Enhanced absorption of SO from phosphogypsum decomposition by phosphate slurry for phosphoric acid production.

Phosphogypsum (PG) is a major industrial by-product of wet process phosphoric acid production, and untreated PG stockpiled on land will cause severe environmental pollution. Thermal treatment of PG is currently the mainstream treatment method PG can be thermally decomposed to produce CaO, and the decomposition process produces large amounts of SO. In this paper, phosphate slurry was used to absorb SO generated during the PG decomposition to produce phosphoric acid. The effects of operating conditions such as pressure, inlet SO concentration, and additive content on the desulfurization efficiency, as well as phosphoric acid yield, were investigated. Under the optimal experimental parameters, the desulfurization efficiency was 100% in the first 3 h, and decreased to 67.42% after 5 h, the maximum phosphate concentration in the solution was 1445.92 mg/L. The Density functional theory (DFT) calculations showed that SO and O adsorbed on the surface of PO underwent to generate SO, which can react with HO to produce HSO. Moreover, it was found that Fe could enhance the catalytic oxidation process of SO and O by decreasing the reaction energy barrier. This study should be helpful for the recycling of phosphorus resources.