Study of defluorination by thermal treatment of phosphogypsum under steam atmosphere

s This study investigates the removal of fluorine (F) impurities from phosphogypsum (PG) using steam as the reaction medium. The effects of the reaction atmosphere, temperature, time, and steam velocity on F impurities removal were systematically examined. The results showed that with a steam velocity of 0.0184 m·s −1 , a reaction temperature of 700 °C, and a reaction time of 60 min, the F removal rate reached 95.87%. Further investigations into the defluorination mechanism revealed that steam and SiO 2 synergistically enhance fluoride removal, playing a crucial role in improving the defluorination efficiency. Kinetic analysis of the defluorination process, based on the shrinking core model (SCM), indicated that internal diffusion is the rate-controlling step, with the activation energy of 30.12 kJ·mol −1 . This study identifies optimal conditions for PG defluorination and proposes a defluorination mechanism, contributing to the theoretical understanding of impurity removal through the thermal treatment of PG.