Species and Distribution of Arsenic in Soil After Remediation by Electrokinetics Coupled with Permeable Reactive Barrier
2020
Ji, Dongli | Zhang, Jing | Meng, Fansheng | Wang, Yeyao | Zhang, Daohong
Arsenic-polluted soil from a mining area in China was treated by electrokinetics coupled with permeable reaction barrier (EK/PRB). Batch tests with PRB media of zero valent iron (ZVI) under electric potential of 2 V cm⁻¹ for 120 h were conducted. Species and distribution of arsenic in soil after remediation were investigated to evaluate the removal mechanisms of arsenic. Results showed that ZVI-PRB was the dominant role in the removal of arsenic in the EK/PRB systems. Arsenic transferring toward the anode was greater than cathode, due to the negatively charged arsenic anions which moved to the anode chamber by electromigration. Pentavalent arsenic (As(V)) in soil could not be reduced to more poisonous trivalent arsenic (As(III)), no matter if it were treated by EK alone or EK/ZVI-PRB. The surface characterization of ZVI, which was carried out using X-ray photoelectron spectrometry (XPS), showed that the ratio of As(V)/As(III) on the surface of PRB media was lower than that in the initial soil; no As(0) was detected on the surface of used ZVI, which indicates that arsenic was removed by surface adsorption/precipitation on ZVI-PRB, accompanied by As(V) partially reduced to As(III). The results reported in this study will be beneficial to optimizing the design of batch EK/PRB system and to enlarging the field-scale system.
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