to the

β

-glycosidic linkages between the glucose units of cellulose.

^{33}

Overall, the presence of these bands indicated that the lignocellulosic matrix of RH remained somewhat
印刷水凝膠的特徵化。使用 FTIR 分析來表徵印刷水凝膠作為前驅材料的化學性質。SA 的 FTIR 光譜（圖 1a）顯示出以

3433 {cm}^{- 1}

為中心的特徵寬帶，這歸因於

O - H

鍵的伸縮，範圍在

2925 - 2865 {cm}^{- 1}

的帶是由於

C - H

鍵（脂肪族

{CH}_{x}

基團）的伸縮，1614 和

1432 {cm}^{- 1}

的帶是由於

C = O

不對稱和對稱伸縮的

C =

O 鍵，範圍在

1100 - 1030 {cm}^{- 1}

的帶可歸因於

C - O - C, C - C

和

C - OH

鍵的伸縮，這些鍵屬於吡喃糖環。

^{31}

生物炭的 FTIR 光譜顯示在

3415 {cm}^{- 1}

的帶是由於

O -

H 鍵的伸縮，而在

2923 {cm}^{- 1}

的帶則歸屬於纖維素和半纖維素的

C - H

鍵的伸縮。觀察到的在

1653 {cm}^{- 1}

的帶指的是半纖維素的

C = C

鍵的伸縮，而在

1118 {cm}^{- 1}

的帶則可歸因於木質素的

C - O

鍵的伸縮。

^{32}

此外，位於

1074 {cm}^{- 1}

的帶源於

C - O

和

O - H

鍵的拉伸與變形的結合，而位於

896 {cm}^{- 1}

的帶則歸因於纖維素中葡萄糖單元之間的

β

-糖苷鍵。

^{33}

總體而言，這些帶的存在表明，稻殼的木質纖維素基質仍然在某種程度上保持不變
intact after hydrothermal treatment. Similar findings were reported in the literature.

^{32}

According to some authors, raw RH consists of approximately

70 - 75 %

organic matter (cellulose, hemicellulose, and lignin), 15-20% ash/silica, and

5 - 15 %

humidity.

^{34}

The preservation of functional groups on RH biochar after hydrothermal carbonization is advantageous for adsorption applications.

^{35}

經水熱處理後仍保持完整。文獻中報導了類似的發現。根據一些作者的說法，原料稻殼大約由

70 - 75 %

有機物（纖維素、半纖維素和木質素）、15-20% 灰分/二氧化矽和

5 - 15 %

濕度組成。水熱碳化後稻殼生物炭上功能團的保存對於吸附應用是有利的。

The FTIR spectrum recorded from the Alg hydrogel exhibited the characteristic bands of alginate as well as some changes. The bands associated with the asymmetric and symmetric stretching of the

C = O

bonds of carboxylic groups were shifted to 1620 and

1450 {cm}^{- 1}

, indicating the replacement of the

{Na}^{+}

ion in the uronic acid residues by

{Ca}^{2 +}

ions after ionotropic cross-linking.

^{36}

Also, the broadband attributable to the stretching of the

O - H

bond was sharpened compared to other bands in the same spectrum likely due to the decrease of inter- and intramolecular H bonds because of the cross-linking of alginate chains by

{Ca}^{2 +}

ions. Bands proceeding from Nafion were observed at 1233 and

1280 {cm}^{- 1}

due to the

- {CF}_{2}

stretching.

^{37, 38}

Compared with the FTIR spectrum of Alg, the Alg/Biochar10 spectrum exhibited minimal discrepancies likely due to the chemical similarity between the two hydrogels. The low amount of biochar utilized to prepare this hydrogel and the overlapping of the main bands of biochar by the bands proceeding from alginate may contribute to this observation too. Overall, Alg/Biochar10 showed a broadening of the band assigned to the stretching of the

O - H

bonds, suggesting the interaction of the hydrogel groups with biochar via H-bonding. Bands in the range of

1600 - 1530 {cm}^{- 1}

are attributable to the stretching of

C - H

bonds of

{CH}_{2}

and

{CH}_{3}

groups proceeding from the lignocellulosic portion of biochar. The band around 1657

{cm}^{- 1}

was also broadened as compared to other bands in the same spectrum due to the contribution of the stretching of the

C = C

bond of lignin. The band at

1518 {cm}^{- 1}

almost disappeared because of the alginate cross-linking with

{Ca}^{2 +}

ions. In addition, it is possible to note that the intensity of the band at

1460 {cm}^{- 1}

increases because of the higher availability of

C - O

groups proceeding from the biochar.

^{39}

Together, these findings suggest that RH biochar was incorporated into the Alg matrix.
從 Alg 水凝膠記錄的 FTIR 光譜顯示了藻酸鹽的特徵帶以及一些變化。與羧基的

C = O

鍵的不對稱和對稱伸縮相關的帶移動至 1620 和

1450 {cm}^{- 1}

，這表明在離子交聯後，尿酸殘基中的

{Na}^{+}

離子被

{Ca}^{2 +}

離子取代。

^{36}

此外，與

O - H

鍵的伸縮相關的寬帶相比於同一光譜中的其他帶變得更加尖銳，這可能是由於藻酸鹽鏈被

{Ca}^{2 +}

離子交聯後，分子間和分子內氫鍵的減少所致。來自 Nafion 的帶在 1233 和

1280 {cm}^{- 1}

處被觀察到，這是由於

- {CF}_{2}

的伸縮。

^{37, 38}

與 Alg 的 FTIR 光譜相比，Alg/Biochar10 光譜顯示出最小的差異，這可能是由於這兩種水凝膠之間的化學相似性。用於製備這種水凝膠的生物炭量少，以及生物炭的主要帶與來自藻酸鹽的帶重疊，也可能有助於這一觀察。總體而言，Alg/Biochar10 顯示出與

O - H

鍵伸展相關的帶寬變寬，這表明水凝膠基團與生物炭之間通過氫鍵的相互作用。範圍在

1600 - 1530 {cm}^{- 1}

的帶可歸因於來自生物炭木質纖維素部分的

{CH}_{2}

和

{CH}_{3}

基團的

C - H

鍵伸展。與同一光譜中的其他帶相比，約 1657

{cm}^{- 1}

的帶也因木質素的

C = C

鍵伸展的貢獻而變寬。位於

1518 {cm}^{- 1}

的帶幾乎消失，這是由於海藻酸鹽與

{Ca}^{2 +}

離子的交聯。此外，可以注意到位於

1460 {cm}^{- 1}

的帶的強度增加，這是因為來自生物炭的

C - O

基團的可用性更高。

^{39}

綜合這些發現表明 RH 生物炭被納入了 Alg 基質中。

Figure 1 b presents the XRD patterns obtained for pure SA, Alg, and the Alg/Biochar 10 hydrogels. The XRD pattern of pure SA exhibited two broad diffraction peaks at

2 θ \approx {13.6}^{\circ}

圖 1b 顯示了純 SA、Alg 和 Alg/Biochar 10 水凝膠的 XRD 圖譜。純 SA 的 XRD 圖譜顯示出兩個寬廣的衍射峰在

2 θ \approx {13.6}^{\circ}

處。

Figure 2. Photographic and SEM images of the printed hydrogels: (a) Alg, (b) Alg/Biocharl, © Alg/Biochar5, and (d) Alg/Biochar10 (SEM magnification

\times 55

).
圖 2. 印刷水凝膠的攝影圖和掃描電子顯微鏡（SEM）圖像：(a) Alg，(b) Alg/Biocharl，(c) Alg/Biochar5，和(d) Alg/Biochar10（SEM 放大倍率

\times 55

）。
and

{21.5}^{\circ}

, which correspond to the reflection of the (110) plane from glucuronic acid units and the (200) plane from mannuronic acid units of alginate, as described elsewhere.

^{39}

In the XRD pattern of the Alg hydrogel, the mixture with Nafion, printing, and cross-linking resulted in the disappearance of the diffraction peaks characteristic of alginate. This indicates that these processes altered the crystalline arrangement of the polysaccharide. Conversely, the XRD pattern of the Alg hydrogel displayed diffraction peaks at

2 θ \approx {29.0}^{\circ}, {35.6}^{\circ}

, and

{43.0}^{\circ}

, which can be attributed to the egg-box structure formed following the ionotropic cross-linking of alginate chains with

{Ca}^{2 +}

ions.

^{40}

Pure Nafion exhibited a diffraction peak around

2 θ

\approx {17.5}^{\circ}

; however, due to its low concentration in the hydrogel matrix, this peak was completely overlapped by the amorphous nature of the alginate

- {Ca}^{2 +}

matrix.

^{41}

The XRD pattern of the Alg/Biochar 10 hydrogel resembled that of the Alg pattern, indicating that the addition of biochar did not affect the crystalline arrangement of the alginate

- {Ca}^{2 +}

matrix. However, a peak emerged at

2 θ \approx {31.8}^{\circ}

, and there was a slight shift in the diffraction peaks associated with the egg-box structure toward lower

2 θ

angles. This observation may be attributed to the physical interaction between the carboxylic groups of alginate and the hydroxyl groups present in the biochar, which is consistent with the FTIR data.
和

{21.5}^{\circ}

，這對應於葡萄糖醛酸單元的 (110) 面和甘露糖醛酸單元的 (200) 面的反射，如其他地方所述。

^{39}

在 Alg 水凝膠的 XRD 圖譜中，與 Nafion 的混合、印刷和交聯導致了特徵於海藻酸鹽的衍射峰的消失。這表明這些過程改變了多醣的結晶排列。相反，Alg 水凝膠的 XRD 圖譜顯示在

2 θ \approx {29.0}^{\circ}, {35.6}^{\circ}

和

{43.0}^{\circ}

的衍射峰，這可以歸因於在與

{Ca}^{2 +}

離子進行離子交聯後形成的蛋盒結構。

^{40}

純 Nafion 在

2 θ

\approx {17.5}^{\circ}

附近顯示出一個衍射峰；然而，由於其在水凝膠基質中的低濃度，這個峰完全被海藻酸鹽

- {Ca}^{2 +}

基質的非晶特性所重疊。

^{41}

Alg/Biochar 10 水凝膠的 XRD 圖譜類似於 Alg 圖譜，表明添加生物炭並未影響海藻酸鹽

- {Ca}^{2 +}

基質的結晶排列。然而，在

2 θ \approx {31.8}^{\circ}

處出現了一個峰值，與蛋盒結構相關的衍射峰略微向較低的

2 θ

角度移動。這一觀察可能歸因於海藻酸的羧基與生物炭中存在的羥基之間的物理相互作用，這與 FTIR 數據一致。
The morphology of the printed hydrogels (Alg and Alg/ Biochar1-10) was examined using images obtained by SEM (Figure 2). The Alg hydrogel exhibited 3D structures composed of irregular filaments with diameters ranging from 100 to

130 μ m

. These filaments displayed dense and homogeneous surfaces without pores, resulting in low spatial resolution. The ionotropic cross-linking step with the

{Ca}^{2 +}

solution contributed to these final morphological and textural characteristics. In general, the deposition of the printed material in the

{Ca}^{2 +}

solution can reduce its viscosity, leading to the collapse of the printed shape.

