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

摘要： 通过批量解吸附实验和电化学修复实验，研究利用柠檬酸工业废水作为电化学修复的增效剂从高缓冲容量的天然土壤中去除镉的可行性。批量实验结果表明，当加入柠檬酸工业废水时，85%以上的镉能在土壤pH≤5.0的条件下从土壤中溶解到溶液中；在pH5.0～8.0范围内镉的解吸附率比用去离子水增加20%～45%。电化学修复实验结果表明，与相同pH值的HNO₃相比，该废水作为电极溶液可使镉在土壤中发生明显迁移；在距离阳极0～4 cm及8～10 cm处土壤镉含量由282 mg·kg^-1降低至167～200 mg·kg^-1，而在距阳极4～8 cm处土壤镉含量升高至约400 mg·kg^-1。经过514 h的电化学修复，约84.7%的镉可以从土壤中去除，其中约94.6%从土壤中去除的镉富集在阴极溶液中。可见柠檬酸工业废水是一种非常有前景的重金属污染土壤电化学修复增效剂。

关键词: 电化学, 修复, 解吸附, 柠檬酸工业废水, 缓冲容量, 镉