Formaldehyde degradation in the presence of methanol by photo-Fenton process

In this study, the photo-Fenton process for the degradation of formaldehyde was investigated in lab-scale experiments. Results showed that methanol, the additive chemical in a commercial product of formaldehyde, was also decomposed during the formaldehyde oxidation reaction. The oxidation reaction was in three-stages. The first stage was the Fe(2+)/H(2)O(2) reaction in which both formaldehyde and methanol were swiftly decomposed. The second and the third stages exerted a somewhat less rapid degradation of both chemicals. The first stage of the oxidation reaction can be discussed by means of the initial average rate and the third stage or Fe(3+)/H(2)O(2) stage was found to follow the first order reaction rate. The reaction was influenced by the initial pH, the concentration of hydrogen peroxide, the amount of ferrous ions. The initial pH at 2.6 provided the highest removal efficiencies in this system. In addition, the competition between formaldehyde and methanol was investigated and described as r(m)/r(f), where r(m) and r(f) were the initial rates of methanol and formaldehyde, respectively. The addition of methanol exhibited a competitive effect on formaldehyde degradation. The removal of formaldehyde decreased with increasing methanol concentration. At the high concentrations of methanol, the oxidation reaction of formaldehyde was repressed. It appears that all values of r(m)/r(f) obtained from the experiments are lower than the theoretical values.     

新装修居室中大芯板释放甲醛的研究

采用环境舱模拟室内微环境,以大芯板作为研究对象,探讨空气交换率、相对湿度、温度等因素对室内甲醛释放的影响,得出室内甲醛释放规律.研究成果对预测室内甲醛浓度,建立室内甲醛释放模型,以及减少甲醛危害等有重要意义.     

室内空气中甲醛的测定方法

介绍了室内空气中甲醛的危害和主要来源，综述了甲醛的测定方法：分光光度法、色谱法、光学法、传感器法和极谱法。     

自身浓度对乙酰丙酮分光光度法测定甲醛的影响

乙酰丙酮法测定甲醛,在一定浓度范围内吸光度与浓度成正比,但随着甲醛自身浓度的不断增加,吸光度先是增加而后减少,出现一个吸光度值对应两个浓度值的现象。针对这一现象进行分析,认为过量的甲醛与产物发生反应使黄色消褪;同时过量的甲醛严重消耗了其中一个反应物,抑制了显色反应。最后提出,可以通过观察显色过程,判断甲醛的浓度范围,避免得出错误的测定结果。     

Formaldehyde degradation by UV/TiO2/O3process using continuous flow mode

The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount on degradation of formaldehyde gas were investigated. The experimental results indicated that the combination of ozonation with photocatalytic oxidation on the degradation of formaldehyde showed a synergetic action, e.g,, it could considerably increase decomposing of formaldehyde. The degradation efficiency of formaldehyde was between 73.6% and 79.4% while the initial concentration in the range of 1.84--24 mg/m^3 by O3/TiO2flJV process. The optimal humidity was about 50% in UV/TiO2/O3 processs and degradation of formaldehyde increases from 39.0% to 94.1% when the ozone content increased from 0 to 141 mg/m^3. Furthermore, the kinetics of formaldehyde degradation reaction could be described by Langmuir-Hinshelwood model. The rate constant k of 46.72 mg/（m^3.min） and Langmuir adsorption coefficient K of 0.0268 m^3/mg were obtained.     

Formaldehyde personal exposure measurements and time weighted exposure estimates in children

Residential concentrations of formaldehyde have been associated with poor respiratory health in children, where formaldehyde has been measured using stationary monitors inside homes. Although children spend most of their time indoors at home, there are few studies of children’s personal exposure to formaldehyde. The aim of this study was to investigate the relationship between personal exposure formaldehyde concentrations, microenvironmental concentrations and time weighted exposure estimates in children.Forty-one primary school children (aged between 9 and 12 years) wore a personal passive sampler over two 24 h periods in two seasons and completed 24 h daily activity diaries and a questionnaire about lifestyle and behaviour. Samplers were co located indoors at home, outdoors at centralised locations and indoors at school for the corresponding period.Personal exposure formaldehyde concentrations in this group of children were generally low with a geometric mean concentration of 9.1 ppb (range <detection limit to 27.3 ppb). There were strong correlations between personal exposure concentrations and both domestic indoor (r_s = .779, p < 0.001) and time weighted estimated (r_s = .802, p < 0.001) concentrations. The time weighted model did not improve the estimate of personal exposure compared with stationary indoor concentrations. Indoor air concentration measured with a single stationary monitor was a suitable surrogate for personal exposure.     

Formaldehyde oxidation on Pd/USY catalysts at room temperature: The effect of acid pretreatment on supports

The complete catalytic oxidation of formaldehyde (HCHO) to CO₂ and H₂O at room temperature is a green route for indoor HCHO removal. Zeolite is an excellent carrier material for HCHO oxidation due to its large surface area, intricate pores and high adsorption capacity. However, the zeolite-supported noble metal catalysts have currently shown relatively low activity especially at room temperature. In this work, we present a facile acid treatment strategy for zeolite catalysts to improve the hydroxyl concentration and further enhance their catalytic activity for HCHO oxidation. Activity tests illustrated that HCHO could be completely oxidized to CO₂ and H₂O at a nearly 100% conversion rate with a weight hourly space velocity (WHSV) of 150,000 mL/(g∙hr) at 25°C, when the support of Pd/USY catalysts was pretreated by hydrochloric acid with a concentration of 0.20 mol/L. The characterization results revealed that the active hydroxyl groups originated from the dealumination in the acid treatment play a key role in the HCHO oxidation reaction. The deduced reaction mechanism suggests that bridging hydroxyl groups may oxidize HCHO to dioxymethylene (DOM) species and terminal hydroxyl groups are responsible for the transformation of DOM groups to formate (HCOO) species.     

大芯板中甲醛的释放规律及影响因素分析

以大芯板为试材,在模拟气候舱中研究密闭状态下甲醛的释放规律及影响因素。发现板材中甲醛的释放为短时间内剧烈释放,约24h后甲醛释放呈缓慢上升状态直至饱和,且板材的不同来源对甲醛的释放规律无显著影响;甲醛的释放速率在释放初期随温度的升高而加快,释放后期受温度影响不显著;湿度对甲醛的释放速率影响不显著;新风的通入会促进短时内甲醛的释放,20h后释放仍符合原规律曲线。     

家居甲醛污染与防治对策

对于家居室内空气而言,甲醛污染主要来源自室内装潢材料以及新购买的家居。甲醛污染随着室内装潢的兴起,对人身健康造成了一定的危害,越来越引起人们的重视。我国的《民用建筑工程室内环境污染控制规范》等4部法律对民用建筑物的甲醛含量进行了规定,但还不尽健全。甲醛的危害可以从完善法律、增强环境意识等方面进行预防,必要时使用物理、化学、生物技术及时治理。     

双氰胺—甲醛絮凝剂对活性污泥的脱水性能研究

研究了有机合成阳离子高分子絮凝剂双氰胺－甲醛絮凝剂在污泥处理中的应用。从絮凝反的理论及其机理上分析了它的絮凝作用，从原理上解释并经实验证明了它在污泥脱水处理中所具有的优越性。