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.