Transport of Cr(VI) in Soils Contaminated with Chromite Ore Processing Residue (COPR)

Abstract

Chromium leaching experiments were conducted using soils rich in chromite ore processing residue (COPR). Experiments were performed with acrylic columns under a constant hydraulic head and a free board. Air was purged continuously through the influent solution (simulated rainwater) in order to create an oxidative condition in soils. It was found that the mass of Cr(VI) leached was strongly dependent on temperature. The leaching process accelerated above 8°C. Under the conditions of an influent solution pH of 4.3, air atmosphere, and temperatures ranging from 3 to 38°C, the total mass of Cr(VI) leached was in the range of 0.206 to 0.260 mg/g, which accounted for about 1% of the total Cr (25.5 mg/g) in the soil sample. A one-dimensional transport model was used to simulate the leaching of Cr(VI) from soils. Model simulation results revealed that the leaching process was governed by adsorption/desorption and was attenuated by redox reactions.