^{17}

In contrast, the Alg/ Biochar1-10 hydrogels exhibited improved printing resolution and quality (Figure 2b-d). The filaments (with diameters of

200 - 210 μ m

) displayed heterogeneous surfaces with noticeable roughness. These morphological changes became more evident as the amount of biochar in the hydrogel increased from

1 %

10 % w / w

. The presence of biochar likely increased the viscosity of the inks by interacting with the alginate chains (as observed in FTIR analysis), thereby enhancing the printability and filament stability. After cross-linking, an excess of

{Ca}^{2 +}

ions was deposited on the filament surfaces, explaining
印刷水凝膠（Alg 和 Alg/ Biochar1-10）的形態學是通過掃描電子顯微鏡（SEM）獲得的圖像進行檢查的（圖 2）。Alg 水凝膠顯示出由不規則纖維組成的三維結構，直徑範圍從 100 到

130 μ m

。這些纖維表現出致密且均勻的表面，沒有孔隙，導致低空間解析度。與

{Ca}^{2 +}

溶液的離子交聯步驟促成了這些最終的形態和質地特徵。一般而言，印刷材料在

{Ca}^{2 +}

溶液中的沉積可以降低其粘度，導致印刷形狀的崩潰。

^{17}

相比之下，Alg/ Biochar1-10 水凝膠顯示出改善的印刷解析度和質量（圖 2b-d）。這些纖維（直徑為

200 - 210 μ m

）顯示出不均勻的表面，具有明顯的粗糙度。隨著水凝膠中生物炭的含量從

1 %

增加到

10 % w / w

，這些形態學變化變得更加明顯。生物炭的存在可能通過與海藻酸鹽鏈的相互作用（如 FTIR 分析所觀察到的）增加了墨水的粘度，從而增強了可印刷性和纖維穩定性。交聯後，過量的

{Ca}^{2 +}

離子沉積在纖維表面上，解釋了
the increase in roughness. Overall, all of the printed hydrogels exhibited good mechanical stability and were easy to handle.
粗糙度的增加。總體而言，所有印刷的水凝膠均顯示出良好的機械穩定性，且易於操作。

The surface texture properties of the Alg and Alg/Biochar10 hydrogels were analyzed by using

N_{2}

adsorption/desorption measurements. The results, including the BET surface area, pore volume, and average pore diameter, are presented in Table S1. It is evident that the presence of biochar led to an increase in all of the investigated parameters. For instance, the surface area of Alg/Biochar10 increased from 82.12 to 153.15

m^{2} / g

, while the pore volume and diameter almost tripled compared to the Alg hydrogel. This enhancement can be attributed to the incorporation of biochar into the alginate matrix and the interactions between them, which resulted in the formation of surface cavities and irregularities in the composite. The presence of biochar also reduced the packing of alginate chains, which positively influenced the textural properties of Alg/Biochar10. The average pore diameter of Alg ( 2.05 nm ) and Alg/Biochar10 ( 9.23 nm ) falls into the category of mesopores, which have an average pore size ranging from 2 to

50 nm .^{42}

The pore size distribution in this range is crucial for the adsorption process, as it correlates with the transport of organic molecules within the adsorbent.
Alg 和 Alg/Biochar10 水凝膠的表面紋理特性通過

N_{2}

吸附/脫附測量進行分析。結果，包括 BET 表面積、孔隙體積和平均孔徑，見於表 S1。顯然，生物炭的存在導致所有調查參數的增加。例如，Alg/Biochar10 的表面積從 82.12 增加到 153.15

m^{2} / g

，而孔隙體積和直徑與 Alg 水凝膠相比幾乎增加了三倍。這一增強可歸因於生物炭的加入到海藻酸鈉基質中及其之間的相互作用，導致複合材料中表面空腔和不規則性的形成。生物炭的存在還減少了海藻酸鈉鏈的堆積，這對 Alg/Biochar10 的紋理特性產生了積極影響。Alg (2.05 nm) 和 Alg/Biochar10 (9.23 nm) 的平均孔徑屬於中孔範疇，其平均孔徑範圍為 2 到

50 nm .^{42}

。這一範圍內的孔徑分佈對於吸附過程至關重要，因為它與有機分子在吸附劑內的運輸相關。

Table 2 presents the total porosity values determined for the printed hydrogels. It is evident that the incorporation of small
表 2 顯示了為印刷水凝膠確定的總孔隙度值。顯然，加入小型

Table 2. Total Porosity, Cross-Link Density, and

{pH}_{PZC}

Values Determined for Alg and Alg/Biochar Hydrogels
表 2. 為 Alg 和 Alg/Biochar 水凝膠測定的總孔隙率、交聯密度和

{pH}_{PZC}

值

hydrogel 水凝膠

總孔隙度

(%)

total porosity

(%)

交聯密度

(mol / {cm}^{3})

cross-link density

(mol / {cm}^{3})

{pH}_{PZC}

Alg 算法

51 \pm 4

0.85 \pm 0.09

6.70 \pm 0.32

Alg/Biochar1 Alg/生物炭 1

56 \pm 6

0.65 \pm 0.16

6.68 \pm 0.97

Alg/Biochar5

63 \pm 5

0.61 \pm 0.12

6.55 \pm 0.65

Alg/ 算法

87 \pm 2

0.58 \pm 1.03

6.42 \pm 0.81

Biochar10 生物炭 10

amounts of biochar (

1 %, 5 %

, or

10 % w / w

) results in an increase in total porosity compared to the Alg hydrogel. For instance, the addition of

10 wt %

biochar leads to a

37 %

increase in the total porosity of the composite. This indicates that biochar modifies the microarchitecture of the hydrogels, and the extent of this change depends on the biochar content in the alginate matrix. The voluminous nature of the lignocellulosic material in biochar hinders the compaction of alginate chains, thereby increasing the number of voids within the hydrogel matrix and consequently enhancing porosity. This finding supports the earlier textual data obtained. The increase
添加生物炭（

1 %, 5 %

或

10 % w / w

）會導致總孔隙度相較於藻酸鹽水凝膠的增加。例如，添加

10 wt %

生物炭會使複合材料的總孔隙度增加

37 %

。這表明生物炭改變了水凝膠的微觀結構，而這種變化的程度取決於藻酸鹽基質中的生物炭含量。生物炭中木質纖維素材料的體積特性妨礙了藻酸鹽鏈的壓實，從而增加了水凝膠基質中的空隙數量，並因此提高了孔隙度。這一發現支持了之前獲得的文本數據。增加
in total porosity is advantageous for these hydrogels, especially in terms of their application as adsorbents. Additionally, it was observed that the cross-linking density of the composites decreased compared to the Alg hydrogel. This observation further supports the notion that biochar interacts with the hydrogel matrix, reducing the degree of cross-linking between alginate and

{Ca}^{2 +}

ions. Moreover, these data align with the previous characterization data. It is important to note that the degree of cross-linking in a hydrogel is closely linked to its swelling capacity and morphology. Changes in this parameter influence the amount of liquid absorbed and retained by the hydrogel.
總孔隙率對這些水凝膠是有利的，特別是在其作為吸附劑的應用方面。此外，觀察到複合材料的交聯密度相較於海藻酸水凝膠有所下降。這一觀察進一步支持了生物炭與水凝膠基質相互作用的觀點，減少了海藻酸鹽與

{Ca}^{2 +}

離子之間的交聯程度。此外，這些數據與先前的表徵數據一致。值得注意的是，水凝膠中的交聯程度與其膨脹能力和形態密切相關。這一參數的變化會影響水凝膠所吸收和保留的液體量。
The estimation of

{pH}_{PZC}

values was also performed for all of the printed hydrogels, as this parameter is relevant for adsorbent materials. Generally,

{pH}_{PZC}

represents the pH at which the surface of the hydrogels is globally neutral, with equal concentrations of

[H^{+}]

and

[{OH}^{-}]

ions.

^{43}

Below the

{pH}_{PZC}

, the surface of the hydrogel is positively charged, while above this pH it becomes negatively charged. The Alg hydrogel exhibited a

{pH}_{PZC}

value of approximately 6.70 , which aligns with previous studies in the literature that focused on the preparation of alginate hydrogels cross-linked with

{Ca}^{2 +} .^{44}

Based on these results, it can be inferred that Nafion molecules were dispersed within the bulk region of the Alg hydrogel and had a negligible effect on the surface, primarily aiding the printing process by imparting a plasticizing effect to the ink preparation.

^{45}

對所有印刷的水凝膠也進行了

{pH}_{PZC}

值的估算，因為這一參數對於吸附材料是相關的。一般而言，

{pH}_{PZC}

代表水凝膠表面整體中性時的 pH 值，此時

[H^{+}]

和

[{OH}^{-}]

離子的濃度相等。

^{43}

在

{pH}_{PZC}

以下，水凝膠的表面帶正電，而在此 pH 值以上則帶負電。Alg 水凝膠的

{pH}_{PZC}

值約為 6.70，這與文獻中關於與

{Ca}^{2 +} .^{44}

交聯的海藻酸鹽水凝膠製備的先前研究一致。根據這些結果，可以推斷 Nafion 分子在 Alg 水凝膠的體積區域內分散，對表面影響微乎其微，主要通過賦予墨水製備塑化效果來幫助印刷過程。

^{45}

The presence of biochar in the Alg/Biochar hydrogels caused a slight shift in the

{pH}_{PZC}

values toward lower values. It was observed that this shift was proportional to the amount of biochar incorporated into the hydrogel formulation. The incorporation of biochar in the polymer matrix expanded the pH range over which the hydrogel surface carried an excess of negative charges. This trend can be attributed to the presence of

{Ca}^{2 +}

on the hydrogel surface. The availability of functional groups of Alg in the bulk region for interaction with

{Ca}^{2 +}

is reduced due to the presence of biochar. Consequently,

{Ca}^{2 +}

ions on the hydrogel surface attract

{OH}^{-}

species, conferring a negative nature to the surface.
生物炭在藻類/生物炭水凝膠中的存在導致

{pH}_{PZC}

值略微向較低值偏移。觀察到這一偏移與納入水凝膠配方中的生物炭量成正比。生物炭在聚合物基質中的納入擴大了水凝膠表面帶有過量負電荷的 pH 範圍。這一趨勢可歸因於水凝膠表面存在

