Study on Screening of Chromium-Contaminated Soil Eluents and Optimization of Elution Conditions

For selecting the best leaching agent and optimizing the leaching conditions, the present study investigated the effects of six leaching agents (hydrochloric acid, oxalic acid, water, citric acid, phosphoric acid, and EDTA) on chromium elution from contaminated soil under various elution conditions. To determine the total chromium concentration in soil, 0.10 g soil sample was digested with a mixture of HNO3-HClO4-HF (5 mL:2 mL:1 mL) for 12 h at 180 degrees C. The total chromium content in soil and the chromium concentration in the leaching agent were determined using a flame atomic absorption spectrophotometer. During the comparative study, the removal of total chromium by multiple leaching agents with the best eluent was studied. Also, the optimum elution conditions and the optimal number of leaches were determined. Conclusively, the removal efficiency of total chromium by composite eluent was investigated. The results showed that high concentrations (1 mol/L) of citric acid and oxalic acid had better chromium removal efficiencies, with removal rates of 58.6% and 54.8%, respectively. The combined eluent composed of equal volumes of 0.6 mol/L oxalic acid and 0.6 mol/L citric acid has a better elution efficiency, with a total chromium removal rate of 62.0%. Citric acid is an environmentally friendly eluent that can avoid secondary pollution. In conclusion, citric acid with a 0.6 mol/L concentration is the best eluent, which conveys higher efficiency (58.6%) at a solid-liquid ratio of 1:10 for 8 h of leaching. This study provides a theoretical basis for the efficient remediation of chromium-contaminated soil by ectopic leaching.

Automated summary

This study investigated the effects of six leaching agents on chromium elution from contaminated soil, finding that citric acid and oxalic acid had higher removal efficiencies. The combined eluent of oxalic acid and citric acid showed the best elution efficiency, with a total chromium removal rate of 62.0%. Citric acid is an environmentally friendly eluent that can avoid secondary pollution.