Recovery of Ca(OH)₂, CaCO₃, and Na₂SO₄ from Moroccan phosphogypsum waste

The phosphate industry is commonly associated with a large amount of waste phosphogypsum in its solid form. The vast majority of phosphogypsum is usually discharged into the environment without any treatment and reuse. In this work, we investigate the valorization of the Moroccan phosphogypsum for manufacturing valuable products such as Ca(OH)₂, CaCO₃, and Na₂SO₄. These compounds are widely used for industrial applications. The reaction for the chemical conversion process of phosphogypsum (PG) is made in the aqueous solution of sodium hydroxide. The experiments were conducted at room temperature with an exact stoichiometric proportion of PG and NaOH. The efficiency of CO₂ capture using phosphogypsum dissolution and portlandite carbonation was established at various concentrations of Ca(OH)₂. Parallel experiments using synthetic gypsum samples were carried out to compare the solid phases precipitated from the by-product phosphogypsum. The pH and electrical conductivity measurements were used to monitor the time evolution of the reaction. In addition, an X-ray diffraction analysis was performed to characterize the starting material, synthetic gypsum, and Moroccan phosphogypsum, and to investigate the carbonation efficiency and purity of the solid products.