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EFFECT OF MAGNESIUM-RICH WATERS ON PHOSPHATE ADSORPTION BY CALCITE
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1984
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Chemical EngineeringEnvironmental ChemistryEngineeringPhosphate AdsorptionEnvironmental EngineeringMineral-fluid InteractionWater TreatmentCalcium AluminateAuthigenic Mineral FormationChemistryP AdsorptionMg2+ ConcentrationWastewater Treatment
We studied the adsorption of phosphate by calcite as influenced by various concentrations of Mg2+ in waters undersaturated and supersaturated with respect to CaCO3. At all Mg2+ concentrations, the amount of P adsorbed from supersaturated waters always exceeded that from undersaturated waters. The effect of Mg2+ in reducing P adsorption was more conspicuous at high than at low initial P levels. The Mg2+ concentration needed to affect a specific reduction in phosphate adsorption was higher in supersaturated than in undersaturated waters. Complete inhibition of P adsorption by CaCO3 was never obtained, even at the highest Mg2+ concentration (4 meq/L). The effect of Mg2+ in reducing P adsorption is ascribed to: (1) masking the adsorption sites on calcite; (2) disrupting the nucleation and crystallization of P precipitates; and (3) increasing the solubility of CaCO3 in the waters.