Composite Material with Calcium Sulfate and Calcium Phosphate for Heavy Metals Retention

AbstractPorous composite materials containing calcium phosphate and calcium sulphate were elaborated by mixing various hydroxyapatites with calcium sulphate hemihydrate, adding water and moulding the paste into shape. The composite material was broken into small granules of 5mm size to test for heavy metal retention in a column configuration. It was found that the amount of zinc ions retained depended on the contents in apatites present in the composite, and that results were similar to the results obtained for equivalent amounts of pure apatite put in the same column. These results are interesting because previous work on pure apatites showed release of small sub-micrometer sized metal phosphates when the apatite particles were contacted with heavy metals in a flow-through experiment. Thus, the plaster matrix does not prevent metal uptake from aqueous solutions and helps minimize release of fines from the used apatite. The breakthrough curves and zinc retention capacities will be presented for various composite compositions, flow rates and zinc concentrations