臭氧微气泡处理有机废水的效果与机制

为解决臭氧氧化有机废水氧化效率差、臭氧利用率低这一问题,本文提出了臭氧微气泡处理有机废水的新技术。采用加压溶气法制备的臭氧微气泡处理苯酚配置的模拟废水,通过显微拍摄、动力学分析、紫外-可见吸收光谱、自由基屏蔽等手段对臭氧微气泡的形态大小、氧化效果、传质特性和氧化机制进行了研究,并对臭氧气泡直径和界面压力之间的关系进行了深入探讨。试验与数值计算表明,臭氧微气泡平均粒径为20.37μm,处理初始COD浓度为51.2mg/L的有机废水,COD去除速率分别是使用1μm曝气头和100μm曝气头曝气的1.59倍和3.61倍,臭氧利用率达到99.19%以上,氧化过程是自由基为主的间接氧化过程,污染物最终氧化产物为小分子烃和羧酸。微气泡影响下,臭氧分子传质速率和分解速率均有所提高,而臭氧微气泡表面较高的界面压力是其高效传质的原因之一。     

UV强化微气泡臭氧化处理酸性大红3R废水研究

将微气泡臭氧化技术与UV照射相结合强化处理酸性大红3R废水,分析了UV强化微气泡臭氧化过程中的臭氧气液传质、酸性大红3R废水脱色和TOC去除效果。结果表明,UV强化微气泡的臭氧传质系数和分解系数分别为单独微气泡臭氧时的1.6、1.2倍。UV强化微气泡臭氧处理酸性大红3R废水的脱色速率常数为0.185 min~(-1),为单独微气泡臭氧处理的1.2倍。TOC去除反应速率常数为0.0255 min~(-1),为单独微气泡臭氧的1.6倍;TOC去除臭氧反应效率为0.1868 mg/mg,为单独微气泡臭氧的1.3倍。     

微泡强化臭氧传质及其对产生羟基自由基的影响

为提高臭氧在水中的传质效率,设计了微泡反应器强化臭氧传质,考察了在该反应器中不同压力、温度、臭氧进口浓度及流量对液相中臭氧浓度以及羟基自由基产生的影响。结果表明,液相中臭氧浓度受压力影响较小,反应器压力增加可使液相中羟基自由基产生量增大;进口臭氧浓度及流量的增加,可使液相中臭氧浓度以及羟基自由基产生量增大;液相温度升高导致液相中臭氧浓度降低,但可以提高液相中羟基自由基产生量。同时还将该微泡反应体系与传统鼓泡反应器进行对比研究,结果表明,微泡反应器能有效地提高传质效率,液相中臭氧浓度达到稳定状态时约为14 mg/L,比鼓泡反应器高约10%。微泡加压反应器中羟基自由基产生效果更好,臭氧通入5 min,微泡反应器中羟基自由基浓度高达121.45×10~(-6)mol/L,比鼓泡反应器提高了约11倍,且微泡反应器中废水脱色及矿化效率都高于传统鼓泡反应器。     

陶瓷粉体催化臭氧化降解水中苯酚

将陶瓷粉末应用于降解苯酚废水用臭氧化催化剂,表征了陶瓷的化学组成、0电荷pH和表面羟基密度,并考察了反应条件的影响.结果表明,陶瓷粉末对于臭氧化降解质量浓度为100mg·L-1的模拟苯酚废水具有较为显著的催化效果.不同温度的影响试验表明,在278～308 K时,苯酚的降解速率随温度升高而加快,然而(与单独臭氧化比较)在较低温度下陶瓷的催化效果更加显著.结合羟基自由基清除剂的影响试验,推断在催化臭氧化过程中臭氧分子和羟基自由基共同氧化污染物,陶瓷粉末的表面羟基促进了臭氧分子到羟基自由基的转变,因而加快了臭氧化过程.     

超声联合臭氧在水处理中的反应机理及应用

超声通过提高臭氧的分解速率、传质速率以及产生更多具有活性的自由基来强化臭氧的氧化能力,提高污染物的降解速率.利用超声与臭氧结合处理含氮染料废水以及水中难降解有机物如硝基芳香烃非常有效.处理过程中,臭氧投加量、超声的声能密度和环境的pH是主要的影响因素.     

