TiO2光催化脱除NOx的研究进展

利用TiO2的光催化效应脱除大气污染物是近十年来国内外学术界的研究热点之一。本文对TiO2光催化脱除NOx方面的研究工作进行了综述,郑重论述了光催化氧化反应及光催化还原反应脱除NOx的反应机理及影响因素,并对应用前景作了展望。     

TiO2光催化氧化脱除模拟烟气中的NOx

采用P25纳米TiO2为催化剂,对NOx浓度360 mg/m3的模拟烟气进行了光催化氧化实验研究,以期为此种方法在电厂烟气脱硝方面的应用提供依据.经SEM、XRD等表征手段,探讨了催化剂晶型尺寸对光催化的作用.实验考察了光催化反应过程规律以及负载量、光照度、NO初始浓度、O2含量、相对湿度和停留时间对光催化氧化效率的影响.结果表明,光催化反应是瞬态到稳态的过程,其催化效率与上述影响因子有密切关系.实验最优条件下NOx的脱除率为46％,但只需适当提高氧化效能,便能达到理想的效果.     

环境污染与防治网络版

过渡金属改性活性炭纤维脱除低浓度羰基硫的研究;混凝沉淀法预处理大豆蛋白和屠宰废水试验研究;天津秋季地面O3和NOx的浓度变化特征与影响因素;TiO2／有机膨润土复合材料光催化降解苯酚;焙烧水滑石去除Cr（Ⅵ）性能研究.     

尿素和添加剂湿法烟气同时脱硫脱氮工艺研究(Ⅰ)

对尿素和添加剂同时吸收烟气中SO2和NOx进行了实验研究.结果表明,烟气中SO2极易脱除,在实验条件下SO2脱除率均大于99%,操作工艺条件变化主要是影响NOx脱除率.尿素和添加剂质量分数对NOx脱除率影响较小,NOx脱除率随尿素和添加剂质量分数的增加而缓慢增加;吸收剂pH和吸收反应温度对NOx脱除率有显著影响,最佳pH为7,最佳反应温度为70～80℃.     

零价铁(Fe~0)共存下TiO_2光催化降解特性的研究

针对TiO2光催化反应中易出现电子-空穴对(e--h+)的复合、而Fenton技术又面临铁污泥的问题,向TiO2光催化反应中加入零价铁(Fe0)。通过调节溶液pH,使Fe0缓释Fe2+,且反应之后的pH仍能满足TiO2光催化反应所需。溶液中的Fe2+,一方面能减弱TiO2光催化产生的e--h+的复合,提高TiO2光催化反应的效率;另一方面,在紫外灯照射下也可以起到光Fenton降解作用。研究结果表明,Fe0共存下TiO2光催化对废水的降解率高于单独使用TiO2光催化或光Fenton对废水的降解率。对Fe0共存下TiO2光催化降解废水的褪色率的动力学研究表明,该反应属于三级动力学反应,且其对有机物的降解具有TiO2光催化和光Fenton加合增效的效果。     

固定化催化剂TiO2膜光催化降解三氯乙醛的研究

研究了负载于玻璃上的固定化催化剂TiO2膜光催化降解水中三氯乙醛的效果,探讨了TiO2膜光催化降解三氯乙醛的机理,考察了溶液pH值和三氯乙醛初始浓度埘TiO2膜光催化降解三氯乙醛的影响,并研究了固定化催化剂TiO2膜光催化降解三氯乙醛的动力学.结果表明,固定化催化剂TiO2膜光催化降解水中三氯乙醛的效果良好,当三氯乙醛初始浓度为2.25 mg/L时,在紫外光照时间3 h下,三氯乙醛的降解率高达100%.在相司紫外光照时间下,三氯乙醛的光催化降解率随着三氯乙醛初始浓度的增大而下降.在溶液pH=6.5时,三氯乙醛的降解效率最高.固定化催化剂TiO2膜光催化降解三氯乙醛的反应遵循一级反应动力学,反应速率常数随三氯乙醛初始浓度的增大而减小.     

