Study On Emergency Treatment Of Dimethyl Phthalate In Drinking Water By Strong Ionization Discharge

Water safety is a popular topic in the field of environmental safety with the acceleration of industrialization.The increasing accidents of water pollution and the problems of water quality safety seriously threaten the safety of drinking water,even threaten human health.Dimethyl phthalate?DMP?is not only the most harmful organics in phthalates?PAEs?.but also a kind of sudden organic matter.A set of 1.4 t/h strong ionization discharge water treatment system was established and used to emergency treatment of DMP in drinking water.The concentration of active particles included hydroxyl radical?·OH?and ozone?O₃?were tested by different detection methods.The effects of different factors on O₃concentration were analyzed.The effects of different parameters included applied voltage,initial DMP concentration,initial pH values,inorganic ions and radical inhibitors on DMP degradation were investigated.The kinetic analysis of oxidative degradation of DMP under different parameters were completed.The best experimental conditions for removal of DMP by strong ionization discharge and the kinetic parameters were determined.The intermediate products in the process of DMP degradation were tested and verified by different analysis equipment,including high performance liquid chromatography?HPLC?,liquid chromatography mass spectrometry?LC-MS?,total organic carbon analyzer?TOC?,UV-visible absorption spectrometer?UV-Vis?and gas chromatography mass spectrometry?GC-MS?.Then,the electric energy and cost,the energy utilization efficiency and the energy consumed to removal of DMP in different periods were calculated by the measured data form oscilloscope.This study provided a theoretical basis for emergency treatment of the sudden organic matter in drinking water and advised an emergency treatment technology to ensure water safety.The detailed conclusions are as follows:?1?A set 1.4 t/h strong ionization discharge water treatment system was established,and the relationship between the applied voltage and amount of active particles was discussed.Different analytical methods were used to verify the production of O₃,·OH and H₂O₂.The experimental results showed that there has no production of H₂O₂ in strong discharge equipment.The concentration of O₃ and·OH continue to rise within the increasing of applied voltage.The concentration of O₃ in outlet of DBD reactor was up to 74.4 mg/L and the concentration of dissolved O₃ in water reached 21.89 mg/L when applied voltage was 3.8 k V.DMP removal efficiency was decreased by 20%after addition of free radical scavenger,indirectly confirmed the production of·OH in sample solution.?2?The effects of different parameters include applied voltage,initial DMP concentration,initial pH,inorganic ions and radical inhibitors on DMP degradation was investigated.It's proved that DMP removal efficiency was up to 93.6%after 60min under the conditions of applied voltage of 3.8 kV,input frequency of 16 kHz,oxygen flow of 5 L/min,initial concentration of 20 mg/L,initial pH of 6.97,water circulation of 1.4 t/h and treated water of 45 L.The neutral and alkaline condition was favor for the rapid removal of DMP.The oxidation reaction process of DMP was slow down after addition of some inorganic ions like SO₄^2-,HCO₃^-,CO₃^2-and Cl^-.The reaction process of DMP oxidation was inhibited by addition of isopropanol?IPA?and tert-butanol?TBA?.The inhibiting effect on·OH after addition of 30 mg/L IPA was more obvious than TBA,and the best inhibiting efficiency was up to 20%.?3?The kinetic analysis of oxidative degradation of DMP under different parameters as conclusion?2?was carried out,and the variation of reaction rate constant?K?and correlation coefficient?R²?were analyzed.The kinetic analysis results found that the DMP oxidation processes were in accordance with quasi-first order kinetics.The values of K and R² were 0.03948 min^-1 and 0.99134 under optimal experimental conditions.It was indirectly verified that the best experimental conditions for degradation of DMP by strong ionization discharge was described as conclusion?2?.?4?The oxidation degradation mechanism of DMP in water was carried out through different analysis equipment,including HPLC,LC-MS,GC-MS,UV-Vis.The main byproducts of DMP degradation by strong ionization discharge was monomethyl phthalate,carbomethoxy phthalate,phthalic acid,catechol and small molecule acids through comparison of retention time after addition of standard sample.Additionally,the analysis results of GC-MS displayed that there have more than 6 kinds of intermediates,including methyl dihydroxybenzoate,ethyl hydroxyacetate,phthalic anhydride,dimethyl 1,2-phthalate.A series of intermediate products were produced under the combined oxidation of O₃ and·OH.After 50 min,the small molecule intermediates were gradually degraded into CO₂,H₂O and inorganic salts.?5?The energy utilization efficiency of removal of DMP by strong ionization discharge in the optimal experiment condition is 2.286 g/?kW·h?.The electric energy consumption was 0.59 kW·h for degradation of 1 m³ DMP sample solution.The electricity fee was 0.59?based on average electricity fee of 1?/kW·h to calculate.Compared with other water treatment technology,the electricity cost has obvious advantages.Through calculating the energy consumed of degradation of unit concentration of DMP,it was found that the first 30 min was the stage of efficient and rapid oxidation degradation of DMP pollutants,another period from 50 min to 60 min was the key stage that intermediate products degraded into CO₂,H₂O and inorganic salts.The total energy consumed by the oxidation degradation reaction of DMP from0 min to 60 min was much higher than the energy consumed by degradation of the intermediate products from 50 min to 60 min,indicating that the energy produced by strong ionization discharge was mainly used in the process of DMP oxidation degradation,and only a small fraction of energy was used for the oxidation removal of these intermediate products.