Leaching behaviour of a chromium smelter waste heap

This paper reports the results of geochemical sampling and modelling of leachates from a chromite ore processing residue (C.O.P.R.) pile under rainwater infiltration. The waste pile is located in the north of England and consists of 800,000 m3 of waste. The pH of fresh leachate is similar to that of a solution in equilibrium with portlandite Ca(OH)2, which is a major constituent of the waste. The in-gassing of CO2(g) causes the pH of the leachates to drop along the drainage ditch and calcite precipitation to occur. The extent of in-gassing is dependent upon the flow rate within the drainage ditch. The dissolution of solid solutions containing residual chromate is likely to control chromate concentrations within the leachate.