Effectiveness and Remediation Mechanisms of Geo-Electrochemical Technology for Arsenic Removal in Paddy Soil from Northern Guangxi.

Abstract

Arsenic pollution in paddy soil is a major environmental issue, and its remediation has become a subject of broad interest. Geo-electrochemical technology has been shown to have significant potential for remediating heavy metal-contaminated soils in recent years. Taking contaminated paddy soil from northern Guangxi as the research subject, this study aims to assess the effectiveness of geo-electrochemical technology for arsenic remediation. An orthogonal experimental design was used to identify the optimal combination of parameters, including power supply duration, voltage gradient, power supply mode, and electrolyte type. The arsenic removal efficiency was thoroughly assessed, and the underlying remediation mechanisms associated with geo-electrochemical technology combined with EDTA-2Na were extensively investigated. The findings revealed a substantial decrease in the residual arsenic fraction after treatment, accompanied by a substantial increase in the mobility and bioavailability of arsenic. The maximum removal rate of arsenic from the soil was determined to be 19.59%. Among the analyzed factors, electrolyte type exerted the most significant influence on the arsenic removal efficiency, followed by power supply duration and voltage gradient, while the impact of the power supply mode was less significant. The optimal remediation effect was achieved under the following conditions: a power supply duration of 108 h, a voltage gradient of 0.6 V/cm, continuous power supply mode, and the use of EDTA-2Na as the electrolyte. The multiple strong coordinating atoms in EDTA-2Na can form stable chelates with Fe³⁺ and Al³⁺ bound to arsenic in the soil, thereby causing the desorption of arsenic. The integration of geo-electrochemical technology with EDTA-2Na forms a synergistic multiphase electrochemical reaction mechanism, significantly improving the overall remediation efficiency in arsenic-contaminated soils.