Chemical treatment of phosphogypsum and its potential application for building and construction

This study investigated the use of a chemical treatment process to treat phosphogypsum waste generated from a phosphoric acid production plant and render the final product useful for building and construction applications. Four reagents namely; citric acid, oxalic acid, sodium carbonate and sodium bicarbonate were used for the reduction and removal of hazardous and radioactive constituents in the material. The results for the untreated gypsum revealed that phosphogypsum used in this study was radioactive and laden with radionuclides such as ²¹⁰Pb, ²¹⁴Pb, ²¹⁴Bi, ²²⁶Ra, ²⁰⁸Tl, ²²⁸Ac, ⁴⁰K. The best leaching reagent was found to be 0.5 M citric acid as it reduced the relative proportion of contaminants contained in the material. The treated product was blended with lime and fly ash and the effect of curing temperature and phosphogypsum content on the unconfined compressive strength was investigated. Curing at higher temperatures proved to improve the strength of the specimen, the highest strength were obtained at PG content of 30%.