Selecting an Effective Extractant for Removing Cr from Contaminated Soil

摘要

The effects of various extractants removing Cr from the soil of chromite ore processing residue (COPR) deposited sites were studied in order to select the optimal extractant agent. The effects of this agent on the removal of Cr(Ⅵ) and Cr(Ⅲ) in the contaminated soil were also investigated. The results showed that organic complexing agents had higher removal efficiency than that of inorganic complexing agents due to the high content of Cr(Ⅲ) in the soil (90.3％). The Cr removal of citric/sodium citrate (mole ratio: 1:1) was 35.95％ in 24h. The reason why citric/sodium citrate removed more Cr than other agents is that citric can solubilize the mineral matrix, compete for the surfaces sites to desorb Cr (Ⅵ) and remove Cr(Ⅲ) by its complexation. The concentration radio of Cr(Ⅵ) and Cr(Ⅲ) in the initial soil was 0.11. Thus improving the removal of Cr(Ⅲ)is the key point of improving the total Cr removal.