紫外光强化Fe(Ⅱ)-EDTA活化过硫酸盐降解直接耐酸大红4BS

摘要

Wastewater containing azo dyes is difficult to be biodegraded because of its structural stability,which poses a serious threat to the environment.In order to study the degradation of azo dyes by SO4-· radicals;degradation of Direct Fast Scarlet 4BS with radicals activated by UV enhanced Fe(Ⅱ)-EDTA persulfate system was investigated.The effects of initial concentration of PDS,Fe (Ⅱ)/EDTA and inorganic anions on the degradation of 4BS in UV/Fe (Ⅱ)-EDTA/PDS system were discussed.The results showed that the 4BS decolorization rate increased with the increasing of PDS concentration,but there was no significant change when PDS was more than 15 mmol/L.At the most optimal Fe (Ⅱ)/EDTA ratio of 5∶ 1,the 4BS could decolorize 93.6％ within 5 min when the initial concentration was 0.0380 mmol/L.It followed the second-order kinetics model.The inorganic anions such as HCO3-,Cl-,NO3-and SO42-showed obviously negative effects for the degradation of 4BS when the inorganic anions were 100 mmol/L;decolorization ratio reduced 66.9％,13.2％,12.1％ and 9.43％,respectively.The relationship between structure and characteristic absorption was analyzed by UV-Vis spectroscopy,and we speculated that the 4BS degradation pathway is as follows:Benzene is broken first,then azo bond cleaves and naphthalene ring cracks.In the presence of PDS-Fe(Ⅱ)-EDTA,the UV radiation could effectively enhance the activation of the persulfate to form SO4-· free radicals,which can decolorize Azo dyes.The decolorization ratio of 4BS was up to 98.1％ within 10 min under the optimum reaction conditions[PDS∶ Fe(Ⅱ) ∶ EDTA =15∶ 5∶1] in the UV-PDS-Fe (Ⅱ)-EDTA system.The results suggested that the oxidation method based on SO4-· radicals may be a very effective technique to be used in the treatment of dye wastewater or other refractory wastewater.%为探索硫酸根自由基对偶氮染料的降解能力,以直接耐酸大红4BS(下称大红4BS)为模拟污染物,通过UV/Fe(Ⅱ)-EDTA/PDS(PDS为过硫酸钠)体系,探讨了初始c(PDS)、Fe(Ⅱ)/EDTA(摩尔比)、无机盐阴离子等对大红4BS降解的影响.结果表明,大红4BS的脱色率随着初始c(PDS)的增加而增大,当c(PDS)超过15 mmol/L时无显著变化.Fe(Ⅱ)/EDTA比在5∶1时效果最好,5 min时使0.038 0 mmol/L大红4BS的脱色率达到93.6％.反应符合二级动力学模型.HCO3-、Cl-、NO3-、SO44-等无机盐阴离子表现出明显抑制作用,c(无机盐阴离子)在100 mmol/L条件下,脱色率分别降低66.9％、13.2％、12.1％、9.43％.利用紫外可见光谱,依据其结构与特征吸收的关系,初步推测自由基离子对大红4BS降解的途径:苯环最先遭到破坏,随后偶氮键断裂、萘环开裂.研究显示,UV光可有效强化Fe(Ⅱ)-EDTA活化过硫酸盐形成SO4-·自由基,对偶氮染料具有很好的脱色能力,最佳反应条件[PDS∶ Fe(Ⅱ)∶EDTA(摩尔比)为15∶5∶1]下,大红4BS在10 min时脱色率高达98.1％.