Pb Mineral Precipitation in Solutions of Sulfate, Carbonate and Phosphate: Measured and Modeled Pb Solubility and Pb2+ Activity

Lead (Pb) solubility is commonly limited by dissolution–precipitation reactions of secondary mineral phases in contaminated soils and water. In the research described here, Pb free Pb2+ ion activities were measured following precipitation minerals from aqueous solutions containing sulfate or carbonate a 1:5 mole ratio absence presence phosphate over pH range 4.0–9.0. Using X-ray diffraction Fourier-transform infrared spectroscopic analysis, we identified anglesite formed sulfate-containing at low pH. At higher pH, carbonate-sulfate minerals, hydrocerussite leadhillite, preference to anglesite. Precipitates Pb-carbonate systems 6 9 composed cerussite hydrocerussite, with latter favored only highest investigated. The addition into Pb-sulfate resulted Pb3(PO4)2 structurally related pyromorphite prevented formation. Phosphate increased efficiency removal solution decreased activity, causing 99.9% be precipitated. Free using ion-selective electrode revealed lower values than predicted thermodynamic constants, indicating that precipitated may have KSP generally reported databases. Conversely, dissolved was frequently greater based on speciation model accepted constants for ion-pair formation solution. tendency models underestimate while overestimating activity these systems, least range, indicates soluble need correction models.