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, Interdisciplinary Sciences Research Institute, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, Guizhou Province, China.
J Hazard Mater. 2021 Feb 5;403:123912. doi: 10.1016/j.jhazmat.2020.123912. Epub 2020 Sep 14.
Iron-manganese binary oxides are characterized by high oxidation and adsorption capability and widely applied to arsenic (As) detoxification in contaminated waters. Despite of their lower preparation cost relative to synthesized iron-manganese binary oxides, the low adsorption capacity of natural iron-manganese oxides largely hinders their application. Here, electrochemically controlled redox was employed to improve the As(III,V) removal performance of iron-manganese nodules in a symmetric electrode system, and the removal mechanism and electrode reusability were also examined. Experimental results showed that both the electrochemical reduction and oxidation of birnessite in iron-manganese nodules contributed much to As(III,V) removal. Higher cell voltage facilitated a higher removal efficiency of total As within 0-1.2 V, which reached 94.7% at 1.2 V for actual As-containing wastewater (4068 μg L). The efficiency was obviously higher than that at open circuit (81.4%). Under electrode polarity reversal, the alternating reduction dissolution and oxidation recrystallization of birnessite in iron-manganese nodules promoted their contact with As, enhancing the total As removal efficiency from 75.6% to 91.8% after five times of repeated adsorption. This research clarifies the effect of electrochemical redox on As(III,V) detoxification by iron-manganese oxides, and expands the application of natural iron-manganese nodules in the treatment of As-contaminated wastewaters.
铁锰二元氧化物具有高氧化和吸附能力，广泛应用于受污染水中的砷解毒。尽管与合成的铁锰二元氧化物相比，天然铁锰氧化物的制备成本较低，但由于其吸附容量较低，在很大程度上限制了它们的应用。在此，采用电化学控制氧化还原法改善了对称电极系统中铁锰结核中铁锰氧化物对砷（III，V）的去除性能，并对去除机制和电极的可重复使用性进行了研究。实验结果表明，铁锰结核中锰矿的电化学还原和氧化都对砷（III，V）的去除有很大贡献。较高的电池电压有利于在 0-1.2 V 范围内提高总砷的去除效率，在 1.2 V 时实际含砷废水（4068μg/L）的去除效率达到 94.7%。该效率明显高于开路时（81.4%）的效率。在电极极性反转下，铁锰结核中锰矿的交替还原溶解和氧化再结晶促进了它们与砷的接触，五次重复吸附后总砷去除效率从 75.6%提高到 91.8%。这项研究阐明了电化学氧化还原对铁锰氧化物解毒砷（III，V）的影响，并扩展了天然铁锰结核在处理含砷废水方面的应用。
