Two different types of chromite ore processing residue(COPR) contaminated soil were selected from one of chromate plants in China as research objects. The removal efficiencies of total chromium and hexavalent chromium were investigated by using three ex-situ remediation technologies which were soil washing

ex-situ stabilization and wet-process detoxication. The removal mechanisms of various forms of chromium by three kinds of remediation technologies were studied using the modified BCR method. The results show that wet-process detoxication technology was favor in Cr(Ⅵ) reducing. Cr(Ⅵ) removal rate of the wet-process detoxication technology for soil A and soil B were up to 83.26%

92.94%

respectively. The Cr(Ⅵ) removal rate of wet-process detoxication technology was higher than soil washing and ex-situ stabilization. For total chromium removal rate

soil washing was the best remediation technology. The total Cr removal rate of the soil washing technology for soil A and soil B were up to 54.87%

80.16%

respectively. Separating soluble Cr(Ⅵ) and acid soluble Cr(Ⅵ) from soil were the main reasons for the reduction of total chromium. The total Cr remove was not significant for ex-situ stabilization and wet-process detoxication technology. Because

acid conditions which was reduced by these two remediation technologies

promote soluble Cr

acid soluble Cr and reducible Cr transformed into oxidizable Cr and the total amount Cr did not change. After remediation

the Cr(Ⅵ) residual of COPR contaminated soil still maintains a high level (the Cr(Ⅵ) residual content of soil A was 736.6 mg·kg-1

the Cr(Ⅵ) residual content of soil B was 245.47 mg·kg-1). The main reason was the acid soluble Cr residue.