1.Introduction

Dimethyl phthalate(DMP)was mainly used in the manufacture of resins,paints,dyes,coatings,plastics,cleaning agents and lubricants.The World Health Organization stipulated that the maximum allowable concentration of DMP in drinking water is 18 μgl-1[1,2].However,researchers have found that DMP in surface water in different regions of the world exceeded the normal standard.For example,the average content of DMP detected in the surface water in different regions of China exceeded the national standard of surface water[3,4].The DMP residue was also detected in the ef fluent from European countries’sewage treatment plants[5–7].DMP was an environmental hormone substances and entered the human body through skin,mouth and nasal cavity.Additionally,it combined with the human body-related hormone receptors and interfered with the normal level of hormones in the blood,thus affected human reproductive and development behavior.At the same time,DMP was highly toxic to aquatic organisms.The systematic functioning of aquatic reproductive system or central nervous system of people around pollutant areas will be disrupted by sudden increase of DMP concentration in the drinking water.At present,physical method,chemical method,biological method and advanced oxidation technology were the commonly used degradation method to remove DMP from drinking water.A comparison of absorption ability of different activated carbon that were used to remove DMP from the　contaminated　water　was　investigated　by　several researchers[8].Some researchers have used the technology of hydrogen peroxide and ultraviolet radiation(H2O2/UV)to remove DMP,phthalic acid(PA)and 4-hydroxy-1,2-benzoic dicarboxylic acid,dimethyl ester were identified as the aromatic oxidation intermediates by gas chromatography mass spectrometer analysis[9].Zhang et al[10]found that freshwater unicellular cyanobacteria can effectively repair contaminated drinking water.PA was detected to be an intermediate degradation product of DMP and accumulated in the culture solution.Wu et al[11]studied the bio-degradation of DMP under the fermentation conditions.Monomethyl phthalate(MMP)and PA were detected as the intermediates of DMP bio-degradation.Nowadays,there have little reports on the mechanism of degradation of DMP in the drinking water by advanced oxidation technology.This paper intends to find a new method to degradation of DMP in drinking water,hoping to achieve the target of Efficiency,convenience and no secondary pollution.

Figure 1.Strong ionization discharge water treatment equipment.

The dielectric thin layer that have the high dielectric strength and high dielectric constant of glass,quartz,ceramics,mica and aluminum oxide(Al2O3)covered in the electrode surface constituted dielectric barrier discharge(DBD)reactor[12].The strong ionization discharge can be achieved at atmospheric pressure or above atmospheric pressure.The obtained electric field strength was greater than 400 Td,the average energy of electrons were greater than 10eV and electron density were higher than 1015cm-3[13,14].This was sufficient to ionize most of the gas molecules in the DBD reactor into electrons,photons,free radicals,excited atoms and molecules.When the strong ionization discharge occurs,the energy obtained by the electrons from the applied electric field was almost completely transferred to the gas molecules.At room temperature and atmosphere pressure,the strong electric field ionization discharge caused discharge in the discharge gap of DBD reactor,which could cause the excitation,super-excitation and ionization reaction of oxygen molecules and water molecules[15].

Compared with other treatment methods,the technology has the advantages of short processing cycle,high processing Efficiency,no secondary pollution,etc.This study adopted strong ionization discharge technology that was able to overcome the shortcomings of traditional technology,such as small amount of treated water,low active particle concentration and large dielectric loss.This equipment can achieve　2t h–1　water treatment volumes　through　the improvement in structure parameters of DBD reactor.In summary,strong ionization discharge is a new type of advanced oxidation technology that can produce·OH,O3and other active particles with high concentration,large scale and low cost.It can be widely used in the field of drinking water disinfection,ship　ballast water treatment and　sewage pretreatment.

