Alternating Direct Current Field Assistant Promoting Chemical Stabilization of Combined Heavy Metals Contaminated Soil

¹ Power China Chengdu Engineering Corporation Limited, 610072 Chengdu, China
² Three Gorges Reservoir Area’s Ecology and Environment Key Laboratory of Ministry of Education, Chongqing University, 400045 Chongqing, China
³ Trinity college of art and sciences, Duke university, 27708 North Carolina, USA

^* Corresponding author: Dingwenchuan@cqu.edu.cn

Abstract

To enhance the remediation efficiency and reduce the chemicals consumption, the combined heavy metals Lead (Pb), Copper (Cu) and Cadmium (Cd) contaminated soil were stabilized by chemical passivators with alternating direct current field (ADC) assistant. The results showed that ADC treatment activated initial heavy metal compounds in the soil. The leaching concentrations of Pb, Cu and Cd in soil under ADC condition increased by 19.61%, 38.77% and 49.10% in comparison with no electric field, respectively. The exchangeable fractions of Pb, Cu and Cd increased while the reducible, oxidizable and residual fractions decreased substantially. Thus, the chemical passivators addition companied with ADC treatment in the beginning increased stabilization efficiency of heavy metals in the soil and reduced over 30% amount of chemical agent consumption, comparing with only chemical passivator stabilization. The mechanism can be speculated that ADC assistant facilitated more heavy metal ions in the soil reacting with phosphorus- containing passivator to formed more complex and stable metal phosphates. It was confirmed by XRD measurement that silicon element in the crystal structure of metallic compound was replaced by phosphorus element.