Barium Carbonate Process for Sulphate and Metal Removal from Mine Water

Abstract

The removal of sulphate and metals from mine water was assessed using the integrated barium carbonate process and the co-precipitation of barium sulphate with calcium carbonate. The rate of sulphate removal was influenced by the BaCO3 concentration and the cation associated with sulphate, and increased with increasing BaCO3-concentration. BaCO3 can only be used for removal of sulphate that is associated with calcium, as calcium is needed to remove the added carbonate associated with the barium cation. Sulphate removal was only marginally influenced by alkalinity. Sulphide can be stripped with CO2 from a BaS-solution. The (CO2 dosed/sulphide removed) molar ratio was close to unity for the first 50% of sulphide in solution. The stripped H2S-gas can be absorbed into zinc acetate. BaSO4 and CaCO3 can be converted simultaneously to BaS and CaO, respectively at an optimum temperature of 1050°C. The CaCO3/BaSO4 molar ratio has little influence on the yield of BaS. The running cost of the barium carbonate process for the removal of 2 g/L of sulphate totalled ZAR1.28/m3 (US$1.00 = ZAR7.0, Feb 2007), the capital redemption cost was R1.08/m3, and the value of the products (water and sulphur) totalled R2.76/m3.