Abstract:

Dye wastewater has the characteristics of large coloring, complex components, strong biological toxicity and difficulty degradation. The Fe⁰/H₂O₂ system can efficiently remove refractory contaminants from dye wastewater because of its great oxidation capability, rapid and efficient response and low cost. In this study, the Fe⁰/H₂O₂ process was utilized to treat simulated dye wastewater and the response surface method was employed to optimize process conditions. Reactive free radicals were detected by using electron paramagnetic resonance (EPR), and the degradation mechanism of dye wastewater was analyzed by comparing the changes in organic components before and after treatment using Fourier transform infrared spectroscopy (FT-IR) and ultraviolet visible light (UV-Vis). The changes of removal efficiencies of crystal violet, saffron T, TOC, COD and chroma in the dye wastewater were investigated. The degradation kinetics and degradation mechanisms of dye wastewater were explored. The results showed that the predicted removal efficiency of crystal violet using response surface method was 97.94%, which was only 0.36% (<2%) lower than the measured value, and the predicted removal efficiency of saffron T was 77.31%, which was only 1.3% (<2%) lower than the measured value, under the initial pH of 3, iron powder concentration of 0.3 g/L and H₂O₂ dosage of 20 ml/L. According to the kinetic study, the degradation processes of crystal violet, saffron T, COD and chroma were consistent with the BMG kinetic model. The correlation coefficient was higher than 0.98 and the initial degradation rate of crystal violet was the fastest. According to EPR analysis, ·OH was the main active substance for degradation of dye wastewater. According to FT-IR and UV-Vis spectroscopy, removal efficiencies of crystal violet and saffron T was the highest using the Fe⁰/H₂O₂ process, and the dye molecules were oxidized into small intermediates or small molecules. According to gas chromatography-mass spectrometry (GC-MS), the molecular structure of crystal violet and saffron T was destroyed by ·OH. The intermediate products were gradually degraded with the reaction, and finally decomposed into CO₂ and H₂O.

Key words: radical, response surface model, dye wastewater, kinetics, degradation

摘要：

染料废水具有色度大、成分复杂、生物毒性强和难降解的特点。Fe⁰/H₂O₂体系氧化能力强、反应快速高效、成本低廉，可有效去除染料废水中的难降解污染物。采用Fe⁰/H₂O₂工艺处理染料废水，利用响应面法优化工艺运行条件，通过电子顺磁共振波谱仪（EPR）检测活性自由基，采用傅里叶变换红外光谱（FT-IR）和紫外-可见光谱（UV-Vis）分析染料废水处理前后有机物成分的变化，考察染料废水中结晶紫、藏红T、TOC、COD和色度的去除率变化，探究染料废水的降解动力学和降解机理。结果表明：在初始pH为3、Fe⁰浓度为0.3 g/L、H₂O₂投加量为20 ml/L的条件下，利用响应面法预测结晶紫去除率为97.94%，与实测值仅相差0.36%（<2%）；藏红T去除率为77.31%，与实测值仅相差1.3%（<2%）。由动力学分析可知：结晶紫、藏红T、COD和色度的降解过程符合BMG动力学模型，相关系数大于0.98，结晶紫的初始降解速率最快。由EPR分析可知：·OH为Fe⁰/H₂O₂降解染料废水的主要活性物种；通过FT-IR和UV-Vis检测分析可知：Fe⁰/H₂O₂工艺对结晶紫和藏红T的去除效果最好，染料分子被氧化成分子量小的中间体或小分子物质；由气相色谱-质谱（GC-MS）分析可知：结晶紫与藏红T分子结构被$·\mathrm{O}\mathrm{H}$破坏，随着反应的进行产生的中间产物逐渐被降解，最终分解为CO₂和${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$。

关键词: 自由基, 响应面模型, 染料废水, 动力学, 降解