2.Materials and methods

2.1.Experimental apparatus

As shown in figure 1,the strong ionization discharge water treatment equipment was mainly consisted of high-frequency and high-voltage power supply,DBD reactor,discharge monitoring equipment and water circulation system,and the treated water reaches 1.6 t h–1.A 45 l sample solution was placed in the sample barrel and stirred well and it was recycled by the action of a pump(800l h-1).The oxygen flow was controlled at 5lmin-1using a rota meter,and cooling water circulation was maintained during the process of equipment operation.The high frequency and high voltage power supply was used to convert common voltage 220V/50Hz into high frequency voltage of 2.1–4.5 kV/15–23 kHz.The raw material(O2)were ionized,generating a large amount of active particles like O3,oxygen radical(·O),oxygen cation　oxygen anion　(O　2-)[16].Pollutants in the water can be oxidized rapidly by active particles,and the purpose of purifying the water will be achieved by strong ionization discharge.DBD reactor structure was shown in figure 2,the structure of the discharge area was made up of several hollow grounding plates(plate size 19.5 cm × 10 cm × 1 cm)and two groups of discharge electrodes　(plate　size　19.5 cm × 10 cm × 1 mm).　A grounding plate was placed in the bottom,with a discharge plate placed above it.The insulating tapes were placed between the discharge plate and the grounding plate to maintain plate clearance of 0.2 mm[14,17].Under the applied voltage,the electrons in the discharge gap of DBD reactor drew energy from the electric field and reacted with the surrounding gas molecules.The electrons transferred energy from the applied electric field to the gas molecules.After the gas molecules were excited,a large number of micro- filamentous micro-discharges were formed in the discharge gap,and the discharge electric field intensity of the discharge gap was expressed by the following formula[17]

Figure 2.Schematic diagram of DBD.

where,Eg(kVcm–1)refers to electric field intensity,V is applied voltage,and lg(cm),ld(cm),εgand εdrepresent the thickness of plate clearance or medium and permittivity,respectively.The dielectric material and processing technology were one of the most important conditions for obtaining strong ionization discharge.The discharge gap on both sides(or side)of the electrode were covered with high insulation,high dielectric constant,high density,high uniformity and low-curvature of the α-Al2O3dielectric thin layer.This effectively suppresses the in finite increase in the discharge current,which prevents the discharge gap from generating a spark electric or arc discharge,and improves the performance of DBD device[18,19].The main characteristic parameters of strong ionization discharge were shown in table 1.

The amount of active particles was the key factor affecting the degradation Efficiency of DMP in the drinking water.Therefore,the concentration of active particles during the reaction was an important part of the mechanism research.In the study,,TBA and IPA were added to prove the existence of O3and·OH.Research has shown that the ozone oxidation can be divided into direct oxidation and indirect oxidation.In the process of DMP degradation,a large number of active particles produced by DBD reactor after entering the gas–liquid mixing device through the Venturi jet would react with the water molecules to produce the strong oxidizing properties of active substances(O3,·OH,etc).The direct oxidation function is that the strong oxidation ability of O3.And then,the indirect oxidation function was reflected through the decomposed of O3.The produced O3was decomposed into strong oxidizing ability of the active group(·OH)in weak alkaline solution which can rapidly oxidize contaminants in water.The oxidation potential of·OH was 2.8V and much higher than other oxidants of chlorine gas(1.36 V)and oxygen(1.23 V)[22,23].Pollutants would be oxidized to CO2,H2O or mineral salt under the attack of active substance,with no secondary pollution.Positive oxygen ions reacted with water to produce hydrated ions under the reaction of strong electric filed,and the decomposition reaction of hydrated ions is the main way of generating·OH,as shown in equation(7).The main reaction pathway of production of·OH by ionizing O2is the decomposition reaction of hydrated ions.The reaction formula is shown in equations(8)–(10).

In summary,each generation of 100 eV energy can produce 5.5·OH,a total of 8.25 or more free radicals.The number of·OH was more than 10 times the weak ionization discharge,resulting in high concentration of O3and·OHand other active particles produced by the DBD reactor in the strong ionization discharge water treatment system entered the gas–liquid mixing device through the Venturi jet and reacted with the water molecules to produce the active substance.DMP and the intermediate products can be rapidly oxidized by the active substance in the water.After 60 min,the removal rate of DMP in water was more than 93%,and a small amount of intermediates was detected by high-performance liquid chromatography(HPLC)and LC-MC.