{Ca}^{2 +}

。由於生物炭的存在，Alg 在體積區域中可用於與

{Ca}^{2 +}

相互作用的官能團的可用性減少。因此，水凝膠表面上的

{Ca}^{2 +}

離子吸引

{OH}^{-}

物種，賦予表面負性質。

Swelling. The liquid uptake behavior of the printed hydrogels was evaluated by using tap water as the swelling medium, and the corresponding swelling kinetic curves are presented in Figure 3. It can be observed that the swelling rate of the Alg hydrogel continuously increased until 90 min , after
膨脹。使用自來水作為膨脹介質來評估印刷水凝膠的液體吸收行為，對應的膨脹動力學曲線如圖 3 所示。可以觀察到，Alg 水凝膠的膨脹速率持續增加，直到 90 分鐘。

Figure 3. Swelling curves of the printed hydrogels in tap water at 25

^{\circ} C

.
圖 3. 在 25°C 自來水中印刷水凝膠的膨脹曲線。
which the curve reached a plateau, indicating the attainment of equilibrium. The maximum swelling rate recorded for this hydrogel was approximately

390 %

. In contrast, the hydrogels containing biochar exhibited higher swelling kinetics and performance. These aspects were found to be directly related to the amount of biochar present in the hydrogel. Overall, increasing the biochar content conferred faster swelling for the hydrogels. Consequently, hydrogels with higher biochar content achieved the equilibrium state earlier (around 40 min ). The maximum swelling rate of Alg/Biocharl and Alg/ Biochar5 was 1.5 times higher than that of Alg, while Alg/ Biochar10 exhibited a maximum swelling rate of 2.2 times greater than the pristine hydrogel. These results are consistent with the previously discussed characterization data. The presence of biochar in the polymer matrix induced changes in the hydrogel morphology, particularly in terms of porosity, which facilitated the uptake of liquid. Additionally, the crosslinking density of the composite hydrogels decreased with increasing biochar content, rendering the polymer network more expandable and, consequently, more prone to swelling. Another contributing factor to these findings is the composition of RH biochar, which predominantly consists of lignocellulosic compounds containing hydrophilic groups that interact with water molecules, thereby promoting swelling.
曲線達到平臺，表明達到平衡。這種水凝膠的最大膨脹速率約為

390 %

。相比之下，含有生物炭的水凝膠顯示出更高的膨脹動力學和性能。這些方面被發現與水凝膠中生物炭的含量直接相關。總體而言，增加生物炭含量使水凝膠的膨脹速度更快。因此，含有較高生物炭含量的水凝膠更早達到平衡狀態（約 40 分鐘）。Alg/Biocharl 和 Alg/Biochar5 的最大膨脹速率是 Alg 的 1.5 倍，而 Alg/Biochar10 的最大膨脹速率則是原始水凝膠的 2.2 倍。這些結果與之前討論的表徵數據一致。生物炭在聚合物基質中的存在引起了水凝膠形態的變化，特別是在孔隙率方面，這促進了液體的吸收。此外，隨著生物炭含量的增加，複合水凝膠的交聯密度降低，使聚合物網絡更具可擴展性，從而更容易膨脹。另一個促成這些發現的因素是 RH 生物炭的組成，主要由含有親水基團的木質纖維素化合物組成，這些基團與水分子相互作用，從而促進膨脹。

The remarkable swelling performance of all printed hydrogels, even when tap water is used as the swelling medium, can be attributed to the hydrophilic nature of the compounds employed in their preparation. It is known that the presence of ions in tap water can negatively impact the swelling behavior of hydrogels, as reported in previous studies.

^{46}

Information on the composition and physicochemical properties of water are presented in Table S2 of the Supporting Information. However, the hydrophilic properties of the materials used in this study, such as alginate, ensured a favorable swelling performance. Alginate contains carboxylic groups with a

p K_{a}

value of approximately 4.5. In tap water with a pH of 7.3 , these carboxylic groups are deprotonated, resulting in increased electrostatic repulsion within the polymer network. This electrostatic repulsion leads to the expansion of the hydrogel and facilitates water uptake. Therefore, despite the presence of ions in tap water, the hydrophilic nature of the hydrogel components, including alginate, enables their favorable swelling behavior.

^{47}

所有印刷水凝膠的顯著膨脹性能，即使在使用自來水作為膨脹介質的情況下，也可歸因於其製備中所使用化合物的親水性質。已知自來水中離子的存在可能會對水凝膠的膨脹行為產生負面影響，這在先前的研究中已有報導。

^{46}

水的組成和物理化學性質的信息列於支持信息的表 S2 中。然而，本研究中所使用材料的親水性質，如海藻酸鹽，確保了良好的膨脹性能。海藻酸鹽含有羧基，其

p K_{a}

值約為 4.5。在 pH 值為 7.3 的自來水中，這些羧基會去質子化，導致聚合物網絡內部的靜電排斥力增加。這種靜電排斥力導致水凝膠的膨脹並促進水的吸收。因此，儘管自來水中存在離子，但水凝膠成分的親水性質，包括海藻酸鹽，使其能夠實現良好的膨脹行為。

^{47}

Adsorption of IBU and MB. The initial adsorption experiment aimed to determine the optimal dosage of hydrogel for achieving maximum adsorption capacity toward IBU and MB at equilibrium. The results shown in Figures 4 a and 4 b indicate that the adsorption capacity

(q_{e})

increased proportionally with the hydrogel dosage and the amount of biochar incorporated into the composite hydrogels. Typically, an increase in the adsorbent dosage is associated with an increase in the number of binding sites available for adsorption, thereby facilitating the adsorption of IBU or MB molecules at the solid-liquid interface.

^{48}

In contrast to the Alg hydrogel, the hydrogels containing biochar exhibited a more expansible network (i.e., lower cross-linking density) and a higher number of binding sites, which enhanced their adsorption performance. The presence of biochar also induced morphological and textural changes in the composite hydrogels, which could explain the observed results. As demonstrated, alterations in the properties of the composite hydrogels were directly related to the amount of biochar embedded within them. Therefore, it is reasonable to conclude that the adsorption performance is
IBU 和 MB 的吸附。初步吸附實驗旨在確定水凝膠的最佳劑量，以實現對 IBU 和 MB 在平衡時的最大吸附能力。圖 4a 和 4b 顯示的結果表明，吸附能力

(q_{e})

隨著水凝膠劑量和納入複合水凝膠中的生物炭量的增加而成比例增加。通常，吸附劑劑量的增加與可用於吸附的結合位點數量的增加相關，從而促進了 IBU 或 MB 分子在固液界面的吸附。

^{48}

與 Alg 水凝膠相比，含有生物炭的水凝膠顯示出更具擴展性的網絡（即，較低的交聯密度）和更高的結合位點數量，這增強了它們的吸附性能。生物炭的存在還引起了複合水凝膠的形態和結構變化，這可以解釋觀察到的結果。如所示，複合水凝膠性質的變化與其內部嵌入的生物炭量直接相關。因此，可以合理地得出結論，吸附性能是

Figure 4. Adsorption capacity at equilibrium of (a) IBU and (b) MB on the printed hydrogels as a function of the hydrogel dosage. Adsorption capacity at equilibrium of © IBU and (d) MB on the printed samples as a function of the solution pH .
圖 4. 在平衡狀態下，(a) IBU 和 (b) MB 在印刷水凝膠上的吸附能力與水凝膠劑量的關係。平衡狀態下，(c) IBU 和 (d) MB 在印刷樣品上的吸附能力與溶液 pH 的關係。
dependent on this variable. Similar findings have been reported by other researchers regarding the increase in adsorption capacity with the incorporation of fillers into the hydrogel matrix.

^{49}

Overall, these results indicate that optimizing the dosage of hydrogel, along with the appropriate amount of biochar, can enhance the adsorption capacity of the composite hydrogels for IBU and MB.

^{48}

依賴於這個變數。其他研究者也報告了在水凝膠基質中加入填料後吸附能力增加的類似發現。

^{49}

總體而言，這些結果表明，優化水凝膠的劑量以及適當的生物炭量，可以增強複合水凝膠對於 IBU 和 MB 的吸附能力。

^{48}

Comparing the experimental data regarding the two tested contaminants (IBU and MB), it is evident that all hydrogels exhibit higher adsorption efficiency for MB, regardless of the dosage. For instance, when 90 mg of

Alg /

Biochar 10 was used, the adsorption capacity for MB was more than 1.7 times higher than that for IBU. This observation can be attributed to the surface properties of the hydrogels. Based on the

{pH}_{PZC}

data, at pH 7.3 (the pH of tap water), the surface of the hydrogels has an excess of negative charges, which facilitates the adsorption of cationic MB.

^{50}

In contrast, IBU molecules (with a

p K_{a}

range of

{4.2 - 4.9)}^{51}

are negatively charged at pH 7.3, which limits their adsorption on the printed hydrogels. Furthermore, the low solubility of IBU compared with that of MB is an additional factor that can affect the adsorption of the drug under the tested experimental conditions. Based on these preliminary results, the optimal dosage of hydrogels selected for treating 50 mL of IBU or MB solutions was determined to be 90 mg .
比較兩種測試污染物（IBU 和 MB）的實驗數據，可以明顯看出所有水凝膠對 MB 的吸附效率均高於 IBU，無論劑量如何。例如，當使用 90 毫克的

Alg /

生物炭 10 時，對 MB 的吸附能力比對 IBU 的吸附能力高出 1.7 倍以上。這一觀察可歸因於水凝膠的表面特性。根據

{pH}_{PZC}

數據，在 pH 7.3（自來水的 pH 值）時，水凝膠的表面帶有過量的負電荷，這有助於陽離子 MB 的吸附。

^{50}

相對而言，IBU 分子（帶有

p K_{a}

範圍的

{4.2 - 4.9)}^{51}

在 pH 7.3 時帶負電，這限制了它們在印刷水凝膠上的吸附。此外，與 MB 相比，IBU 的低溶解度也是影響在測試實驗條件下藥物吸附的另一個因素。根據這些初步結果，選擇用於處理 50 毫升 IBU 或 MB 溶液的水凝膠的最佳劑量被確定為 90 毫克。
The effect of pH on the adsorption capacities of IBU and MB is demonstrated in Figures 4 c and 4d, respectively. The data were examined by adjusting the pH of tap water to values ranging from 5 to 7 , which corresponds to the typical pH range of water and wastewater sources.

