Solubility study and valorization of phosphogypsum salt solution

This paper aims to transform a phosphogypsum (PG) solution to non-toxic and industrially useable compounds. For that, the solubility of the Tunisian PG was studied in different aqueous solutions in order to determine which of them is best for its dissolution. After monitoring the ionic conductivity of each solution as a function of the added amount of PG, it was concluded that the latter is better dissolved in a sodium chloride solution. A maximum value (5.3 g/L) was obtained in 25 g/L NaCl solution. The analysis of the filtrate, obtained after PG dissolution, had shown that it mainly contains sodium, sulfate and calcium ions. The suggested valorization method comprises formation of calcium carbonate after (NH4)2CO3 addition to the filtrate's solution, decarbonation with H2SO4 and evaporation of the final solution. The formed NaHSO4.H2O crystals were washed with acetone and dried in the air. All the compounds produced in this work were identified by infrared spectroscopy and X-ray diffraction.