Development and optimization of ammonium sulfate and hydroxyapatite production process from phoshogypsum

Process development and optimization studies were conducted for the production of ammonium sulfate (AS) and hydroxyapatite (HAP) from phosphogypsum (PG), by-product of phosphate fertilizer production process, within the scope of this Ph.D. Thesis, which is held in co-operation between University and Industry program. It was aimed to provide a novel approach to the industry in terms of PG management within the compliance with technology development objectives, Circular Economy, and national priorities by utilizing sustainable and domestic raw materials. PG sampling and further salt solution treatments were performed for purification. Further AS and HAP production studies were conducted through PG- H3PO4 reaction at alkali conditions (pH 9, 10 and 11) and 1/5, 1/7,5 and 1/10 solid/liquid (g/mL) ratio. After process modification studies within reaction sets, nitrogen and sulfur content of produced AS samples were characterized in comparison with pure AS product. Product grade, mass conversion (%) and reaction efficiency were calculated. HAP samples were characterized by Ca/P content, and their utilization in bone china production was investigated. Optimum process conditions were determined in terms of product grade and process economic analysis. Optimum process conditions resulted 63% reaction efficiency and 94,95% grade AS product. Ca/P ratio in the HAP samples were analyzed in comparison with commercial bone ash sample and determined as 2,091 and 2,098, respectively.