整流电絮凝技术对缺氧地下水中As(Ⅲ)的原位修复

Rectified-alternating-current electrocoagulation for As(Ⅲ) remediation in the anoxic groundwater

地下水中砷污染的原位修复治理对人类社会的可持续发展具有重要意义.本文研发了一种新型整流电絮凝反应体系,可实现对缺氧地下水As(Ⅲ)的原位修复.实验结果表明,最优操作条件为:电流密度为4.4 m A·cm^(-2),铁棒和MMO的阳极工作时间比值(TFe-anode/TMMO-anode)为1∶2,反应周期为24 s.在最优条件下,含有500μg·L^(-1)As(Ⅲ)的模拟地下水经过30 min电絮凝处理后砷的固定脱除效率达92%,总能耗为0.11 kW·hm^(-3).此外,水体中的HCO_3^-和PO_4^(3-)等无机阴离子对砷的固定具有抑制作用.在该反应体系内,电解生成的Fe(Ⅱ)与O2之间的氧化反应生成具有强氧化性的Fe(Ⅳ)可有效将As(Ⅲ)氧化成毒性较小且更易于固定脱除的As(Ⅴ),进而显著促进了砷在Fe(Ⅲ)絮凝沉淀作用下的固定脱除.

In situ remediation of arsenic in anoxic groundwater is significant for the sustainable development of humankind. In this study,a wave rectified alternating current electrocoagulation process was developed for the oxidative sequestration of As( Ⅲ) in the simulated anoxic groundwater. The optimal current density,TFe-anode/TMMO-anoderatio and reaction period for As( Ⅲ)sequestration were 4. 4 m A·cm-2,1 ∶ 2 and 24 s,respectively. Under the optimal conditions,approximately 92% of 500 μg·L-1 As( Ⅲ) was removed after 30 min reaction at pH 8 with the energy consumption of 0.11 kW·hm-3. In addition,the presence of HCO3- and PO43- deteriorated the efficiency of As( tot) sequestration. In this process,the oxidation of As( Ⅲ) to As( Ⅴ) was induced by the intermediate oxidant,i. e.,Fe( Ⅳ),produced in the process of O2 reacting with Fe( Ⅱ),followed by the sequestration of As( Ⅴ) by the freshly generated amorphous Fe( Ⅲ)( oxyhydr)oxides.