Study of phosphogypsum transformation into calcium silicate and sodium sulfate and their physicochemical characterization

Abstract The valorization of phosphogypsum (PG) is an efficient way to minimize its negative environmental impacts. This work is built on the use of PG as an environmental-friendly source for the production of sodium sulfate and calcium silicate. The reaction of PG transformation is carried out at room temperature using sodium silicate prepared from Tunisian silica sand. The results show that the highest reaction yield (98%) is obtained when the sodium silicate solution ([SiO 3 2− ] = 1.7 mol L −1 ) is dropwise added during 30 min to the aqueous slurry of PG (m water /m PG  = 12) under stirring for 60 min. The liquid product leads to a sodium sulfate salt with high purity by simple evaporation. The solid product retains the majority of impurities and their concentrations are two times lower compared to raw PG, as confirmed by inductively coupled plasma and X-ray fluorescence spectroscopies.