【作者】 张延宗；

【导师】 郑经堂；

【作者基本信息】 中国石油大学 ， 化学工程与技术， 2008， 博士

【摘要】 非平衡等离子体水处理技术是集羟基（·OH）等自由基和过氧化氢（H₂O₂）、臭氧（O₃）等活性物质的作用于一体的高级氧化技术,因其能耗少、处理效率高、反应迅速且无选择性、无二次污染等优势,使该技术呈现出良好的应用前景和很大的市场潜力。从目前研究的现状看,放电反应器的结构以及吸附/催化剂的合理选择是限制该技术优势充分发挥的主要障碍。为此,本论文设计了一种新型的放电反应器,以甲基橙为模拟污染物,考察了反应器电极结构及各种工艺参数对降解率、矿化度和能量效率的影响。探索了非平衡等离子体与颗粒活性炭（GAC）、活性炭纤维（ACF）、活性炭纤维复合光催化材料（TiO₂/ACF）联合处理的协同效应,考察了GAC和ACF的吸附性能、催化O₃转化成·OH的性能以及TiO₂/ACF的吸附和光催化性能;分析了脉冲放电对其孔结构和表面化学性质的影响,探讨了非平衡等离子体与上述材料联合处理的协同机制。通过一系列的实验研究和分析,取得了如下研究成果:高压脉冲电源向液相中的高压针电极和气相中地电极施加脉冲高压后,在液相和气相同时放电,液相产生·OH、H₂O₂等活性物种,气相产生O₃。在地电极之上注入处理溶液并且在处理溶液中设置阻挡网,提高了O₃的利用率。循环管和蠕动泵使预氧化区和主氧化区中的溶液构成循环,使预氧化区中经O₃氧化的溶液在主氧化区进一步得到处理,实现了多种氧化技术的有机结合,提高了处理效率。主氧化区降解有机污染物的主要途径是·OH进攻,预氧化区降解有机污染物存在两种机理,即O3的亲电子进攻和O3分解产生?OH的进攻。处理40mg/L的0.1L溶液,降解率达到90%,实验误差小于3.4%。增加溶液初始浓度或处理液量能提高O3的利用率,从而提高反应器的能量效率,处理0.1L浓度为40、60、80、100mg/L的溶液,反应器的能量效率分别达到2.1、2.8、3.4、3.6g/（kWh）;处理液量增大1倍,反应器的能量效率分别增加到4.1、5.4、5.9和5.9g/（kWh）。脉冲放电与GAC或ACF联合处理显示出很好的协同效应,协同效应的产生主要归因于GAC和ACF的吸附和催化作用。GAC和ACF是一个浓集中心,在其表面及其周围毗邻区域通过吸附创造了高浓度的环境,而GAC和ACF表面则是转化分解中心,其表面上的碱性官能团能促进O₃分解产生·OH,从而提高了甲基橙的降解率和COD的去除率。由于孔结构和表面化学性质的差异,使ACF表现出比GAC更优异的吸附和催化性能,脉冲放电与GAC联合处理浓度为60mg/L的0.2L溶液,降解率始终维持在92%左右,COD的去除率达到78%,能量效率达到6.2g/（kWh）;脉冲放电与ACF联合处理浓度为80mg/L的0.2L溶液,降解率始终维持在92%左右,COD的去除率达到82%,能量效率达到8.3g/（kWh）。重复使用表明GAC和ACF的吸附和催化活性未因使用次数的增加而降低,而且GAC和ACF在脉冲放电过程中获得了原位再生,再生率分别达到80%和90%。在脉冲放电过程中,由于非平衡等离子体和O₃的共同氧化,GAC和ACF表面的酸性和碱性官能团都具有不同程度的增加,比表面积和孔容具有不同程度的增加或减少,因此,GAC和ACF在联合处理过程中起着催化O₃转化成·OH的引发剂或催化助剂的作用。脉冲放电与TiO₂/ACF的联合处理表现出明显的协同效应,协同效应的产生主要归因于TiO₂/ACF的吸附和TiO₂的光催化作用。由于吸附的溶解O3很容易与TiO₂表面上的电子反应,减少了TiO₂表面上电子与空穴的复合,提高了光催化反应的光量子效率,从而使反应趋于更彻底。重复使用过程中TiO₂/ACF的催化活性基本保持不变,处理0.2L浓度为80mg/L的溶液,降解率维持在97%,COD的去除达到91%,能量效率达到8.7g/（kWh）,且TiO₂/ACF的再生率达到了95%。在重复使用过程中,TiO₂/ACF的表面形态和性质不受脉冲放电的影响,而孔结构仅有较小的改变。用ACF做光催化剂的载体既可达到固载的效果,同时又藉以良好的界面传质实现了吸附与催化的有机结合。更多还原