2.2.Experimental materials

Additionally,the MS displayed molecular ion peak at 225.33m/z(MEPA + H),and other detected peaks in figure　10(b)　were　241.23m/z　(MEPA + Na - 6H),243.12m/z(MEPA + Na - 4H),245.31m/z(MEPA +Na - 2H).These peaks indicated the presence of MEPA.There also have some small molecular organic as shown in figures 9(a),(b)and 10(b),it can be speculated that the following mass-to-charge ratios correspond to acetic acid(AA),oxalic acid(OA),maleic acid(MA),succinic acid(SA),adipic acid(ADA).The peaks in the mass spectrum were 99.0m/z(AA + Na + 2H),131.02m/z(OA + Ca + H),132.41m/z(MA + 2H),159.04m/z(SA + Ca + H)and 187.27m/z(ADA + Ca + H).

第四，进一步加强“行知合一”的研究。所谓“知行合一”的研究，就是指在构建过程中如何避免行为和理念脱节问题的研究。一方面，应加强对人类命运共同体理念的研究，找到一条可以向世界正确传递人类命运共同体理念的途径且不让人产生“排中”心理。另一方面，还应加强对构建人类命运共同体的主要力量即对各国政党的研究，要加强政党角色的研究，让各国政党在推进人类命运共同体过程中形成更多共识；要加强政党责任研究，让各国政党在推进人类命运共同体过程中凝聚更多智慧；加强政党治理研究，让各国政党在推进人类命运共同体过程中分享更多经验。总之，要进一步重视世界政党的研究，这样才能达到“知行合一”的境界。

2.3.Experimental methods

巴基斯坦杜伯华水电站项目位于巴基斯坦西北边界省Indus Kohistan 区, 是一座高水头、长隧洞引水式水电站，该工程主要有堰坝、引水系统、压力系统、发电厂房、沉沙系统、冲砂系统等建筑物组成。

Table 1.The main characteristic parameters of strong ionization discharge.

Characteristic parameters　Values　Characteristic parameters　Values Gas pressure　　≥0.01 MPa　Electronic average energy　　＞1015cm-3 Excitation discharge electric field strength　　＞10 kV cm-1　Excitation discharge reduced electric field intensity　400 Td Duty cycle　　≥0.5%　Ionization degree　10-4 Electron concentration　10 eV　Gas temperature　　～300 K

3.Results and discussion

3.1.Detection of active particles

The microscopic morphology of electron motion,excitation and ionization of atoms and molecules were defined by the magnitude of electron energy or the strength of electric field,by which the chemical reaction ability and the properties of the corresponding matter was determined[20,21].The main reason for the ionization of O2molecules were given as equations(2)–(6).

Figure 3.The effect of inhibitors on degradation of DMP(DMP concentration = 20 mg l-1,voltage = 3.3 kV,oxygen flow = 5 l min-1,pump flow = 800 l h-1,pH = 6.97).

In this experiment,the concentration of·OH was proved indirectly by calculating variation of DMP degradation Efficiency after adding free radical inhibitors.As shown in figure 3,there was a large difference in DMP degradation Efficiency between the presence or absence of inhibitors under the same experimental conditions.After 60min,the removal Efficiency of DMP was 80.4%,78.9%,76.6%and 74.4%after addition of TBA and IPA,but it was up to 93.69%in only DMP sample solution.It can be seen that the presence of·OH promotes the reaction process of DMP degradation,indicating that addition of free radical inhibitors slows down the chain reaction process,inhibiting the formation of·OH and degradation of DMP.The UV ozone analyzer was used to detect ozone concentration generated by DBD reactor in this experiment.As shown in figure 4,the ozone concentration at the DBD reactor outlet were 51.9mgl-1,63.5mgl-1,74.4mgl-1,74.1mgl-1,respectively at the voltage of 2.1kV,2.6kV,3.3kV and 3.8kV.The ozone generation at the DBD reactor outlet was slower at 3.8kV when compared to the ozone concentration at 3.3kV,possibly due to the sharp increasing in the temperature of DBD reactor at 3.8kV.The overheating phenomenon caused the decline in ozone production.Additionally,the electric energy consumed during the reaction was calculated from the measured voltage and current values,as shown in equations(11),(12).When the concentration　of DMP solution decreased from　20 to 1.29mgl-1,the energy consumption per unit volume of wastewater was 507.9kJ(mgl–1)-1after 60min,and electric energy　consumption　per unit volume waste water was 0.21kJml-1when the discharge voltage is 3.3kV,initial concentration is 20mgl-1.In order to ensure better experimental results,the applied voltage in the experimental study is 3.3kV.