臭氧在对硝基苯酚溶液中的吸收与模拟过程

研究了鼓泡塔中臭氧在对硝基苯酚溶液中的吸收传质过程。首先探讨了pH值和气速对对硝基苯酚降解速率的影响。在 298K下,臭氧被连续通入对硝基苯酚溶液中,臭氧的传质速率因为溶解臭氧与对硝基苯酚的快速反应而大大加强。然后运用与实验条件相同的操作参数,进行了臭氧在鼓泡塔中吸收过程的模拟研究,采用MATLAB软件求解吸收过程的质量平衡方程,模拟了吸收过程中臭氧和对硝基苯酚浓度的变化,并与实验值进行了比较。结果表明,在短的鼓泡塔中,应用全混流模型来描述气相和液相的流体状态是可行的,在 80%的对硝基苯酚降解之前,模拟值和实验值能很好地一致。     

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。     

氯代硝基苯类废水臭氧化动力学和机理

采用半连续臭氧化工艺处理氯代硝基苯类废水,对氯代硝基苯（ClNBs）臭氧化过程反应动力学、臭氧分子与自由基氧化反应的贡献、过程降解机理等方面进行了研究。结果表明,ClNBs降解遵循准一级反应动力学,降解速率顺序为o-CNB相似文献   

活性炭纤维-臭氧氧化处理对硝基苯酚废水的研究

文章采用活性炭纤维吸附处理对硝基苯酚生产废水,回收其中的对硝基苯酚,并通过臭氧氧化进一步去除有机杂质,回收废水中的氯化钠以循环利用。     

微纳米气泡应用于水中污染物氧化降解的进展与挑战

微纳米气泡以其粒径小、存在时间长、传质效率高以及可产生羟基自由基等特性,已在水污染氧化降解领域受到广泛关注。介绍了微纳米气泡的产生机制与行为特性,系统概述了微纳米气泡氧化技术在地下水水体修复、废水处理及地表水净化方面的研究进展。最后,提出了微纳米气泡氧化技术应用于水污染消除的挑战,并展望了微纳米气泡氧化技术在水环境控制中的应用前景和后续研究方向。     

Catalytic decomposition of ozone and para-Chlorobenzoic acid (pCBA) in the presence of nanosized ZnO

This research forwards the evaluating of the efficiency of nanosized ZnO in the application of the catalytic ozonation, determines the reaction kinetics of ozone with the nanosized ZnO, and delineates the characteristics of the decomposition of para-Chlorobenzoic acid (pCBA) and ozone in catalytic ozonation using the nanosized ZnO particles. It was found that the nanosized ZnO enhanced the degradation of ozone and the catalytic ozonation on the surface of the nanosized ZnO significantly enhanced the degradation of pCBA. In catalytic reactions the degradation of pCBA followed two-stage kinetics, initial rapid removal phase (Phase I) and a slower decomposition phase (Phase II). The total degradation rate of pCBA was well matched with the initial removal of pCBA in Phase I. The R_ct values representing the ratio of hydroxyl radicals [OH] and ozone [O₃] were found to increase with an increased concentration of the nanosized ZnO indicating the enhanced transformation of ozone into OH.     

Enhancement of Ozone Mass Transfer by Stainless Steel Wire Mesh and Its Effect on Hydroxyl Radical Generation

ABSTRACT

In order to improve the mass transfer efficiency of ozone in water, stainless steel wire mesh (SSWM) corrugated structure was packed into a microbubble ozone reactor to enhance the mass transfer efficiency. The results showed that the SSWM/O₃ system could effectively improve the mass transfer efficiency. When the concentration of ozone in the liquid phase reached a stable state, it was about 21 mg/L, which was about 14% higher than that of ozone alone; the apparent mass transfer coefficient (K_La) was 0.7255 min^?1, which was about 51% higher than that by ozone alone systems. The hydroxyl radicals in the SSWM/O₃ system were more generated than that of ozone alone. After 6 min of operation, the concentration of hydroxyl radicals increased by 60 µmol/L compared with that in ozone alone system. The Chemical Oxygen Demand (COD) removal efficiency of biologically treated leachate by SSWM/O₃ system was about 10% higher than that of ozone alone system after 120 min of reaction. The effects of pressure, temperature, ozone inlet concentration, and flow rates on the ozone concentration in the liquid phase and the generation of hydroxyl radicals were also investigated. The results indicated that reactor pressure has little effect on ozone concentration in liquid phase, but increasing pressure helps to generate ·OH; ozone concentration and ·OH generation in liquid phase increase with the increase of inlet ozone concentration and flow rate; ozone concentration in the liquid phase decreases with the increase of temperature, but ·OH generation increases with the increase of temperature. Our results indicate that the system consisting of SSWM and microbubble column reactor is an efficient process for the intensification of ozone-based advanced oxidation processes.     

