Study On Atmospheric Low-Temperature Plasma In The Treatment Of Antibiotics And Other Typical Organic Pollutants

Currently,the development of new pollutant control technologies has become a research hotspot,it is important to explore efficient and green technology for pollutant treatment.Low-temperature plasma technology,as one emerging advanced oxidation method,has been introduced to treat various pollutants,and has received widespread attention based on its advantages of high efficiency,simplicity,and environmentallyfriendly approach.However,there are still some issues need to be further explored in the process of realizing the plasma application such as improving the treatment efficiency for different contaminants,optimizing the treatment method for different application scenarios,exploring the treatment efficiency and degradation mechanism for different pollutants and evaluating bio-toxicity for degradation products.To this end,this thesis would construct different treatment devices,optimize different treatment methods and explore the treatment efficiency,degradation mechanism and biological safety of plasma treatment for several typical pollutants in environmental water,namely antibiotics(tetracycline,norfloxacin,levofloxacin,sulfadiazine and chloramphenicol),organophosphorus pesticides(methyl parathion)and persistent organic pollutants(3,3,4,4,-tetrachlorobiphenyl).The obtained the main results are as follows:1.The treatment efficiency and degradation mechanism of tetracycline in water were explored by low-temperature plasma(LTP),showing that the removal efficiency of tetracycline was higher at the acidic solution compared to alkaline solution,and the main degradation mechanisms involved include the fracture reaction of amino groups,hydroxylation reaction and ring-opening reaction.The E.coli DH5α was used as a model organism for biological toxicity assessment,and the toxicity estimation software tool(T.E.S.T)was used to predict the toxicity of the product,which verified the bio-safety of the degradation product.Therefore,this work provides a new idea for improving the treatment efficiency of tetracycline.2.The levofloxacin and sulfadiazine mixtures were treated by dielectric barrier discharge(DBD)plasma,showing that the treatment efficiency for the mixture of antibiotics was enhanced as compared to the treatment of single antibiotics.In the DBD treatment with different working gas components,the removal rate of levofloxacin was increased with the increase of oxygen-nitrogen ratio,while the removal rate of sulfadiazine was decreased with the increase of oxygen-nitrogen ratio.The E.coli DH5α.zebrafish(Danio rerio),and Hela cells(human cervical cancer cells)were used to evaluate the bio-toxicity and cytotoxicity of the degradation products,and the evaluation results verified the bio-safety of the degradation products.As such,this work may provide a new idea for the effective treatment of mixed antibiotics in wastewater.3.The norfloxacin and chloramphenicol mixtures were treated by applying lowtemperature atmospheric pressure plasma jet(CAPJ)and plasma activated water(PAW),and the treatment conditions were optimized and the relevant mechanism was explored.The analysis of the plasma-induced RONS confirmed that·OH and 1O2 played the major role in norfloxacin and chloramphenicol treatment.Besides,it was verified that PAW produced by air-plasma could enhance the removal efficiency due to the continuous release of 1O2 in the PAW after the direct CAPJ processing.Especially,the additional increase in norfloxacin removal rate can attribute to the active chlorine contribution produced by the oxidation of chloride ions from the decomposition of chloramphenicol.The E.coli DH5α,zebrafish(Danio rerio),and mouse fibroblasts(L-929)were used to evaluate the bio-toxicity and cytotoxicity of the degradation products,and the evaluation results verified the bio-safety of the degradation products.As such,this work not only demonstrates the new features in the CAPJ treatment of mixed antibiotics,but also provides a new effective way of application of plasma technology in the treatment of multiple antibiotics contaminated wastewater.4.The methyl parathion was treated by dielectric resistance barrier discharge(DBD)plasma.The detoxification effect was explored based on different working gases and found that the oxidation by O3 should be avoided as it could produce the more toxic substance,methyl paraoxon.The treatment of methyl parathion with a higher removal rate and detoxification effect could be achieved using He and N2 as the working gas.E.coli DH5α,Hela cells and acetylcholinesterase were used to evaluate the bio-toxicity,cytotoxicity and neurotoxicity of the degradation products,and the evaluation results verified the bio-safety of the degradation products.As such,the present work demonstrate that the selection of plasma discharge conditions(working gas)was important for detoxification effect in some special cases.5.The PCB77(a typical POPs)was treated by dielectric barrier discharge(DBD)plasma.The results show that DBD can effectively degrade and remove PCB77 in aqueous solution.He-DBD showed the highest removal efficiency of PCB77 compared to other working gases,in which hydroxyl radical plays the major role in the PCB77 treatment.E.coli DH5α was used to evaluate the bio-toxicity,and the evaluation results verified low bio-toxicity of the degradation products.As such,this work provides an alternative effective approach for treatment of POPs in the environment.In summary,this thesis focused on the important issues and technical bottlenecks in promoting the application of plasma technology in wastewater treatment,provides relevant results and elaborates mechanisms,and further provides guidance for the application and development of low-temperature plasma technology in the field of environmental pollutant removal.