水动力传质在臭氧氧化水处理工艺的研究进展

臭氧氧化具有氧化能力强、反应速率快、对环境友好等特点，在水处理工艺中受到广泛关注。但臭氧在水处理中的应用存在利用率低、能源和运营成本高等问题。根据反应器的复杂程度以及规模扩大化应用，水动力传质技术是提高气液传质和臭氧氧化效率的重要手段，这已成为臭氧强化传质发展的趋势。文中阐述了传统反应器和微气泡反应器面临的问题，介绍了基于填料式反应器、振荡流反应器、气-液膜接触器、水动力空化等多种水动力传质技术在臭氧氧化水处理工艺的研究进展，并讨论了水动力传质技术在臭氧氧化工艺未来的发展方向以及待解决的问题。     

臭氧催化氧化反应器模拟与分析

臭氧催化氧化法是一种高效的污水处理技术,是目前污水高级处理的主要手段之一。传统的建模方法无法研究反应器内污水浓度的时空分布和操作条件对反应器的影响,本研究利用计算流体力学（CFD）,耦合多孔介质流动与传质和化学反应动力学多物理场模型,研究臭氧催化氧化过程中目标污染物浓度随时间和空间的分布情况,计算结果与实验结果有良好的一致性。进一步研究臭氧浓度和流量、循环水流量、催化剂层高度、催化剂颗粒大小等对臭氧催化氧化处理废水效率的影响,评估出最优的实验方案。结果表明,在不改变当前反应器主体结构的情况下,最优的操作条件是：臭氧浓度30～40mg/L,臭氧进口流量40～60mL/min,循环水量200～250mL/min,催化剂层填充高度600～800mm,催化剂颗粒半径大小为2mm。该研究有助于理解、设计和优化污水处理反应器。     

转鼓反应器中油酸氧化裂解制备壬二酸的研究

在转鼓反应器中实现了油酸臭氧氧化裂解制备壬二酸的连续化操作。考察了转鼓转速、液体流量、气体流量对转鼓反应器内气液传质反应速率的影响。在双膜理论的基础上,利用恩田公式来计算气相传质系数、液相传质系数,建立了转鼓反应器中两步反应速率模型,并将模型预测值与实验值进行了比较。实验结果表明:在转鼓反应器中,油酸氧化裂解反应速率分别随转鼓转速和液体流量的增大,先增大后趋于平缓;随着气体通量的增加,转鼓反应器内油酸氧化裂解反应速率先增大然后减小;在转鼓转速为1 699 r/min、液体流量为45 mL/min、气体流量为3 L/min时,在转鼓内油酸氧化裂解可获得最大的气液传质反应速率。模型预测值与实验值比较,两者吻合得较好,验证了模型的可靠性。     

Ce3+的臭氧氧化动力学研究

为探究Ce3+的臭氧氧化机理,在间歇式鼓泡反应器中,研究了温度、硝酸浓度和初始Ce3+浓度等对臭氧(O3)氧化三价铈Ce3+生成四价铈Ce4+过程的影响。在对体积传质系数、液相传质系数等传质特性参数分析的基础上,证明了臭氧与Ce3+反应的过程主要发生在液相主体,反应处于慢速动力学区域,并据此建立了反应的动力学模型。通过与实验数据进行比对,拟合得到了相应的模型参数。其宏观反应速率常数与温度的关系为:k=733585.9exp(-39257.1/RT),活化能Ea为39.2571 kJ·mol-1。在实验条件下,动力学模型的计算结果与实验结果吻合较好。     

微反应器内甲苯气固催化氧化反应动力学

微通道反应器具有优良的传热、传质性能，能有效避免催化剂床层内热点的形成，为研究强放热反应动力学提供有利条件。开展了微反应器内的V2O5/TiO2催化剂上的甲苯气相选择氧化动力学研究，在简化反应网络的基础上建立了动力学模型，并给出动力学参数。该模型能较好地反映和预测较宽的反应条件范围内的甲苯气固相催化氧化反应转化率及产物分布，为优化操作条件提供依据。     

