Sustainable Approach for Recovery of Sulfur from Phophogypsum

Phosphogypsum releases have a detrimental effect on flora and fauna and also cause economic loss due to the loss of sulfur. This study contributes to solving this problem using a process that consists of the valorization of this byproduct. A new sustainable method that consists of using sulfuric acid is proposed to process the Algerian phosphogypsum to recover the sulfur, which is imported in huge quantities until today. The experiments carried out in this investigation have enabled us to recover sulfur in the form of SO₂ using appropriate additives such as silica, alumina, clay, and charcoal as reducing agents. These additives accelerate the desulfurization process and decrease the decomposition temperature of calcium sulfate. As a result, these additives allow the reduction of energy used and simultaneously increase the concentration of SO₂. X-ray diffraction shows that thermochemical decomposition is not complete and that the sulfur present in the residue exists in the form of CaSO₄ and CaS at 1150 °C. After calcination of phosphogypsum, the analysis of the residues obtained shows that they have a chemical composition almost identical in terms of quality to that of clinker, which can further be used in the cement production.