Abstract:

The purification process of high concentration methanol wastewater intensified by non-thermal plasma(NTP) combined with packed adsorption bed had been investigated. The results showed that the four types of packed bed materials, 4A molecular sieves, ceramsite, ceramic Rasching ring and γ-Al₂O₃, could adsorb methanol rapidly, but reached the adsorption saturation easily. The adsorption velocity and equilibrium absorption capacity of 4A molecular sieves was better than the others. In the multi-needle-plate DBD (dielectric barrier discharge) non-thermal plasma purification system, the degradation rate of COD increased with increasing discharge time and discharge voltage. The degradation effect of NTP combined with packed bed was better than single purification process. In the initial reaction stage of combination process, the rapid degradation of COD was dominated by packed bed adsorption process. However, NTP played a main role in the degradation process with prolongation of discharge time. The methanol, both in liquid phase and adsorbed in packed bed, had been oxidized by active groups which generated by NTP. The maximum degradation rate of COD was more than 90% in this experiment. The adsorption process of packed bed followed the pseudo-second order adsorption kinetic equation. The reaction order of NTP degradation process increased with the decline of pollutant concentration and the prolongation of discharge time. In the synergistic purification system, the adsorption process of packed bed would be influenced by NTP, and vice versa. The active groups generated by NTP had an activating effect on the contaminant, both in liquid phase and adsorbed in packed bed. Therefore, the concentration ratio of contaminant and hydroxyl radical(·OH) in liquid phase would be changed constantly under the process of packed bed adsorption and NTP oxidation. The reaction order of macroscopic reaction kinetics of synergistic process increased with the decrease of methanol concentration in liquid phase.

Key words: non-thermal plasma, packed bed, adsorption, methanol wastewater, macroscopic reaction kinetics

摘要：

采用低温等离子体协同填料床吸附强化氧化降解高浓度甲醇废水。研究表明单独采用4A分子筛、陶粒、陶瓷Rasching环和γ-Al₂O₃不同填料均可吸附废水中甲醇，但较易达到吸附饱和，其中4A分子筛的吸附速率和平衡吸附量优于其他3种填料。单独采用多针板式介质阻挡放电低温等离子体技术，化学需氧量（COD）降解率随放电时间和放电电压增加而增大。采用低温等离子体协同填料降解甲醇废水优于单一净化过程，协同初始阶段以吸附为主，随放电时间延长以等离子体降解反应为主，液相和填料吸附的甲醇同时被等离子体活性基团逐渐氧化降解，最大降解率达90%以上。单独填料吸附过程符合准二级吸附动力学方程。低温等离子体对COD降解反应级数随污染物浓度降低和反应时间延长逐渐增大。低温等离子体协同填料吸附对降解过程相互影响，等离子体活性基团对液相和固相吸附的污染物都有一定的活化作用。填料的吸附作用和等离子体氧化作用会不断改变液相中的污染物浓度与·OH浓度比值，降解过程宏观反应动力学级数随着液相中甲醇浓度降低而逐渐增大。

关键词: 低温等离子体, 填充床, 吸附, 甲醇废水, 宏观反应动力学