Nickel sulfate solution fluoride separation with hydrous zirconium oxide

Fluoride is an impurity in nickel sulfate production, which is required for electric vehicle batteries. Hydrous zirconium oxide (HZO) was evaluated for removing fluoride from nickel sulfate solution. Maximum fluoride removal occurred at pH value 4 and optimal pH value is 4-5, considering Zr solubility. Fluoride availability decreases with pH due to hydrogen fluoride and zirconium fluoride aqueous species. Fluoride removal is initially rapid, with 50 wt.% removal in 7 min, followed by slow removal up to 68 wt.% after 72 h and follows second order rate kinetics. Fluoride removal was dominated by an ion exchange mechanism and resulting Zr-F bonds were observed using Fourier-transform infrared spectroscopy. The presence of nickel sulfate decreased loading capacity compared to a salt-free solution. HZO maintained adsorption capacity through five cycles of loading and regeneration.

Automated summary

This study evaluated the removal of fluoride from nickel sulfate solution using hydrous zirconium oxide (HZO). The optimal pH range for fluoride removal was found to be 4-5, and the removal process followed second order rate kinetics, primarily controlled by an ion exchange mechanism.