【作者】 李英柳；

【导师】 胡将军；

【作者基本信息】 武汉大学 ， 环境工程， 2004， 硕士

【摘要】 当今室内空气质量状况越来越受到人们的重视。由于室内装修、暖通空调及大量家用化工产品的使用,室内空气污染日趋严重,尤其是挥发性有机物对室内空气的污染很严重,甲醛就是其中常见的一种挥发性有机污染源。在治理上,传统的负离子空气净化器实际上只能达到“清新”空气的效果,大部分的污染物无法消除;活性炭空气净化器则受到饱和吸附的制约,而光催化净化则可以克服上面两种空气净化器的技术局限性,达到彻底清除室内空气污染物的效果。针对目前室内空气净化不尽人意的现状,本文主要研究如何提高光催化氧化室内低浓度有机气体的效率。 试验采用纳米TiO₂作光催化剂,活性炭纤维做载体在室内污染模拟箱内进行光催化氧化气态甲醛的研究,通过优化催化剂材料性能和光催化反应条件两个方面达到高效清除甲醛的目的。 纳米TiO₂光催化剂采用溶胶-凝胶法制备,搀杂过渡金属离子修饰以提高其活性。试验分别考察了溶剂的种类、溶液酸碱度、掺杂金属离子种类及含量、R值、焙烧温度和焙烧时间等制备条件对催化剂活性的影响,得到了最佳的催化剂制备条件,即采用无水乙醇为溶剂,溶液pH值在8附近,R=50,掺杂3.5wt%的Fe³⁺在650℃温度下焙烧2小时,催化剂的活性最高。经XRD和SEM分析,此时催化剂组成为70%锐钛矿和30%金红石,平均粒径30纳米。 试验首次采用活性炭纤维作为催化剂载体。通过对普通玻璃、活性炭颗粒及活性炭纤维三种载体负载二氧化钛光催化效率的比较,发现活碳纤维做载体时,对光催化的促进作用最大。在室内空气污染模拟箱内考察了空气流速、光源、催化剂负载量和反应物的浓度等因素对TiO₂/ACF吸附-光催化氧化低浓度甲醛的影响。实验结果表明,在常温常压和254nm紫光灯照射下,23.5g活性炭纤维负载3.5gTiO₂,甲醛浓度在18mg/m³的范围内,处理率均高于90%。最后还考察了载体在充分光反应后重复使用的情况,试验表明活性炭纤维仍有较高的吸附能力。二氧化钛可以作为活性炭纤维原位再生的一种有效手段。 二氧化钛廉价易得,性质稳定,光催化活性高,负载于活性炭纤维可以外挂在空调上或者单独使用,作为居室、超市、宾馆、博物馆等场所室内空气净化之用。更多还原

【Abstract】 Indoor air quality has been taken more and more into account in recent years. Indoor decoration, air conditioning and central heating system and a wide application of chemical articles in everyday use have resulted in serious indoor air contamination, especially volatile organic compounds （VOCs） plays an important part in it. Formaldehyde is a commonly detected VOCs pollutant in the door. However, there hasn’t been a satisfactory method for controlling small sources of indoor air organic pollutants at present. In fact the conditional negative ion air cleaner is unable to decompose the pollutants but only refresh the air; activated carbon air cleaner is confined to its saturation absorption while photocatalytic oxidation can solve these problems and clean the air completely as well as conveniently. So how to improve photocatalytic oxidation efficiency of low-contamination volatile organic compounds is mainly studied.TiO₂ was used as photocatalyst and loaded on activated carbon fibre in an indoor air contamination box simulator to study photocatalytic oxidation of gas formaldehyde. Amending TiO₂ material and reaction condition increased the photocatalytic oxidation efficiency.TiO₂ nano-material was prepared by sol-gel method and modified with Fe³⁺ to enhance its photocatalytic activity. In order to get a highly activated photocatalyst, the affection of some preparation conditions on titanium dioxide’s activity have been studied such as the kinds of solvents, the pH of solution, the sorts and different contents of doping metal irons, the value of R, and the sintering temperature and the hours of sintering. It showed that when absolute alcohol was chose as solvent and the pH of the solution was kept around 8.00, R=50 and the doping Fe³⁺ was at 3.5wt%, TiO₂ behaved a much higher activity after being sintered at 650℃ for 2 hours. The crystal type of the sample was found to possess a mixture of 70% anatase and 30% rutile by XRD. It was obtained by scanning electron microscope （SEM） that its average pore size was 30nm.ACF was firstly used as supporter in our research. TiO₂ samples prepared under the optimal condition were respectively supported on glass, granule activated carbon（GAC） and activated carbon fibres （ACF） separately to carry out the reaction of photocatalytic oxidation of formaldehyde. It indicated that ACF was superior to the other supports and exhibited a higher efficiency under the same conditions. So ACF was elected as the support in the following experimentation.Using a 20W pen lamp emitting light at a wavelength of 254 nm as the light source, the photocatalytic reaction was carried out at room temperature and atmospheric pressure. The roles of reaction conditions such as gas velocity, light source, reaction time, usage of TiO2 and concentration of formaldehyde were studied. It was found that the light, the concentration of formaldehyde and the dosage of TiO2 have distinct influence over the efficiency of photocatalytic oxidation. A processing rate more than 90% could be obtained when 3.5g TiC>2 was loaded on 23.5g ACF and the concentration of formaldehyde was within 18mg/m3. The test of used ACF in photocatalytic reaction showed it still had a good absorption capacity. It also indicated that photocatalytic oxidation can be an effective regenerative technique for ACF.TiC?2 is of high photocatativity and stable nature, and it is abundant to be obtained at low cost. When loaded on ACF, a highly effective adsorbent, it can be attached to air conditioning equipment or used alone to clean the air in residence, supermarket, hotel and museum and etc.更多还原