Recovery of drinking water and by-products from gold mine effluents via alkali-bariumcalcium processing

Abstract

Acid mine drainage results from active as well as decommissioned mines in the gold mining and coal mining fields. This water is highly acidic, containing sulphate, iron, aluminium, heavy metals and some radioactivity. When discharged into the environment in untreated form, the damage to human and animal health can hardly be repaired. Moreover, this water represents a loss of potentially valuable water that could be used in the water stressed South African interior. The CSIR chemical desalination process was designed to neutralise acid mine drainage (AMD) and to recover metals and sulphate. The water treatment is integrated with a thermal sludge treatment process to recover alkali, barium and calcium from the chemical sludge. Ideally, the only reagents entering this integrated process would be AMD, coal and heat, while export products are drinking water, metal sulphides and-oxides, magnesium oxide, H2S and CO2. The H2S is concentrated and available for further processing to elemental sulphur or sulphuric acid. The only inevitable waste products are CO2and a small fraction of the metal sludge that include heavy metals and radioactivity