非热等离子体结合CuO催化剂或Ca(OH)2吸收剂去除氮氧化物

采用非热等离子体结合催化或现场化学吸收的2种方法来去除气流中的NO_x.结果表明,非热等离子体结合催化,反应器内的CuO催化剂能有效地促进NO的还原反应;相对于催化还原NO而言,脉冲电晕作用下能有效地降低NO催化还原的反应温度.当催化剂为CuO,脉冲电压为18kV,反应温度为200℃,还原剂为1%CO及NO进口浓度为719 mg/m³条件下,NO的去除率达到了100%.非热等离子体结合现场化学吸收方法,是一种在常温下从气流中净化氮氧化物的有效方法,NO的去除率远远高于反应器内没有吸收剂的情况.可以认为反应器内的Ca(OH)₂吸收剂通过与NO的氧化产物NO₂或NO₃的吸收反应促进了NO的去除.当反应器内有Ca(OH)₂吸收剂存在时,在脉冲电压为18kV,O₂浓度为2%及NO进口浓度为1 050 mg/m³条件下,NO的去除率达到了100%.     

Degradation of endocrine disruptor bisphenol A in drinking water by ozone oxidation

The ozone oxidation of endocrine disruptor bisphenol A in drinking water was investigated. A stainless completely mixed reactor was employed to carry out the degradation experiments by means of a batch model. With an initial concentration of 11.0 mg/L, the removal efficiencies of BPA (bisphenol A) could be measured up to 70%, 82%, and 90% when the dosages of ozone were 1, 1.5, and 2 mg/L, respectively. The impacts on BPA degradation under the conditions of different ozone dosages, water background values, BPA initial concentrations, and ozone adding time were analyzed. The results showed that ozone dosage plays a dominant role during the process of BPA degradation, while the impact of the contact time could be ignored. UV wavelength scanning was used to confirm that the by-products were produced, which could be absorbed at UV254. The value of UV254 was observed to have changed during the ozonation process. Based on the change of UV254, it could be concluded that BPA is not completely degraded at low ozone dosage, while shorter adding time of total ozone dosage, high ozone dosage, and improvement of dissolved ozone concentration greatly contribute to the extent of BPA degradation. The effects of applied H₂O₂ dose in ozone oxidation of BPA were also examined in this study. The O₃-H₂O₂ processes proved to have similar effects on the degradation of BPA by ozone oxidation. Translated from Environmental Science, 2006, 27(2): 294–299 [译自: 环境科学]     

Numerical evaluation of the effectiveness of NO2 and N2O5 generation during the NO ozonation process

Wet scrubbing combined with ozone oxidation has become a promising technology for simultaneous removal of SO₂ and NO_x in exhaust gas. In this paper, a new 20-species, 76-step detailed kinetic mechanism was proposed between O₃ and NO_x. The concentration of N₂O₅ was measured using an in-situ IR spectrometer. The numerical evaluation results kept good pace with both the public experiment results and our experiment results. Key reaction parameters for the generation of NO₂ and N₂O₅ during the NO ozonation process were investigated by a numerical simulation method. The effect of temperature on producing NO₂ was found to be negligible. To produce NO₂, the optimal residence time was 1.25 sec and the molar ratio of O₃/NO about 1. For the generation of N₂O₅, the residence time should be about 8 sec while the temperature of the exhaust gas should be strictly controlled and the molar ratio of O₃/NO about 1.75. This study provided detailed investigations on the reaction parameters of ozonation of NO_x by a numerical simulation method, and the results obtained should be helpful for the design and optimization of ozone oxidation combined with the wet flue gas desulfurization methods (WFGD) method for the removal of NO_x.     

