A chemical method for removing calcium sulfate saturated solutions(0.016 mol/L CaSO_(4))using barium chloride(BaCl_(2)∙2H_(2)O)and sodium phosphate(Na_(3)PO_(4))was experimentally studied.The main interest is to remove these ions from the solution through the precipitation of two solid species:sulfate(SO_(4)^(2−))as barite(BaSO4),and calcium(Ca^(2+))as hydroxyapatite(Ca_(5)(PO_(4))_(3)OH).Additionally,a solid/liquid separation method(i.e.,flotation)was explored,using oleic acid and dodecylamine as collectors.The results show that,the chemical treatment of saturated solutions at 60℃,pH 11.5 and using 3.9 g/L BaCl_(2)·2H_(2)O and 1.6 g/L Na_(3)PO_(4),promotes the precipitation of barium sulfate and calcium-deficient hydroxyapatite(Ca_(10−x)(HPO_(4))_(x)(PO_(4))_(6−x)(OH)_(2−x)),with residual concentrations of calcium and sulfate below 0.10 and 5 mg/L,respectively.The residual calcium concentration increases to 28 mg/L when using the same amount of reactants,at temperature and pH values below those quoted.The highest flotation recovery of hydroxyapatite with oleic acid at pH 9.5 was about 80%,while that of barite floated with dodecylamine at pH 6.5 was about 90%.
Elvis BUSTOS-FLORESMartha Araceli ELIZONDO-ÁLVAREZAlejandro URIBE-SALAS
