Intensified peroxydisulfate/microparticles-zero valent iron process through aeration for degradation of organic pollutants: Kinetic studies, mechanism and effect of anions

Water pollution by organic dyes has been considered by water and wastewater engineers. Several methods have been suggested in literature especially advanced oxidation processes. Peroxydisulfate (PDS)-based processes are a powerful technique for the degradation of organic pollutants. Micro-zero valent iron (mZVI)/aeration is also a simple method for the generation of Fenton reagent. In this study, PDS/mZVI/aeration was used for the first time to degrade Acid Blue 9 (AB9). Operating parameters, various anions, iron release and reaction kinetic were comprehensively investigated. A rapid degradation of AB9 was observed after only 10 min under conditions of PDS = 1.5 mM and mZVI = 0.5 g/L. Pseudo-first order kinetic model was fitted for AB9 degradation with the rate constant of 0.2039 min−1. In contrast with mZVI, zero valent aluminum was ineffective to activate PDS. Scavenging tests demonstrated that sulfate radical (SO4 [rad]-) was dominated for the degradation of AB9. Carbonate and nitrite anions almost completely suppressed AB9 degradation. The negative effect of anions on the process was based on this order CO3 2− > NO2 − > I− > H2PO4 − > Br− > Cl− > NO3 − ≥ SO4 2−. Carboxylic acids generated arise from AB9 degradation were monitored. The results showed that further oxidation led to the generation of the small molecules of carboxylic acids. Around 60% of organic carbon of AB9 was mineralized during 120 min reaction. 7.0% of mZVI was released in the solution. FESEM, EDS, and XRD analyses showed that mZVI was oxidized to Fe2O3. Finally, PDS/mZVI/aeration showed a simple and efficient process for degradation of organic dye. © 2020 Elsevier Ltd