Precipitated CaCO3 compounds recovered from pulped waste gypsum using some carbonate and hydroxide-based reagents were evaluated for their utilization in acid mine drainage (AMD) neutralization. The neutralization potentials, acid neutralization capacities and compositions of the CaCO3 compounds were determined and compared with some commercial CaCO3. It was observed that CaCO3 recovered from waste gypsum using Na2CO3 significantly neutralized AMD compared with commercial CaCO3 and that recovered using both (NH4)2CO3 or NH4OH-CO2 reagents. Moreover, a higher acid neutralization capacity of 1,370 kg H2SO4/t was determined for CaCO3 recovered from waste gypsum using Na2CO3 compared with an average of 721 and 1,081 kg H2SO4/t for ammonium-based CaCO3 and commercial CaCO3 respectively. The inorganic carbon content for the CaCO3 recovered using Na2CO3 and ammonium-based reagents of 49 and 34% respectively confirmed their observed neutralization potentials and acid neutralization capacities, while energy dispersive X-ray fluorescence suggested absence of major oxide impurities, with the exception of residual SO42− and Na2O which still requires further reduction in the respective compounds.

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