Preparation of a novel ZnFe2O4 /oyster shell powder composite photocatalyst for visible-light-driven photocatalytic degradation of ammonia nitrogen wastewater

Abstract

In this study, ZnFe2O4/oyster shell powder (ZF-OSP) composite photocatalyst was successfully synthesized via sol-gel method for the purpose of removing ammonia nitrogen (NH4+-N) from wastewater. The NH4+-N degradation rate by ZF at pH of 6.2 in 210 min was observed to be 19.5%. To improve the NH4+-N treatment efficiency of ZF, a high pH level of 11 was required by adding NaOH. In comparison, the ZF-OSP composite photocatalyst with a mass ratio of 1:1 achieved an impressive 91.8% elimination of NH4+-N at pH of 6.2 in 210 min without the requirement for additional pH adjustment and pH was stably maintained at 9.5–10.0. In addition, NO3--N and NO2--N were barely accumulated during the NH4+-N degradation process. Quenching experiments demonstrated that the degradation of NH4+-N in wastewater was significantly mediated by the participation of h+, •OH and •O2-. Moreover, NH4+-N removal rate of recovered ZF-OSP/1:1 composite photocatalyst by magnetic force after the first reuse cycle remained above 80.8%. Overall, the ZF-OSP/1:1 composite photocatalyst could not only address the challenge of recovery for non-magnetic powder photocatalysts, but also reduce the use of NaOH and offer a potentially effective and environmentally friendly solution for water treatment.