LAUSR

Abstract This study investigated the electrokinetic (EK) treatment of Cr from chromite ore processing residue (COPR) using rhamnolipid as the electrolyte. Chemical fractions were analyzed to better understand the transformation and migration of Cr from COPR with different electrolytes and time. The results showed the removal efficiency of Cr(Ⅵ) was enhanced to 90.04% with a concentration of rhamnolipid at 15 g/L, and the total Cr increased to 19.65% at 20 g/L; the above values are higher than 65.74% and 9.52% when using deionized water, respectively. After the EK treatment, the concentrations of Cr in the form of exchangeable (EXC), carbonates (CAR), Fe–Mn oxides (FM) and residual (RES) decreased while the organic matter (OC) form increased. Rhamnolipid greatly promoted a transformation between the chemical fractions and the migration of Cr. The transformation was most effective on the third day, and the removal efficiency gradually increased until reaching the best result on the fifth day; however, a further extension of time was detrimental to the transformation and migration of Cr. After the controlled experiment, the environmental toxicity of the remaining Cr decreased as the Cr in the high-risk fraction was effectively removed.