关键词: 电化学, 修复, 解吸附, 柠檬酸工业废水, 缓冲容量, 镉

Abstract: Batch desorption and bench-scale electrochemical remediation experiments were conducted to investigate the feasibility of using citric acid industrial wastewater (CAIW) as the enhancement agent to extract cadmium from natural soil of high buffer capacity. The results of the desorption experiments indicated that it was very difficult to dissolve cadmium without any enhancement agent when the soil pH was above 7.0. The addition of CAIW, however, could make more than 85% of the sorbed cadmium dissolved into solution at pH≤5.0. The proportion of cadmium desorption was 20%-45% higher with the enhancement of CAIW compared with DI water at pH 5.0-8.0. The results of the electrochemical remediation experiments showed that CAIW as the electrolyte could cause significant migration of cadmium in soil compared with HNO₃ solution of the same pH. Cadmium concentration in soil samples at 0-4 cm and 8-10 cm from the anode decreased to approximately 167-200 mg·kg^-1 from the initial value of 282 mg·kg^-1, while it increased to 400 mg·kg^-1 at 4-8 cm from the anode. Approximately 84.7% of the spiked cadmium could be removed after 514 h of electrochemical treatment enhanced by CAIW. Approximately 94.6% of the removed cadmium was collected in the catholyte. It is concluded that CAIW can be a promising alternative for other expensive metal chelating agents for enhancing electrochemical remediation of heavy metal-contaminated soils of high buffer capacities.

Key words: electrochemistry, remediation, desorption, citric acid industrial wastewater, buffer capacity, cadmium