^{52}

The results from these

pH -

dependent adsorption experiments confirmed the trend
pH 對於 IBU 和 MB 的吸附能力的影響分別在圖 4c 和 4d 中顯示。數據是通過將自來水的 pH 值調整至 5 至 7 之間來檢驗的，這對應於水和廢水來源的典型 pH 範圍。這些依賴於吸附實驗的結果確認了該趨勢。
observed in the dosage experiment. Under normal water pH conditions, the adsorption of MB was superior to that of IBU, and the hydrogels containing higher amounts of biochar exhibited the best performance. The data suggest that the adsorption of both contaminants is pH -dependent, which aligns with the observed

{pH}_{PZC}

results. According to the

{pH}_{PZC}

data, all hydrogel samples exhibited an excess of positive charges on their surface at pH values below 6.4. Therefore, at pH 5 , IBU molecules exist predominantly in their dissociated form (i.e., anionic form),

^{51}

which may facilitate electrostatic interactions with the surface of the hydrogels. As the pH increases to 6 , the drug molecules become fully ionized, leading to increased adsorption on the hydrogels. However, at pH 7 , the values of

q_{e}

for IBU slightly decrease because the surface of the hydrogels carries an excess of negative charges under this condition. This decrease in the adsorption capacity is more prominent in samples Alg/Biochar5 and Alg/ Biochar10, which have the lowest

{pH}_{PZC}

values. Overall, the pH -dependent adsorption behavior observed for both contaminants supports the influence of surface charge and electrostatic interactions in the adsorption process on the hydrogels.
在劑量實驗中觀察到。在正常水 pH 條件下，MB 的吸附優於 IBU，而含有較高量生物炭的水凝膠表現最佳。數據顯示，兩種污染物的吸附均依賴於 pH，這與觀察到的

{pH}_{PZC}

結果一致。根據

{pH}_{PZC}

數據，所有水凝膠樣本在 pH 值低於 6.4 時，其表面均顯示出過量的正電荷。因此，在 pH 5 時，IBU 分子主要以其解離形式（即陰離子形式）存在，

^{51}

這可能促進與水凝膠表面的靜電相互作用。隨著 pH 增加至 6，藥物分子完全離子化，導致在水凝膠上的吸附增加。然而，在 pH 7 時，IBU 的

q_{e}

值略有下降，因為在此條件下水凝膠的表面帶有過量的負電荷。這種吸附能力的下降在樣本 Alg/Biochar5 和 Alg/Biochar10 中更為明顯，這些樣本的

{pH}_{PZC}

值最低。整體而言，對於兩種污染物觀察到的 pH 依賴性吸附行為支持了表面電荷和靜電相互作用在水凝膠吸附過程中的影響。

The effect of the initial concentrations of IBU and MB on the adsorption capacity of Alg and

Alg /

Biochar 10 hydrogels was evaluated through kinetic experiments. The concentration range of these contaminants in different water sources can vary from 12.1 to

373.1 μ g / L

for

{IBU}^{53}

and from 0.1 to

0.22 mg / L

for MB.

^{54}

In these experiments, only the composite hydrogel with the largest amount of biochar (Alg/Biochar10) was investigated because it demonstrated superior adsorption
初始濃度的 IBU 和 MB 對 Alg 和

Alg /

Biochar 10 水凝膠的吸附能力的影響通過動力學實驗進行了評估。這些污染物在不同水源中的濃度範圍可以從 12.1 到

373.1 μ g / L

（對於

{IBU}^{53}

）以及從 0.1 到

0.22 mg / L

（對於 MB）不等。

^{54}

在這些實驗中，僅研究了含有最多生物炭的複合水凝膠（Alg/Biochar10），因為它顯示出優越的吸附性能。

Figure 5. Adsorption kinetics for different initial concentrations of IBU on (a) Alg and (b) Alg/Biochar10 and adsorption kinetics for different initial concentrations of MB on © Alg and (d) Alg/Biochar10.
圖 5. 不同初始濃度的 IBU 在(a) Alg 和(b) Alg/Biochar10 上的吸附動力學，以及不同初始濃度的 MB 在(c) Alg 和(d) Alg/Biochar10 上的吸附動力學。
performance compared to the samples with

1 %

and

5 %

biochar.
與含有

1 %

和

5 %

生物炭的樣本相比的表現。
Figure 5 illustrates the data obtained from these experiments. It can be observed that the adsorption kinetics and adsorption capacity are dependent on the initial concentration of the contaminant in the solution. For the adsorption of IBU (Figures 5 a and 5 c ), the values of

q_{t}

(amount of adsorbed contaminant) increased rapidly in the first

30 - 40 \min

of the experiment. The adsorption kinetics appear to accelerate as the initial IBU concentration in the solution increases, indicating that a higher concentration of the drug leads to a greater level of interaction with the surface of the adsorbent. After this initial rapid increase, the adsorption curves reach a plateau, indicating the attainment of equilibrium, and the adsorption of IBU on the hydrogels remains relatively constant until the end of the experiment. In contrast, the adsorption of MB on Alg and

Alg /

Biochar 10 showed a slower initial increase in the values of

q_{t}

(Figures 5 b and 5 d ). This slower increase may be attributed to the presence of interfering species in tap water, which could hinder the adsorption of MB to a greater extent compared to IBU. The adsorption equilibrium for MB on Alg and

Alg /

Biochar 10 was achieved at around 60 min , as indicated by the stabilization of the adsorption curves.
圖 5 顯示了從這些實驗中獲得的數據。可以觀察到，吸附動力學和吸附容量依賴於溶液中污染物的初始濃度。對於 IBU 的吸附（圖 5 a 和 5 c），在實驗的前

30 - 40 \min

中，

q_{t}

（吸附的污染物量）的值迅速增加。隨著溶液中初始 IBU 濃度的增加，吸附動力學似乎加速，這表明藥物的較高濃度導致與吸附劑表面之間的相互作用增強。在這一初始快速增長之後，吸附曲線達到平穩狀態，表明達到平衡，IBU 在水凝膠上的吸附在實驗結束之前保持相對穩定。相比之下，MB 在 Alg 和

Alg /

生物炭 10 上的吸附顯示出

q_{t}

的值（圖 5 b 和 5 d）初始增長較慢。這一較慢的增長可能歸因於自來水中干擾物質的存在，這可能在更大程度上妨礙 MB 的吸附，相較於 IBU。 MB 在 Alg 和

Alg /

生物炭上的吸附平衡約在 60 分鐘時達成，這由吸附曲線的穩定性所指示。
These results highlight the influence of the initial concentration of the contaminants on the adsorption kinetics and the capacity of the hydrogels. Higher initial concentrations lead to more rapid adsorption and increased adsorption capacity, while interfering species in water may affect the adsorption of certain contaminants.
這些結果突顯了污染物初始濃度對吸附動力學和水凝膠容量的影響。較高的初始濃度導致更快速的吸附和增加的吸附容量，而水中的干擾物質可能會影響某些污染物的吸附。

The maximum values of

q_{t}

for IBU and MB on the Alg hydrogel increased by

87 %

and

62 %

, respectively, when their initial concentrations were increased from 1.0 to

12.0 mg / L

. For the Alg/Biochar 10 hydrogel, the increase in IBU and MB concentrations from 1.0 to

12.0 mg / L

resulted in an increase in

q_{t}

54 %

and

35 %

, respectively. The increment in

q_{t}

for the Alg hydrogel was higher than that for

Alg /

Biochar 10 due to the accelerated kinetics of the adsorption process in the pure alginate hydrogel. The faster initial adsorption process renders the surface-active sites of the material unusable in less time, which is proportional to the increase in pollutant concentration in the medium.

^{55}

At the highest initial concentrations of both contaminants (

12 mg / L

), the maximum values of

q_{t}

for the Alg hydrogel were 83.25 and

124.2 mg / g

for IBU and MB, respectively. Under the same conditions, the values of

q_{t}

for the Alg/Biochar10 hydrogel were 111.4 and

214.6 mg / g

for IBU and MB , respectively. This indicates that under similar experimental conditions, the hydrogel containing

10 % w / w

of biochar can adsorb

48 %

and

58 %

more IBU and MB, respectively, compared to Alg hydrogel. These data highlight the superior performance of the composite hydrogel as an adsorbent for the removal of IBU and MB from tap water. Additionally, it is noteworthy that the adsorption of MB is preferential over IBU, regardless of the hydrogel sample. This trend can be attributed to the slower and more efficient adsorption process of the dye molecules, where their interaction with the hydrogel matrices is gradual, allowing their movement until the binding sites are filled.

^{56}

Furthermore, the cationic nature of MB favors its interaction
在 Alg 水凝膠中，IBU 和 MB 的最大值隨著其初始濃度從 1.0 增加到

12.0 mg / L

，分別增加了

87 %

和

62 %

。對於 Alg/Biochar 10 水凝膠，IBU 和 MB 濃度從 1.0 增加到

12.0 mg / L

，導致

q_{t}

分別增加了

54 %

和

35 %

。Alg 水凝膠的

q_{t}

增量高於

Alg /

Biochar 10，這是由於純海藻酸鈉水凝膠中吸附過程的動力學加速。更快的初始吸附過程使材料的表面活性位點在更短的時間內變得不可用，這與介質中污染物濃度的增加成正比。

^{55}

在兩種污染物的最高初始濃度（

12 mg / L

）下，Alg 水凝膠的 IBU 和 MB 的最大值分別為 83.25 和

124.2 mg / g

。在相同條件下，Alg/Biochar10 水凝膠的 IBU 和 MB 的值分別為 111.4 和

214.6 mg / g

。這表明在類似的實驗條件下，含有

10 % w / w

的生物炭的水凝膠能夠比 Alg 水凝膠吸附更多的 IBU 和 MB。這些數據突顯了複合水凝膠作為去除自來水中布洛芬（IBU）和美藍（MB）的吸附劑的優越性能。此外，值得注意的是，無論水凝膠樣本如何，對美藍的吸附優先於布洛芬。這一趨勢可歸因於染料分子的吸附過程較慢且更有效，其中它們與水凝膠基質的相互作用是逐漸進行的，允許它們移動直到結合位點被填滿。此外，MB 的陽離子特性有利於其相互作用

Table 3. Kinetic Parameters Calculated for IBU and MB Adsorption on Alg and Alg/Biochar 10 Hydrogels at Different Initial Concentrations

