不同晶型二氧化锰催化臭氧化降解亚甲基蓝废水
Degradation of methylene blue by catalytic ozonation with different crystalline MnO2
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摘要: 采用水溶液化学沉积法制备纳米二氧化锰，生成了δ-MnO2、γ-MnO2、α-MnO2，采用XRD、SEM和BET等手段进行了表征。以碱性染料亚甲基蓝为目标污染物，不同晶型纳米二氧化锰作吸附剂进行了静态吸附实验；在催化臭氧化亚甲基蓝的实验中，研究了溶液的pH值、催化剂的加量以及自由基引发剂与促灭剂对催化效果的影响。结果表明：3种催化剂δ-MnO2、γ-MnO2和α-MnO2的平衡吸附量分别为58.47、50.87和40.52 mg·g-1，其中δ-MnO2的吸附性能较强；3种催化剂的吸附动力学符合准二级吸附动力学。当溶液pH=11时，催化臭氧化反应体系对亚甲基蓝的降解效果最佳。在此催化臭氧化系统下，主要遵循的是羟基自由基的反应机理。δ-MnO2应用于催化臭氧化亚甲基蓝，不仅具有良好的脱色效果，并具有一定的矿化能力。Abstract: Nano manganese dioxide was prepared by an aqueous solution chemical deposition method, which generated δ-MnO2, γ-MnO2, and α-MnO2. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. The adsorption of methylene blue by different types of crystalline MnO2 was studied. In addition, the effects of the initial pH of the solution, dose of catalyst, quenching agent, and promoter agent were investigated. The results showed that the equilibrium adsorptions of the three types of catalysts were 58.47 mg·g-1, 50.87 mg·g-1, and 40.52 mg·g-1, respectively. The δ-MnO2adsorption performance was the strongest. The adsorption kinetics of the three types of catalysts were more in line with quasi two stage adsorption kinetics. When the initial pH of the solution was 11, a catalytic ozonation reaction system was best for the degradation of methylene blue. In this catalytic ozonation system, the reaction mainly followed a hydroxyl-free radical reaction mechanism. δ-MnO2in the catalytic ozonation of methylene blue not only showed good decolorizing ability but also caused a certain degree of mineralization.
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Key words:
- manganese dioxide /
- ozone /
- adsorption /
- methylene blue
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