Figure 4.The concentration variation of O3in water at different applied voltage.

3.2.1.Variation of TOC,COD and pH.The mineralization degree of organic matter in water is an important index to measure the removal effect of organic matter.In order to investigate the mineralization degree of DMP in the sample solution,the changes of TOC value during different reaction time was measured in the experiment of DMP degradation.As shown in figure 5(a),TOC decreased from 30.15 to 16.67 mgl-1after 60 min,and its removal rate reached 45%.It can be inferred that the TOC removal Efficiency should be higher when the reaction time is prolonged.This indicates that most of DMP in the water was oxidized to CO2,H2O and other small molecules substance under the attack of O3and·OH.The TOC analyzer showed that TOC value of DMP solution decreased by 45%and the organic carbon(TC)decreased from 32.92 to 19.28 mgl-1,which was 41.4%;the inorganic carbon(IC)decreased from 2.766 to 2.661 mgl-1,a decrease of 3.8%.From the point of view of material balance,most of carbon in the solution was decomposed into organic carbon in the solution and the other was converted to IC.

The removal Efficiency of DMP was decreased from 93%to below 75%after addition of different free radical inhibitors,which revealed that O3play a key role in the oxidation process of DMP.Simultaneously,the maximum concentration of O3in this experiment is up to 74.4mg l-1.It also displayed that the oxidation process of DMP was influenced by the species of O3.Therefore,the Significant variation of DMP degradation Efficiency after addition of free radical inhibitors and high concentration of O3produced both revealed that the oxidation reaction of DMP was carried out under the combined action of O3and·OH.In addition,the continuous improvement of DBD reactor structure to produce higher concentrations of O3was the major focus of future experimental research.

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3.2.Degradation mechanism of DMP

Figure 5.The variation of TOC,COD and pH values in the DMP solution during the treatment time of 0–60 min(DMP concentration = 20 mg l-1,voltage = 3.3 kV,frequency = 15 kHz,oxygen flow = 5 l min-1,pump flow = 800 l h-1).

where,R(kJ(mgl–1)–1)refers to the energy consumed when degradation of unit concentration wastewater,E(kJ)is the the electric energy consumed in the unit time,U(V),I(A)and t(s)represents the measured voltage,the measure current and the reaction time,respectively,and ΔC(mgl–1)is reduced concentration of DMP in the unit time.

Figure 6.The variation of UV–vis of DMP solutions during the treatment time of 0–60 min(voltage = 3.3 kV,frequency = 15 kHz,oxygen flow = 5 l min-1,pump flow = 800 l h-1,pH = 6.97,DMP concentration = 20 mg l-1,detection wavelength = 190–400 nm).

3.2.3.HPLC analysis.The variation of DMP chromatographic peak　were　shown　as figure　7,the　retention　time　of chromatographic peak was controlled within 6min.A1,A2,A3and B chromatographic peak can be seen clearly.The maximum peak B had the obvious down trend and was determined to the area peak of DMP according to the peak time of 2.10min.This indicated that DMP was progressively degraded by active substance during the reaction.The reason was that the aromatic ring and branched chain of DMP was more easily broken by the strong oxidizing performance of·OH and O3produced in the strong ionization discharge water treatment equipment.At the same time,it can be seen that the intermediate product peaks A1,A2and A3continuously generated in the period of 1.28–2.80min,and the peak area of the intermediate product gradually increased with the reaction.After 60min,the maximum peak B was the smallest,and the peak area of A1,A2and A3byproducts reached the maximum,which indicated that the degradation process of DMP continued to produce other different kinds of intermediates.Next,LC-MC was used to determine the possible intermediate products in the degradation of DMP.Additionally,some byproducts that maybe exist but not detected were not discussed in this study.

