Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture and Rural Affairs, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture and Rural Affairs, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, China.
Chemosphere. 2020 May;247:125822. doi: 10.1016/j.chemosphere.2020.125822. Epub 2020 Jan 6.
Manganese oxides are potentially used for the electrochemical removal of heavy metals from wastewater. However, little is known about the performance and mechanism of simultaneous electrosorption for multiple heavy metals, especially for coexisting anions and cations. In this work, birnessite-type manganese oxide was used for the electrochemical adsorption of coexisting Cd(II) cations and As(V) anions with a symmetrical electrode system, and the effects of the concentrations of coexisting metal ions and applied voltage were investigated. The results indicated that both the Cd(II) and As(V) adsorption capacity of birnessite increased in a mixed solution containing Cd(II) cations and As(V) anions, compared with that in single heavy metal solution. This synergistic effect was mainly ascribed to the formation of manganese arsenate precipitate and the reduction dissolution of birnessite on the cathode and the re-oxidation of Mn(II) with subsequently increased fresh adsorption sites on the anode. The electrochemical adsorption capacity for As(V) increased from 52.7 to 88.0 and 496.0 mmol kg with increasing Cd(II) concentration from 0.1 to 1.5 mM, respectively, in the mixed solution containing 0.5 mM As(V). The removal efficiency of heavy metals increased first and then decreased with increasing voltage from 0 to 1.2 V. Under the optimum condition at 0.6 V for 12 h, the electrochemical adsorption capacity increased with increasing Cd(II) and As(V) concentrations and the highest capacity reached 2132.0 mmol kg for Cd(II) and 1996.0 mmol kg for As(V). This work provides a facile technique for the treatment of wastewaters containing metal anions and cations.
二氧化锰有望用于电化学去除废水中的重金属。然而，对于多种重金属的同时电吸，特别是共存的阴离子和阳离子的同时电吸的性能和机理，人们知之甚少。在这项工作中，采用八面体型二氧化锰在对称电极体系中对共存的 Cd(II)阳离子和 As(V)阴离子进行电化学吸附，并研究了共存金属离子浓度和外加电压的影响。结果表明，与单一重金属溶液相比，在含有 Cd(II)阳离子和 As(V)阴离子的混合溶液中，八面体型二氧化锰对 Cd(II)和 As(V)的吸附容量均增加。这种协同效应主要归因于砷酸锰沉淀的形成以及阴极上八面体型二氧化锰的还原溶解，以及随后在阳极上 Mn(II)的再氧化和新的吸附点位的形成。当混合溶液中 As(V)浓度保持在 0.5 mM 时，Cd(II)浓度从 0.1 mM 增加到 1.5 mM，As(V)的电化学吸附容量分别从 52.7 mmol kg 增加到 88.0 mmol kg 和 496.0 mmol kg。在 0 到 1.2 V 的外加电压下，重金属的去除效率先增加后降低。在 0.6 V 下 12 h 的最佳条件下，电化学吸附容量随 Cd(II)和 As(V)浓度的增加而增加，最大容量分别达到 2132.0 mmol kg 对 Cd(II)和 1996.0 mmol kg 对 As(V)。这项工作为处理含金属阴离子和阳离子的废水提供了一种简便的技术。
