Study On Formation Process And Control Strategies Of Disinfection By-product 2,6-Dichloro-1,4-Benzoquinonele In Drinking Water

The disinfection by-products have carcinogenic,teratogenic and mutagenic effects on human health,which has become one of the most concerned issues.Therefore,the study on its formation process and control strategies is of great importance and necessity for the safety of drinking water.In this study,2,6-dichloro-1,4-benzoquinone?2,6-DCBQ?,one kind of disinfection by-products was used to evaluate its formation mechanism and the influencing factors during chlorination.And in order to remove the2,6-DCBQ,the removal efficiency,influencing factors,degradation mechanism and kinetics using potassium ferrate and a combination technique of ozone with granular activated carbon?O₃/GAC?were investigated.The following main results have been achieved.?1?The method for the 2,6-DCBQ determination by liquid-liquid extraction and high performance liquid chromatography?LLE/HPLC?was established.At the optimal conditions,the measurement method for2,6-DCBQ was highly accurate and the recovery rate was between 93.1%and 104.9% with the relative standard deviation from 4.19% to 8.72% and minimum detection limit of 0.88-2.76?g/L.The accuracy and precision of this analysis method for 2,6-DCBQ was much higher.?2?The factors,such as reaction time,pH value,chlorine dosage and temperature have an important effect on 2,6-DCBQ formation from phenol in the process of chlorination disinfection.The results showed that the2,6-DCBQ amount increased with the increase of pH value at the acid conditions.However,the increased pH value had a negative effect on the2,6-DCBQ formation at the alkali condition.It was also found that the increase of chlorine addition improved the 2,6-DCBQ when the dosage of chlorine ranged from 0.3mmol/L to 0.5mmol/L.The generated amount of2,6-DCBQ also increased as the temperature was raised from 10 oC to 30 oC.The formation process of 2,6-DCBQ consisted of two reactions,substitution and oxidation.?3?Potassium ferrate could effectively remove 2,6-DCBQ.The potassium ferrate dosage was a great impact on 2,6-DCBQ removal and the removal increased dramatically with the increase of potassium ferrate dosage.When the initial concentration of 2,6-DCBQ was 50?g/L,after reaction time of 30 min,the removal of 2,6-DCBQ was enhanced from46.39% to 87.12% with the increase of potassium ferrate dosage from10mg/L to 90mg/L.The optimum removal was obtained when the pH value in the range of 4-6 and the higher the pH value was,the better the removal efficiency was.The degradation process of 2,6-DCBQ by potassium ferrate followed the first-order kinetic model.?4?Meanwhile,the O₃/GAC process was applied to remove2,6-DCBQ 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 2,6-DCBQ at the initial concentration of 20?g/L reached 85.37% after reaction time of 90 min.The increasing dosage of GAC benefited the removal efficiency of 2,6-DCBQ and reaction rate greatly in the O₃/GAC process.In addition,the increase of O₃ concentration and initial concentration of 2,6-DCBQ was also found to help to improve the 2,6-DCBQ removal efficienc.The 2,6-DCBQ degradation by O₃/GAC process also accorded with the first-order kinetic model.