3.2.2.UV–vis analysis.The UV absorption spectra variation of DMP during different reaction time was shown as figure 6.As the reaction progresses,the characteristic peaks of DMP at 230nm in the visible region were weakened faster.During 0–10 min,the characteristic peak disappearance velocity was the fastest at 230nm.After 60 min,the absorption peak almost disappeared,indicating that the aromatic ring of DMP was destroyed and degraded to the straight chain.The absorption peak of DMP in range of 190–200 nm also weakened,but did not completely disappear.With the reaction time to continue,these absorption peaks gradually reduced.It can be seen from figure 6 that existing a product still had a strong absorption peak at 200nm after 60 min,probably because one of the intermediate product produced in the process of DMP degradation still had an ultraviolet absorption peak in the vicinity of 190–200nm.The possible intermediates in the DMP oxidation process need to be further analyzed by HPLC and LC-MC.

The initial concentration of DMP in the aqueous solution was up to 20mgl-1.The concentration variation of DMP during the reaction was measured by a ultraviolet–visible(UV–vis)spectrophotometer(UV-9600,Rayleigh Corporation,China).During DMP degradation,the maximum absorption wavelength and peak variation of DMP were measured using an UV–vis(UV2450,Shimadzu Corporation,Japan).The intermediates and final products was measured by HPLC(LC-10AVP,Shimadzu Corporation,Japan)and LC-MC(Thermo-LXQ,Thermo Corporation,USA).All the sample solution were filtered using a 0.3μm polyether sulfone membranes(W2545,JinTeng,China).The parameter conditions of HPLC were as follows:the temperature of chromatographic column(Symmetry®C18,Waters,Ireland,5 μm × 4.6mm × 250mm)was 30 °C,the mobile phase was methanol and water(volume radio = 80%:20%),the flow rate was 1.0mlmin-1,the injection volume was 20μl,the wavelength was set at 230nm,and the retention time was 6min.The chromatographic parameters of LC-MC are consistent with those of the HPLC.Electrospray ionization sources were used for detection and the scanning range was up to 50–500mAU.The changes of pH,chemical oxygen demand(COD)and total organic carbon(TOC)values of samples solution were measured by the pH meter(FE20,Mettler Toledo Corporation,China),COD analyzer(DR890,Hatch Corporation,USA)and TOC analyzer(VCPH/CPN,Shimadzu Corporation,Japan).The ozone generated by DBD reactor and the concentration of ozone dissolved in water were measured using an ozone monitor(KEN-2000,Evergreen,Italy)and ozone concentration analyzer(CL-7685,B&C electzanice,Italy),respectively.

Figure 7.HPLC of DMP solutions during the treatment time of 0–60 min(voltage = 3.3 kV,frequency = 15 kHz,oxygen flow = 5 l min-1,pump flow = 800 l h-1,pH = 6.97,DMP concentration = 20 mg l-1, flow rate = 1 ml min-1,injection volume = 20 μl,volume ratio of methanol and water = 80%:20%,detection wavelength = 230 nm,temperature = 30 °C).

In the process of DMP oxidation,the changes of pH and COD values was also studied.As shown in figure 5(b),pH rose from 6.97 to 7.54 within 60 min.Before 30 min,the change of pH was slower,probably because the intermediate products of DMP was rapidly oxidized by the active substance and accumulated to a certain amount at 30min,and resulting in weak acid solution.The oxidizing ability of O3and·OH was very strong,all intermediate products including some small molecular organic acid produced in the reaction were oxidized to CO2and H2O.Thus,pH of DMP solution during 40–60min kept a slow down trend.The COD change of DMP solution was shown in figure 5(b),COD decreased from 40 to 23 mgl-1after 60 min,and the removal Efficiency was 42.5%.The change of TOC,COD and pH of DMP solution in the study show that the degradation of DMP in the drinking water can achieve good effect by strong ionization discharge.

