Degradation Of Paracetamol By Non-thermal Plasma

In recent years,the frequent detection of paracetamol which is one of non-steroidal anti-inflammatory drugs（NSAID）in the effluent of sewage treatment plants,surface water,groundwater and even drinking water increased environmental concerns.Because the persistence of paracetamol in the aquatic environment is a potential threat to both humans and ecosystems.Therefore,the efficiency and influencing factors of paracetamol removal by non-thermal plasma generated by spray dielectric barrier discharge（DBD）were studied.The applicability of adding oxidants to remove NSAID paracetamol and diclofenac sodium was explored.The experiments showed that:It was found that air plasma used in paracetamol solution will inevitably lead to the production of reactive oxygen species（ROS）and reactive nitrogen species（RNS）,and then·OH,O₃,H₂O₂,NO₂^-and NO₃^-can be detected in the solution.Among them,the presence of·OH,O₃ and H₂O₂ improves the oxidation capacity of non-thermal plasma.NO₂^-reacted with paracetamol to form an intermediate product of 3-nitro-4-acetamidophenol.The presence of NO₂^-retarded the removal of 3-nitro-4-acetamidophenol and thus the TOC,however,the nitrate ion did not.The orthogonal experiment showed that the removal of TOC was significantly influenced by the recirculation flow rate,treatment time and discharge power.Reducing the recirculation flow rate,extending the treatment time and increasing the discharge power can significantly improve the TOC removal rate.Considering the energy yield,the optimal parameters for paracetamol mineralization were treatment for 30 min,discharge power of 500 W,and recirculation flow rate of 50 mL/min,under which a TOC removal rate of 47.4%was achieved.The degradation of paracetamol followed a sequence of 3-nitro-4-acetamidophenol,nitrosophenol/acetamide,N-methylacetamide,acetamide and small molecule organic acids in the DBD reactor,and these intermediates were finally oxidized to CO₂、H₂O and NO₃^-.When adding 2.00 mmol/L sodium persulfate and 1.35 mmol/L hydrogen peroxide to the solution respectively,the TOC removal rates of paracetamol were increased by 9.6 and 26.2 times,and the TOC removal rates of diclofenac sodium were increased by 0.6 and 1.7 times.Oxidants had synergistic effect on DBD treatment of pollutants,and the TOC removal rate of pollutants increased with the increase of oxidants concentration.