Synthesis of high purity calcium fluoride from fluoride-containing wastewater

The present reports a new process for recovering high purity calcium fluoride from wastewater. A column reactor system with calcium sulfate dihydrate as reaction medium was used. It was found that spherical calcium fluoride with the purity of beyond 99 % was successfully obtained, and meanwhile the concentration of fluoride in wastewater was reduced to less than 10 mg/L. The present process realized the effective removal of fluoride while recovering high-purity calcium fluoride. Parameters including initial fluoride concentration, the influent flow rate, wastewater pH and time had a great effect on the fluoride removal efficiency. The fluoride recovery process included dissolution of calcium sulfate dihydrate and formation of calcium fluoride by the reaction of Ca2+ ion and F- ion. When the initial concentration of fluoride in wastewater was 1000 mg/L, the fluoride removal efficiency of the two column reactors in series was more than 99 %. This work provides an effective strategy which can be adopted in resource utilization and standard discharge of fluorine-containing wastewater.

Automated summary

This study presents a new process for recovering high purity calcium fluoride from wastewater. A column reactor system with calcium sulfate dihydrate as reaction medium was used, resulting in the successful production of calcium fluoride with purity exceeding 99% and reducing fluoride concentration in wastewater to less than 10 mg/L. The process effectively removes fluoride while recovering high-purity calcium fluoride and various parameters such as initial fluoride concentration, flow rate, pH, and time significantly influence fluoride removal efficiency. The study offers an effective strategy for resource utilization and standard discharge of fluorine-containing wastewater.