Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China; Shanghai Institute of Pollution Control and Ecological Security, 1239 Siping Road, Shanghai 200092, China.
Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620, China.
Sci Total Environ. 2019 Dec 10;695:133926. doi: 10.1016/j.scitotenv.2019.133926. Epub 2019 Aug 14.
Being able to simultaneously reduce and adsorb highly toxic Cr(VI) from bodies of water would provide a significant advance in the treatment of water pollution. Herein, we report on the design of an electroactive filter consisting of nanoscale polyaniline modified carbon nanotubes (PANI-CNT). In an electric field, both Cr(VI) reduction kinetics and Cr(III) sorption capacity were enhanced as the flow rate and voltage increased. At pH 7, Cr(VI) removal efficiency increased from 29.3% at 0 V to 70.2% at 2.5 V. This can be ascribed to superior electrical conductivity, more available active sites and limited pore size of the PANI-CNT filter, further boosted by the flow-through operation. Due to convection-enhanced mass transport, the proposed continuous-flow PANI-CNT filter demonstrated an evidently enhanced kinetic process when compared to conventional batch system. Various advanced assessments and density functional theory calculations verified the essential role of the electric field during Cr(VI) removal. Scanning transmission electron microscopy (STEM) examinations showed that the Cr was mainly sequestered by the PANI. It was also confirmed that an exhausted PANI-CNT filter can be regenerated by chemical washing with an HCl solution. Experiments with actual Cr(VI)-contaminated electroplating wastewater further verified the effectiveness of the system, with complete Cr(VI) transformation and a 50% Cr removal efficiency at 2.5 V with a flow rate of 3 mL/min. This study provides new insights into practical continuous-flow solutions to the effective removal of highly toxic Cr(VI).
能够同时从水体中还原和吸附高毒性的六价铬（Cr(VI)）将是水污染处理的重大进展。在此，我们报告了一种由纳米级聚苯胺修饰的碳纳米管（PANI-CNT）组成的电活性过滤器的设计。在电场作用下，随着流速和电压的增加，Cr(VI)的还原动力学和 Cr(III)的吸附容量都得到了增强。在 pH 7 时，Cr(VI)去除效率从 0 V 时的 29.3%提高到 2.5 V 时的 70.2%。这可以归因于 PANI-CNT 过滤器的优异导电性、更多可用的活性位点和有限的孔径，而这种效果又因流经操作而得到进一步增强。由于对流增强了质量传递，与传统的分批系统相比，所提出的连续流动 PANI-CNT 过滤器表现出明显增强的动力学过程。各种先进的评估和密度泛函理论计算验证了电场在 Cr(VI)去除过程中的重要作用。扫描透射电子显微镜（STEM）检查表明，Cr 主要被 PANI 隔离。还证实了可以通过用 HCl 溶液进行化学清洗来再生耗尽的 PANI-CNT 过滤器。实际含 Cr(VI)电镀废水的实验进一步验证了该系统的有效性，在 2.5 V 和 3 mL/min 的流速下，Cr(VI)完全转化，Cr 的去除效率达到 50%。本研究为有效去除高毒性 Cr(VI)的实际连续流动解决方案提供了新的见解。
