Recovery and removal of fluoride from fluorine industrial wastewater by crystallization process: a pilot study

Recovering fluoride from wastewater has large economic and environmental significance within the fluorine industry. A novel crystallization process was proposed for the recovery and the removal of fluorine-containing industrial wastewater by steps. A pilot-scale reaction-separation integrated reactor was used to recover the sandy cryolite via crystallization. A pilot-scale fluidized bed reactor was used to recover the sandy calcium fluoride via crystallization. The results showed that the recovery rate of cryolite was greater than 70%, with a purity of more than 89%. The qualities of cryolite products could meet the national standard for synthetic cryolite in China. The purity of the calcium fluoride was greater than 71%, with a particle size of 153.1 μm, and a water content of 27%. The qualities of calcium fluoride products could meet the national standard of comminuted fluorspar in China. Both the cryolite products and the calcium fluoride products could be reused as raw materials. The fluoride concentration of the wastewater was less than 10 mg/L, which met the national discharge standard in China.