Effect of additives on electrokinetic remediation of arsenic and cadmium contaminated soil: Ethylene diamine tetraacetic acid, citric acid, and rhamnolipid

The co-contamination of arsenic and cadmium in China's soil is escalating, presenting a significant problem for remediation, and the features and migration-transformation processes of this co-contamination are intricate. Consequently, it is imperative to investigate effective remediation techniques. This research examines simulated arsenic-cadmium-contaminated soil to assess the effects of various additions on the concurrent removal of arsenic and cadmium by electrokinetic (EK) technology. Ethylene diamine tetraacetic acid (EDTA), citric acid, and rhamnolipid were employed as additives to investigate the remediation properties and impacts on arsenic-cadmium-contaminated soil subjected to a uniform electric field. The experimental results demonstrate that the incorporation of the three additives under electrokinetic remediation conditions effectively removes arsenic and cadmium from the soil. C/C 0 is used as an indicator to evaluate the remediation effectiveness, defined as the ratio of the average heavy metal content in the soil after electrokinetic remediation (C) to the initial average concentration of the heavy metal in the simulated contaminated soil before remediation (C 0 ). The average arsenic content C/C 0 in the EDTA, citric acid, and rhamnolipid systems post-electrokinetic remediation was diminished to 0.68, 0.51, and 0.72, respectively, whereas the average cadmium content C/C 0 was lowered to 0.46, 0.29, and 0.91, respectively. The incorporation of three additives during electrokinetic remediation enhanced metal mobility by generating soluble complexes in various additive environments, thereby elevating the heavy metal removal rate and significantly diminishing the mass fraction of acid-extractable and residual arsenic, along with acid-extractable cadmium in the soil, to 0.02-0.82 times, 0.36-0.86 times, and 0.015-0.349 times that of the original soil, respectively. In conclusion, various additives demonstrate significant efficacy and potential in the electrokinetic remediation of arsenic-cadmium-contaminated soil, which is crucial for the subsequent integration of additives to facilitate the simultaneous and rapid extraction of arsenic and cadmium. • The average arsenic content C/C 0 in the citric acid system was diminished to 0.51. • The average cadmium content C/C 0 in the citric acid system was diminished to 0.29. • The predominant form of arsenic was acid extractable state. • The predominant form of cadmium was acid extractable state and reducible state.