Degradation of 4-chlorophenol using catalyzed peroxymonosulfate with nano-MnO2/UV irradiation: Toxicity assessment and evaluation for industrial wastewater treatment

4-chlorophenol (4-CP) is one of the most important phenolic compounds in various industries. Different technologies have been applied for 4-CP degradation in aquatic environment. Current study is focused on 4-CP degradation by the combination of UV and MnO2 for peroxymonosulfate (PMS) activation to degrade 4-CP. MnO2 nanoparticles were synthesized and characterized by X-ray powder diffraction, field emission scanning electron microscope, energy-dispersive X-ray spectroscopy and Brunauer Emmett Teller (BET). The effects of operational parameters were evaluated and their results indicated the highest performance in pH = 4.0, 1 mM PMS and 0.25 g/L MnO2. Complete degradation of 4-CP during 30 min was a representative of high performance of UV/MnO2/PMS. Kinetic study showed that the co-activation of PMS by MnO2 and UV had a synergistic effect on 4-CP degradation. MnO2 could keep its performance at least 4th cycle while Mn leaching was negligible. Bicarbonate and hydrogen phosphate ions suppressed the performance of the process in degradation of 4-CP whereas no change was observed in the presence of chloride ions. Quenching experiments showed that hydroxyl radical was dominant radical for 4-CP degradation. The results of toxicity and biodegradability tests indicated that treated sample by UV/MnO2/PMS process was relatively non-toxic and easy biodegradable. The function of UV/MnO2/PMS system for treatment of real industrial wastewaters (pharmaceutical and petrochemical wastewaters) was tested. Finally, it was concluded that hybrid activation of PMS can be a new perspective for PMS-based processes to treat industrial wastewater. (C) 2018 Elsevier Ltd. All rights reserved.