Abstract:

To illustrate the influence of zwitterionic surfactants on the degradation of dye wastewater by thermally activated sodium persulfate (SPS), C.I. Reactive Black 5 (RB5) and dodecyl betaine (BS-12) were identified as research subjects to study the effects of BS-12, SPS and temperature on the degradation of RB5. It revealed the relationship between the degradation effect of RB5 and the type of free radicals, and explained the possible degradation pathways of RB5. The results showed that the critical micelle concentration (CMC) of BS-12 in the dye solution was 0.03mmol/L. The concentration of BS-12 affected the rate of RB5 decolorization in the initial stage, but did not change the degree of final decolorization. Compared with the decolorization of the dye solution without BS-12 for 10min, the addition of 0.5CMC BS-12 increased the decolorization rate by 10.45%, while 5CMC BS-12 decreased the decolorization rate by 14.72%. In the thermally activated SPS-degraded RB5 system, dye degradation was attributed to the synergistic effect of ·SO₄^- and ·OH, but ·SO₄^- dominated. Under the synergistic action of free radicals, the —N\stackrel{}{̿}N— and C—N bonds in RB5 were opened to form intermediates containing benzene and naphthalene rings, and the addition of BS-12 was detrimental to the degradation of RB5 when the concentration of free radicals was low.

Key words: reactive dyes, dodecyl betaine, sodium persulfate, sulfate radicals, wastewater

摘要：

为诠释两性表面活性剂在热活化过硫酸钠（SPS）降解染料废水过程中的作用，以C.I.活性黑5（RB5）和十二烷基甜菜碱（BS-12）为例，探究了BS-12浓度、SPS浓度及温度对RB5降解性能的影响，揭示了RB5降解效果与自由基类型的关系，阐释了RB5可能的降解路径。结果表明：BS-12在染液中的临界胶束浓度（CMC）为0.03mmol/L；BS-12浓度影响RB5初始阶段脱色速率，但不改变最终脱色程度。与不含BS-12的染液相比，脱色10min时，加入0.5CMC BS-12可将脱色率提高10.45%，而5CMC BS-12却将脱色率降低了14.72%。在热活化SPS降解RB5体系中，染料降解归因于·SO₄^-和·OH协同作用的结果，但·SO₄^-占主导地位。在自由基的协同作用下，RB5中的—N\stackrel{}{̿}N—和C－N键被打开，形成含有苯环和萘环的中间产物，自由基浓度较低时，加入BS-12不利于RB5降解。

关键词: 活性染料, 十二烷基甜菜碱, 过硫酸钠, 硫酸根自由基, 废水