^{a}

表 3. 在不同初始濃度下計算的 IBU 和 MB 在 Alg 及 Alg/Biochar 10 水凝膠上的吸附動力學參數

^{a}

hydrogel 水凝膠	pseudo-first-order model 偽一階模型
	IBU						MB
	$C_{0}$	$q_{e (th)}$	$q_{e}$	$k_{1}$	$R^{2}$	$χ^{2}$	$C_{0}$	$q_{e (th)}$	$q_{e}$	$k_{1}$	$R^{2}$	$χ^{2}$
Alg 算法	1.0	7.41	7.23	0.051	0.986	0.004	1.0	50.22	48.53	0.052	0.966	0.058
	3.0	21.06	19.86	0.030	0.973	0.072	3.0	64.57	62.12	0.041	0.978	0.096
	5.0	34.74	33.12	0.038	0.981	0.079	5.0	88.90	86.23	0.052	0.980	0.082
	9.0	43.25	42.56	0.051	0.989	0.011	9.0	110.53	105.04	40.045	0.946	0.286
	12.0	53.69	53.78	0.082	0.986	0.000	12.0	129.78	124.78	0.046	0.984	0.200
Alg/Biochar 10	1.0	55.05	52.32	0.038	0.950	0.142	1.0	163.06	140.38	0.021	0.955	3.664
	3.0	78.93	76.25	0.044	0.964	0.094	3.0	180.72	164.06	0.027	0.948	1.691
	5.0	84.36	81.24	0.051	0.964	0.119	5.0	214.11	191.93	30.024	0.968	2.563
	9.0	96.88	93.25	0.058	0.962	0.141	9.0	218.67	201.46	60.027	0.979	1.470
	12.0	113.89	112.23	0.071	0.991	0.024	12.0	230.64	215.14	40.031	0.973	1.116
	pseudo-second-order model 偽二級模型
	IBU						MB
hydrogel 水凝膠	C	$q_{e (th)}$	$q_{e}$	$k_{2} (\times 10^{- 4})$	$R^{2}$	$χ^{2}$	C	$q_{e (th)}$	$q_{e}$	$k_{2} (\times 10^{- 5})$	$R^{2}$	$χ^{2}$
Alg 算法	1.0	8.67	7.23	0.008	0.960	0.286	1.0	60.74	48.53	8.793	0.937	3.071
	3.0	28.05	19.86	9.107	0.961	3.377	3.0	79.27	62.12	5.761	0.956	4.734
	5.0	43.88	33.12	8.215	0.965	3.495	5.0	107.03	86.23	4.972	0.959	5.017
	9.0	51.30	42.56	0.001	0.979	1.794	9.0	138.00	105.04	2.991	0.920	10.342
	12.0	60.16	53.78	0.001	0.977	0.756	12.0	161.83	124.78	2.467	0.967	11.000
Alg/Biochar10	1.0	69.95	52.32	5.149	0.928	5.940	1.0	236.71	140.38	6.551	0.945	66.102
	3.0	97.78	76.25	4.475	0.942	6.079	3.0	246.84	164.06	9.049	0.9335	41.768
	5.0	101.68	81.24	5.374	0.935	5.142	5.0	298.91	191.93	6.386	0.957	59.629
	9.0	114.66	93.25	5.622	0.928	4.915	9.0	296.73	201.46	7.552	0.969	45.052
	12.0	130.43	112.23	6.857	0.968	2.951	12.0	304.39	215.14	8.834	0.960	37.025
$^{a}$ Units: $C_{0} (mg / L); q_{e} (mg / g); q_{e (th)} (mg / L); k_{1} (1 / \min)$ ; and $k_{2} (g mg / \min)$ . $^{a}$ 單位： $C_{0} (mg / L); q_{e} (mg / g); q_{e (th)} (mg / L); k_{1} (1 / \min)$ ；以及 $k_{2} (g mg / \min)$ 。

| hydrogel | pseudo-first-order model | | | | | | | | | | | | | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | | | IBU | | | | | | MB | | | | | | | | $\mathrm{C}_{0}$ | $q_{\mathrm{e}(\mathrm{th})}$ | $q_{\mathrm{e}}$ | $k_{1}$ | $R^{2}$ | $\chi^{2}$ | $\mathrm{C}_{0}$ | $q_{\mathrm{e}(\mathrm{th})}$ | $q_{\mathrm{e}}$ | $k_{1}$ | $R^{2}$ | $\chi^{2}$ | | Alg | 1.0 | 7.41 | 7.23 | 0.051 | 0.986 | 0.004 | 1.0 | 50.22 | 48.53 | 0.052 | 0.966 | 0.058 | | | 3.0 | 21.06 | 19.86 | 0.030 | 0.973 | 0.072 | 3.0 | 64.57 | 62.12 | 0.041 | 0.978 | 0.096 | | | 5.0 | 34.74 | 33.12 | 0.038 | 0.981 | 0.079 | 5.0 | 88.90 | 86.23 | 0.052 | 0.980 | 0.082 | | | 9.0 | 43.25 | 42.56 | 0.051 | 0.989 | 0.011 | 9.0 | 110.53 | 105.04 | 40.045 | 0.946 | 0.286 | | | 12.0 | 53.69 | 53.78 | 0.082 | 0.986 | 0.000 | 12.0 | 129.78 | 124.78 | 0.046 | 0.984 | 0.200 | | Alg/Biochar 10 | 1.0 | 55.05 | 52.32 | 0.038 | 0.950 | 0.142 | 1.0 | 163.06 | 140.38 | 0.021 | 0.955 | 3.664 | | | 3.0 | 78.93 | 76.25 | 0.044 | 0.964 | 0.094 | 3.0 | 180.72 | 164.06 | 0.027 | 0.948 | 1.691 | | | 5.0 | 84.36 | 81.24 | 0.051 | 0.964 | 0.119 | 5.0 | 214.11 | 191.93 | 30.024 | 0.968 | 2.563 | | | 9.0 | 96.88 | 93.25 | 0.058 | 0.962 | 0.141 | 9.0 | 218.67 | 201.46 | 60.027 | 0.979 | 1.470 | | | 12.0 | 113.89 | 112.23 | 0.071 | 0.991 | 0.024 | 12.0 | 230.64 | 215.14 | 40.031 | 0.973 | 1.116 | | | pseudo-second-order model | | | | | | | | | | | | | | IBU | | | | | | MB | | | | | | | hydrogel | C | $q_{\mathrm{e}(\mathrm{th})}$ | $q_{\text {e }}$ | $k_{2}\left(\times 10^{-4}\right)$ | $R^{2}$ | $\chi^{2}$ | C | $q_{\mathrm{e}(\mathrm{th})}$ | $q_{\mathrm{e}}$ | $k_{2}\left(\times 10^{-5}\right)$ | $R^{2}$ | $\chi^{2}$ | | Alg | 1.0 | 8.67 | 7.23 | 0.008 | 0.960 | 0.286 | 1.0 | 60.74 | 48.53 | 8.793 | 0.937 | 3.071 | | | 3.0 | 28.05 | 19.86 | 9.107 | 0.961 | 3.377 | 3.0 | 79.27 | 62.12 | 5.761 | 0.956 | 4.734 | | | 5.0 | 43.88 | 33.12 | 8.215 | 0.965 | 3.495 | 5.0 | 107.03 | 86.23 | 4.972 | 0.959 | 5.017 | | | 9.0 | 51.30 | 42.56 | 0.001 | 0.979 | 1.794 | 9.0 | 138.00 | 105.04 | 2.991 | 0.920 | 10.342 | | | 12.0 | 60.16 | 53.78 | 0.001 | 0.977 | 0.756 | 12.0 | 161.83 | 124.78 | 2.467 | 0.967 | 11.000 | | Alg/Biochar10 | 1.0 | 69.95 | 52.32 | 5.149 | 0.928 | 5.940 | 1.0 | 236.71 | 140.38 | 6.551 | 0.945 | 66.102 | | | 3.0 | 97.78 | 76.25 | 4.475 | 0.942 | 6.079 | 3.0 | 246.84 | 164.06 | 9.049 | 0.9335 | 41.768 | | | 5.0 | 101.68 | 81.24 | 5.374 | 0.935 | 5.142 | 5.0 | 298.91 | 191.93 | 6.386 | 0.957 | 59.629 | | | 9.0 | 114.66 | 93.25 | 5.622 | 0.928 | 4.915 | 9.0 | 296.73 | 201.46 | 7.552 | 0.969 | 45.052 | | | 12.0 | 130.43 | 112.23 | 6.857 | 0.968 | 2.951 | 12.0 | 304.39 | 215.14 | 8.834 | 0.960 | 37.025 | | ${ }^{a}$ Units: $C_{0}(\mathrm{mg} / \mathrm{L}) ; q_{\mathrm{e}}(\mathrm{mg} / \mathrm{g}) ; q_{\mathrm{e}(\mathrm{th})}(\mathrm{mg} / \mathrm{L}) ; k_{1}(1 / \mathrm{min})$; and $k_{2}(\mathrm{~g} \mathrm{mg} / \mathrm{min})$. | | | | | | | | | | | | |

with the anionic surface of the adsorbent under the experimental conditions employed in the study.
在本研究所採用的實驗條件下，與吸附劑的陰離子表面相互作用。
Kinetic and Isothermal Analyses. The analysis of adsorption kinetics and its parameters is crucial for understanding the interaction between the adsorbate and the adsorbent in water treatment studies.

^{56}

It provides valuable information for characterizing the process and can guide the application of adsorption on an industrial scale, allowing for the determination of the required amount of adsorbent to remove a specific concentration of the adsorbate. This information helps in reducing the working time and costs associated with the adsorption process.
動力學與等溫分析。吸附動力學及其參數的分析對於理解水處理研究中吸附劑與被吸附物之間的相互作用至關重要。

^{56}

它提供了有價值的信息以表徵該過程，並能指導吸附在工業規模上的應用，從而確定去除特定濃度的被吸附物所需的吸附劑量。這些信息有助於減少與吸附過程相關的工作時間和成本。
Kinetic studies, along with mathematical models, provide insights into the speed of adsorption and possible mechanisms involved.