Kinetics and mechanism of nitrobenzene degradation by hydroxyl radicals-based ozonation process enhanced by high gravity technology

This study investigated the indirect oxidation of nitrobenzene (NB) by hydroxyl radicals (·OH) in a rotating packed bed (RPB) using competitive kinetics method with p-nitrochlorobenzene as a reference compound. The rate constants of NB with ·OH are calculated to be between (1.465±0.113) × 10⁹ L/(mol·s) and (2.497±0.192) × 10⁹ L/(mol·s). The experimental data are fitted by the modified Arrhenius equation, where the activation energy is 4877.74 J/mol, the order of NB concentration, rotation speed, and initial pH is 0.2425, 0.1400 and 0.0167, respectively. The ozonation process of NB could be enhanced by RPB, which is especially effective for highly concentrated NB-containing wastewater under alkaline conditions. The high gravity technology can accelerate ozone mass transfer and self-decomposition of ozone to produce more ·OH, resulting in an increase in the indirect oxidation rate of NB by ·OH and consequently effective degradation of NB in wastewater.     

A Novel Method for Degradation of DDT in Contaminated Soil

A novel method for remediation of DDT contaminated soil based on advanced oxidation processes including reactions with hydroxyl radicals and ozone has been developed. On the basis of the conducted experiments the authors concluded that ozone did not degrade DDT in soil. Analysis of degradation products that were formed during exposure to a stream of gaseous ozone indicated that hydroxyl radicals might play a key role in degradation of this compound. In the modified fluidized bed reactor where hydroxyl radicals could be generated from ozone and water vapor, reduction of over 90% of DDT residue level has been achieved. Authors proposed a pathway of DDT degradation, under the influence of hydroxyl radicals and ozone. As a result of this research, an effective method for remediation of DDT-contaminated soil has been proposed.     

Application of Response Surface Methodology for Coffee Effluent Treatment by Ozone and Combined Ozone/UV

This paper reports a study using ozone (O₃) and combined ozone/ultraviolet (O₃/UV) processes for color removal and caffeine degradation from synthetic coffee wastewater using a second-order response surface methodology (RSM) with a three-level central composite face-centered (CCF) design. The effects of O₃ concentration, initial pH, and reaction time were examined for both processes. The reaction time and pH were statistically significant for caffeine degradation and color removal. In the ozonation process, higher caffeine degradation and color removal were observed in alkaline pH, indicating that ozone attacks indirectly, consequently generating hydroxyl radicals. Regarding the ozone/UV process, it was observed that lower caffeine degradation and color removal occurred at neutral pH, indicating an adverse effect due to lower ozone dissolution and consequently the production of a smaller amount of free hydroxyl radicals. The achieved results showed that the techniques were efficient for color removal (85% and 99%, respectively) and caffeine degradation (88% and 98%, respectively).     

Free Radical and Direct Ozone Reaction Competition to Remove Priority and Pharmaceutical Water Contaminants with Single and Hydrogen Peroxide Ozonation Systems

From the application of concepts derived from the gas-liquid absorption film model, the competition between ozone reactions with 72 water emerging or priority contaminants (pharmaceuticals, pesticides, polynuclear aromatic hydrocarbons, etc.) and the initiation steps of the hydroxyl radical decomposition of ozone in ozone alone and combined with hydrogen peroxide oxidation systems has been studied. With this information, the ozone preferential reaction, that is, the ozone direct reaction or the formation of free radicals and the kinetic absorption regime are known. In a second step, the ratio of removal rates of the contaminants studied by reacting with hydroxyl radical and ozone has also been estimated. With this, the way contaminants are preferentially removed (from their reaction with ozone or from the reaction with free radicals) can also be known and, hence, whether or not an ozone advanced oxidation system is convenient to be applied. For instance, most of the contaminants studied in this work at concentrations lower than 50 μgL^?1 and hydrogen peroxide at concentrations lower than 50 mgL^?1 react with ozone under chemical control regime so that both direct and free radical reactions theoretically compete. However, under chemical control, typical concentration of scavengers present in wastewater or surface water would inhibit the free radical reactions and, at least theoretically, for many contaminants studied here, the direct ozone reaction is the principal removal way. When mass transfer controls the process rate only contaminants with a hydroxyl and ozone rate constant ratio ≥ 1.6x10⁶ M^-1s^-1 would be preferentially removed through free radical way.     

Application of Ozone Involving Advanced Oxidation Processes to Remove Some Pharmaceutical Compounds from Urban Wastewaters

Different UVA radiation and advanced oxidation systems, most of them involving ozone, have been applied to remove mixtures of three contaminants of pharmaceutical type: diclofenac (DCF), sulfamethoxazole (SMT) and caffeine (CFF), both in ultrapure and secondary treated wastewater. The influence of the water matrix has been studied in terms of individual compound concentration and TOC removal. Also, biodegradability of the treated wastewater before and after the advanced oxidation process, as BOD/COD ratio, the partial oxidation yield, the increment of average state of carbon oxidation and ozone consumption have been determined. For mgL^?1 to 100 μgL^?1 concentrations and regardless of the ozone process and water type, DCF and SMT are removed in less than 10 min mainly by direct reaction with ozone, especially in the case of DCF. CFF, on the contrary, is mainly removed through hydroxyl radicals. For lower concentration (≤100 μgL^?1), DCF still disappears by direct ozonation, CFF by hydroxyl radicals oxidation and SMT through both direct ozonation and hydroxyl radical oxidation. Once DCF and SMT have disappeared, TOC is removed by reacting with hydroxyl radicals, regardless of the water matrix. Photocatalytic ozonation allows the highest TOC degradation rate, partial oxidation yield, increment of average state of carbon oxidation and biodegradability together to the lowest ozone consumption per mg TOC eliminated.     

