Research on the Effect of Chemical Reduction-Stabilization Combined Remediation of Cr-contaminated Soil

Abstract

BACKGROUND Cr(Ⅵ) is one of the 47 internationally recognized most dangerous wastes. Study on the remedy of Cr-contaminated soil is of great significance for risk control of contaminated soil. OBJECTIVES To build a reliable method for Cr-contaminated soil, and to screen the optimal remediation conditions. To propose a chemical reduction-stabilization combined method for remediation of Cr(Ⅵ) contaminated soil and screen the remediation conditions including choice of reductant, soil/liquid ratio and stabilizer. METHODS Soil from a typical chromium contaminated site in Jinan is used as the research object, and the idea of 'chemical reduction + solidification stability' is suggested, which is aimed at the types of repair agent, dosage ratio, reaction time, reduction efficiency, repair cost and environmental effect. The optimal conditions for the repair process were determined and the remediation effects of contaminated soil were evaluated. RESULTS The results demonstrated that the optimal parameter for Cr(Ⅵ) treatment was using ferrous chloride as the reductant and treating for 2 days, controlling the addition amount of the reductant at 5 times of its stoichiometric need. Calcium magnesium phosphate was used as the stabilizer and its addition amount was controlled as 10%. After remediation, the bioavailable efficients of Cr in the soil reduced from 0.4398 to 0.0017. The results showed that contents of Cr(Ⅵ) in the treated soil were 0.315-0.501mg/kg, and 99.5% of Cr(Ⅵ) was reduced. CONCLUSIONS The remedied soil satisfies the risk screen number for residual land. This result could provide reference and theoretical basis for soil remediation and decision-making.

Keywords

• chemical reduction
• stabilization
• cr(ⅵ)
• soil remediation
• combined method