^{57}

In this study, the experimental adsorption data presented in Figure 5 were fitted to pseudo-first-order (eq 12) and pseudo-second-order kinetic models (eq 13), which are expressed as follows:
動力學研究以及數學模型提供了對吸附速度和可能機制的洞察。

^{57}

在本研究中，圖 5 中呈現的實驗吸附數據被擬合到擬一階（方程式 12）和擬二階動力學模型（方程式 13），其表達如下：

\begin{aligned} q_{t} = q_{e (th)} (1 - e^{- k_{1} t}) \\ q_{t} = \frac{k_{2} q_{e (th)^{t}}^{2}}{1 + k_{2} q_{e (th)^{t}}^{2}} \\ χ^{2} = \sum \frac{{(q_{t} - q_{e (th)})}^{2}}{q_{e (th)}} \end{aligned}

where

q_{e (th)}

refers to the theoretical value calculated for

q_{e}, k_{1}

and

k_{2}

refer to the pseudo-first-order and pseudo-second-order kinetic constants, and

t

is the contact time. To validate the
其中

q_{e (th)}

代表為

q_{e}, k_{1}

計算的理論值，而

k_{2}

代表偽一級和偽二級動力學常數，

t

是接觸時間。為了驗證該結果
best-fitting kinetic model, two commonly used parameters were employed: the coefficient of determination

(R^{2})

and the nonlinear

χ^{2}

test

(χ^{2})

, which is a statistical error function represented by eq 14 . The kinetic parameters were calculated by performing a nonlinear regression fit of the pseudo-firstorder and pseudo-second-order plots, as shown in Figures S1 and S2 (Supporting Information). The calculated parameters are given in Table 3.
最佳擬合動力學模型中，使用了兩個常用參數：決定係數

(R^{2})

和非線性

χ^{2}

測試

(χ^{2})

，這是一個由方程式 14 表示的統計誤差函數。動力學參數是通過對擬似一級和擬似二級圖進行非線性回歸擬合計算得出的，如圖 S1 和 S2（支持信息）所示。計算出的參數列於表 3。

The pseudo-first-order kinetic model provided higher values of

R^{2}

compared to the pseudo-second-order model for both IBU and MB adsorption on Alg and Alg/Biochar10, regardless of the concentration conditions. Additionally, the calculated

q_{e (th)}

values closely matched the experimental

q_{e}

values, as indicated by the low

χ^{2}

values. These findings confirm that the adsorption process of both contaminants on the printed hydrogels primarily followed pseudo-first-order kinetics.
偽一階動力學模型提供了比偽二階模型更高的

R^{2}

值，無論在濃度條件下對於 IBU 和 MB 在 Alg 和 Alg/Biochar10 的吸附。此外，計算出的

q_{e (th)}

值與實驗的

q_{e}

值非常接近，這一點由低

χ^{2}

值所表明。這些發現確認了兩種污染物在印刷水凝膠上的吸附過程主要遵循偽一階動力學。

The pseudo-first-order kinetic model suggests that the rate of change of solute adsorbed per unit of time is directly proportional to the difference between the amount of solute adsorbed at equilibrium

(q_{e})

and the amount adsorbed at any given time

(t)

. This kinetic model is controlled by physisorption, where the adsorbate and adsorbent interact through electrostatic forces and no significant molecular changes occur. Agbovi and Wilson

^{58}

explained that the reaction rate is determined solely by the concentration of the adsorbate. It is worth mentioning that Franco et al.

^{59}

also observed a pseudo-first-order kinetics for the adsorption of IBU on an alginate-based aerogel, further supporting the applicability of this kinetic model to similar systems.
偽一階動力學模型表明，單位時間內吸附的溶質變化速率與平衡時吸附的溶質量

(q_{e})

與任意給定時間吸附的溶質量

(t)

之間的差異成正比。這一動力學模型受物理吸附控制，其中吸附劑和吸附材料通過靜電力相互作用，且不會發生顯著的分子變化。Agbovi 和 Wilson

^{58}

解釋說，反應速率僅由吸附劑的濃度決定。值得一提的是，Franco 等人

^{59}

也觀察到 IBU 在基於海藻酸鹽的氣凝膠上的吸附呈現偽一階動力學，進一步支持了這一動力學模型在類似系統中的適用性。

In addition to the kinetic analysis, adsorption isotherm models were employed to describe the interaction of IBU and
除了動力學分析外，還使用了吸附等溫線模型來描述 IBU 的相互作用

MB with Alg and Alg/Biochar10 hydrogels. The selection of appropriate isotherm models aids in understanding how the adsorbate molecules interact with the adsorbent and evaluates the practical application of the adsorption process.

^{60}

In this study, Langmuir (eq 15), Freundlich (eq 16), and Temkin (eq 17) isotherm models were used to analyze the experimental data. These isotherm models express the relationship between the amount of IBU and MB adsorbed on the hydrogels and their equilibrium concentrations in tap water. The equations for these isotherm models are as follows:
MB 與 Alg 及 Alg/Biochar10 水凝膠。選擇適當的等溫模型有助於理解吸附劑分子如何與吸附劑互動，並評估吸附過程的實際應用。在本研究中，使用了 Langmuir（方程式 15）、Freundlich（方程式 16）和 Temkin（方程式 17）等溫模型來分析實驗數據。這些等溫模型表達了 IBU 與 MB 在水凝膠上吸附的量及其在自來水中的平衡濃度之間的關係。這些等溫模型的方程式如下：

\begin{aligned} \frac{C_{e}}{q_{e}} = \frac{1}{K_{L} q_{m}} + \frac{C_{e}}{q_{m}} \\ \ln q_{e} = \ln K_{F} + \frac{1}{n} \ln C_{e} \\ q_{e} = \ln K_{T} + \frac{R T}{b_{T}} \ln C_{e} \end{aligned}

where

q_{m}

represents the theoretical maximum adsorption capacity of the adsorbent in the Langmuir isotherm, while

K_{L}

is the net enthalpy of adsorption. The Freundlich isotherm model uses

K_{F}

as the adsorption intensity parameter and

1 / n

as the dissimilarity factor. The Temkin isotherm model involves the constants

K_{T}

, which represents the maximum binding energy, and

b_{T}

, which is the energy in the form of heat of adsorption. To determine these isothermal and constant parameters, nonlinear regression fits were performed on the isothermal plots (Figures S4 and S5). This analysis allows for estimation of the parameters that characterize the adsorption process. The calculated isothermal parameters and

R^{2}

values are summarized in Table 4.
其中

q_{m}

代表朗格穆爾等溫線中吸附劑的理論最大吸附容量，而

K_{L}

是吸附的淨焓。弗倫德利希等溫線模型使用

K_{F}

作為吸附強度參數，

1 / n

作為不相似性因子。坦金等溫線模型涉及常數

K_{T}

，代表最大結合能量，以及

b_{T}

，即以熱的形式存在的吸附能量。為了確定這些等溫線和常數參數，對等溫線圖（圖 S4 和 S5）進行了非線性回歸擬合。這一分析允許估算表徵吸附過程的參數。計算出的等溫線參數和

R^{2}

值總結於表 4。

Table 4. Langmuir, Freundlich, and Temkin Isotherm Parameters for Adsorption of IBU and MB on Alg and Alg/ Biochar 10 Hydrogels at

25^{\circ} C

表 4. IBU 和 MB 在 Alg 及 Alg/生物炭 10 水凝膠上的 Langmuir、Freundlich 和 Temkin 等溫參數於

25^{\circ} C

isotherm 等溫線

parameter 參數

IBU

Alg 算法

生物炭 10

Alg /

Biochar10

Alg 算法

Alg/ 生物炭 10

Alg/

Biochar10

Langmuir 朗缪爾

q_{m} (mg / g)

510.810

202.217

119.864

233.396

K_{L} (L / mg)

0.023

0.396

2.108

9.996

R^{2}

0.909

0.882

0.866

0.856

Freundlich 弗倫德里希

1 / n

0.933

0.525

0.315

0.142

1.071

1.903

3.168

7.035

\begin{aligned} K_{F} (mg / \\ g (L / \\ mg)^{1 / n}) \end{aligned}

11.770

60.564

76.801

205.441

R^{2}

0.969

0.935

0.939

0.925

Temkin 特姆金

K_{(L / mg)}^{K_{1}}

1.474

5.808

25.883

1547.876

b_{T}

24.555

37.652

24.345

28.158

R^{2}

0.943

0.889

0.914

0.922

As observed, the Freundlich isotherm model provided the best fit for describing the experimental data of IBU and MB adsorption on Alg and

Alg /

Biochar10, as indicated by the highest

R^{2}

values. This model suggests that the adsorption process involves multilayer deposition on the surface of the adsorbent. The calculated values of

1 / n

, which were below unity, confirm the favorable nature of the adsorption process.

^{61}

The

n

values in the range of

1 - 10

further support the favorable adsorption of IBU and MB on Alg and Alg/Biochar10.

^{61}

Notably, Alg/Biochar10 exhibited higher values of

n

, indicating
根據觀察，Freundlich 等溫線模型最能適合描述 IBU 和 MB 在 Alg 及

Alg /

Biochar10 的吸附實驗數據，這一點由最高的

R^{2}

值所指示。該模型表明，吸附過程涉及在吸附劑表面上的多層沉積。計算出的

1 / n

值低於 1，確認了吸附過程的有利性。

^{61}

在

n

值範圍內的

1 - 10

進一步支持了 IBU 和 MB 在 Alg 及 Alg/Biochar10 上的有利吸附。

^{61}

值得注意的是，Alg/Biochar10 顯示出更高的

n

值，這表明
a stronger interaction between the contaminants and the composite hydrogel. The higher values of the adsorption intensity parameter (

K_{F}

) for Alg/Biochar10, especially for MB adsorption, align with the electrostatic interactions between the cationic dye and the negatively charged surface of Alg/ Biochar10. Based on these findings, some hypotheses can be formulated regarding the adsorption mechanism involving the contaminants and Alg/Biochar10. The existence of -OH functional groups within the adsorbent originating from alginate and biochar implies the potential for H -bonding interactions with the contaminants. Furthermore, the carbonaceous nature of biochar promotes

π - π

and van der Waals interactions. In addition to these interaction forces, the adsorption of MB is influenced by electrostatic interactions. For a visual representation of the adsorption mechanism, Figure 6 illustrates the probable interactions between IBU and MB and the composite hydrogel.
污染物與複合水凝膠之間的相互作用更為強烈。Alg/Biochar10 的吸附強度參數（

K_{F}

）的較高值，特別是在 MB 吸附方面，與陽離子染料與 Alg/Biochar10 的負電荷表面之間的靜電相互作用相符。根據這些發現，可以對涉及污染物與 Alg/Biochar10 的吸附機制提出一些假設。來自海藻酸鹽和生物炭的吸附劑中存在的-OH 官能團暗示了與污染物之間潛在的氫鍵相互作用。此外，生物炭的碳質特性促進了

π - π

和范德瓦耳斯相互作用。除了這些相互作用力外，MB 的吸附還受到靜電相互作用的影響。為了視覺化吸附機制，圖 6 展示了 IBU 與 MB 及複合水凝膠之間的可能相互作用。

The adsorption capacity of the Alg/Biochar10 hydrogel under experimental conditions is advantageous for large-scale applications. As demonstrated in Table S3, the adsorption capacity of Alg/Biochar10 is comparable to or better than other tested adsorbent materials for the removal of IBU or MB from water. Additionally, the 3D printing approach used to prepare the material allows for the easy production and replication of a specific mass of adsorbent, reducing production costs and enabling adaptation to different systems. The estimated cost of preparing one gram of Alg/Biochar 10 hydrogel is around US$ 1.06, which is competitive with other adsorbents.

