Enhanced visible-light-assisted peroxymonosulfate activation of low-cost perovskite CaFe2O4 for tartrazine degradation: Experimental design modelling

CaFe2O4 (CFO) prepared by a hydrothermal method was used as a catalyst to generate radicals via peroxymonosulfate (PMS) activation for excellent tartrazine (TZ) degradation. Response surface methodology (RSM) with Box-Behnken design (BBD) was used to evaluate the effects of catalyst dosage, PMS and initial dye concentration on the removal. The removal was improved with increasing dosage of PMS or catalyst but declined with increasing initial concentration. The optimum conditions were determined as 0.51 g/L catalyst dosage, 2.4 mM PMS concentration and 10 mg/L initial TZ concentration, achieving with 98.1% degradation of TZ (98.8%). Radical trapping tests showed that the oxidation reactions were mainly directed by sulfate (SO4 center dot(-)) and hydroxyl radicals (OH center dot). Furthermore, CFO/PMS/vis system had no obvious deactivation after five cycles, which implied stability of the catalyst. Thus, the CFO/PMS/vis system was found to be promising approach for wastewater treatment.