The practical applicability of decolorization techniques for synthetic textile wastewater (STW) mimicking real conditions in terms of organic matter and carbonate alkalinity content remains unclear. To address this issue, this study investigated the decolorization of an anthraquinone dye, Acid Blue 25 (AB-25), in STW using advanced oxidation processes (AOPs). The oxidation kinetics of AB-25 in STW and ultra-pure water (UPW) under UV-H₂O₂ and UV-TiO₂ were comparatively studied. In UPW, the first-order rate constant with UV-TiO₂ (0.5 g/L; k: 2.79 × 10⁻² 1/min) was more than twice that with UV-H₂O₂ (100 mg/L; k: 1.14 × 10⁻² 1/min), corresponding to 85% and 72% decolorization, respectively. Interestingly, in STW, the decolorization was slightly higher with UV-H₂O₂ than with UV-TiO₂; at neutral pH, the first-order rate constants were 2.1 × 10⁻³ 1/min and 1.8 × 10⁻³ 1/min, accounting for 29% and 21% decolorization, respectively. This behavior can be attributed to the influence of background constituents, especially alkaline components (carbonate, bicarbonate). The combined influence of alkalinity and pH accounted for ~ 45%. For practical application, these results suggest that pH should be kept under 4.5 to ensure feasible treatment of STW via AOPs. Furthermore, the oxidation patterns reveal that decolorization of AB-25 results in the formation of sulfates due to desulfonation.

Graphical abstract

中文翻译：

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通过高级氧化工艺对纺织废水进行化学脱色：酸性蓝25关键参数的案例研究

在有机物质和碳酸盐碱度含量方面模拟实际条件的合成纺织废水（STW）的脱色技术的实际适用性仍不清楚。为了解决这个问题，本研究使用高级氧化工艺（AOP）研究了STW中蒽醌染料酸性蓝25（AB-25）的脱色。比较研究了UV-H ₂ O ₂和UV-TiO ₂下AB-25在STW和超纯水（UPW）中的氧化动力学。在UPW中，UV-TiO ₂（0.5 g / L; k：2.79×10 ^-2  1 / min）的一级速率常数是UV-H ₂ O ₂（100 mg / L; k）的一级速率常数的两倍以上。：1.14×10 ^-2  1 / min），分别对应于85％和72％的脱色。有趣的是，在STW中，UV-H ₂ O ₂的脱色略高于UV-TiO ₂的脱色。在中性pH下，一级速率常数为2.1×10 ^-3  1 / min和1.8×10 ^-3 1 / min，分别占脱色的29％和21％。此行为可归因于背景成分的影响，尤其是碱性成分（碳酸盐，碳酸氢盐）的影响。碱度和pH的综合影响约占45％。对于实际应用，这些结果表明pH值应保持在4.5以下，以确保通过AOP对STW进行可行的处理。此外，氧化图表明AB-25的脱色导致由于脱磺而形成硫酸盐。

图形概要