Preparation of magnetic ZnFe2O4 nanosphere photocatalyst for high concentration ammonia nitrogen wastewater treatment

High concentration ammonia nitrogen (NH4+-N) wastewater caused a great threat on the safety of water resources. Consider that photocatalysis is an environmentally friendly technology, which can effectively removel pollutants. Herein, magnetic ZnFe2O4 nanosphere photocatalyst was prepared by sol-gel method at a calcination temperature of 300 °C, 400 °C and 500 °C and applied in eliminating high concentration NH4+-N wastewater pollutants under economical 400 °C temperature in this study. The effect of pH on magnetic ZnFe2O4 nanosphere photocatalyst treating high concentration NH4+-N wastewater was investigated. Optimally, 100 % of the initial NH4+-N (1000 mg/L) was removed, photocatalytic rate and stripping rate were 84.9% and 15.1% respectively, and NO3--N and NO2--N were barely detected at pH of 9.0 in 120 min. The quenching experiments showed that h+ and •O2- were the key reactive species to photodegrade NH4+-N. The mechanism of high concentration NH4+-N removal were proposed. Moreover, NH4+-N removal rate of recovered magnetic ZnFe2O4 nanosphere photocatalyst by magnetic force after five cycles still remained over 90%. This study demonstrated that magnetic ZnFe2O4 nanosphere photocatalyst could be a promising catalyst for the treatment of the high concentration NH4+-N wastewater.