Removal of fluoride from sodium sulfate brine by zirconium pre-loaded chelating resins with amino-methyl phosphonic acid functionality

Fluoride can be removed from brine by loading it onto an aluminum pre-loaded chelating cation exchange resin. In this work, zirconium pre-loaded chelating resin with amino methyl phosphonic acid (AMPA) functional group was investigated and compared with the resin in aluminum pre-loaded form to remove fluoride (<25 mg/L) from sodium sulfate electrodialysis brine solution. With the resin in zirconium pre-loaded form, a series of batch isotherm studies suggested that a change in Na2SO4 brine concentration (6-24 wt%) resulted in a negligible effect on fluoride adsorption. Solution pH in the range of 3-9 was observed to be optimal, and further increase in pH resulted in significant decrease in fluoride loading capacity. Increase in temperature (303 333 K) resulted in lower fluoride loading capacity. Cyclical load-regenerate column studies with zirconium pre-loading solution resin regeneration method showed that a noticeable improvement in the fluoride adsorption was attainable. Notably, for every load-regenerate cycle, fluoride concentration of below 1 mg/L was achieved in effluent. Zirconium concentration in the product solutions were less than 1 mg/L Zr, suggesting that displacement of zirconium from the resin is minimal. This result therefore demonstrated the outstanding stability of zirconium with the AMPA resin.

Automated summary

In this study, zirconium pre-loaded chelating resin with AMPA functional group was found to effectively remove fluoride from sodium sulfate electrodialysis brine solution. The resin demonstrated stability and achieved desirable fluoride adsorption results under a range of operating conditions.