The discovery of cheap and eco-friendly functional materials for the removal of anionic heavy metal ions is still challenging in the treatment of heavy metal-contaminated water. Herein, a new poly(allyltrimethylammonium) grafted chitosan and biochar composite (PATMAC-CTS-BC) was introduced for the removal of selenate (SeO₄²⁻) in water. Results suggest that the PATMAC-CTS-BC showed a rapid removal of SeO₄²⁻ with efficiency of >97% within 10 min and it followed a pseudo-second-order model. High capacity of SeO₄²⁻ adsorption by the composite was achieved, with maximum value of 98.99 mg g⁻¹ based on Langmuir model, considerably higher than most of reported adsorbents. The thermodynamic results reflected the spontaneous and exothermic nature of SeO₄²⁻ adsorption onto the composite. The composite could be applied at a wide initial pH range (2–10) with high removal efficiency of SeO₄²⁻ because of permanent positive charges of quaternary ammonium groups (=N⁺–). The removal mechanisms of SeO₄²⁻ were mainly attributed to electrostatic interactions with =N⁺– and protonated –NH₃⁺ groups, and redox-complexation interactions with –NH₂, –NH–, and –OH groups. Besides SeO₄²⁻, the hexavalent chromium (Cr₂O₇²⁻) was considered as example to further demonstrate the anion removal capability of cationic hydrogel-BC composite. The study outcomes open up new opportunities to efficiently remove anionic heavy metal ions (e.g., SeO₄²⁻ and Cr₂O₇²⁻) in water using these materials.

在处理重金属污染的水时，发现用于去除阴离子重金属离子的廉价且环保的功能材料仍然是一项挑战。本文介绍了一种新型的聚（烯丙基三甲基铵）接枝的壳聚糖和生物炭复合物（PATMAC-CTS-BC），用于去除水中的硒酸盐（SeO ₄ ^2-）。结果表明，PATMAC-CTS-BC在10分钟内显示出SeO ₄ ^2-的快速去除，效率> 97％，并且遵循伪二级模型。复合材料对SeO ₄ ^2-的吸附能力高，最大值为98.99 mg g ^-1根据Langmuir模型，大大高于大多数报道的吸附剂。热力学结果反映了SeO ₄ ^2-在复合材料上的自发和放热性质。由于季铵基团具有永久性正电荷（= N ⁺ –），因此该复合材料可以在宽的初始pH范围（2–10）下使用，并具有较高的SeO ₄ ^2-去除效率。SeO ₄ ^2-的去除机理主要归因于与= N ⁺ -和质子化-NH ₃ ⁺基团的静电相互作用，以及与-NH ₂，-NH-和-OH基团的氧化还原络合相互作用。除了SeO ₄ ²⁻以六价铬（Cr ₂ O ₇ ^2-）为例，进一步证明了阳离子水凝胶-BC复合材料的阴离子去除能力。研究结果为使用这些材料有效去除水中的阴离子重金属离子（例如SeO ₄ ^2-和Cr ₂ O ₇ ^2-）开辟了新的机会。