Abstract:

When alkali catalyzes hydrogen peroxide to degrade pollutants, different alkali catalysts have different mechanisms of catalyzing hydrogen peroxide to degrade pollutants. The study selected sodium hydroxide, sodium carbonate, sodium bicarbonate, and disodium hydrogen phosphate as different alkali catalysts, and used tetracycline as the target pollutant to explore the rules and mechanisms of the degradation of tetracycline by alkali-catalyzed hydrogen peroxide systems. The effects of pH, tetracycline concentration, H₂O₂ concentration, buffer substance dosage, buffer substance type and pre-reaction time on the degradation of tetracycline were investigated. The results showed that pH had the most significant effect on the degradation effect of tetracycline, with the best effect at pH 10.00—10.50, and the rest of the influencing factors did not produce significant effects within the gradient range studied in this paper. Meanwhile, it was found that the pH of different alkali-catalyzed hydrogen peroxide systems had different trends during the reaction process. In other systems, the pH decreased continuously as the reaction proceeded, while the pH increased continuously during the degradation of tetracycline in the NaHCO₃-H₂O₂ system, and it was speculated that this phenomenon was caused by the process of $\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{4}}^{-}$ production after the analysis of the carbon conversion mechanism. The degradation of tetracycline was divided into two processes, decolorization and mineralization: free radical quenching experiments proved that free radicals did not contribute much to the decolorization process of tetracycline. CO₂ flux experiments confirmed that $\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{4}}^{-}$ does not oxidize tetracycline and that the main acting substance in tetracycline decolorization is $\mathrm{H}{\mathrm{O}}_{\mathrm{2}}^{-}$. By comparing the TOC test results of NaOH-H₂O₂ system and NaHCO₃-H₂O₂ system, it was found that the mineralization degree of NaOH-H₂O₂ system was higher than that of NaHCO₃-H₂O₂ system, and EPR electron paramagnetic resonance experiments revealed that the signals of HO^· and ${\mathrm{O}}_{\mathrm{2}}^{·-}$ in the NaOH-H₂O₂ system were higher than that of the NaHCO₃-H₂O₂ system, and that mineralization process of free radicals are the main oxides.

Key words: tetracycline, bicarbonate, hydrogen peroxide, alkaline catalytic, mechanism of action

摘要：

在碱催化过氧化氢降解污染物时，不同的碱催化剂催化过氧化氢降解污染物的作用机制有所不同。选取氢氧化钠、碳酸钠、碳酸氢钠、磷酸氢二钠作为不同的碱催化剂，以四环素作为目标污染物，探究碱催化过氧化氢体系降解四环素的作用规律与机制，考察了pH、四环素浓度、H₂O₂浓度、缓冲物质投加量、缓冲物质种类、预反应时间对四环素降解效果的影响。结果表明：pH对四环素降解效果影响最为显著，在pH为10.00~10.50时效果最佳，其余影响因素在本研究梯度范围内未产生显著影响。同时发现不同碱催化过氧化氢体系的pH在反应过程中的变化趋势不同，在其他体系中随反应进行pH不断降低，而在NaHCO₃-H₂O₂体系降解四环素过程中pH不断升高，经过碳转换机制分析推测该现象是由$\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{4}}^{-}$产生过程造成的。四环素的降解分为脱色与矿化两个过程，自由基淬灭实验证明其对四环素脱色过程贡献度不高。CO₂通入实验证实$\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{4}}^{-}$不氧化四环素，四环素脱色的主要作用物质是$\mathrm{H}{\mathrm{O}}_{\mathrm{2}}^{-}$。对NaOH-H₂O₂体系与NaHCO₃-H₂O₂体系的TOC检测结果对比发现，NaOH-H₂O₂体系的矿化度高于NaHCO₃-H₂O₂体系。EPR电子顺磁共振实验发现，NaOH-H₂O₂体系中HO^·与${\mathrm{O}}_{\mathrm{2}}^{·-}$信号高于NaHCO₃-H₂O₂体系，矿化过程中自由基是主要氧化物。

关键词: 四环素, 碳酸氢盐, 过氧化氢, 碱催化, 作用机制