Heterogeneous catalytic degradation of methylparaben using persulfate activated by natural magnetite; optimization and modeling by response surface methodology

Abstract BACKGROUND In this study, a naturally magnetic semiconductor mineral (NM‐SCM) was used as a highly active, easily separable and green catalyst to activate persulfate (SPS) for the degradation of methylparaben (MeP) in aqueous solution by a heterogeneous catalyst system (SPS/NM‐SCM). NM‐SCM properties were characterized using field emission scanning electron microscope (FESEM), Brunauer–Emmett–Teller (BET), X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. The effects of contributing factors such as solution pH, NM‐SCM loading, SPS dosage and initial MeP concentration on MeP degradation were analyzed using response surface methodology (RSM) and Box–Behnken design (BBD). RESULTS The RSM model obtained from the present study ( R 2 > 0.99) showed a suitable correlation between the predicted values and experimental results of MeP degradation. Under optimized conditions (pH 6.5, SPS 5 mmol L −1 , NM‐SCM 0.3 g L −1 and MeP 10 µmol L −1 ), a removal efficiency of 99.5% and a mineralization degree of 37% were achieved. The removal efficiency of MeP was reduced in the presence of inorganic ions as follows: chloride > nitrate > carbonate > phosphate. After five successive catalyst reuses, the degradation efficiency was >90%, indicating the excellent potential reusability of NM‐SCM catalyst. CONCLUSION Owing to the generation of highly reactive oxidizing species (SO 4 •− ) and easy separation of the catalyst, the integration of NM‐SCM and SPS has great potential for the degradation of MeP from water and wastewater matrices. © 2019 Society of Chemical Industry