用光催化氧化法处理垃圾渗滤液的实验研究

以城市生活垃圾渗滤液作为研究对象 ,采用悬浮态半导体催化剂对渗滤液进行处理试验。研究了ZnO TiO2复合半导体催化剂的催化活性 ,并研究了各种实验条件、影响因素及处理效果。研究表明 ,在一定的试验条件下 ,用ZnO TiO2 复合半导体催化剂处理城市垃圾渗滤液效果较好 ,可作为垃圾渗滤液的深度处理。同时得到光催化氧化法处理渗滤液的最佳试验参数。     

用光催化氧化法处理垃圾渗滤液的实验研究

以城市生活垃圾渗滤液作为研究对象，采用悬浮态半导体催化剂对渗滤液进行处理试验。研究了ZnO／Tio2复合半导体催化剂的催化活性，并研究了各种实验条件、影响因素及处理效果。研究表明，在一定的试验条件下，用ZnO／TiO2复合半导体催化剂处理城市垃圾渗滤液效果较好，可作为垃圾渗滤液的深度处理。同时得到光催化氧化法处理渗滤液的最佳试验参数。     

半导体存储介质破碎-分选系统的因子优化设计

废弃半导体存储介质一方面载有隐私信息,需要被安全销毁,另一方面富含金属导体、半导体、绝缘体材料,极具回收价值。提出用破碎-风力-高压静电分选系统对其进行安全销毁和物料分选,其中多级破碎部分使信息半导体硅存储材料破碎至0.80 mm以下,而风力-高压静电分选部分能实现半导体、导体、绝缘体的分选。为确定系统工艺参数,实验对风机蝶阀角度(α),风机频率(f),电选电压(U),电选机转辊转速(n)等因素对半导体收集量(M)的影响进行研究,通过因子设计建立了非线性数学模型:M=1.943 8-0.418 7α*+0.306 2f*-0.193 7 f*U*n*+0.181 3α*f*U。进而通过响应优化得出最优工艺参数设置为:α=30°,f=45 Hz,U=30 k V,n=40 r·min-1。在此参数下,金属导体收集率达90.3%,半导体硅收集率达61.0%,实现了半导体存储介质破碎销毁和物料分选。     

光催化降解有机污染物的进展

综合国内外资料,探讨了半导体光催化氧化降解不中有机污染物的机理,综述了半导体光催化剂在降解水中有机物方面的研究现状及其进展情况。并对半导体光催化氧化法催化剂本身存在的问题提出了一些看法。     

半导体光催化剂及其改性技术进展

本文介绍了用于水处理的半导体光催化剂的作用原理，综述了近年来有关贵金属淀积、金属离子掺杂、表面光敏化、半导体复合和粘土交联等半导体改性技术的研究，并对其原理进行解释和说明。     

半导体企业环境风险防范措施建议

当前国际形势下,中国半导体行业不断创新发展。由于半导体行业的工艺技术特点,生产过程中必然涉及各类易燃易爆、有毒有害化学品。根据半导体生产行业特征及其环境风险水平,提出环境风险预防、控制、减缓措施,明确环境风险防范及应急要求,运用科学的技术手段和管理方法,尽可能降低环境风险事故发生。     

半导体照明面临绿色机遇

20世纪90年代末,随着第三代半导体材料氮化镓的突破和蓝、绿、白发光二极管的问世,一场新的产业革命——照明革命开始：如同晶体管替代电子管一样,半导体灯将逐步替代白炽灯、荧光灯。     

高级氧化技术去除水体中氯贝酸的研究进展

药品及个人护理品中的氯贝酸在水体环境中不断富集,对生态系统造成了潜在威胁.介绍了氯贝酸的性质、环境中的赋存浓度、生态毒性及污水处理厂的处理效率.鉴于传统处理工艺不能有效去除水体中的氯贝酸,归纳总结了紫外光降解、多相半导体光催化、臭氧氧化、电化学氧化及光/电Fenton法等多种高级氧化技术对氯贝酸的反应机制、影响因素及优缺点,并展望了今后氯贝酸有效去除技术的研究重点和方向.     

