Phosphogypsum valorization as building material: mineralogical and chemical characterization before pretreatment
Résumé
Phosphogypsum (PG) is the byproduct of the production of phosphoric acid. Even though valorization is technically possible most of the PG produced worldwide is still stockpiled. Knowledge of geochemical characterization and investigation of his evolution in time could contribute to the choice of management strategy and evaluation of reclaim suitability. This study focused on the geochemical characterization of a gypstack including mineralogical characterization, leaching test and geochemical modeling of four core samples. Mineralogical characterization and total content showed a homogeneous waste. Nevertheless residual acidity varied considerably, clearly showing an evolution of the PG with depth. The existence of a trend with depth was confirmed by leaching tests. Leachates of deeper samples showed a higher concentration in most of the analyzed elements. At a later stage, investigations on elements solubility as a function of pH provided evidences on the effect of neutralization on metals, fluorine and phosphates availability.