Sorption and coprecipitation of trace concentrations of thorium with various minerals under conditions simulating an acid uranium mill effluent environment

Sorption of thorium by pre-existing crystals of anglesite (PbSO₄), apatite (Ca₅(PO₄)₃(HO)), barite (BaSO₄), bentonite (Na_0.7Al_3.3Mg_0.7Si₈O₂₀(OH)₄), celestite (SrSO₄), fluorite (CaF₂), galena (PbS), gypsum (CaSO₄·2H₂O), hematite (Fe₂O₃), jarosite (KFe₃(SO₄)₂(OH)₆), kaolinite (Al₂O₃·2SiO₂·2H₂O), quartz (SiO₂) and sodium feldspar (NaAlSi₃O₈) was studied under conditions that simulate an acidic uranium mill effluent environment. Up to 100% removal of trace quantitiees of thorim (approx. 1.00 ppm in 0.01 N H₂SO₄) from solution occurred within 3 h with fluorite and within 48 h in the case of bentonite. Quartz, jarosite, hematite, sodium feldspar, gypsum and galena removed less than 15% of the thorium from solution. In the coprecipitation studies, barite, anglesite, gypsum and celestite were formed in the presence of thorium (approx. 1.00 ppm). Approximately all of the thorium present in solution coprecipitated with barite and celestite; 95% coprecipitated with anglesite and less than 5% with gypsum under similar conditions. When jarosite was precipitated in the presence of thorium, a significant amount of thorium (78%) was incorporated in the precipitate.