Study On The Decomposition Of Polymer In Circulating Water By UV Photooxidation

Polymer scale inhibitors are an important class of water treatment agents.Because of their good effect and low dosage,they are widely used in circulating cooling water systems to prevent corrosion and leakage of pipelines caused by pipeline fouling.Since polymer scale inhibitors are well dispersed in circulating water and are difficult to biodegrade.Therefore,direct or indirect discharge of wastewater can result in enrichment of the polymer and environmental pollution in the water.The method for removing the polymer scale inhibitor in the circulating water mainly includes membrane separation,flocculation method,Fenton method and the like However,such methods have the disadvantages of complicated operation,high cost.and easy introduction of new pollutantsIn order to make up for the deficiencies of the above methods,PAA,PESA,TH-2000 and TH-3100 were used as research objects.The polymer scale inhibitor in the circulating water was decomposed by ultraviolet-oxidation hydrogen peroxide method,and the concentration of the polymer was measured by the 1227 turbiditY method.The optimal experimental conditions for oxidative decomposition were determined,and the initial pH of the solution and the effect of common ion-to-decomposition rates in circulating water were investigated.The decomposition curves of high-concentration polymer wastewater were investigated,and the decomposition products of the polymer were analyzed by C NMR and H NMR characterization and determination of solid content.The main test contents and conclusions are as follows:(1)The initial concentrations of PAA,PESA,TH-2000 and TH-3100 were selected to be 10 mg/L,10 mg/L,20 mg/L and 20 mg/L,respectively.Under the oxidative photolysis condition of 10 W UV lamp at 254 nm,hydrogen peroxide was used as the oxidant to study the effect of hydrogen peroxide dosage on the decomposition rate of four polymer scale inhibitors.With the increase of the dosage of oxidant,the decomposition tendency of the four polymer scale inhibitors was about the same,and the decomposition rate increased first and then stabilizes.The optimum hydrogen peroxide dosages for PAA,PESA,TH-2000,and TH-3100 were 150 mg/L,150 mg/L,200 mg/L and 200 mg/L,respectively.(2)The effect of UV photolysis time on the decomposition rate of four polymer scale inhibitors in the UV device at 254 nm was investigated when the hydrogen peroxide dosage was optimal.With the increase of photolysis time,the decomposition tendency of the four polymer scale inhibitors was about the same,and the decomposition rate increased first and then stabilizes.The best UV photolysis times of PAA,PESA,TH-2000 and TH-3100 were 15 min,12 min,8 min and 15 min,respectively.The decomposition rates were 87.64%,89.21%,95%and 96.04%,respectively(3)The effect of the initial pH of the solution on the decomposition rate of various polymer scale inhibitors was studied when both hydrogen peroxide dosage and UV photolysis time were optimal.It could be found through experiments that at the pH of 3-9,the decomposition tendency of the four polymer scale inhibitors was basically stable,and the decomposition rate did not change much.The pH had little effect on the decomposition rates of PAA.PESA,TH-2000,and TH-3100.The pH of the circulating cooling water is generally 7.5 to 9.so that it is not necessary to adjust the pH in the treatment of the actual polymer wastewater.(4)The effect of common ions in circulating water on the decomposition rate of four polymer scale inhibitors was studied when both hydrogen peroxide dosage and UV photolysis time were optimal.The change of ion concentration had no effect on the decomposition of PAA,PESA,TH-2000 and TH-3100,when the concentration of CI-was 0-1500mg/L,the concentration of SO42-was 0-2000mg/L,the concentration of Ca2+ was 0-1500mg/L and the concentration of Mg2+ is 0-1000 mg/L.Therefore,it is not necessary to adjust the concentration of Ca2+,Mg2+,Cl-,SO42-in water when the four polymer type scale inhibitors in the circulating cooling water are decomposed by ultraviolet light oxidation technology.This method provides great convenience in the application of actual industrial wastewater.(5)In order to explore the decomposition curves of PAA,PESA,TH-2000,and TH-3100,the concentrations of PAA,PESA,TH-2000 and TH-3100 were lOg/L,10g/L,20g/L,and 20g/L,respectively.The hydrogen peroxide concentration was 90 g/L.Oxidative decomposition was carried out using a 254nm ultraviolet photolysis apparatus.With the increase of photolysis time,the concentration of polymer in the solution decreased rapidly and then stabilized.When the photolysis time was 9.5h,the decomposition rate of PAA was 97.66%.When the photolysis time was 10h,the decomposition rate of PESA was 93.57%;When the photolysis time was 16h,the decomposition rate of TH-2000 was 75.84%,and the decomposition rate of TH-3100 was 89.04%.(6)In order to investigate the decomposition products of PAA,PESA,TH-2000,and TH-3100,the solutions before and after decomposition were subjected to CNMR and HNMR characterization and solid content determination.PAA,PESA,TH-2000,and TH-3100 generated small molecular substances and acids by oxidative decomposition of ultraviolet light.The solid content measurement showed that the solid content of PAA and PESA changed greatly before and after decomposition,and the solid content of TH-2000 and TH-3100 remained basically unchanged,which proved that PAA and PESA after decomposition may contain CO2 or H2O.In summary,this experiment uses ultraviolet light oxidation technology to decompose polymer scale inhibitors in circulating water.The method does not need to adjust pH,has simple operation,low energy consumption,good removal effect,and is not affected by common ion concentration in circulating cooling water.The problem of difficult treatment of polymer wastewater is solved,which provides a new possibility for the treatment of polymer wastewater in industrial circulating water system.