UV—H_2O_2工艺去除饮用水中二氯乙酸的研究

Study on Removing Dichloroacetic Acid from Drinking Water Using UV/H_2O_2 Process

采用间歇式反应器考察了UV—H2O2高级氧化技术去除饮用水中二氯乙酸的效果及其影响因素,并进行了相关的动力学分析。结果表明,在紫外线辐照度为1 048μW/cm2、H2O2投加量为60 mg/L、原水pH值为7.1、DOC浓度为5.13 mg/L、二氯乙酸初始浓度约为100μg/L的条件下,UV—H2O2工艺对二氯乙酸的去除率>90%。pH值为中性或偏酸性时,更有利于系统对二氯乙酸的去除;在其他条件一定的情况下,系统对二氯乙酸的去除效果随紫外线辐照度或H2O2投量的增加而增加,但当紫外线辐照度>640μW/cm2或H2O2投量>40 mg/L时,系统对二氯乙酸的去除率增加缓慢;在二氯乙酸初始浓度约为100μg/L及其他条件一定的情况下,当原水DOC浓度<2.39 mg/L时,180 min内二氯乙酸即可被降解完毕;其他条件不变,当二氯乙酸的初始浓度>109.48μg/L时,系统对二氯乙酸的去除率随其初始浓度的增加而变得非常缓慢。UV—H2O2工艺对二氯乙酸的降解符合一级反应动力学,UV与H2O2发生协同效应,使得在两者同时增加的情况下,反应速率常数大幅增加。

The removal efficiency of dichloroacetic acid from drinking water using the advanced oxidation technology UV/H2O2 and the influencing factors were investigated in batch reactors, and the relevant dynamic analysis was carried out. The results indicate that when UV irradiation intensity is 1 048 μW/cm^2, H2O2 dosage being 60 mg/L, pH of raw water being 7. 1, DOC concentration being 5. 13 mg/L, and initial dichloroacetic acid concentration being around 100 μg/L, the resulting removal rate of dichloroacetic acid reaches above 90%. The neutral or slightly acidic pH is favourable for removing the dichloroacetic acid. Under the other given conditions, the removal efficiency of dichloroacetic acid is directly proportional to the UV irradiation intensity and H2O2 dosage. However, when UV irradiation intensity exceeds 640 μW/cm^2 or H2O2 dosage exceeds 40 mg/L, the acceleration of dichloroacetie acid removal is decreased. When the initial concentration of dichloroacetie acid is around 100 μg/L, DOC concentration in raw water is less than 2.39 mg/L, and under the other given conditions, dichloroacetic acid can be completely degraded by UV/H2O2 within 180 min. When the initial concentration of dichloroacetic acid is greater than 109.48 μg/L and other conditions remain unchanged, the acceleration of dichloroacetic acid removal with the increase of its initial concentration is low. The degradation of dichloroacetic acid accords with first-order reaction kinetics. Due to the synergistic effect between UV irradiation intensity and H2O2 dosage, the reaction rate increases greatly under the condition of simultaneous increase of both.