Efficacious degradation of ethylene glycol by ultraviolet activated persulphate: reaction kinetics, transformation mechanisms, energy demand, and toxicity assessment.

Ethylene glycol or 1,2-ethanediol (EG) is a persistent and toxic substance in the environment and extensively applied in petrochemical, surfactants, antifreeze, asphalt emulsion paints, cosmetics, plastics, and polyester fiber industries. Degradation of EG by using ultraviolet (UV) activated hydrogen peroxide (H2O2) and persulfate (PS) or persulfate anion (S2O82-) based advanced oxidation processes (AOPs) were explored. The result obtained demonstrate that UV/PS (85.7 ± 2.5%) has exhibited improved degradation efficiency of EG as compared to UV/H2O2 (40.4 ± 3.2%) at optimal operating conditions of 24 mM of EG concentration, 5 mM of H2O2, 5 mM of PS, 1.02 mW cm-2 of UV fluence, and pH of 7.0. Impacts of operating factors, including initial EG concentration, oxidant dosage, reaction duration, and the impact of different water quality parameters, were also explored in this present investigation. The degradation of EG in Milli-Q® water followed pseudo - first order reaction kinetics in both methods having a rate constant of about 0.070 min-1 and 0.243 min-1 for UV/H2O2 and UV/PS, respectively, at optimum operating conditions. Additionally, an economic assessment was also conducted under optimal experimental conditions, and the electrical energy per order and total operational cost for treating per m3 of EG-laden wastewater was observed to be about 0.042 kWh m-3 order-1 and 0.221 $ m-3 order-1, respectively, for UV/PS, which was slightly lower than UV/H2O2 (0.146 kWh m-3 order-1; 0.233 $ m-3 order-1). The potential degradation mechanisms were proposed based on intermediate by-products detected by Fourier transform infrared (FTIR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). Moreover, real petrochemical effluent containing EG was also treated by UV/PS, demonstrating 74.7 ± 3.8% of EG and 40.7 ± 2.6% of total organic carbon removal at 5 mM of PS and 1.02 mW cm-2 of UV fluence. A toxicity tests on Escherichia coli (E. coli) and Vigna radiata (green gram) confirmed non-toxic nature of UV/PS treated water.

Advanced oxidation processes: Performance, advantages, and scale-up of emerging technologies.

Advanced oxidation processes (AOPs) are promising technologies for partial or complete mineralization of contaminants of emerging concern by highly reactive hydroxyl, hydroperoxyl, superoxide, and sulphate radicals. Detailed investigations and reviews have been reported for conventional AOP systems that have been installed in full-scale wastewater treatment plants. However, recent efforts have focused on the peroxymonosulphate, persulphate, catalytic ozonation, ultrasonication and hydrodynamic cavitation, gamma radiation, electrochemical oxidation, modified Fenton, and plasma-assisted AOPs. This critical review presents the detailed mechanisms of emerging AOP technologies, their performance for treatment of contaminants of emerging concern, the relative advantages and disadvantages of each technology, and the remaining challenges to scale-up and implementation. Among the evaluated technologies, the modified electrochemical oxidation, gamma radiation, and plasma-assisted systems demonstrated the greatest potential for successful and sustainable implementation in wastewater treatment due to their environmental safety, compatibility, and efficient transformation of contaminants of emerging concern by a variety of reactive species. The other emerging AOP systems were also promising, but additional scale-up trials and a deeper understanding of their reaction kinetics in complex wastewater matrices are necessary to determine the technical and economic feasibility of full-scale processes.