Treatment of chromium contaminated soil by co-pyrolysis with rice straw

The direct discharge of tannery waste and effluent could result in severe chromium (Cr) contamination in soils. This study focused on the remediation of Cr-contaminated soil via co-pyrolysis with rice straw. The influence of co-pyrolysis temperature, rice straw / soil mixing ratio and reaction time on Cr immobilization were investigated. Compared to untreated soil, the leachable Cr and total Cr(VI) in co-pyrolyzed soil were decreased by up to 95 % and 86 %, respectively. With increasing temperature and rice straw addition, the leachable Cr and total Cr(VI) were reduced. Reaction time did not show a significant effect on Cr immobilization. The time-varying desorption test indicated that the equilibrium amount of released Cr in various extractants was inhibited by co-pyrolysis. The Simple Bioaccessibility Extraction Test also showed that the bioaccessible Cr in the gastric phase was decreased after co-pyrolysis. The results suggested that co-pyrolysis was beneficial on Cr immobilization.