Enhanced reactivity of apatite composite derived by phosphate treatment of gypsum with fluoride ions

Abstract

Waste gypsum board is one of the severe wastes that requires recycling because its emission annually increases. In this study, we attempted to produce a composite consisting of dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAp) from gypsum and phosphate ions in an aqueous solution. The DCPD-HAp composite was successfully obtained by modifying the pH in the solution to be more basic after the preparation of DCPD. The composite material appeared to have enhanced reactivity toward fluoride ions. These results highlight a novel use of gypsum, which is helpful for the multiple recycling of phosphate and fluoride ions in wastewater without any virgin resources.