Removal of Sunset Yellow dye using heterogeneous catalytic degradation with magnetic Fe3O4/persulfate/ultrasound system

Azo dyes with a complex aromatic structure released into the environment by various industries and make the main concern for humans. In this study, nanoparticles of magnetic Fe3O4 were synthesized with co-precipitation method and employed as an activator for persulfate (PS) for degradation of Sunset Yellow (SSY) molecules in the presence of ultrasound irradiation (US). Decolorization tests were carried out as a control test with different processes (Fe3O4, Fe3O4/PS, Fe3O4/PS/US, zerovalent iron (ZVI)/PS/US, US, and PS). Adsorption study before the oxidation experiments showed that the maximum adsorption occurred at an initial 30 mM and then reached the equilibrium at 60 min. In addition, the oxidation experiments revealed that the maximum degradation rate was obtained at acidic pH, 0.4 g/L of catalyst dose and 4 mM of persulfate so that at a reaction time of 120 min, 97.4% of dye with the initial concentration of 20 mg/L was removed. The effect of various anions showed that anions especially carbonate acted as a radical scavenger and decreased the degradation of dye molecules. Also, the enhancement factor (R = 1.08) indicated that the synergetic effect that occurred at Fe3O4/PS/US system and catalytic activity can critically affect the removal rate of SSY. The Fe3O4/PS/US system as a promising method could be considered as an efficient and effective technique for the degradation of dye molecules of wastewater.