催化臭氧氧化降解水中有机污染物的研究进展

水污染是当前工业发展中亟待解决的问题之一,催化臭氧氧化降解有机污染物工艺具有绿色、高效和工艺简单的优点而被广泛应用,而其中的关键在于催化剂的选用。本研究对均相催化臭氧氧化和非均相催化臭氧氧化过程的机理进行了分析和总结,着重讨论了非均相催化臭氧氧化过程常采用的贵金属催化剂、过渡金属催化剂、碱土金属催化剂和非金属催化剂对臭氧氧化降解有机污染物的促进作用,对提高这些催化剂催化活性的方法进行了综述,总结了pH值、臭氧浓度、催化剂剂量和有机污染物浓度对催化臭氧氧化降解有机物过程的影响。指出目前催化臭氧氧化降解有机污染物过程面临的主要问题是活性组分的流失导致催化剂催化活性下降。在今后的研究中,开发和制备新型、高效、绿色、稳定的催化剂以及探究最佳工艺条件仍是研究的重点。可以通过提高催化剂的吸附能力以改善臭氧在水溶液中的传质,促进臭氧分子的分解,还可以通过不同活性组分的协同偶联有效抑制活性组分的流失,提高催化剂催化活性的同时提高催化剂的稳定性,以达到高效降解有机化合物的目的。     

臭氧催化氧化技术在废水处理中的研究进展

介绍了催化臭氧氧化的主要类别,分别叙述了均相和非均相臭氧催化氧化技术在降解废水中的应用及作用机理。分析了溶液pH值,臭氧投加量、投加方式、反应器,催化剂,反应温度等因素对臭氧催化氧化体系的影响。针对催化剂在催化臭氧氧化处理废水中存在的问题,对催化剂的制备指出改进的建议。根据不同的工业废水制备专项催化剂,并且与高效反应器结合是未来非均相催化臭氧化技术的发展方向。     

臭氧催化氧化技术在废水处理中的研究进展

介绍了催化臭氧氧化的主要类别,分别叙述了均相和非均相臭氧催化氧化技术在降解废水中的应用及作用机理。分析了溶液pH值,臭氧投加量、投加方式、反应器,催化剂,反应温度等因素对臭氧催化氧化体系的影响。针对催化剂在催化臭氧氧化处理废水中存在的问题,对催化剂的制备指出改进的建议。根据不同的工业废水制备专项催化剂,并且与高效反应器结合是未来非均相催化臭氧化技术的发展方向。     

臭氧催化剂的制备及其应用研究进展

催化臭氧氧化技术在处理难降解有机废水领域具有很大应用前景,催化剂是实现催化臭氧氧化的关键材料。本文综述了近年来在臭氧催化剂的制备及其应用方面的进展。臭氧催化剂主要是以Mn、Fe、Co等过渡金属氧化物为活性组分,负载型催化剂的载体主要有氧化铝、分子筛、活性炭等。与金属氧化物催化剂相比,负载型催化剂和碳质材料催化剂具有较好的催化效果。催化剂应用性能研究大多为实验室单一成分的有机废水,面向实际复杂工业废水研究开发优良的催化剂,并与具有高效臭氧传质性能的反应器相结合,是未来催化臭氧化技术研究开发的趋势。     

微气泡催化臭氧化-生化耦合工程装置运行性能

采用首例微气泡催化臭氧化—生化耦合工程装置深度处理煤化工废水,对其长期连续运行性能进行评估。结果表明,该工程装置能够稳定可靠运行,微气泡催化臭氧化可有效降解大分子有机污染物并改善废水可生化性,耦合生化处理可进一步去除小分子产物。较优运行条件下,整体COD去除率为57.5%,臭氧投加量/COD去除量为0.63。生化处理中细菌种群受有机污染物变化和DO浓度影响较大。该工程装置为微气泡催化臭氧化-生化耦合工艺实际应用提供了良好示范。     