【Abstract】 Non-equilibrium plasma water treatment is an advanced oxidation technology, which integrates effectiveness of many active species including hydroxyl radical, hydrogen peroxide, ozone, etc., and bears preferable future application and large market potential because of its advantages such as low energy consumption, high treatment efficiency, rapid and non-selective reactivity, and free of secondary pollution, etc.. The current difficulties for widely application of this technology exist mainly in structure-designing of electrical discharge reactors and selection of appropriate adsorbents and catalysts. In this work, a novel electrical discharge reactor was designed for degrading methyl orange as the model pollutant in water. The effect of electrode configuration and influence of technological parameters on degradation efficiency, mineralization and energy efficiency were investigated. The synergistic effect of non-equilibrium plasma combined with granular activated carbon （GAC）, activated carbon fiber （ACF）, and TiO₂/ACF composite for treatment of methyl orange in water was investigated. The performance of GAC and ACF for adsorption of pollutants and catalytic conversion of ozone to hydroxyl radical was evaluated. The effectiveness of photocatalysis by TiO₂/ACF composite was also testified with analyzing the influence of pulsed discharge on its pore structure and surface chemistry. And the synergistic mechanism of photocatalysis with non-equilibrium plasma was discussed.With pulsed voltage supplied between the high voltage needle electrode in the aqueous phase and the ground electrode in gas phase, activate species of hydroxyl radical and hydrogen peroxide were produced in liquid phase and that of ozone in gas phase. The utilization efficiency of ozone was increased by injection of pretreatment solution and setup of mesh barrier therein. The solution was circulated in pre- and main-oxidation zone driven by a peristaltic pump through circulation pipes in order to further treat the solution in main-oxidation zone which has been pre-oxidized in pre-oxidation zone. In the main-oxidation zone, the organic pollutants were mainly degraded by hydroxyl radical attack. While in pre-oxidation zone, there exist two ozone degradation passways, which were direct electrophilic attack and hydroxyl radical attack. The degradation efficiency of 0.1 L solution with concentration of 40 mg/L was 90% with experimental error lower than 4%. The ozone utilization efficiency could be enhanced by increase of solution concentration or handling capacity, by which the reactor energy efficiency was improved. The reactor energy efficiency were 2.1, 2.8, 3.4 and 3.6 g/（kWh） for 0.1 L solutions with concentrations of 40, 60, 80, and 100 mg/L, respectively, and 4.1, 5.4, 5.9, and 5.9 g/（kWh） respectively for doubled handling capacity of solutions with above mentioned concentrations.The combined treatment by pulse discharge with GAC or ACF showed good synergistic effect due to the adsorption and catalysis of GAC and ACF. A high concentration of methyl orange on GAC and ACF surfaces was achieved by adsorption. And the surfaces performed as conversion and decompose centers of methyl orange, where the basic functional groups on GAC and ACF accelerated the conversion of ozone to hydroxyl radical, which increased methyl orange degradation and COD removal efficiency. Due to its distinct difference of pore structure and surface chemistry to GAC, ACF showed superior adsorption and catalytic performance. The adsorption and catalytic activity of both GAC and ACF do not showed observable decrease in recycle utilization. In combined treatment of 0.2 L solution with concentration of 60 mg/L, the degradation efficiency remained around 92%, and COD removal at 82%, and energy efficiency reached 8.3 g/（kWh）. The GAC and ACF used were regenerated in-situ by the pulsed discharge process, with regeneration efficiency of 80% and 90%, respectively. Owing to co-oxidation of non-equilibrium plasma and ozone, the surface acidic and basic functional groups on GAC and ACF increased to various extent, and specific surface area and pore volume changed in various degrees. Therefore, it is reasonable to assert that GAC and ACF act as initiator or promoter for ozone conversion to hydroxyl radical in the process of combined treatment.The combination of pulsed discharge and TiO₂/ACF showed more distinctive synergistic effect, which was mainly ascribed to the adsorption of TiO₂/ACF and photocatalysis. The easy reaction of dissolved ozone with electrons on TiO₂ surface decreased the recombination of surface electrons with cavities, and increased photon quantum efficiency of photocatalysis to impel the reactions to complete conversion. The catalytic activity of TiO₂/ACF kept unchanged during recycling. In the combined treatment of 0.2 L solution with concentration of 80 mg/L, the degradation efficiency maintained at 97%, and COD removal reached 91%, with energy efficiency of 8.7 g/（kWh） and TiO₂/ACF regeneration efficiency of 95%. The surface morphology and property of TiO₂/ACF did not influenced by pulse discharge with minor change in pore structure. Therefore, with ACF as support of photocatalyst, adsorption and photocatalysis was combined to obtain favorable performance by interfacial mass transfer.更多还原