The effective removal of elemental mercury (Hg⁰) is a global challenge due to its toxicity and bioaccumulation threat to public health and ecosystems. Photocatalytic technology by visible light-driven photocatalysts is promising for Hg⁰ removal. However, effective separation of photocatalyst powders from reaction solution limits its widespread use. To solve the problem, we report for the first time the successful fabrication of recoverable Bi₂O₂S/Bi₅O₇I/ZA hydrogel beads for enhanced photocatalytic Hg⁰ removal in the presence of H₂O₂. Characterization techniques such as XRD, TEM, EDS, XPS, UV–vis DRS, PL, etc. are employed to understand the physicochemical properties and photoelectric performance of the photocatalysts. The serial BOSI photocatalysts all outperform the single component, which is attributed to the formation of a heterojunction between Bi₅O₇I and Bi₂O₂S. The coupling of 2-BOSI-ZA beads with H₂O₂ shows favorable synergistic effect, with Hg⁰ removal efficiency in the following order: H₂O₂ + 2-BOSI-ZA < 2-BOSI-ZA + FSL < H₂O₂ + 2-BOSI-ZA + FSL. TPC, EIS, and PL tests confirm that the introduction of Bi₂O₂S effectively suppresses charge carrier recombination. ESR and free radicals capture experiments demonstrate that the main species responsible for removal of Hg⁰ are ^•O₂^– and ^•OH. Density functional theory calculations exhibit that the internal electric field (IEF) between Bi₅O₇I and Bi₂O₂S contributes to the spatial charge separation of the heterojunction. The IEF leads to an S-scheme carrier transfer mechanism at the Bi₂O₂S/Bi₅O₇I interface that benefits the carrier separation on Bi₅O₇I, resulting in an enhanced photocatalytic performance. This work can provide further inspiration for designing hydrogel photocatalysts with an excellent activity in conjunction with oxidants in the field of mercury pollution control.

中文翻译：

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制备可回收的 Bi2O2S/Bi5O7I/ZA 水凝胶珠，用于在 H2O2 存在下增强光催化 Hg0 去除


有效去除元素汞 （^{Hg 0}） 是一项全球性挑战，因为其毒性和生物积累对公共卫生和生态系统构成威胁。可见光驱动光催化剂的光催化技术有望去除^{Hg 0}。然而，光催化剂粉末与反应溶液的有效分离限制了其广泛使用。为了解决这个问题，我们首次报道了在 H₂O₂ 存在下成功制造可回收的 Bi₂O₂S/Bi₅O₇I/ZA 水凝胶珠，用于增强光催化 Hg⁰ 去除。采用 XRD、TEM、EDS、XPS、UV-vis DRS、PL 等表征技术来了解光催化剂的物理化学性质和光电性能。系列BOSI光催化剂的性能都优于单一组分，这归因于Bi₅O₇I和Bi₂O₂S之间异质结的形成。2-BOSI-ZA 珠子与 H₂O₂ 的偶联显示出良好的协同效应，Hg⁰ 去除效率按以下顺序排列：H₂O₂ + 2-BOSI-ZA < 2-BOSI-ZA + FSL < H₂O₂ + 2-BOSI-ZA + FSL。TPC、EIS 和 PL 测试证实，Bi₂O₂S 的引入有效抑制了电荷载流子复合。ESR 和自由基捕获实验表明，负责去除 Hg⁰ 的主要物质是 ^•O₂^– 和 ^•OH。 密度泛函理论计算表明，Bi₅O₇I 和 Bi₂O₂S 之间的内电场 （IEF） 有助于异质结的空间电荷分离。IEF 导致 Bi₂O₂S/Bi₅O₇I 界面的 S 型载流子转移机制，有利于 Bi₅O₇I 上的载流子分离，从而增强光催化性能。这项工作可以为在汞污染控制领域设计具有优异活性的水凝胶光催化剂提供进一步的灵感。