超重力强化臭氧高级氧化技术的研究进展

臭氧高级氧化技术因其绿色高效、适用性广、操作简便等优势,成为当前水处理领域前沿技术之一,但臭氧在传统反应器内普遍存在吸收效果差,臭氧利用率低等缺陷。旋转填料床（RPB）利用高速旋转的填料产生超重力场,将液体剪切破碎为细小的液膜、液丝或液滴,其较高的相界面积、不断更新的界面以及内部流体的强制湍动,加快了臭氧的传质与分解,该技术对于传质受限的臭氧高级氧化过程的强化有着突出的优势。本文简述了超重力强化臭氧氧化过程的原理,介绍了RPB与O₃、O₃/H₂O₂、O₃/Fenton、O₃/PS（过硫酸盐）、催化臭氧氧化等高级氧化法耦合应用处理有机废水的研究现状,并对超重力技术的优势及技术突破进行了述评,总结了超重力应用臭氧高级氧化技术的潜在经济效益和环境效益,提出功能化填料及大型RPB的开发需求,以期为超重力技术在废水处理领域的拓展应用提供理论基础和技术参考。     

2,4-Xylidine Degradation with Ozonation: Mass Transfer and Reaction Kinetics

The kinetics of the degradation of 2,4-xylidine by ozonation as well as the ozone mass transfer in a wetted-wall column were investigated. A laboratory-scale ozone contactor was designed, and a steady-state wetted wall reactor model was developed. The model was based on countercurrent-connected and perfectly mixed mass transfer stages. It was possible to describe the evolution of the pollutant and ozone concentrations along the reactor length coordinate in various conditions. The model was used for the evaluation of the ozone mass transfer coefficient, reaction rate kinetics, and stoichiometric coefficient from experimental data. The ozone mass transfer coefficient for the wetted-wall column was estimated from the experiments in the absence of chemical reactions. When the estimated parameters were applied, the ozonation model of the wetted-wall column showed good agreement between the fitted and experimental data.     

Development of a tool, using CFD, for the assessment of the disinfection process by ozonation in industrial scale drinking water treatment plants

Foreseen standards regarding microorganism content for drinking water require assessment of the capability of existing plants to reach the upcoming requirements. This paper presents the development of a tool to assess this capability in a commonly encountered key step of water disinfection: ozonation. In this paper, this tool is applied to the test case of an ozonation channel of the Belgian drinking water producer Vivaqua. This tool is based on a mathematical model of the momentum and mass transport phenomena in an ozonation channel. The gas–liquid flow is coupled to ozone mass transfer and kinetics describing the ozone and microorganisms concentrations decay. The degradation of Bacillus subtilis spores, as a representative of resistant microorganisms, is implemented in the model. The model takes explicitly into account the bubble size variation and its impact on mass transfer. Bubbles sizes and kinetics parameters are estimated based on dedicated experiments. The model is partially validated by comparing simulations results, obtained using computational fluid dynamics, to experimental residence time distributions, residual ozone concentration and Bacillus subtilis spores degradation efficiency measurements obtained on the studied ozonation channel. It is shown that, at the industrial scale, bubble diameter variation has a significant impact on ozone concentration in the liquid at the reactor exit. Using the tool, it is also shown that, the ozonation channel of Vivaqua can be used to achieve degradation of resistant microorganisms but only with its maximal flow rate and concentration of ozone injection. Moreover, at low operating temperature, some microorganisms that present latency towards reaction with dissolved ozone might hardly be destroyed.     

Ozonation Dynamics and Its Implication for Off-Gas Ozone Control in Treating Pulp Mill Wastewaters

Ozonation of biologically pretreated pulp mill wastewaters was studied using both bench and pilot scale fine bubble contactors to determine the oxidation efficiencies, mass transfer coefficients (k_La) and enhancement factors (E) due to the occurrence of chemical reactions. A sensitivity analysis based on the measured process parameters was then used to reveal the interrelated effects of key factors on off-gas ozone concentrations. It was shown that the removal efficiencies of color and AOX were simply related to the amount of utilized ozone, regardless of variation of other operating conditions. Furthermore, the rate of absorption fell within the fast or instantaneous kinetics regimes due to the occurrence of rapid chemical reactions. The Ek_La values were found to vary substantially during the course of ozonation, indicating that the enhancement factors were not only affected not only by operating conditions but also by wastewater characteristics. To effectively control the off-gas ozone emission, measures should be taken to minimize the backmixing, use a counter-current flow arrangement and provide adequate contact time.     