尿素和添加剂湿法烟气同时脱硫脱氮工艺研究(Ι)

对尿素和添加剂同时吸收烟气中 SO2 和 NOx 进行了实验研究。结果表明 ,烟气中 SO2 极易脱除 ,在实验条件下 SO2 脱除率均大于 99%,操作工艺条件变化主要是影响 NOx脱除率。尿素和添加剂质量分数对 NOx 脱除率影响较小 ,NOx脱除率随尿素和添加剂质量分数的增加而缓慢增加 ;吸收剂 p H和吸收反应温度对 NOx脱除率有显著影响 ,最佳 p H为 7,最佳反应温度为 70～80℃。     

掺Ni2+的TiO2颗粒光催化性能的研究

通过溶胶-凝胶法制备掺杂Ni2 的纳米TiO2,并用XRD和TEM进行了表征,发现Ni2 的掺杂减小了TiO2颗粒的粒径,Ni2 /TiO2晶型为锐钛型.通过对目标物罗丹明B的光催化降解实验,发现Ni2 的掺杂提高了TiO2的光催化活性,其降解罗丹明B的反应遵从一级反应动力学方程,Ni2 惨杂量为1.2%时的光催化活性最高.     

光和TiO2对酒石酸还原Cr(Ⅵ)的催化作用研究

研究了避光、可见光照及紫外光照条件和TiO2对酒石酸还原Cr(Ⅵ)的催化作用及其作用机制.结果表明:(1)避光条件下,酒石酸对Cr(Ⅵ)的还原作用很微弱,外加TiO2对该反应也仅有微小变化.TiO2对酒石酸还原Cr(Ⅵ)的催化作用只有在光照下才能产生.紫外光照下,仅酒石酸存在时,150 min后Cr(Ⅵ)即被反应完全,外加TiO2催化7 min后Cr(Ⅵ)即被反应完全.(2)光照能诱导并加速酒石酸还原Cr(Ⅵ)的光催化作用,紫外光照下的光催化还原反应速率远快于可见光照.(3)pH对TiO2光催化酒石酸还原Cr(Ⅵ)的反应速率有明显的影响,pH越小,光催化还原反应速率越快.(4)酒石酸初始浓度的增大有利于Cr(Ⅵ)光催化还原.     

微波辅助光催化降解高浓度活性黑

利用改装的家用微波炉、微波无极灯和TiO2催化剂研究了水中高浓度活性黑的光催化降解.系统考察了TiO2投加量、pH、微波无极灯数量对微波辅助光催化处理效果的影响,得出微波辅助光催化的最佳操作条件,并在最佳条件下对活性黑的脱色及矿化效果进行研究.结果表明,TiO2投加量存在最佳值2 g/L,降低pH和增加微波无极灯数量均可提高活性黑的降解率.在TiO2的投加量为2 g/L,pH =3,微波无极灯数量为3的最佳光催化条件下,400 mg/L的活性黑溶液反应180 min时可实现完全脱色,反应300 min时,TOC去除率高达89.1％.     

Radiolysis of aqueous phenol solutions with nanoparticles. 1. Phenol degradation and TOC removal in solutions containing TiO2 induced by UV,gamma-ray and electron beams

Aqueous phenol solutions containing TiO(2) nanoparticles were irradiated with ultraviolet (UV), gamma-ray and electron beams. Organic compounds were fully removed by each type of radiation in the presence of the particles. The absorbed energy of the ionizing radiation (gamma-ray and electron beams) needed for removal was much lower than that of UV photocatalysis. Phenol was decomposed by the ionizing radiation in the absence of the nanoparticles and the addition of TiO(2) had no significant effect on phenol decomposition rate. Instead, total organic carbon (TOC) removal using the ionizing radiation was accelerated drastically by TiO(2). It is suggested that TiO(2) particles affect the intermediate compounds produced through the decomposition of phenol. The amount of removed TOC per absorbed energy were compared in the absence and the presence of TiO(2) nanoparticles. Radiolysis with the nanoparticles showed consistently high rate and high efficiency of TOC removal.     

