Acid mine water neutralisation with ammonium hydroxide and desalination with barium hydroxide

Abstract

South Africa, acid mine drainage is polluting increasingly scarce ground- and surface water. The ammonium-barium (NB) process described in this paper consists of neutralisation and metal removal with NH4OH, sulphate removal with Ba(OH)2 and Ca removal with CO2. Laboratory studies showed that metals are removed to low levels. This includes Fe(II), the predominant metal in mine water. It is first oxidised to Fe(III), whereafter it precipitates as Fe(OH)3. Sulphate is removed to low concentrations as BaSO4. During CO2 dosing, CaCO3 is precipitated to its saturation level. The simulation predictions followed the same pattern as the experimental results obtained. This study showed that NH4OH can be used for treatment of acid mine drainage rich in sulphates and NH4OH can be recycled in the process. Hydrated lime treatment resulted in removal of the remaining ammonia using a rotary evaporator.

Keywords: acid mine water, ammonium hydroxide, barium hydroxide, sulphate removal