Urban Wastewater Treatment by Catalytic Ozonation

This study focuses on the catalytic ozonation of organic matter recalcitrant to usual water treatment technologies. Experiments aimed to investigate the efficiency of the process TOCCATA®, which uses a granular catalyst coupled with ozonation. Comparison was made between single ozonation, single adsorption onto the catalyst and catalytic ozonation. Adsorption was proven to contribute to decreased dissolved organic carbon. Catalytic ozonation enhanced organic matter removal and ozone transfer compared to single ozonation. Catalytic ozonation was modeled with global apparent first-order kinetics and single adsorption with pseudo–second-order sorption kinetics.     

臭氧相关水处理工艺及其传质特征研究进展

通过对臭氧的性质和不同的反应机理介绍,回顾了臭氧在水处理中的应用发展概况,并介绍了臭氧在实际处理应用中的设备的3个关键部分,包括臭氧发生器、臭氧接触反应系统和臭氧破坏装置。在工艺设计、活化及催化方法开发的基础上,臭氧在水中传质过程的优化也是技术创新的重要环节,所以本文阐述了臭氧的传质速率影响因素,而臭氧接触器是改善传质的具体工程手段。基于人们对臭氧传质过程的理解,逐渐对臭氧接触器进行了设计和改进,本文对几种典型类型的接触器的发展历程和研究现状进行了介绍,并且对其各自的传质特征研究进行对比与总结,结果得出大流量工况下静态混合器的体积传质系数K_La高达2s^-1,而小流量工况下射流式接触器和微气泡反应器的K_La可分别达到216.15s^-1和4000s^-1,并且发现臭氧反应中仍有某些问题需要进一步研究,如气泡直径等参数可以多加注意和臭氧体系中的界面反应的进一步研究。     

Ozonation of CI Reactive Black 5 using rotating packed bed and stirred tank reactor

This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry     

Ozonation of the reactive dye intermediate 2‐naphthylamine 3,6,8‐trisulphonic acid (K‐Acid): kinetic assessment,ozonation products and ecotoxicity

Ozonation of the commercially important, recalcitrant reactive dye intermediate 2‐naphthylamine 3,6,8‐trisulphonic acid (K‐Acid) was investigated. Ozonation performance was examined by following ozone absorption rates and K‐Acid, chemical oxygen demand and total organic carbon removals. Mean oxidation states and unidentified organic products were also determined. At pH 3, where direct ozone reactions are dominant, the second‐order rate constant between K‐Acid and molecular ozone was determined as 20 m ^?1 s^?1 for steady‐state aqueous ozone concentration. The competition kinetics approach was also adopted where a reference compound, phenol, and K‐Acid were subjected to ozonation. By applying this method, the second‐order reaction rate constant was found to be 76 m ^?1 s^?1. Common oxidation products formed during ozonation at pH 3, pH 7 and pH 7 with 1 mm hydrogen peroxide were identified as methoxy‐phenyl‐oxime, phenol, benzene, benzaldehyde and oxalic acid via high‐performance liquid chromatography and gas chromatography/mass spectrometry analyses. Continuous nitrate and sulphate evolution were observed during K‐Acid ozonation as a consequence of the abrupt release and subsequent oxidation of its amino and sulphonate groups. The number and amount of reaction products were most intensive for K‐Acid ozonation at pH 7 with 1 mm hydrogen peroxide. According to the acute toxicity tests conducted with Vibrio fischeri, ozonation products were not less toxic than the original K‐Acid solution that caused only 15% inhibition.     

溶气过程原理、技术特征及其水处理工程应用

化工、能源和环保等领域都存在气液混合、反应与分离的不同原理的技术应用,涉及多相混合传质及其反应器的工程/工业化生产需求,其中,溶气过程原理与技术特征对应用技术具有重要支撑作用。综合文献及技术报道,从气泡特征、絮体特征来讨论溶气气浮技术,从传质过程、反应过程与能耗评价方面来讨论废水生物处理好氧技术,从O₃发生与性质、传质与催化过程来讨论生物处理尾水的O₃催化氧化深度净化技术。在回顾原理以及分析技术特征的基础上,结合工程案例总结和讨论了溶气原理的废水处理技术/工程实践的发展与潜力。