Phosphate release from synthetic glasses and inhibition of phosphate fixation on ferric hydroxide

Abstract

Release of phosphate from glasses in the systems basalt-K₃PO₄ granite-K₂SiO₃ Na₂SiO₃-apatite has been studied. Equilibrium leachate concentrations in water are attained in 3-5 hr (K⁺, 5-60 μg cm^-3; PO₄ ³-, 2-15 μg cm^-3). Glass composition, pH, and grain size influence solubility. Phosphate fixation on freshly precipitated Fe(OH)₃ and on iron-rich laterites appear to be inhibited when glasses are rich in Na-K silicates. This may be due to surface modification of Fe(OH)₃ by the formation of sodium ferric silicates which are known to be stable at low temperatures.