Reaction mechanism and metal ion transformation in photocatalytic ozonation of phenol and oxalic acid with Ag+/TiO2

Photocatalytic ozonation of phenol and oxalic acid （OA） was conducted with a Ag^＋/TiO2 catalyst and different pathways were found for the degradation of different compounds. Ag^＋ greatly promoted the photocatalytic degradation of contaminants due to its role as an electron scavenger. It also accelerated the removal rate of OA in ozonation and the simultaneous process for its complex reaction with oxalate. Phenol could be degraded both in direct ozonation and photolysis, but the TOC removal rates were much higher in the simultaneous processes due to the oxidation of hydroxyl radicals resulting from synergetic effects. The sequence of photo-illumination and ozone exposure in the combined process showed quite different effects in phenol degradation and TOC removal. The synergetic effects in different combined processes were found to be highly related to the properties of the target pollutants. The color change of the solution and TEM result confirmed that Ag＋ was easily reduced and deposited on the surface of Tit2 under photo-illumination, and dissolved again into solution in the presence of ozone. This simple cycle of enrichment and distribution of Ag^＋ can greatly benefit the design of advanced oxidation processes, in which the sequences of ozone and photo-illumination can be varied according to the needs for catalyst recycling and the different properties of pollutants.     

Addition of hydrogen peroxide for the simultaneous control of bromate and odor during advanced drinking water treatment using ozone

Complete removal of the characteristic septic/swampy odor from Huangpu River source water could only be achieved under an ozone dose as high as 4.0 mg/L in an ozone-biological activated carbon （O3- BAC） process, which would lead to the production of high concentrations of carcinogenic bromate due to the high bromide content. This study investigated the possibility of simultaneous control of bromate and the septic/swampy odor by adding H2O2 prior to the O3-BAC process for the treatment of Huangpu River water. H2O2 addition could reduce the bromate concentration effectively at an H2O2/O3 （g/g） ratio of 0.5 or higher. At the same time, the septic/swampy odor removal was enhanced by the addition of H2O2, although optimization of the H2O2/O3 ratio was required for each ozone dose. At an ozone dose of 2.0 mg/L, the odor was removed completely at an H2O2/O3 ratio of 0.5. The results indicated that H2O2 application at a suitable dose could enhance the removal of the septic/swampy odor while suppressing the formation of bromate during ozonation of Huangpu River source water.     

Co-adsorption of gaseous benzene, toluene, ethylbenzene, m-xylene (BTEX) and SO2 on recyclable Fe3O4 nanoparticles at 0-101% relative humidities

We herein used Fe3O4 nanoparticles(NPs) as an adsorption interface for the concurrent removal of gaseous benzene, toluene, ethylbenzene and m-xylene(BTEX) and sulfur dioxide(SO2), at different relative humidities(RH). X-ray diffraction, Brunauer–Emmett–Teller, and transmission electron microscopy were deployed for nanoparticle surface characterization.Mono-dispersed Fe3O4(Fe2O3·Fe O) NPs synthesized with oleic acid(OA) as surfactant, and uncoated poly-dispersed Fe3O4 NPs demonstrated comparable removal efficiencies.Adsorption experiments of BTEX on NPs were measured using gas chromatography equipped with flame ionization detection, which indicated high removal efficiencies(up to(95 ± 2)%) under dry conditions. The humidity effect and competitive adsorption were investigated using toluene as a model compound. It was observed that the removal efficiencies decreased as a function of the increase in RH, yet, under our experimental conditions, we observed(40 ± 4)% toluene removal at supersaturation for Fe3O4 NPs, and toluene removal of(83 ± 4)% to(59 ± 6)%, for OA-Fe3O4 NPs. In the presence of SO2, the toluene uptake was reduced under dry conditions to(89 ± 2)% and(75 ± 1)% for the uncoated and coated NPs, respectively, depicting competitive adsorption. At RH 100%,competitive adsorption reduced the removal efficiency to(27 ± 1)% for uncoated NPs whereas OA-Fe3O4 NPs exhibited moderate efficiency loss of(55 ± 2)% at supersaturation.Results point to heterogeneous water coverage on the NP surface. The magnetic property of magnetite facilitated the recovery of both types of NPs, without the loss in efficiency when recycled and reused.     