纳米复合ZnO-TiO2晶体的制备及其光电催化性能研究

采用溶胶-凝胶法制备了纳米复合半导体ZnO-TiO2薄膜,并进行了结构和光电催化性能的测试.TiO2薄膜对五氯酚溶液的光电催化降解结果表明当输入正向偏压后,其光催化性能有较大提高.由于ZnO的掺入,半导体薄膜电极的光吸收能力增强;同时,Zn2+可能作为光生载流子的浅俘获中心,导致表面界面电荷转移加速,从而延长光生电子/空穴对的寿命并抑制其复合,有效地提高了TiO2薄膜光电催化活性.     

水溶液中残留四环素的光催化降解的实验研究

由于抗菌素具有抑制微生物生存的作用，通常处理工业废水最有效的“生物氧化降解法”却无法用来有效处理四环素废液，简述了半导体光催化剂在紫外光照射下降解难溶或难分解有机物基本原理，以半导体ＴｉＯ２和ＺｎＯ粉粒为光催化剂进行催化降解四环素废液的实验，其结果表明：半导体ＴｉＯ２光催化降解效果比较好；另外，Ｈ２Ｏ２可以作为ＴｉＯ２光催化剂的助氧化剂来加快四环素的降解，该实验结果有助于光催化剂的深入研究和太阳能     

Mechanically induced self-propagating reactions: analysis of reactive substrates and degradation of aromatic sulfonic pollutants

Mechanochemical reactions have been identified as a valuable alternative to conventional methodologies for the degradation of toxic pollutants as well as for their abatement in contaminated matrices. This paper discusses the application of the mechanochemical technique to the degradation of sulfonic acids in a contaminated matrix. The degradation of the pollutant compound was carried out by taking advantage of combustive reactions on a suitable reactive system ignited under mechanical treatment conditions. Two systems have been investigated as possible reactive substrates. The first one was a Mg-SiO2 powder mixture while the second system was a Ca-SiO2 powder mixture. Milling trials performed under different mechanical processing conditions allowed one to characterise the reactivity of these chemical systems, which basically undergo a reduction/oxidation reaction involving the formation of MgO and Si phases when the Mg-SiO2 system is considered and CaO and Si phases when the Ca-SiO2 system is employed, respectively. The systematic change of the stoichiometric ratios Mg:SiO2 and Ca:SiO2 permitted to identify the minimum Mg or Ca content necessary for the ignition of the combustive reactions. The experimental runs performed with such systems have shown a greater effectiveness of the Mg-SiO2 because of less energy inputs required to ignite a combustion. For this reason the Mg-SiO2 has been considered as a reactive substrate in the following trials. Since the SiO2 amount in stoichiometric excess may be regarded as inert phase, it was substituted with a different phase consisting of the matrix contaminated by sulfonic acids. This aspect permitted to ignite a combustive reaction with the minimum possible content of Mg-SiO2 reacting mixture. The chemical analyses performed after the combustive reaction proved the complete removal of the sulfonic acid from the contaminated matrix.     

Photoelectrocatalytic degradation of recalcitrant organic pollutants using TiO2 film electrodes: an overview

Photoelectrocatalytic (PEC) technology involved applying an electrical bias to a TiO₂ film electrode, has been widely applied to the degradation of refractory organic pollutants, owing to its high degradation efficiency. This paper reviews recent developments in the PEC degradation of recalcitrant organic contaminants using a TiO₂ film electrode. The preparation and application of various TiO₂ film electrodes have been investigated, as well as the parameters that influence PEC activity such as the crystal structure, the film thickness and substrate material, the applied electrical bias, the solution pH and conductivity. The improvement of PEC activity by doping the TiO₂ film electrode with metal and non-metal ions has been discussed. The mechanism and kinetics for the PEC degradation of organic pollutants have also been highlighted.     

