Application of the UV/sulfoxylate/phenol process in the simultaneous removal of nitrate and pentachlorophenol from the aqueous solution

This study was aimed to evaluate the performance of hydrated electron (e(aq)(-)) and SO2-center dot generated from reaction between UV/sulfoxylate/phenol ring (USP) for the simultaneous removal of nitrate and pentachlorophenol (PCP) from aqueous solutions. The results indicated, with adding PCP (50 mg L-1) in the photoreactor, 94% of NO3- reduction (50 mg L-1) (with N-2, NO2- and NH4+ selectivity of 98.9%, 021% and 0.85%, respectively) was achieved; while in the backbite of PCP in solution, 91.6% of NO3- was reduced (with N-2, NO2- and NH4+ selectivity of 80.15%, 19.6% and 0.19%, respectively). Therefore, it turned out that the hydrated electrons generated in UV/phenol process, has a significant role in the reduction of nitrate and resulted in the higher N-2 selectivity and the lower nitrite selectivity. This point can be the great importance from the public health point of view. Also 96% of PCP degradation and 87% of PCP mineralization were obtained by SO2-center dot generated from UV/sulfoxylate. The optimum conditions (the maximum degradation and mineralization of PCP and also the maximum nitrate reduction (with the higher N-2 selectivity and the lower nitrite selectivity)), were obtained at sulfoxylate dosage, 100 mg L-1; reaction time, 180 min and pH, 7.0. The USP process indicated the higher performance of USP than the UV alone and sulfoxylate alone, as nitrate and PCP reduction rates by UV alone, sulfoxylate alone and USP processes were obtained (24% and 66%), (18% and 17%) and (94% and 96%), respectively. Also kinetic studies were proved the results mentioned above, as values of r(ob)(s), for USP in the nitrate reduction and degradation of PCP were (17 and 31 times) and (1.4 and 4.25 times) than that of the sulfoxylate alone and UV alone, respectively. Values of energy consumption for the removal of nitrate and PCP were 26 kWh m(-3) and 22 kWh m(-3), respectively. The several intermediate products including acetic acid, ethane-1,2-diol, acetic acid dihydroxyethene isomers, benzoquinone, 2-chlorobenzene-1,4-diol, adipic acid were identified by the LC/MS analysis. Therefore, it was found the USP process clue to smaller total cost and energy consumption and also the higher r(ob)(s), might be an efficient method for the simultaneous removal of nitrate and pentachlorophenol (PCP) form aqueous solution. (C) 2020 Elsevier B.V. All rights reserved.