超声、臭氧、光催化及其组合工艺处理苯酚废水

研究了在一定条件下,超声、臭氧、光催化等高级氧化技术的不同组合方法对苯酚的降解效果。结果表明,对于质量浓度为100 mg/L的苯酚溶液,反应时间为1 h时,超声、臭氧氧化、光催化三者单独降解率分别为8%、36%、35%。紫外光光催化分别与超声波或臭氧组合对苯酚降解有一定的协同作用,降解率分别为50%、78%;而声光催化技术与臭氧三者组合降解苯酚的效果尤佳,降解率达到85%。这归功于超声波的机械作用对臭氧扩散引起的积极作用以及声光催化协同产生的H2O2,从而生成的羟基自由基。     

基于催化臭氧氧化去除煤化工废水中污染物——苯系物

苯、甲苯、乙苯和二甲苯(BTEX)是煤化工废水中典型的难降解有机污染物,通常情况下BTEX较难通过传统的化学氧化技术去除。笔者自主制备了多孔臭氧催化剂,并对催化剂进行表征分析;考察了催化臭氧化降解BTEX的最佳反应条件,并对不同反应体系中自由基的激发情况进行比对;在此基础上探究催化臭氧化对BTEX的去除机理,为BTEX在实际处理过程中的技术应用提供理论基础。XRD分析结果表明,多孔臭氧催化剂含有氧化铝、氧化硅等,且含有沸石结构的化合物。XPS分析结果表明,所合成的催化剂含Si、O、Cu、Fe、Mn、Al等元素。SEM结果表明,催化剂由许多不规则的细小块状粉末构成,且表面非常蓬松,堆叠成多级结构,使催化剂呈多孔性。比表面积分析表明,催化剂的比表面积为20.8 m^2/g,孔隙直径主要集中在3.8 nm。使用该催化剂对BTEX进行催化臭氧化试验,结果表明,反应温度为30℃、溶液pH=8、臭氧投加量为3.5 mg/L、催化剂投加量为5 g/L时,BTEX的降解效果最佳。在该反应体系中有机物去除率为99.1%,其中苯、甲苯、乙苯、二甲苯的去除率分别为95.6%、98.2%、100%、100%。ESR分析结果表明,催化臭氧化反应体系中羟基自由基和超氧自由基的激发强度明显高于臭氧氧化反应体系,这是因为本文制备的催化剂含有Al、Fe、Mn、Cu氧化物,使催化反应过程中负载的金属氧化物价态间相互变化,转移的电子可促进臭氧分子分解,从而产生更多的自由基。催化臭氧化技术是以羟基自由基为主导,超氧自由基、催化剂吸附为辅助,协同实现煤化工废水中典型有机污染物BTEX的高效去除。     

耐低温对硝基苯酚降解菌的降解动力学研究

以对硝基苯酚在10℃条件下的微生物降解过程为研究对象,融合单因素实验、细胞疏水性实验、细胞膜通透性实验与降解动力学实验探究菌株Pseudomonas sp. ZL对对硝基苯酚的低温降解特性。实验结果表明,在10℃条件下菌株Pseudomonas sp. ZL能够耐受并降解303.71 mg·L^-1的对硝基苯酚,最佳降解条件为pH=8.0,0.5% NaCl,1 g·L^-1 NH₄NO₃,该条件能够显著促进对硝基苯酚的降解速率并大大缩短降解的延迟时间。在10℃、单因素最佳条件下,对硝基苯酚降解菌的抑制降解动力学拟合符合Aiba模型,其中μ_max（最大比生长速率）为0.205 h^-1,K_s（半饱和系数）为3.40 mg·L^-1,K_i（底物抑制系数）为166.86 mg·L^-1,因此166.86 mg·L^-1即为该条件下菌株的低温降解抑制浓度。与其他降解菌株相比,菌株Pseudomonas sp. ZL的K_i和μ_max/K_s较大、K_s/K_i值较小,说明对硝基苯酚对该菌株的抑制作用较小,菌株的有效利用率更高,在原位修复低温地下水及土壤污染方面具有较高的应用潜力。