活性炭与pH值对臭氧化过程动力学参数影响

Effects of Activated Carbon Particles and pH on Ozonation Kinetic Parameters

以亚甲基蓝为典型的合成大分子化合物,实验考察了pH值以及粒状非均相填料活性炭对臭氧化反应动力学参数的影响。实验证明,在充分的臭氧提供较高的传质势能下,底物的降解遵循稳定的准一级动力学。pH值可大幅度地改变反应的速率常数,碱性可导致溶解的臭氧分子生成有效自由基,进而促进与底物反应。粒状活性炭在反应过程中起到吸附、催化和缓冲三重作用。活性炭的吸附中和效应有利于体系pH维持在所需相对稳定值,可减少臭氧的反应需求量。研究推测了可能的反应机理,表明臭氧-活性炭工艺在适宜的条件下对大分子有机物的降解具有良好效果。

Ozonation of methylene blue （MB） was studied in a semi-batch bubble column. The stable and prolonged pseudo-first-reaction kinetics was observed during decolorization process of MB, which is due to higher driven force of feeding-gas leading to over-dosed property of dissolved ozone. In buffered solutions, the decolorization rate constant increased with pH value exponentially by nonlinear regression analysis, showing a high correlation. At higher concentrations of 0.003 mol/L in basic conditions of pH 12.7, bicarbonate presented stronger scavenging effect in comparison with tert- butanol, and different pathways of scavenging were deduced based on experimental data of ozone consumption rate. With finite catalytic effect on decolorization of MB, granular activated carbon（GAC） acts both as adsorbent of some intermediates and catalyst during ozonation process, and possible catalytic mechanisms of GAC were speculated. Apart from its catalytic contribution to both MB removal and TOC abatement, the GAC system can save more feeding-ozone for its other possible utilization.