| Summary: | Minerals from the phosphate groups are used in environmental engineering as thermodynamically stable vehicles for heavy metals such as zinc. The hopeite Zn3(PO4)2·4H2O was synthesized and characterized by X-ray diffraction and scanning electron microscopy. The solubility of the hopeite was measured at 25°C. The average solubility product, log Ksp, for the reaction Zn3(PO4)2·4H2O ⇔ 3Zn2+ + 2PO43- + 4H2O at 25°C is –35.72 ± 0.03. The free energy of formation, ΔG°f,298, calculated from this measured solubility product is –3597.4 ± 1.0 kJ mol-1. The immobilization of zinc in the hopeite structure offers the possibility of developing an effective method for removing Zn from wastewater, water and soils.
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