Effect of ascorbic acid and combination with fulvic acid on the electrokinetic remediation of paddy soil contaminated by arsenic-containing acid mine drainage

Electrokinetic remediation (EKR) of soil contaminated by arsenic-containing acid mine drainage is usually challenging due to the strong adsorption capacity of iron oxides to arsenic. To solve this problem, ascorbic acid and fulvic acid were used as additives to enhance the mobility of arsenic in this study. Both ascorbic acid (EK-AA) and its combination with fulvic acid (EK-AF) increase soil water content and conductivity, forming more conducive reducing conditions, and augmenting the reduction and removal of iron, especially in the EK-AF treatment. After 14 days of EKR, the arsenic removal efficiency in EK-AF treatment reached 29.1%, while the control group was only 5.5%. The removal of arsenic in this study was attributed to the reductive dissolution of iron oxides and the activation of residual arsenic. The co-existing heavy metals antimony, copper, lead, and zinc could also be removed, with the highest antimony removal efficiency of 31.7%. Our results demonstrated that ascorbic and fulvic acids can be ideal green additives to achieve the reductive dissolution of iron oxides and activate arsenic, while maintaining soil physicochemical properties favorable to EKR, which effectively improves the removal of arsenic and co-existing heavy metals.