电催化氧化中的三种催化材料处理酸性红B染料的比较研究

本文采用三种不同催化机理的材料———半导体材料TiO2 、软锰矿石和混合稀土进行了电催化氧化 (ECO)染料酸性红B的研究 ,结果表明 ,稀土材料在ECO体系中呈负催化效应 ;软锰矿石的色度去除催化效果明显 ;TiO2 的催化效果最显著 ,其色度和COD去除效果可比无催化剂时效果分别提高60 %和 75% ,可以作为电催化氧化的催化剂。并进一步研究了TiO2 用量对电催化氧化 (ECO)的影响。     

添加壳聚糖溶胶-凝胶法制备的TiO2光催化剂及其光催化性能研究

采用添加壳聚糖（CTS）的溶胶-凝胶法制备了具有较高光催化活性的TiO2光催化剂，并用XRD、TEM、BET和IR等手段对其进行表征。结果表明，CTS的添加使TiO2衍射强度增强、分散性提高、比表面积增大从而使光催化活性提高；用所制备的催化剂光催化降解甲基橙反应60min后，其去除率由不添加CTS所制备TiO2的32％提高到48％，TOC去除率由14％提高到23％。     

Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

Studies on applying the photochemical UV/TiO2 oxidation process to treat the lignin-containing wastewater for dissolved organic carbon (DOC), color and reducing A254 (the absorption at the wavelength of 254 nm) have been carried out. The data obtained in this study demonstrate that the UV/TiO2 process is effective in oxidizing the lignin thus reducing the color and DOC of the wastewater treated. The combined UV/TiO2 treatment can achieve better removal of DOC and color than the UV treatment alone. Color removal, based on American Dye Manufacture Index (ADMI) measurement, is greater than 99% if the pH is maintained at 3.0 with the addition of 1 g l(-1) TiO2. When 10 g l(-1) TiO2 is applied, the oxidation reduction potential (ORP) value is reached to result in an 88% removal of both DOC and color. A model was developed based on the variation of ORP during the photochemical reaction to simulate the decoloring process. The proposed model can be used to predict the color removal efficiency of the UV/TiO2 process.     

Removal of arsenic from groundwater by granular titanium dioxide adsorbent

A novel granular titanium dioxide (TiO2) was evaluated for the removal of arsenic from groundwater. Laboratory experiments were carried out to investigate the adsorption capacity of the adsorbent and the effect of anions on arsenic removal. Batch experimental results showed that more arsenate [As(V)] was adsorbed on TiO2 than arsenite [As(III)] in US groundwater at pH 7.0. The adsorption capacities for As(V) and As(III) were 41.4 and 32.4 mgg(-1) TiO2, respectively. However, the adsorbent had a similar adsorption capacity for As(V) and As(III) (approximately 40 mgg(-1)) when simulated Bangladesh groundwater was used. Silica (20 mgl(-1)) and phosphate (5.8 mgl(-1)) had no obvious effect on the removal of As(V) and As(III) by TiO2 at neutral pH. Point-of-entry (POE) filters containing 3 l of the granular adsorbent were tested for the removal of arsenic from groundwater in central New Jersey, USA. Groundwater was continuously passed through the filters at an empty bed contact time (EBCT) of 3 min. Approximately 45,000 bed volumes of groundwater containing an average of 39 microgl(-1) of As(V) was treated by the POE filter before the effluent arsenic concentration increased to 10 microgl(-1). The total treated water volumes per weight of adsorbent were about 60,000 l per 1 kg of adsorbent. The field filtration results demonstrated that the granular TiO2 adsorbent was very effective for the removal of arsenic in groundwater.     

超声波-TiO_2光催化联合处理垃圾渗滤液

采用超声波强化TiO2光催化技术处理垃圾渗滤液。研究了TiO2催化剂用量、光照作用、超声波作用、pH值、曝气作用等因素对垃圾渗滤液中COD和氨氮去除率的影响。结果表明,在TiO2粉末的投加量为2 g/L、pH值为11时,先采用功率为292.5 W的超声波辐射3 min,再以高压汞灯(250 W)照射3 min,垃圾渗滤液中的COD和NH3-N去除率分别达到50.1%和75%。若在同一条件下进行饱和曝气可以使NH3-N去除率进一步达到85.3%,但会降低COD的去除率。     