Ce-Mn/Al2O3-H2O2催化氧化皮革废水的研究

以浸渍法制备了Ce-Mn/Al_2O_3催化剂,研究该催化剂在H_2O_2非均相类Fenton体系中对皮革废水污染物的催化降解性能.在单因素试验的基础上,以COD去除率为响应值,采用Box-Behnken响应曲面法考察了催化剂投加量、H_2O_2投加量、初始pH、反应时间等4个因素之间的单独作用及交互作用,实验数据用Design-Expert 8.0.6软件进行处理,得到二次响应曲面模型.结果表明,4个独立变量对响应值的影响顺序如下:初始pHH_2O_2投加量催化剂投加量反应时间,数学模型拟合度高(R_(adj)~2=0.9349),利用该模型预测的最大COD去除率为78.86%,最佳反应条件为:催化剂投加量56.63 g·L~(-1),H_2O_2投加量315.15 mg·L~(-1),初始pH3.51,反应时间2 h,经实验验证COD去除率为80.94%,与模型预测值偏差2.08%.     

超声、紫外增强H2O2/KI降解磺胺甲基嘧啶

实验以H_2O_2和KI作为分子碘(I2)的来源,研究比较了超声、紫外分别增强H_2O_2/KI降解磺胺甲基嘧啶(sulfamerazine,SMR)的效果、主要影响因素、分子碘的生成、主要活性物种和产物.结果表明,超声、紫外均能有效增强H_2O_2/KI对磺胺甲基嘧啶的降解,超声的增强效果明显;pH值对磺胺甲基嘧啶的去除率影响较大,pH为2.6~5.6,去除率随pH升高而降低;自由基抑制结果表明,碘自由基(I·和I-2·)是超声、紫外增强H_2O_2/KI降解磺胺甲基嘧啶的主要活性物质.HPLC/MS/MS分析检测到一碘代苯.     

双氧水协同生化法强化处理印染废水

传统生化法对印染废水的处理有一定的局限性.本文研究了双氧水协同水解酸化-接触氧化系统,对印染废水进行强化处理.采用污泥挂膜、生化系统启动、双氧水协同启动的方法,将双氧水投加到水解酸化时的条件严格控制为:投加3m L·L~(-1)、投加量100.0 m L、流速0.67 m L·min-1、投加频率1次·d-1,可使整个系统成功启动与稳定运行.实验结果表明,双氧水协同水解酸化-接触氧化可对印染废水中的特征污染物进行有效强化处理.其中,COD平均去除率为89.8%,氨氮平均去除率为96.7%,PVA平均去除率为87.4%,废水平均脱色率为92.1%.采用16S rDNA宏基因组高通量测序技术,对比分析了接种种泥、水解酸化污泥和接触氧化污泥微生物的群落结构.结果表明,经过驯化,水解酸化和接触氧化微生物群落均发现了显著变化.其中,水解酸化污泥优势菌门主要为变形菌门Proteobacteria、拟杆菌门Bacteroidetes和疣微菌门Verrucomicrobia;接触氧化污泥优势菌门主要为浮霉菌门Planctomycetes、变形菌门Proteobacteria和酸杆菌门Acidobacteria.该实验从宏观和微观角度,均证实双氧水协同生化法强化处理印染废水具有技术可行性.     

Decontamination of alachlor herbicide wastewater by a continuous dosing mode ultrasound/Fe2+/H2O2 process

We used a ultrasound/Fe2+/H2O2 process in continuous dosing mode to degrade the alachlor.Experimental results indicated that lower pH levels enhanced the degradation and mineralization of alachlor. The maximum alachlor degradation(initial alachlor concentration of 50 mg/L) was as high as 100% at pH 3 with ultrasound of 100 Watts, 20 mg/L of Fe2+, 2 mg/min of H2O2 and 20℃ within60 min reaction combined with 46.8% total organic carbon removal. Higher reaction temperatures inhibited the degradation of alachlor. Adequate dosages of Fe2+and H2O2 in ultrasound/Fe2+/H2O2process not only enhance the degradation efficiency of alachlor but also save the operational cost than the sole ultrasound or Fenton process. A continuous dosing mode ultrasound/Fe2+/H2O2 process was proven as an effective method to degrade the alachlor.     

