Valorisation of phosphogypsum waste as K2SO4fertiliser and portlandite Ca(OH)2

Series of experiments were performed to follow the reactivity of Moroccan phophogypsum with KOH in order to valorise this environmentally harmful solid waste. The experiments were carried out in aqueous solution under different conditions: with excess of reagent KOH or in stoichiometric proportions and by varying reaction duration at room temperature. The complete decomposition of phosphogypsum (PG) waste into portlandite Ca(OH)2and arkanite K2SO4was evidenced by X-ray diffractometry and Fourier transform infrared spectroscopy. The optimum decomposition was obtained with stoichiometric mixture using 0.6 M phosphogypsum and 1.2 M KOH. The full decomposition of phosphogypsum was achieved at room temperature in one hour. The results show how phosphogypsum can efficiently converted to valuable products with high purity and in mild conditions.