Behavior of heavy metals and natural radionuclides along the Moroccan phosphogypsum carbonation process with several alkaline reagents

Phosphogypsum (PG) is the main by-product from the phosphoric acid (PA) production industry being the PA production the basic raw material for producing the modern fertilizers. Because of its high calcium and sulfate content, it is important to emphasize that ecological benefits come from recycling and eventually converting PG into value-added compounds are obtained. This work aims to remedy the environmental problems associated to the large quantities of PG generated in Morocco. Furthermore, three procedures for PG conversion into Ca(OH)2, CaCO3, Na2SO4, K2SO4 and (NH4)2SO4 using hydroxide aqueous mediums were studied. The impurity traces contained in the PG were generally found to be completely transferred into the final calcite. The sulfates produced here are recommended for the use as a fertilizer (K2SO4 and (NH4)2SO4) and in the manufacture of detergents (Na2SO4), and the obtained calcite could be used in cement production, concretes, permeable reactive barriers for pollutants removing, etc.