3.2.4.LC-MC analysis.Under the influence of O3and·OH,the molecular structure of DMP was destroyed through two different forms[24,25].(i)The side chain(ester group)of DMP was simultaneously hydrolyzed to form a monoester product.(ii)The aromatic ring was broken,the C–C bond linking the carbonyl and aromatic ring was opened.After reaction time of 20 min,it was evident that there were four noticeable peaks in the MS with retention time at 1.38min,1.74 min,2.10min and 2.78min respectively( figure 8(a)).After 60 min,there have no any chromatographic peaks as shown in figure 8(b).DMP and all intermediate products have been degraded into other small molecular mater completely.As shown in figures 9(a)and(b),the mass ratio of different intermediates was detected by LC-MC.The damage of DMP molecular structure may yield four intermediate product with molecular ion peaks at 167.13 m/z,181.27 m/z,195.21m/z and 225.33m/z,other peaks also detected in the DMP pro file as shown in figure 10.The molecular weight of 166,180,224 were MMP,PA and methyl ester PA(MEPA)according to the molecular structure of DMP.

Figure 8.Liquid chromatography of DMP degradation after 20 and 60 min.

In the mass spectrum( figure 9(a)),mass ratio of products at 2.10min was 195.21m/z(DMP + H).It has the same retention time with standard sample of DMP.Other detected peaks in the mass spectrum were 218.34m/z(DMP + Na + H),219.29m/z(DMP + Na + 2H),corresponding to the addition of 24–25 mass units( figure 10(b)).The MS displayed molecular ion peak at 167.13m/z(PA + H),it could be proposed to the standard sample of PA.As shown in figure 10(b),other discernible peaks were 241.14m/z(PA + Ca + K - 3H),245.25m/z(PA + K + Ca).PA was further con firmed by comparing the LC-MC pro files of PA standard with this product.

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For the peak at retention time of 1.74–2.10min,the MS displayed molecular ion peak(MMP + H)at 181.27m/z.It was similar to that for standard sample of MMP.Other major peaks with m/z of 261.23(MMP + K + Ca + 2H),279.13(MMP + Ca + K + Na - 3H),303.0(MMP + 2Na + K +Ca - 2H)were identified as MMP( figures 9(c)and 10(a)).

②核糖的制作：DNA的基本单位是脱氧核苷酸，一般用五边形材料代替脱氧核糖，制作模型时会用“直线”把磷酸和五边形连接起来，这是有悖科学事实的，会使得学生无法理解教材上连接脱氧核糖和磷酸的为什么是“折线”。这是因为五边形的五个顶点并不都代表碳原子。其实五边形的顶点是氧原子，其他四个顶点才是碳原子（从右侧顺时针依次是1、2、3、4号位碳原子），而第5号位碳原子不在五边形上，是通过化学键与4号位碳原子相连的。因此仅用五边形不能准确代表脱氧核糖，所以应在在五边形的4号碳原子处延伸出一个短枝。这样就可以按照脱氧核苷酸的分子式准确构建出脱氧核苷酸的模型。

DMP,Tert-butanol(TBA),isopropyl alcohol(IPA),and other analysis reagents were purchased from Shanghai Sinopharm Group Chemical Reagent Co.,Ltd China,including methanol,ethanol,anhydrous sodium carbonate,sodium thiosulfate,sodium　bicarbonate,sodium　sulfate,sodium　chloride,hydrochloric acid and sodium hydroxide.All experimental solutions were prepared with deionized water without other buffers.DMP was added to deionized water stirred for 8h by magnetic stirrer until the initial oil in water drop disappeared,yielding a 1000 mgl-1DMP stock solution.The stock solution was diluted with tap water to prepare into different initial concentrations according to specific requirement of the research.

From the result of HPLC and LC-MC,it can be inferred that PA,MMP and MEP could be the major intermediates during the degradation of DMP.Some small molecular organic acid were producted including AA,OA,MA,SA,ADA.The research result is in agreement with most of previous study findings on degradation of DMP[8,26,27].

