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

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 mu mol 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 (SO4 center dot-) 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. (c) 2019 Society of Chemical Industry