^{62}

This cost includes the preparation of RH biochar, polymer solutions, and energy consumption. Future optimization efforts may involve exploring lower-cost plasticizers compared to Nafion for the preparation of the polymeric ink, which could lead to a material with comparable adsorption capabilities for cationic and anionic compounds.
在實驗條件下，Alg/Biochar10 水凝膠的吸附能力對於大規模應用具有優勢。如表 S3 所示，Alg/Biochar10 的吸附能力與其他測試的吸附材料在去除水中 IBU 或 MB 的效果相當或更佳。此外，用於製備該材料的 3D 打印方法使得特定質量的吸附劑的生產和複製變得容易，降低了生產成本並使其能夠適應不同的系統。製備一克 Alg/Biochar 10 水凝膠的估計成本約為 1.06 美元，這在其他吸附劑中具有競爭力。此成本包括 RH 生物炭、聚合物溶液的製備以及能源消耗。未來的優化工作可能涉及探索與 Nafion 相比成本更低的增塑劑，以製備聚合物墨水，這可能導致具有可比的陽離子和陰離子化合物吸附能力的材料。

Selectivity and Reuse Experiments. In this study, the ability of the Alg/Biochar10 hydrogel to selectively adsorb one of the tested contaminants was assessed using an equimolar solution of IBU and MB. The results, as depicted in Figure S5a, demonstrated that the adsorption of both contaminants on the composite hydrogel occurred simultaneously for the first 30 min. Afterward, the increase in adsorption slowed down, reaching equilibrium. However, the adsorption of MB continued to increase until the 90 min mark. These findings indicated different adsorption kinetics for each contaminant. At the end of the experiment, the maximum adsorption capacities for IBU and MB were 40.9 and

70.6 mg / L

, respectively.
選擇性與重複使用實驗。在本研究中，評估了 Alg/Biochar10 水凝膠選擇性吸附所測試污染物之一的能力，使用了等摩爾的 IBU 和 MB 溶液。結果如圖 S5a 所示，顯示在前 30 分鐘內，兩種污染物在複合水凝膠上的吸附同時發生。之後，吸附的增加速度減緩，達到平衡。然而，MB 的吸附仍持續增加，直到 90 分鐘時。這些發現表明每種污染物的吸附動力學不同。在實驗結束時，IBU 和 MB 的最大吸附容量分別為 40.9 和

70.6 mg / L

。
According to Figure S5b, after adsorption, the removal rate for MB was

62 %

, which was 1.5 times higher than that of IBU (

41 %

removal). Consequently, the selectivity parameter was calculated as

63 %

for MB and

37 %

for IBU. The results from individual adsorption experiments with each contaminant showed contrasting removal values, suggesting competitive adsorption between IBU and MB. In mixed solutions, various factors such as solubility, mobility, electronegativity, and acidity influence the adsorption process. In water, MB exists as monovalent cations that exhibit a strong affinity for the Alg/ Biochar 10 hydrogel. On the other hand, IBU has an anionic nature under the tested experimental conditions, resulting in different adsorption behavior. The higher solubility of MB in water enhances its mobility and facilitates its access to active sites on the adsorbent. Once adsorbed, MB molecules remain stable due to fewer reactive interactions with the anionic surface of the adsorbent. These observations align with
根據圖 S5b，吸附後，MB 的去除率為

62 %

，比 IBU 的去除率（

41 %

）高出 1.5 倍。因此，MB 的選擇性參數計算為

63 %

，IBU 的選擇性參數為

37 %

。每種污染物的單獨吸附實驗結果顯示出對比的去除值，這表明 IBU 和 MB 之間存在競爭性吸附。在混合溶液中，溶解度、流動性、電負性和酸性等各種因素影響吸附過程。在水中，MB 以單價陽離子的形式存在，對 Alg/ Biochar 10 水凝膠表現出強烈的親和力。另一方面，IBU 在測試的實驗條件下具有陰離子特性，導致其吸附行為不同。MB 在水中的較高溶解度增強了其流動性，並促進了其進入吸附劑的活性位點。一旦被吸附，MB 分子由於與吸附劑的陰離子表面之間的反應性相互作用較少而保持穩定。這些觀察結果與

Figure 6. Scheme reporting the different interactions between the adsorbent and the MB and IBU molecules.
圖 6. 報告吸附劑與美藍（MB）和布洛芬（IBU）分子之間不同相互作用的示意圖。

Figure 7. (a) Removal efficiency of IBU by Alg/Biochar10 hydrogel as a function of the consecutive reuse cycles and (b) photographic images taken from the hydrogel after the 10th, 15th, and 20th reuse cycle. © Removal efficiency of MB by Alg/Biochar 10 hydrogel as a function of the consecutive reuse cycles and (d) photographic images taken from the hydrogel after the 10th, 15th, and 20th reuse cycle.
圖 7. (a) Alg/Biochar10 水凝膠在連續重複使用循環中的 IBU 去除效率，(b) 在第 10、15 和 20 次重複使用循環後拍攝的水凝膠照片。© Alg/Biochar 10 水凝膠在連續重複使用循環中的 MB 去除效率，(d) 在第 10、15 和 20 次重複使用循環後拍攝的水凝膠照片。
previous experimental and theoretical data on the kinetics and isotherms.
先前關於動力學和等溫線的實驗及理論數據。

Desorption experiments were done to investigate the release of adsorbed IBU and MB molecules from Alg/Biochar10 as well as the recycling potential of the adsorbent. This is a crucial feature considering the reusability of

Alg /

Biochar10 and its
脫附實驗旨在研究從 Alg/Biochar10 中釋放吸附的 IBU 和 MB 分子的情況，以及吸附劑的回收潛力。這是一個關鍵特徵，考慮到

Alg /

Biochar10 的可重用性。
practical application. To explain, both studies (desorption and reuse) were done only with the Alg/Biochar10 hydrogel because this sample exhibited superior adsorption performance.
實際應用。解釋來說，兩項研究（脫附和再利用）僅使用了 Alg/Biochar10 水凝膠，因為該樣本顯示出優越的吸附性能。
The consecutive reuse cycles of the Alg/Biochar10 hydrogel were analyzed in terms of the removal rate of IBU and MB, as
Alg/Biochar10 水凝膠的連續重複使用週期在去除 IBU 和 MB 的效率方面進行了分析，因為
shown in Figures 7a and 7b. Remarkably, even after 20 cycles, the ability of Alg/Biochar10 to remove both contaminants was minimally affected. The reduction in removal rate for IBU and MB after the last reuse cycle did not exceed

10 %

compared to the first cycle, highlighting the exceptional reusability of this composite hydrogel. Furthermore, the adsorption capacity

(q_{e})

Alg /

Biochar10 after the 20th reuse cycle was calculated as

101.1 mg / g

for IBU and

191.6 mg / g

for MB, representing

91 %

and

89 %

of the initial

q_{e}

values, respectively.
如圖 7a 和 7b 所示。值得注意的是，即使在經過 20 個循環後，Alg/Biochar10 去除兩種污染物的能力仍然受到最小影響。與第一次循環相比，最後一次重複循環後 IBU 和 MB 的去除率下降不超過

10 %

，突顯了這種複合水凝膠的卓越重用性。此外，經過第 20 次重複循環後，

Alg /

Biochar10 的吸附能力

(q_{e})

被計算為 IBU 的

101.1 mg / g

和 MB 的

191.6 mg / g

，分別代表初始

q_{e}

值的

91 %

和

89 %

。
The impressive reusability of Alg/Biochar10 can be attributed to its recyclability. After each reuse cycle, the IBU and MB molecules were completely desorbed from the composite hydrogel using a methanol/distilled water extraction solution. This solution protonated the binding sites on the hydrogel surface, disrupting their interaction with the adsorbed molecules and releasing them into the extraction medium. The recycled hydrogels were then washed with distilled water, collected, dried, and reused in subsequent adsorption cycles. This operational approach is simple, cost-effective, and outperforms other systems used for the removal of IBU and MB from water.

^{63}

Alg/Biochar10 的卓越重複使用性可歸因於其可回收性。在每個重複使用循環後，IBU 和 MB 分子完全從複合水凝膠中脫附，使用的是甲醇/蒸餾水提取溶液。該溶液使水凝膠表面的結合位點質子化，破壞了它們與吸附分子的相互作用，並將其釋放到提取介質中。回收的水凝膠隨後用蒸餾水清洗、收集、乾燥，並在隨後的吸附循環中重新使用。這種操作方法簡單、成本效益高，並且在去除水中 IBU 和 MB 的效果上優於其他系統。
Figures 7 b and 7 d provide insights into the impact of consecutive reuse cycles on the morphology of the composite hydrogel. It is evident that the structure of the hydrogel begins to experience shape-collapsing damage from the 15 th cycle onward. These changes are more pronounced in the sample used for MB adsorption. In fact, the cross-linking density of this sample decreased by

46 %

after the last reuse cycle. This decrease in cross-linking density can be attributed to the electrostatic interaction between MB and Alg/Biochar10, which may interfere with the ionic cross-linking mediated by

{Ca}^{2 +}

ions. This phenomenon of competition between the cross-linker and ionized pollutants has been demonstrated by Sharma et al.

^{64}

In contrast, the hydrogel used for IBU adsorption experienced a smaller decrease in cross-linking density, around

8.2 %

. Considering the stability of the hydrogels, it was observed after the last cycle that the mass of the sample used for IBU adsorption decreased by

11.5 %

, while the mass of the sample used for MB adsorption decreased by

19.2 %

. These changes in the cross-linking density and mass of the adsorbent can be associated with the observed decrease in the removal capacity after the 20th reuse cycle.
圖 7b 和 7d 提供了連續重複循環對複合水凝膠形態影響的見解。顯然，水凝膠的結構從第 15 個循環開始經歷形狀崩潰的損壞。這些變化在用於 MB 吸附的樣本中更為明顯。事實上，該樣本的交聯密度在最後一次重複循環後減少了

46 %

。這一交聯密度的減少可歸因於 MB 與 Alg/Biochar10 之間的靜電相互作用，這可能干擾了由

{Ca}^{2 +}

離子介導的離子交聯。Sharma 等人已經證明了交聯劑與離子污染物之間的競爭現象

^{64}

。相比之下，用於 IBU 吸附的水凝膠經歷了較小的交聯密度減少，約為

8.2 %

。考慮到水凝膠的穩定性，在最後一次循環後觀察到，用於 IBU 吸附的樣本質量減少了

11.5 %

，而用於 MB 吸附的樣本質量減少了

19.2 %

。這些吸附劑交聯密度和質量的變化可以與第 20 次重複使用循環後觀察到的去除能力下降相關聯。
In summary, the findings of this study strongly support the practical applicability of the Alg/Biochar10 composite hydrogel as an efficient adsorbent for the removal of various organic contaminants, including drugs and dyes, from real-world water sources. The simplicity of its production, utilization, and recovery processes makes this composite economically advantageous compared to other materials previously reported for similar purposes. The porous structure of biochar is particularly well-suited for water filtration and remediation applications. Ongoing research highlights the potential of biochar as a filler in polymeric composites, leveraging its porous structure, excellent thermal stability, low production cost, and potential reduction in environmental impact. Different types of fillers and biomass sources can have varying effects on the polymeric matrix, as previously discussed.

