Amorphous calcium silicate as a chemisorbent for phosphate

Amorphous calcium silicate (ACS), a novel silicate material developed as filler for use in paper manufacture, has shown an affinity for the chemisorption of orthophosphate from an aqueous solution obeying a Freundlich isotherm. Removal efficiencies of up to 100% were achieved at environmental- and waste-scale concentrations of phosphate of between 0.01 and 100 mg P l−1. Chemisorption studies indicated loadings up to 1.9 mmol HxPO4(3−x)− g−1 ACS were achievable. Kinetics studies comparing the rate of consumption of phosphate have shown that H2PO4− is kinetically favoured and chemisorbed with higher loadings, and hence greater efficiency. This is a significant improvement on other adsorbent-based methods for the removal of phosphate.