Study On Degradation Of Oxytetracycline In Simulated Wastewater By Strong Ionization Discharge

Oxytetracycline（OTC）is one of the largest antibiotics in China,and is widely used in medical,aquatic and livestock breeding.Its discharge is huge,into the water,polluting the groundwater and drinking water sources of water,posing a threat to the safety of drinking water,causing harm to human health.The most widely used tetracycline OTC is treated as the target pollutant and its degradation was studied by using strong ionization discharge method in the paper.H₂ O and O₂ molecules can be ionized,a large number of high concentrations of ozone O₃,hydroxyl · OH and other free radicals would be produced by using strong ionization discharge method,of which can effectively oxidized OTC.The optimum experimental parameters were obtained by orthogonal test of OTC initial concentration,applied voltage,pH value of solution,inorganic ions and inhibitors in water.The experimental parameters were obtained by ultraviolet spectrophotometer（UV）,high-performance liquid chromatography（HPLC）,ultraviolet full band scanner（Uv-Vis）,total organic carbon analyzer（TOC）,and liquid chromatography mass spectrometrywere（LCMC）used to analyze the products in the degradation process.At the same time,the energy consumption and operating cost of the wastewater treatment were calculated and the kinetics of the free radical degradation of OTC were analyzed.The treatment method can effectively solve the shortcomings in the existing process,can produce high concentration of · OH or other free radicals,improve the processing efficiency and reduce processing costs,is expected to achieve industrial applications as soon as possible.This technology can provide an effective emergency treatment method for the sudden pollution of water in drinking water sources caused by contaminants such as antibiotics,chemical organic matter and pathogenic microorganisms in China.The results of the study are as follows:（1）It is proved that the mechanism of · OH and O₃ plays an important role in the degradation of OTC by strong ionization process and the mechanism of degradation of organic matter by active particles.The relationship between O₃ production and discharge voltage is determined.The results show that with the increase of the input voltage,the amount of active particles increases,and the degradation efficiency of OTC is improved.When the input voltage is 3.8kV,the amount of O₃ can be as high as 58.2mg/L,and the dissolved amount of O₃ in water is 13.39mg/L.After 20 min treatment with 20 mg/L OTC,the degradation rate of OTC in water was 94.85%.（2）The effects of OTC initial concentration,applied voltage,pH value,inhibitor and inorganic ions on the degradation efficiency of OTC were determined and orthogonal test was carried out.The results showed that the initial concentration of OTC solution was negatively correlated with the degradation rate.When the initial concentration of OTC was 13mg/L,the degradation efficiency was 99.68%.When the concentration was increased to 98mg/L,the degradation efficiency of OTC was 79.60%;The voltage was positively correlated with the degradation rate,and the degradation efficiency of OTC is 95.68% when the voltage is 3.8k V.Under the acidic condition,OTC can decompose more easily,and the degradation rate of OTC is 92.93% when the pH value is 4.5.The degradation of OTC was inhibited by HCO₃-and CO₃2-ions in water,CO₃2-had the greatest effect on OTC degradation,and NO₃-has little effect on the degradation of OTC in water.The results of orthogonal test show that the factors influencing the efficiency of OTC removal are: the applied voltage,the initial concentration of OTC,and the pH value.The best experimental conditions were the initial concentration of OTC was 13mg/L,the applied voltage was 3.8kV,the pH was 4.5,and the degradation rate of OTC was 99.87% after 60 min.（3）The use of strong ionization discharge to produce · OH and other free radicals to degrade OTC in wastewater in this paper.The calculated energy consumption of 1t of waste water is 0.133 kWh,which is 0.11 yuan per 1t OTC wastewater.Compared with the existing organic wastewater treatment method and its power consumption,the method has low power consumption.（4）By means of LC-MS,HPLC,Uv-Vis,TOC and UV,it was found that OTC gradually degraded and produced a large amount of inorganic salts and small molecule organic matter after hydroxylation,demethylation,decarbonylation and dehydration.The corresponding product mass ratio m/z was 426,477,444 and 443 respectively when the degradation time of OTC was 10 min,and the retention time was 4.75 min,9.60 min,9.71 min and 13.52 min respectively.The final product was tested for the degradation of OTC for 60 min.The retention time was 5.18 min,6.59 min,6.60 min and 7.69 min,respectively.The corresponding product mass ratio m / z was 159,350,261 and 333,respectively.（5）The reaction process of active species oxide OTC was calculated and analyzed:The results show that the matching equation is y =-0.018211x-0.05531 and R²= 0.97595,which means that Cpand t have a good linear relationship.It is verified that the process of oxidative degradation of OTC by the active ionization system produced by strong ionization discharge water treatment system is in accordance with the reaction kinetics secondary reaction.Under the above conditions,the reaction rate between the OTC solution and the active particles at a concentration of 20 mg / L was 0.018211 min^-1.