^{65}

Further optimization is required to enhance the adsorption capacity specifically toward anionic compounds and improve the physical durability of the composite throughout multiple adsorption cycles. This can potentially be achieved through alternative cross-linking processes, such as chemical cross-
總結來說，本研究的結果強烈支持 Alg/Biochar10 複合水凝膠作為有效吸附劑的實際應用，能夠去除來自現實水源的各種有機污染物，包括藥物和染料。其生產、使用和回收過程的簡便性使得這種複合材料在經濟上相較於其他先前報告的類似材料具有優勢。生物炭的多孔結構特別適合用於水過濾和修復應用。持續的研究突顯了生物炭作為聚合物複合材料填料的潛力，利用其多孔結構、優良的熱穩定性、低生產成本以及潛在的環境影響減少。不同類型的填料和生物質來源對聚合物基體的影響可能各不相同，如前所述。進一步的優化是必要的，以增強對陰離子化合物的吸附能力，並改善複合材料在多次吸附循環中的物理耐久性。這可以通過替代的交聯過程來實現，例如化學交聯
linking, or by exploring different shapes and geometries in the printing of materials.
連結，或通過探索材料印刷中的不同形狀和幾何形狀。

Beyond the noticeable performance of the fabricated adsorbent, the utilization of 3 D printing offers numerous advantages over traditional processing methods for the preparation of hydrogels used in this kind of application. These advantages include easy operation, precise control over structural properties, high cost-effectiveness, and other benefits. It is anticipated that the utilization of additive manufacturing techniques will continue to increase in the future, enabling the development of advanced materials for water remediation purposes.
除了所製造的吸附劑顯著的性能外，3D 打印的使用相較於傳統加工方法在製備用於此類應用的水凝膠方面提供了許多優勢。這些優勢包括操作簡便、對結構特性的精確控制、高性價比及其他好處。預計未來增材製造技術的使用將持續增加，促進水質修復材料的發展。

CONCLUSION 結論

Composite hydrogels were produced via 3D printing, utilizing inks containing alginate, Nafion, and biochar from rice husk. Characterization analyses confirmed the presence of biochar in the hydrogel matrices and revealed its interaction with alginate, facilitated by biochar’s lignocellulosic nature. The incorporation of biochar induced modifications in diverse properties of the composite hydrogels, including structure, cross-linking density, morphology, and swelling capacity. Among the hydrogels tested, the variant containing 10 wt % biochar exhibited the highest adsorption capacity for both contaminants. In comparison to the hydrogel lacking biochar, the composite hydrogel demonstrated a

48 %

increase in adsorption capacity for IBU and a

58 %

increase for MB. The adsorption process of IBU and MB onto the printed hydrogels adhered to pseudo-first-order kinetics. The isothermal analyses indicated that adsorption transpired via a blend of surface and multilayer mechanisms, fitting well with the Freundlich model. In summary, this study introduces an innovative approach for crafting effective adsorbents using 3D printing and harnessing the synergy between polysaccharides and biochar.
複合水凝膠是通過 3D 列印製作的，使用的墨水包含海藻酸鹽、Nafion 和來自稻殼的生物炭。特徵分析確認了生物炭在水凝膠基質中的存在，並揭示了其與海藻酸鹽的相互作用，這是由於生物炭的木質纖維素特性所促進的。生物炭的加入引起了複合水凝膠在結構、交聯密度、形態和膨脹能力等多種性質上的變化。在測試的水凝膠中，含有 10 wt %生物炭的變體對兩種污染物表現出最高的吸附能力。與不含生物炭的水凝膠相比，複合水凝膠對 IBU 的吸附能力增加了

48 %

，對 MB 的吸附能力增加了

58 %

。IBU 和 MB 在列印水凝膠上的吸附過程遵循偽一級動力學。等溫分析表明，吸附是通過表面和多層機制的結合進行的，與 Freundlich 模型非常吻合。總之，本研究提出了一種創新的方法，利用 3D 列印製作有效的吸附劑，並利用多醣類和生物炭之間的協同作用。

■ ASSOCIATED CONTENT ■ 相關內容

(s) Supporting Information
（s）支持信息

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsapm.3c01534.
支持信息可免費獲得，網址為 https://pubs.acs.org/doi/10.1021/acsapm.3c01534。

Surface area and porosity data; tap water characteristics; pseudo-first-order plots for IBU and MB adsorption; pseudo-second order plots for IBU and MB adsorption; isotherm plots for IBU adsorption; isotherm plots for MB adsorption; comparative of adsorption performance for different adsorbents; and adsorption and removal data from the experiments using binary solutions (PDF)
表面積和孔隙率數據；自來水特性；IBU 和 MB 吸附的偽一級圖；IBU 和 MB 吸附的偽二級圖；IBU 吸附的等溫線圖；MB 吸附的等溫線圖；不同吸附劑的吸附性能比較；以及使用二元溶液進行實驗的吸附和去除數據（PDF）

AUTHOR INFORMATION 作者資訊

Corresponding Author 通訊作者
André R. Fajardo - Laboratório de Tecnologia e Desenvolvimento de Compósitos e Materiais Poliméricos (LaCoPol), Federal University of Pelotas (UFPel), 96010900 Pelotas-RS, Brazil; ©orcid.org/0000-0001-53626478; Email: andre.fajardo@ufpel.edu.br
安德烈·R·法哈多 - 複合材料與聚合物材料技術與發展實驗室（LaCoPol），巴西佩洛塔斯聯邦大學（UFPel），96010900 佩洛塔斯-RS；©orcid.org/0000-0001-53626478；電子郵件：andre.fajardo@ufpel.edu.br

Authors 作者

Emilly C. Silva - Laboratório de Tecnologia e Desenvolvimento de Compósitos e Materiais Poliméricos (LaCoPol), Federal University of Pelotas (UFPel), 96010900 Pelotas-RS, Brazil
艾米莉·C·席爾瓦 - 複合材料與聚合物材料技術與發展實驗室 (LaCoPol)，巴西佩洛塔斯聯邦大學 (UFPel)，96010900 佩洛塔斯-RS，巴西
Victória R. Soares - Laboratório de Tecnologia e Desenvolvimento de Compósitos e Materiais Poliméricos
維多利亞·R·索阿雷斯 - 複合材料與聚合物材料技術與發展實驗室
(LaCoPol), Federal University of Pelotas (UFPel), 96010900 Pelotas-RS, Brazil
（LaCoPol），巴西佩洛塔斯聯邦大學（UFPel），96010900 佩洛塔斯-RS，巴西
Andressa B. Nörnberg - Laboratório de Tecnologia e Desenvolvimento de Compósitos e Materiais Poliméricos (LaCoPol), Federal University of Pelotas (UFPel), 96010900 Pelotas-RS, Brazil
安德蕾莎·B·諾恩貝格 - 複合材料與聚合物材料技術與發展實驗室 (LaCoPol)，巴西佩洛塔斯聯邦大學 (UFPel)，96010900 佩洛塔斯-RS，巴西
Complete contact information is available at:
完整的聯絡資訊可在以下查詢：
https://pubs.acs.org/10.1021/acsapm.3c01534

Author Contributions 作者貢獻

E.C.S, A.B.N., and A.R.F. designed the overall research project. E.C.S, A.B.N., and V.R.S. did the manufacturing and characterization of the composite hydrogels and the adsorption experiments. E.C.S, A.B.N., and A.R.F. wrote and revised the manuscript.
E.C.S、A.B.N. 和 A.R.F. 設計了整體研究項目。E.C.S、A.B.N. 和 V.R.S. 進行了複合水凝膠的製造和表徵以及吸附實驗。E.C.S、A.B.N. 和 A.R.F. 撰寫並修訂了手稿。

Funding 資金來源

This work was funded by the National Council for Scientific and Technological Development (CNPq, Brazil) (Processes 422645/2021-4 and 303125/2022-5) and Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior (CAPES/ Brazil)-Finance Code 001.
本研究由巴西國家科學技術發展委員會（CNPq，巴西）（流程 422645/2021-4 和 303125/2022-5）及巴西高等教育人員培訓協調委員會（CAPES/巴西）資助，財務代碼 001。

Notes 註解

The authors declare no competing financial interest.
作者聲明沒有競爭性的財務利益。

ACKNOWLEDGMENTS 致謝

The authors are grateful to 3D Biotechnology Solutions for technical support.
作者感謝 3D 生物技術解決方案公司提供的技術支持。

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β

-Cyclodextrin/Activated Charcoal/Na
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β

-環糊精/活性炭/鈉的聚合物複合材料從水溶液中吸附陽離子染料、藥物和金屬。

Received: July 10, 2023 收到日期：2023 年 7 月 10 日
Accepted: September 7, 2023
接受日期：2023 年 9 月 7 日
Published: September 14, 2023
發表日期：2023 年 9 月 14 日

Recyclable 3D-Printed Composite Hydrogel Containing Rice Husk Biochar for Organic Contaminants Adsorption in Tap Water 可回收的 3D 列印複合水凝膠，含有稻殼生物炭，用於自來水中有機污染物的吸附

Abstract 摘要

INTRODUCTION 引言

MATERIALS AND METHODS 材料與方法

RESULTS AND DISCUSSION 結果與討論

CONCLUSION 結論

■ ASSOCIATED CONTENT ■ 相關內容

(s) Supporting Information（s）支持信息

AUTHOR INFORMATION 作者資訊

Authors 作者

Author Contributions 作者貢獻

Funding 資金來源

Notes 註解

ACKNOWLEDGMENTS 致謝

REFERENCES 參考文獻

Recyclable 3D-Printed Composite Hydrogel Containing Rice Husk Biochar for Organic Contaminants Adsorption in Tap Water
可回收的 3D 列印複合水凝膠，含有稻殼生物炭，用於自來水中有機污染物的吸附

(s) Supporting Information
（s）支持信息