O3/H2O2氧化苯乙烯气体性能及机制

O3/H2O2体系能产生大量自由基,臭氧与自由基的耦合氧化作用能提高苯乙烯的氧化去除效率.采用O3/H2O2氧化高浓度苯乙烯有机废气,研究了臭氧投加量、停留时间、H2O2体积分数、循环液喷淋密度和O3/C8H8摩尔比对苯乙烯去除率的影响.结果表明,O3/H2O2气液两相氧化能高效净化苯乙烯有机废气,苯乙烯去除率可达85.7%.适宜运行条件:停留时间为20.6 s,H2O2体积分数为10%,喷淋密度为1.72 m3·(m2·h)-1,O3/C8H8摩尔比为0.46.采用GC-MS分析O3/H2O2气液两相高级氧化苯乙烯出口气样,研究结果表明苯甲醛(C6H5CHO)和苯甲酸(C6H5COOH)为O3/H2O2氧化苯乙烯的中间产物,并推测出苯乙烯的降解机制.     

次氯酸钠湿法烟气脱硝及同时脱硫脱硝技术研究

采用NaClO作氧化吸收剂,在鼓泡反应装置进行了湿法烟气脱硝实验研究,考察了NaIO、NO浓度、液相温度、气体流量、pH对脱硝效率的影响以及SO2对同时脱硫脱硝效率的影响,并结合液相产物分析探讨了同时脱硫脱硝反应机理.研究结果表明,pH值是影响活性成分HClO存在形式的重要因素,同时也是影响氧化吸收的关键因素;在一定范...     

基于反硝化脱氮的硫铁复合填料除磷机制

为提高硫铁复合填料反硝化脱氮同步除磷效果,对比研究了不同填料和耦合微生物后的除磷效果,分析了微生物耦合硫铁复合填料反硝化脱氮同步实现除磷的机制.结果表明与单纯海绵铁填料比较,硫磺与海绵铁复合填料除磷效率提高30%,达到95%以上,出水磷含量可降至0.1 mg·L~(-1)以下.X射线衍射(XRD)和总铁浓度分析表明,硫铁复合填料除磷系统反应产物主要为FeOOH、FeS和Fe_4(PO_4)_3(OH)_3固体物质和溶解性铁离子,产生于海绵铁的腐蚀和除磷过程;腐蚀产生的Fe~(2+)及Fe~(3+)的水解产物FeOOH和Fe S通过吸附沉淀作用将PO_4~(3-)转化为Fe_4(PO_4)_3(OH)_3去除.微生物耦合硫铁炭复合填料反应器运行稳定后,TN、TP去除率分别在90%左右和83%以上;硫自养反硝化产生的H~+和生物铁作用也可以促进海绵铁腐蚀和除磷过程,体系将"异养协同自养"复合反硝化与化学除磷有机结合,实现了城市污水处理厂尾水高效反硝化脱氮同步除磷的目的.     

氮掺杂生物炭催化臭氧对于布洛芬的降解特性与机制

系统研究了新型氮掺杂生物炭材料(N-C)催化臭氧对于水中布洛芬(IBP)的氧化降解效能及机制,并深入探究了初始pH、臭氧投加量、催化剂投加量、不同阴离子和背景水质条件对IBP降解效率的影响.结果 表明,相较于一些常见的碳基催化剂(g-C3N4、生物炭、颗粒活性炭)及金属催化剂(MnO2、Fe3O4),N-C催化臭氧体系...     

等离子体催化降解甲苯途径的原位红外研究

考察了在常温常压条件下,等离子体分别协同SiO₂、Al₂O₃、NiO/Al₂O₃降解甲苯的性能,并从材料的介电常数、对甲苯的吸附性及臭氧分解能力等角度分析了不同活性表现的原因,同时,采用原位红外技术研究了甲苯降解过程中催化剂表面吸附物种的变化.结果表明,当甲苯浓度为100 ppm,气体流量为100 mL·min^-1时,一定范围内,甲苯降解率随着能量密度、介电常数、吸附性及臭氧分解能力的提高而提高.甲苯在催化剂表面的吸附对其降解途径有十分重要的影响:在放电区域中加入SiO₂,甲苯仍然在气相中完成降解;而存在Al₂O₃ 及NiO/Al₂O₃时,甲苯氧化成苯甲酸的过程主要发生在催化剂表面,是甲苯催化降解的关键步骤,苯甲酸在活性位点的积累将降低催化剂的反应活性.     

