Water decontamination from the toxic effluents, for the safe use of human, is the hottest area of research nowadays. 4-nitrophenol and Cr(VI) are the two pollutants of high environmental concern due to their toxic and carcinogenic nature. Furthermore, their remediation is a laborious, time consuming and challenging task. In this context, photocatalysis is believed to be an efficient and safe remediation process, however, photocatalysts suffer from inferior stability and efficiency. Similar problems are also associated with CdS, which is considered a low cost and visible light absorbing material. To improve efficiency and stability of CdS, the CdS-polymer nanocomposites were prepared by the deposition of CdS on the polymeric beads (CS/PVA/TEOS) at ambient conditions. CdS-polymer nanocomposites were observed to be better photocatalysts under solar light than the bare CdS for the reduction of {4-nitrophenol and Cr(VI)} carcinogens. The photoreduction followed pseudo first order kinetics. Notably, the rate of photoreduction was observed to increase with an increase in the percentage of degree of deacetylation (DDA) of the chitosan polymer. Among the four synthesized catalysts, the B4/CdS presented the best catalytic efficiency: Cr(VI) reduced in 4 min with TOF = 6.4 × 10 mmol Cr(VI)/(mg⋅min), ΔH = 5.008 kJ/mol and ΔS = - 0.856 kJ/mol.K and 4-NP in 8 min with TOF = 4.1 × 10 mmol 4-NP/(mg⋅min), ΔS = - 2.817 kJ/mol.K and enthalpy ΔH = 14.26 kJ/mol. The effect of various parameters: temperature, pH and catalytic dose was also investigated to assess the optimal conditions for photocatalysis. It is anticipated that a unique combination of chitosan polymer and CdS might offer efficient adsorption and electron transfer, which ultimately triggered the reduction.

中文翻译：

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CdS-聚合物纳米复合材料光催化还原水中致癌污染物

为了人类的安全使用，有毒废水的水净化是当今最热门的研究领域。 4-硝基苯酚和六价铬由于具有毒性和致癌性，是两种受到高度关注的环境污染物。此外，它们的修复是一项费力、耗时且具有挑战性的任务。在这种情况下，光催化被认为是一种有效且安全的修复过程，然而，光催化剂的稳定性和效率较差。类似的问题也与 CdS 相关，CdS 被认为是一种低成本且可见光吸收的材料。为了提高 CdS 的效率和稳定性，通过在环境条件下将 CdS 沉积在聚合物珠 (CS/PVA/TEOS) 上来制备 CdS-聚合物纳米复合材料。研究发现，在太阳光下，CdS-聚合物纳米复合材料是比裸 CdS 更好的光催化剂，可减少 {4-硝基苯酚和 Cr(VI)} 致癌物。光还原遵循伪一级动力学。值得注意的是，观察到光还原速率随着壳聚糖聚合物脱乙酰度(DDA)百分比的增加而增加。在四种合成的催化剂中，B4/CdS 表现出最好的催化效率：Cr(VI) 在 4 分钟内被还原，TOF = 6.4 × 10 mmol Cr(VI)/(mg·min)，ΔH = 5.008 kJ/mol 和 ΔS = - 0.856 kJ/mol.K 和 4-NP 在 8 分钟内，TOF = 4.1 × 10 mmol 4-NP/(mg·min)，ΔS = - 2.817 kJ/mol.K 和焓 ΔH = 14.26 kJ/mol。还研究了温度、pH 值和催化剂量等各种参数的影响，以评估光催化的最佳条件。预计壳聚糖聚合物和 CdS 的独特组合可能提供有效的吸附和电子转移，最终引发还原。