Design of Recyclable Adsorbent for Water Pollutants Based on Chitosan-Coated Carboxymethyl Cellulose-Calcium Alginate Wrapped Iron Oxide-Copper Oxide Composite Beads

In this study, an efficient nanocomposite based on calcium alginate-carboxymethyl cellulose/iron oxide-copper oxide (CA-CMC/Fe2O3-CuO) is developed in beads form and utilized as nanoadsorbent and nanocatalyst. Further, the beads were coated with chitosan, resulting in Cs@CA-CMC/Fe2O3-CuO beads. The prepared beads exhibited exceptional adsorption capabilities for selected heavy metal ions. Notably, the Cs@CA-CMC/Fe2O3-CuO beads displayed remarkable adsorption among the other beads toward the three selected metal ions. Ag(I) was highly adsorbed by Cs@CA-CMC/Fe2O3-CuO beads, and the adsorption capacity of beads was 4.91 mgg−1, while 4.5 mgg−1 and 3.0 mgg−1 for Co(II) and Ni(II), respectively. Beads’ ability to adsorb Ag(I) varied depending on several factors. It was observed that the adsorption capacity of Ag(I) ions increased as the interaction time and metal concentration rose. However, increasing the beads dose led to a decrease in the Ag(I) ion adsorption. Further, the waste beads after Ag(I) adsorption were treated with reducing agent to form beads supported Ag nanoparticles (Ag/Cs@CA-CMC/Fe2O3-CuO) and used as effective catalyst for reducing 4-nitrophenol in the presence of NaBH4 as a reducing agent. Ag/Cs@CA-CMC/Fe2O3-CuO achieved reduction up to 93% for 4-NP within 30 min. The designed nanocomposite beads displayed several desirable attributes, including eco-friendliness and robust catalytic performance, making them highly promising for useful reduction of 4-NP.

本研究开发了一种以海藻酸钙-羧甲基纤维素/氧化铁-氧化铜（calcium alginate-carboxymethyl cellulose/iron oxide-copper oxide, CA-CMC/Fe₂O₃-CuO）为基材的高效纳米复合材料，制备为微球形态，用作纳米吸附剂与纳米催化剂。随后，将该微球用壳聚糖包覆，得到Cs@CA-CMC/Fe₂O₃-CuO复合微球。所制备的微球对选定的重金属离子展现出优异的吸附性能。值得注意的是，相较于其他微球，Cs@CA-CMC/Fe₂O₃-CuO复合微球对三种目标金属离子均表现出突出的吸附能力。其中，Cs@CA-CMC/Fe₂O₃-CuO微球对银离子（Ag(I)）的吸附效果最佳，吸附容量达4.91 mg·g⁻¹，对钴离子（Co(II)）与镍离子（Ni(II)）的吸附容量分别为4.5 mg·g⁻¹与3.0 mg·g⁻¹。微球对Ag(I)的吸附能力受多种因素影响：研究发现，Ag(I)的吸附容量随作用时间与金属离子浓度的升高而提升，但随着微球投加量的增加，Ag(I)的吸附量反而下降。此外，吸附了Ag(I)的废弃微球经还原剂处理后，可制备得到负载银纳米颗粒的复合微球（Ag/Cs@CA-CMC/Fe₂O₃-CuO），并以硼氢化钠（sodium borohydride, NaBH₄）为还原剂，用作还原4-硝基苯酚（4-nitrophenol, 4-NP）的高效催化剂。Ag/Cs@CA-CMC/Fe₂O₃-CuO可在30分钟内实现93%的4-NP还原率。所设计的纳米复合微球具备多项优良特性，包括环境友好性与优异的催化性能，在4-NP的高效还原领域具有极高的应用前景。