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Synthesis and solubility of hopeite Zn3(PO4)2·4H2O

Bajda Tomasz, Rogowska Melania, Pawłowska Agnieszka

Mineralogia

2023

Vol. 54, iss. 1

78--81

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+ + 2PO4 3− + 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.

Synthesis and solubility of brompyromorphite Pb5(PO4)3Br

Janicka U., Bajda T., Manecki M.

Mineralogia

2012

Vol. 43, iss. 1/2

129--135

The bromide analogue of pyromorphite Pb5(PO4)3Br was synthesized and characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The solubility of the brompyromorphite was measured at 25°C and pH values of 2.0, 2.6 and 3.2. For the 3 pH measurements, the average solubility product, log KSP, for the reaction Pb5(PO4)3Br ⇔ 5Pb2+ + 3PO4 3– + Br– at 25ºC is –77.38 ± 0.70. The free energy of formation, ΔG˚f,298, calculated from this measured solubility product is –3724.7 ± 4.3 kJ mol−1. These results confirm that brompyromorphite is more soluble than pyromorphite.