A modified EK method with an I~- /I_2 lixiviant assisted and approaching cathodes to remedy mercury contaminated field soils

摘要

Wanshan mercury mine is the largest cinnabar deposit in Guizhou, China. Few effective methods had been achieved to remedy Hg heavily contaminated field soils. In this paper, a modified EK method with approaching cathodes (AC-EK) and an I~-/I_2 lixiviant was described to remedy mercury-contaminated field soils near Wanshan mercury mine. Paddy Soil Ⅰ and Paddy Soil Ⅱ were sampled and contained 576.73 ± 45.50 and 491.35 ± 4.73 mg/kg Hg, respectively. Although they contained 6.9 and 9.4% organic matter respectively, more than 92 and 89% Hg were removed by AC-EK within 5 days. Removal ratio increased by 0.21 and 0.68 times using EK process with ACs over that with one single cathode (SC-EK). AC-EK method saved nearly 26.4-28.1% electric power as compared to SC-EK method. As an I~-/I_2 lixiviant solution was used to solubilizernHgS(HgO) during EK process, the bonding of Hg to organic functional S groups should be less important than the binding to inner sites of organic matter in soil. The relationship between EK remediation effect and soil organic matter content was fitted to a linear model. It turned out that when soil OM increased by 1.0%, EK removal ratio (%) of Hg would decrease by 2.63%.