Guangdong Provincial Key Lab of Green Chemical Product Technology, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, PR China.
Key Lab of Pollution Control and Ecosystem Restoration in Industry Cluster, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
J Hazard Mater. 2022 Oct 5;439:129581. doi: 10.1016/j.jhazmat.2022.129581. Epub 2022 Jul 15.
Chromium(Ⅵ) and arsenic(Ⅲ) as typical anionic heavy metal pollutants normally coexist in the environment, greatly aggravating their environmental risks and elevating the difficulty of remediation. Here, a novel polyethyleneimine modified magnetic mesoporous polydopamine nanocomposite (FeO @mesoPDA/PEI) with abundant active functional groups was exploited as the synchronous adsorbent of Cr(Ⅵ) and As(Ⅲ). The results showed that Cr(Ⅵ) and As(Ⅲ) could mutually promote their conversions and adsorptions on FeO @mesoPDA/PEI. The adsorption mechanisms of FeO @mesoPDA/PEI were primarily redox chemistry and also involved electrostatic interactions and coordination. Cr(Ⅵ) was mainly reduced by reductive catechol, while As(Ⅲ) was oxidized to As(Ⅴ) by oxidative active substances (e.g., HO, •OH, and quinone). Meanwhile, active intermediate (semiquinone radicals) generated during the Cr(Ⅵ) reduction and As(Ⅲ) oxidation could constitute redox microcirculation with Cr(Ⅵ) and As(Ⅲ) to further accelerate redox reactions of Cr(Ⅵ) and As(Ⅲ) on FeO @mesoPDA/PEI, thereby exhibiting a synergistic effect. Moreover, newly immobilized Cr(Ⅲ) onto FeO @mesoPDA/PEI became extra active sites for As adsorption through cation bridges and then recovered by magnetic separation in favor of diminishing the environmental hazards of Cr and As. These findings also provide new inspirations for the roles of redox-active functional groups in the remediation of multiple redox-sensitive heavy metals including Cr(Ⅵ) and As(Ⅲ).
六价铬和砷（Ⅲ）作为典型的阴离子重金属污染物通常共存于环境中，极大地加重了它们的环境风险，并增加了修复的难度。在这里，我们开发了一种具有丰富活性官能团的新型聚乙烯亚胺修饰的磁性介孔聚多巴胺纳米复合材料（FeO@mesoPDA/PEI），作为 Cr(Ⅵ)和 As(Ⅲ) 的同步吸附剂。结果表明，Cr(Ⅵ)和 As(Ⅲ)可以相互促进它们在 FeO@mesoPDA/PEI 上的转化和吸附。FeO@mesoPDA/PEI 的吸附机制主要是氧化还原化学，同时还涉及静电相互作用和配位。Cr(Ⅵ)主要通过还原性儿茶酚还原，而 As(Ⅲ)则被氧化活性物质（如 HO、•OH 和醌）氧化为 As(Ⅴ)。同时，Cr(Ⅵ)还原和 As(Ⅲ)氧化过程中生成的活性中间产物（半醌自由基）可以与 Cr(Ⅵ)和 As(Ⅲ)构成氧化还原微循环，进一步加速 FeO@mesoPDA/PEI 上 Cr(Ⅵ)和 As(Ⅲ)的氧化还原反应，从而表现出协同效应。此外，新固定在 FeO@mesoPDA/PEI 上的 Cr(Ⅲ)通过阳离子桥成为 As 吸附的额外活性位点，然后通过磁分离回收，有利于减少 Cr 和 As 的环境危害。这些发现也为氧化还原活性官能团在修复包括 Cr(Ⅵ)和 As(Ⅲ)在内的多种氧化还原敏感重金属方面的作用提供了新的启示。
