title: An evaluation of waste gypsum-based precipitated calcium carbonate for acid mine drainage neutralization.
abstract: Precipitated CaCO(3) 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 CaCO(3) compounds were determined and compared with some commercial CaCO(3). It was observed that CaCO(3) recovered from waste gypsum using Na(2)CO(3) significantly neutralized AMD compared with commercial CaCO(3) and that recovered using both (NH(4))(2)CO(3) or NH(4)OH-CO(2) reagents. Moreover, a higher acid neutralization capacity of 1,370 kg H(2)SO(4)/t was determined for CaCO(3) recovered from waste gypsum using Na(2)CO(3) compared with an average of 721 and 1,081 kg H(2)SO(4)/t for ammonium-based CaCO(3) and commercial CaCO(3) respectively. The inorganic carbon content for the CaCO(3) recovered using Na(2)CO(3) 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 SO(4)(2-) and Na(2)O which still requires further reduction in the respective compounds.
authors.affiliation: Council for Scientific and Industrial Research, Natural Resources and the Environment, Pretoria, Gauteng-South Africa. jzvimba@csir.co.za
authors.forename: J N
authors.initials: JN
authors.lastname: Zvimba
authors.forename: J
authors.initials: J
authors.lastname: Mulopo
authors.forename: L T
authors.initials: LT
authors.lastname: Bologo
authors.forename: M
authors.initials: M
authors.lastname: Mathye
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008906:Mining; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014877:Water Pollution, Chemical / Q000517:prevention & control; D018508:Water Purification
chemical_list: D014874:Water Pollutants, Chemical; D002119:Calcium Carbonate; D002133:Calcium Sulfate