3.3.Pathway of DMP degradation

Based on the UV–vis,HPLC and LC-MC results of DMP,the degradation pathway of DMP by strong ionization discharge could be proposed as figure 11.The high concentration of·OH and O3produced by strong ionization discharge technology played the key role in the DMP degradation.The attack of·OH leads to the destruction of DMP molecular structure.The side chain(–COOCH3)lost a methoxyl group(–OCH3)and addition of one ·OH to formation of the product 1(MMP).Then,the side chain(–COOCH3)of the product 1 was broken and one or two·OH was added to form the isomer 3 or 4.Based on the study data,it was presumed that the product 3 and product 4 may be PA and TPA,respectively,depending on the·OH position.The two side chains of DMP were simultaneously cleaved to form product 2.It was added·OH to form products 5(HADE)(it maybe exist but not detected)and product 6(MEPA).In addition,product 2 did not detected by LC-MC analysis.The reason may be that the presence of product 2 was particularly short and was rapidly oxidized to product 5 and product 6 under the action of O3and·OH.Finally,the aromatic ring of DMP and intermediate product were destroyed to produce various small molecule organic acids under the attack of O3and·OH.According to the mass spectrum at 20min and the reaction process,it was speculated that the organic acid may be product 7(AA),product 8(OA),product 9(MA),product 10(SA),product 11(ADA),etc.After 60min of reaction,all the products in the solution were decomposed into carbon dioxide,water and other inorganic salts,achieving the target of complete degradation.

2）新梢生长。叶芽萌发后1周左右是新梢初生长期。开花期间，新梢基本停止生长；花谢后再转入迅速生长期；以后当果实发育进入成熟前的迅速膨大期，新梢停止生长。果实成熟采收后，生长势比较强的树，新梢又一次迅速生长，到秋季还能长出秋梢；生长势比较弱的树，只有春梢一次生长。幼树营养生长比较旺盛，第1次生长高峰在5月上中旬，到6月上旬延缓生长或停长，第2次在雨季之后，继续生长形成秋梢。

Figure 9.The mass spectrum of main intermediate products during the degradation process of DMP(DMP concentration = 20 mg l-1,voltage = 3.3 kV,oxygen flow = 5 l min-1,pump flow = 800 l h-1,pH = 6.97,detection wavelength = 230 nm, flow rate = 1 ml min-1,injection volume = 20 μl,temperature = 30 °C,volume ratio of methanol and water = 80%:20%).

Figure 10.The mass spectrum of main intermediate products during the degradation process of DMP(voltage = 3.3 kV,pump flow = 800 l h-1,oxygen flow = 5 l min-1,DMP concentration = 20 mg l-1,pH = 6.97,detection wavelength = 230 nm, flow rate = 1 ml min-1,temperature = 30 °C,injection volume = 20 μl,volume ratio of methanol and water = 80%:20%).

4.Conclusion

In this study,the DBD reactor was constructed to produce high concentration of O3,·OH and other active particles that was used to efficiently remove DMP from the solution.The UV ozone detector displayed the content of O3was up to 74 mg l-1within 60 min when 30 mgl-1ofTBA and IPA was added to the samples,the degradation rate of DMP declined from 93.6%to 80.4%,78.9%,76.6%and 74.4%,respectively.The comparative experiment of DMP removal Efficiency revealed that O3and·OH generated by the DBD reactor played key roles in degradation of DMP from solution.The UV–vis spectra,pH,COD and TOC studies indicated that DMP and all the products were mineralized into CO2and H2O.The intermediates from the degradation of DMP were determined by HPLC and LC-MC analysis including MMP,PA(TPA),

MEPA and several small molecular organic acids(AA,MA,OA,SA,ADA,etc).As the reaction progresses,all the products in the solution were decomposed into carbon dioxide,water and other inorganic salts.Based on these analysis results,the degradation pathway of DMP were proposed.The study provided a theoretical and experimental basis for the removal of organic pollutants from drinking water by strong ionization discharge.

由图5可以看出，任务点大多都分布在所拟合出的曲面附近，说明所做曲面能较好地表示任务的分布情况，可以从图中验证任务的定价与任务的经纬度具有明显的函数关系，任务点相对聚类中心点越偏远，任务定价就越高.

Figure 11.The proposed degradation pathway of DMP by strong ionization discharge.

This work was supported by the Science and Technology Support Project Plan and Social Development of Jiangsu Province,China(Grant No.BE2011732);the Science and Technology Support Project Plan and Social Development of Zhenjiang city,China(Grant No.SH2012013).

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