School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China.
School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China.
Water Res. 2022 Aug 15;222:118919. doi: 10.1016/j.watres.2022.118919. Epub 2022 Jul 29.
Efficient removal of toxic hexavalent chromium (Cr(VI)) under alkaline conditions is still a challenge due to the relatively low reactivity of CrO. This study proposed a new sulfite/iodide/UV process to remove Cr(VI). The removal of Cr(VI) followed pseudo-zero-order kinetics at alkaline pHs, and was enhanced by sulfite and iodide with synergy. Compared with sulfite/UV, iodide in sulfite/iodide/UV showed about 40 times higher concentration-normalized enhancement for Cr(VI) removal, and reduced the requirement of sulfite ([S(IV)]/[Cr(VI)] of about 2.1:1) by more than 90%. The Cr(VI) removal was accelerated by decreasing pH and by increasing temperature, and was slightly influenced by dissolved oxygen, carbonate, and humic acid. The process was still effective in real surface water and industrial wastewater. Mechanism and pathways of Cr(VI) removal were revealed by quenching experiments, competition kinetic analysis, product identification and quantification, and mass and electron balance. Both e and SO were responsible for Cr(VI) removal, making contributions of about 75% and 25%, respectively. When e mainly reacted with Cr(VI), SO participated in reduction of Cr(V) and Cr(IV) intermediates, with Cr(III), SO, and SO as the final products. A model was developed to predict removal kinetics of Cr(VI), and well interpreted the roles of S(IV) and iodide in the process. This study sheds light on mechanism of Cr(VI) removal at alkaline pHs by kinetic modeling, and thus advances the applicability of this promising process for water decontamination.
在碱性条件下，由于 CrO 的相对低反应性，高效去除有毒六价铬 (Cr(VI)) 仍然是一个挑战。本研究提出了一种新的亚硫酸盐/碘化物/UV 工艺来去除 Cr(VI)。在碱性 pH 值下，Cr(VI)的去除遵循准零级动力学，并且亚硫酸盐和碘化物具有协同作用得到增强。与亚硫酸盐/UV 相比，亚硫酸盐/碘化物/UV 中的碘化物对 Cr(VI)去除的浓度归一化增强约 40 倍，并且减少了对亚硫酸盐的需求 ([S(IV)]/[Cr(VI)] 约为 2.1:1) 超过 90%。通过降低 pH 值和升高温度可以加速 Cr(VI)的去除，并且溶解氧、碳酸盐和腐殖酸的影响较小。该工艺在实际地表水和工业废水中仍然有效。通过猝灭实验、竞争动力学分析、产物鉴定和定量、质量和电子平衡揭示了 Cr(VI)去除的机制和途径。e 和 SO 都负责 Cr(VI)的去除，各自的贡献约为 75%和 25%。当 e 主要与 Cr(VI)反应时，SO 参与 Cr(V)和 Cr(IV)中间产物的还原，最终产物为 Cr(III)、SO 和 SO。建立了一个模型来预测 Cr(VI)的去除动力学，该模型很好地解释了 S(IV)和碘化物在该过程中的作用。本研究通过动力学建模揭示了碱性 pH 下 Cr(VI)去除的机制，从而推进了该有前途的工艺在水净化中的应用。