Removal of Cr(VI) and humic acid by using TiO2 photocatalysis

The removal efficiencies of Cr(VI) and HA, using a TiO(2)-mediated photocatalytic process, were investigated with variations in the pH, TiO(2) dosage and Cr(VI)/HA ratio. During the photocatalytic reaction, the total removal of Cr(VI) occurred through adsorption onto TiO(2), as well as its reduction to Cr(III). However, oxidation and adsorption were identified as important removal processes for the treatment of HA. Due to the anionic type adsorption onto TiO(2) and its acid-catalyzed photocatalytic reduction, the removal of Cr(VI) decreased with increasing pH, while that of HA increased with increasing pH. The TiO(2) dosage was also an important parameter for the removal of Cr(VI). As the TiO(2) dosage was increased to 2.5 g l(-1), the removal of Cr(VI) was continuously enhanced, but decreased at dosages above 3 g l(-1) due to the increased blockage of the incident UV light used for the photocatalytic reaction. The removal of Cr(VI) was greatly enhanced when the system contained both HA and Cr(VI) compared to Cr(VI) alone. Also, the removal of HA was greatly enhanced when the system contained both HA and Cr(VI) compared to HA alone. The removal of Cr(VI) was continuously enhanced as the HA concentration gradually increased; however, no further increase was observed above 20 mg l(-1) HA due to the increased absorption of the UV light. This result supports that the photocatalytic reaction, with illuminated TiO(2), could be applied to more effectively treat wastewater containing both Cr(VI) and HA than that containing a single species only.     

负载型Mn-Ce／TiO2催化剂的制备及其低温脱硝活性

以成型TiO2作为载体，通过浸渍法制备了Mn-Ce／TiO2低温SCR催化剂，并系统研究了制备方法、煅烧条件、活性组分担载量、Mn含量等参数对催化剂催化还原NO性能的影响。结果表明，煅烧温度的升高会促使活性组分结晶度的提高，从而引起催化活性的降低，在500℃和600℃下所得Mn-Ce／TiO2催化剂活性组分为无定型态，表现出较高的脱硝活性。活性组分担载量的增加有利于催化活性的提高。Mn含量对Mn-Ce／TiO2催化剂的活性有较大影响，当Mn／（Mn＋Ce）摩尔比为40％和85％时，催化剂活性最高。     

Decomposition of gas-phase trichloroethene by the UV/TiO2 process in the presence of ozone.

The decomposition of gas-phase trichloroethene (TCE) in air streams by direct photolysis, the UV/TiO2 and UV/O3 processes was studied. The experiments were carried out under various UV light intensities and wavelengths, ozone dosages, and initial concentrations of TCE to investigate and compare the removal efficiency of the pollutant. For UV/TiO2 process, the individual contribution to the decomposition of TCE by direct photolysis and hydroxyl radicals destruction was differentiated to discuss the quantum efficiency with 254 and 365 nm UV lamps. The removal of gaseous TCE was found to reduce by UV/TiO2 process in the presence of ozone possibly because of the ozone molecules could scavenge hydroxyl radicals produced from the excitation of TiO2 by UV radiation to inhibit the decomposition of TCE. A photoreactor design equation for the decomposition of gaseous TCE by the UV/TiO2 process in air streams was developed by combining the continuity equation of the pollutant and the surface catalysis reaction rate expression. By the proposed design scheme, the temporal distribution of TCE at various operation conditions by the UV/TiO2 process can be well modeled.     

TiO2光催化对微滤去除腐殖酸的膜污染控制研究

着重研究了不同紫外灯光源和照射时间条件下，TiO2光催化（PCO）对微滤去除腐殖酸过程中的膜污染控制，并探讨了膜污染的控制机理。研究结果表明，TiO2光催化能有效提高微滤对腐殖酸的去除，同时降低膜通量的下降，起到有效控制膜污染的作用。进一步的实验分析表明，TiO2光催化控制膜污染的主要机理在于将腐殖酸降解为易于被TiO2吸附的小分子量物质，吸附腐殖酸降解产物后的TiO2聚合颗粒粒径增大，易于在膜表面形成更为松散的沉积层，并使膜污染从以膜孔堵塞和沉积层污染为主转化为以沉积层污染为主的可逆性污染。