零价铁活化过硫酸钠对偶氮染料4BS的脱色机理

Decoloration mechanism of azo dye 4BS by zero valent iron activated sodium persulfate

以直接耐酸大红4BS为研究对象,利用零价铁(ZVI)活化过硫酸钠(PDS)对其进行脱色研究,考察了PDS浓度、ZVI浓度、pH、温度等对脱色的影响.结果表明,一定浓度的ZVI与PDS联合使用能促进大红4BS的脱色,在20 min时脱色率达98.79%,远高于使用单一药剂的效率,且反应符合准一级反应动力学方程.低pH有利于反应的进行,随着pH值降低,反应速率逐渐加快,在pH=10.42时,反应90 min仅脱色9.41%,而在pH=3.03时脱色率达95.57%.温度的升高虽然能加快大红4BS的脱色,但是会使PDS的利用率降低,当温度由20℃增大到60℃时,PDS的利用率降低12%,且温度对大红4BS降解速率的影响符合阿伦尼乌斯模型(R2=0.988),计算的活化能为14.44 k J·mol-1.分别以叔丁醇与异丙醇为分子探针的自由基清除实验显示:ZVI活化PDS降解大红4BS是以SO-4·为主导的自由基反应过程.

Decolorization of direct fast scarlet 4 BS by zero-valent iron activated persulfate was investigated in the present paper. The effects of PDS concentration,ZVI concentration,pH,and temperature on the decolorization effiecency were evaluated. The results show that the decolorization rate of 4 BS gradually increased with the increase of PDS concentration and ZVI concentration. In a certain concentration range of ZVI and PDS the decolorization of red 4 BS was significantly promoted,and the decolorization rate reached 98.79% within 20 min,much higher than the efficiency of any single agent. The pH value had a significant influence on the reaction,and the decolorization ratio were 9. 41% and 95. 57% at pH 10. 42 and 3. 03 within 90 min,respectively. Although the temperature accelerated the red 4 BS decolorization,but PDS utilization was reduced about 12%when the temperature increased from 20 ℃ to 60 ℃. The influence of temperature on the degradation rate of red 4 BS was in accordance with the Arrhenius model（R^2= 0. 988）,and the calculated activation energy was 14. 44 kJ·mol^-1. Radical scavenging by tert-butanol and isopropanol as molecular probes show that the degradation of red 4 BS by ZVI activated persulfate is a SO^-4·dominanted reaction process.