HCO3-浓度对厌氧氨氧化反应器脱氮效能的影响

采用序批式生物膜反应器,通过氮去除速率的测定,研究了HCO3-浓度对厌氧氨氧化反应器脱氮效能的影响.结果表明,当HCO3-与NH4+-N进水浓度比值为0.21时,反应器出水pH值大幅升高,抑制了厌氧氨氧化菌活性,使得氮去除速率大幅下降.当其比值为1.13时,反应器内pH能够降低到厌氧氨氧化菌生长所需要的环境,同时,反应器的氮去除速率开始逐步升高.当过量的HCO3-进入反应器后对厌氧氨氧化反应无影响,说明HCO3-对厌氧氨氧化反应器脱氮效能具有重要的影响,对维持反应器pH值与脱氮效能十分重要.在厌氧氨氧化反应器启动过程中HCO3-与NH4+-N进水浓度最佳比值为1.13.     

CoCuMnOx光催化氧化多组分VOCs特性及其动力学

实验采用共沉淀法制备太阳能吸收涂料Co Cu Mn O_x,探究可见光下甲苯、乙酸乙酯和丙酮混合3组分VOCs的光催化氧化性能,并从动力学角度分析各自的反应速率变化.结果表明,单组分VOCs初始浓度400 mg·m~(-3)、光照距离120 mm,350cm~2镜面载体负载1 g Co Cu Mn O_x下用100 W卤钨灯照射6 h后,甲苯转化率为57%、乙酸乙酯为62%、丙酮为58%;由于3组分VOCs之间相互竞争,甲苯、乙酸乙酯和丙酮的转化率较单组分下降了5%~26%.单组分与3组分VOCs的光催化均符合假一级反应动力学,单组分甲苯、乙酸乙酯和丙酮的反应速率分别为0.002、0.002 8和0.002 33 min~(-1);混合3组分中其反应速率为单组分的0.49~0.88倍.     

Efficient degradation of chlorobenzene in a non-thermal plasma catalytic reactor supported on CeO2/HZSM-5 catalysts

Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO₂/HZSM-5 catalysts. The performance of catalysts was evaluated in terms of removal and energy efficiency. The decomposition products of chlorobenzene were analyzed. The results show that CeO₂/HZSM-5 exhibited a good catalytic activity, which resulted in enhancements of chlorobenzene removal, energy efficiency, and the formation of lower amounts of by-products. With regards to CO₂ selectivity, the presence of catalysts favors the oxidation of by-products, leading to a higher CO₂ selectivity. With respect to ozone, which is considered as an unavoidable by-product in air plasma reactors, a noticeable decrease in its concentration was observed in the presence of catalysts. Furthermore, the stability of the catalyst was investigated by analyzing the evolution of conversion in time. The experiment results indicated that CeO₂/HZSM-5 catalysts have excellent stability: chlorobenzene conversion only decreased from 78% to 60% after 75 hr, which means that the CeO₂/HZSM-5 suffered a slight deactivation. Some organic compounds and chlorinated intermediates were adsorbed or deposited on the catalysts surface as shown by the results of Fourier Transform Infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of the catalyst before and after the reaction, revealing the cause of catalyst deactivation.     

Toluene removal characteristics by a superimposed wire-plate dielectric barrier discharge plasma reactor

A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD （dielectric barrier discharge） with Co3O4/Al2O3/foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO2 when oxygen was more than 5%.     

介质阻挡放电等离子协同TiO_2-GAC降解甲基橙的研究

采用介质阻挡放电(DBD)等离子协同颗粒活性炭负载TiO2(TiO2-GAC)对甲基橙进行降解,研究了该体系的协同处理效果,探讨了放电电压、初始pH、初始电导率、初始浓度和TiO2-GAC投加量等操作参数的影响,并建立了协同体系的表观反应动力学模型.实验结果表明,DBD与TiO2-GAC联合处理表现出明显的协同效应,处理25min后,协同体系对甲基橙的降解率和COD去除率分别为96.2%和90%,与单独DBD体系相比,分别提高了52.7%和50.4%;协同体系降解甲基橙的过程符合表观反应动力学模型,模型值与实验值吻合良好,总级数为2.352;体系中H2O2、O3浓度测定结果表明,与单独DBD体系对比,协同体系的H2O2浓度增高,而O3浓度降低,说明TiO2-GAC起到了催化作用;TiO2-GAC在DBD体系中获得了原位再生,五次再生循环后再生率达80%.