Comparative study of Fe(III)/peroxymonosulfate, Fe(III)/hydrogen peroxide and Fe(III)/peroxydisulfate systems modified by sinapic acid for micropollutants degradation

Sinapic acid (SA) as an environmentally friendly natural phenolic acid, has the properties of antioxidant because of containing –OH and –OCH 3 on the benzene ring and it is safe. The Fe(III)/peroxymonosulfate (PMS) system modified by SA for enhancing micropollutant degradation had been studied, while weather SA could improve micropollutant degradation in other Fe(III)/oxidants systems was still unclear. The Fe(III)/hydrogen peroxide (H 2 O 2 ) and Fe(III)/peroxydisulfate (PDS) systems modified by SA for micropollutants degradation were studied, the results indicated that SA could enhancing micropollutants degradation by accelerating the Fe(III)/Fe(II) cycle in both systems. In addition, the PMS, the H 2 O 2 and the PDS systems were compared, and ten micropollutants commonly present in natural water were selected to evaluate the oxidation capacity of different systems. The PMS and PDS systems have higher oxidation degradation capacity for ten micropollutants than that of H 2 O 2 system, attributed to the SO 4 •− , HO • and Fe(IV) all contributing to micropollutants degradation. However, in the H 2 O 2 system, ten micropollutants degradation almost entirely relied on HO • . In the PMS and PDS systems, the SO 4 •− played a dominated role for micropollutants removal, attributed to its higher steady-state concentration than HO • and its higher second-order reaction rate with micropollutants than Fe(IV). Economic evaluation indicted that the H 2 O 2 system was more cost-effective than the PMS and PDS systems for micropollutants removal. This was because the cost of H 2 O 2 was lower than PMS and PDS, and concentration of Fe(III), oxidants and SA requirements in the H 2 O 2 system were lower than that in the PMS and PDS systems. Overall, this study provided an economical and environmental-friendly method for the efficient treatment of harmful micropollutants in wastewater.