Research On Control Strategies Of Tetrachloro-p-benzoquinone Disinfection By-product In Drinking Water

In the drinking water treatment process,the general method of chlorination disinfection,which produces carcinogenic,teratogenic and mutagenic disinfection by-products,has serious harm to human health.Therefore,it is very important to study the control technology of disinfection by-products.In this study,tetrachloro-p-benzoquinone?TCBQ?which was one kind of disinfection by-products was used to evaluate the influencing factors during removing.And in order to remove the TCBQ,the removal efficiency,influencing factors,degradation mechanism and kinetics using potassium ferrate,ultraviolet?UV?light and a combination technique of ozone with granular activated carbon?O₃/GAC?were investigated.The following main results had been inspected.First,the method for the TCBQ determination by solid phase extraction and high performance liquid chromatography?SPE/HPLC?was established.The chromatographic grade methanol was used as solid phase extraction elution machine and high performance liquid chromatography mobile phase.Under the experimental conditions,the linear range of the method was between 5?g/L to 120?g/L.The recovery rate of TCBQ between 96.3% and 102.1%.The relative standard deviation?RSD?between 2.50% and 5.35%,and the minimum detection limit less than 2?g/L,which had high accuracy and precision.Second,the potassium ferrate was effective in removing TCBQ.The removal efficiency of TCBQ was greatly affected by the addition of potassium ferrate.The removal rate of TCBQ increased with the increase of potassium ferrate dosage,which increased significantly.When the initial concentration of TCBQ was 50?g/L and after reaction time of 30 min,the removal of TCBQ was enhanced from 57.42% to 92.25%with the increase of potassium ferrate dosage from 10mg/L to 50mg/L.Because of the increase of the concentration of potassium ferrate,hydroxyl radical and ferric hydroxide in the solution,the degradation effect of TCBQ was improved.When the dosage of potassium ferrate is 30mg/L,the removal rate of TCBQ is obviously increased with the increase of p H.While the pH was in the alkaline condition,the removal rate of TCBQ did not change obviously.According to the linear correlation coefficient was fitted by the experimental results,the degradation of TCBQ by potassium ferrate was in accordance with the first order reaction model.Third,the TCBQ removal was improved with the increasing intensity of UV light during the ultraviolet light process.When TCBQ absorbs UV photons,it became the benzoquinone in the excited state,and product hydroxyl,which can attackd TCBQ during UV irradiation.Thus it achieved the purpose of removing TCBQ.Selecting the greater intensity of UV light,the more photons generated,which can increase TCBQ removal.When the initial concentration of TCBQ was 50?g/L and the light intensity of UV was 110?w/cm²,after 180 min reaction the removal rate of TCBQ was 60.56%.At the same time with the increase of pH,TCBQ removal rate was decreasing.In acidic conditions the removing effect was higher than the alkaline conditions or neutral degradation effect.According to the linear correlation coefficient was fitted by the experimental results,the degradation of TCBQ by potassium ferrate was in accordance with the first order reaction model.Fourth,the O₃ and GAC were separated for TCBQ had certain removal efficiency.Meanwhile,the O₃/GAC process was applied to remove TCBQ and it performed better compared to the individual process of O₃ and GAC.When the O₃ concentration of was 10.06mg/L with the GAC dosage of 0.5g/L,the removal efficiency of TCBQ at the initial concentration of 50?g/L reached 79.57% after reaction time of 90 min.When the TCBQ initial concentration of 50 ?g/L and using O₃ alone which dosing quantity was 10.06 mg/L and single GAC which dosing quantity was 0.5g/L,their removal rates were 42.66% and 32.54%,respectively after reaction time of 90 min.TCBQ removal rate was significantly higher than using separate O₃ and the removal rate of GAC.This was due to the fact that ozone can turn the structure of TCBQ that had been adsorbed on the GAC into a small molecule,which released the GAC adsorption void,increased the GAC adsorption capacity,and improved the removal efficiency.According to the linear correlation coefficient was fitted by the experimental results,the degradation of TCBQ by potassium ferrate was in accordance with the first order reaction model.