Phosphate recovery from treated municipal wastewater using hybrid anion exchangers containing hydrated ferric oxide nanoparticles

BACKDROUND This study presents the evaluation of two ion exchangers (granular and fibrous) impregnated with nanoparticles of hydrated ferric oxide (HFO) as selective sorbents for phosphate recovery from aqueous solutions. The hybrid impregnated anion exchangers combine the durability and mechanical strength of a polymeric weak base anion exchange resin with the high sorption affinity of HFO towards phosphate species. Dynamic experiments were carried out and data obtained were fitted to a well-known fixed-bed sorption model. RESULTS The theoretical sorption capacities reported by the Thomas model were in good agreement to the breakthrough experimental capacities determined from the sorption data. The sorption capacity decreased when using wastewater treatment plant secondary effluents in comparison with synthetic water mainly due to the presence of organic matter and suspended solids. The phosphate sorbed on the impregnated ion exchangers were efficiently desorbed by using a 0.5 mol/L sodium hydroxide solution, reporting up to 90% of recovery. CONCLUSION The reusability of sorbents was evaluated through five sorption–desorption working cycles. Fiban-As was able to operate up to three consecutive cycles with good sorption performance whilst a significant decrease of sorption capacity after the first cycle was observed for FO36 resin.