Electrochemical combustion of herbicide mecoprop in aqueous medium using a flow reactor with a boron-doped diamond anode

The anodic oxidation of 1.8l of solutions with mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid or MCPP) up to 0.64 g l(-1) in Na2SO4 as background electrolyte within the pH range 2.0-12.0 has been studied using a flow plant containing a one-compartment filter-press electrolytic reactor with a boron-doped diamond (BDD) anode and a stainless steel cathode, both of 20-cm2 area. Electrolyses carried out in batch under steady conditions and operating at constant current density between 50 and 150 mA cm(-2) always yield complete mineralization due to the great concentration of hydroxyl radical generated at the BDD anode. The degradation rate is practically independent of pH and Na2SO4 concentration, but it becomes faster with increasing MCPP concentration, current density, temperature and liquid flow rate. The effect of these parameters on current efficiency and energy cost has also been investigated. Generated weak oxidants such as H2O2 and peroxodisulfate ion have little influence on the mineralization process. The kinetics for the herbicide decay follows a pseudo first-order reaction with a higher rate constant when current density increases. Aromatic products such as 4-chloro-o-cresol, 2-methylhydroquinone and 2-methyl-p-benzoquinone, and generated carboxylic acids such as maleic, fumaric, lactic, pyruvic, tartronic, acetic and oxalic, have been identified as intermediates by chromatographic techniques. The initial chlorine is completely released in the form of chloride ion, which is slowly oxidized to Cl2 at the BDD anode. A reaction pathway for MCPP mineralization involving all products detected is proposed.     

Biofiltration Control of Hydrogen Sulfide 1. Design and Operational Parameters

Laboratory scale biological filter systems for control of hydrogen sulfide (H₂S) in waste gas have been studied and the optimum design and operating parameters determined. Extensive tests have been conducted to evaluate the effect of various filter bed operating parameters such as temperature, retention time, H₂S concentration, and H₂S loading rate. Variable properties of new and used composts such as sulfate content, acidity, and water content have been studied for their influence on H₂S removal efficiency. The effects of compost particle size distribution on system pressure drop and the maximum H₂S elimination capacity were examined. Biofiltration systems containing various types of yard waste compost as the filter material have been observed to remove hydrogen sulfide with efficiencies greater than 99.9 percent for H₂S inlet concentrations in the range from 5 to 2650 ppmv.     

Synthesis of environmentally relevant fluorinated surfactants--a review

In the past years there has been a growing interest in fluorinated persistent organic pollutants such as perfluorooctanesulfonic acid, perfluorooctanesulfonamides, perfluorinated carboxylic acids and fluorotelomer alcohols. Although these compounds have probably been present in the environment for many decades, we are only now beginning to realize that these environmental contaminants may have serious environmental and health effects. This article gives a state-of-the-art review of synthetic approaches that have been employed for the synthesis of these environmentally relevant fluorinated compounds. Perfluorooctanesulfonic acid derivatives, in particular, pose a problem because only a few perfluorooctanesulfonic acid derivatives are available from commercial sources--a fact that limits the ability of researchers worldwide to further study these compounds. Because of the limited literature available, this article also describes synthetic approaches for shorter chain homologues or perfluoroether analogues that can potentially be applied for the synthesis of perfluorooctanesulfonic acid derivatives. The preparation of typical starting materials for the synthesis of perfluorooctanesulfonic acid derivatives such as the perfluoroalkanesulfonyl fluorides and chlorides will be discussed. Subsequently, their conversion into relevant perfluoroalkane sulfonate salts (R(F)SO3M), sulfonamides (R(F)SO2NH2), N-alkyl sulfonamides (R(F)SO2NHR, R = alkyl), N,N-dialkyl sulfonamides (R(F)SO2NR2, R = alkyl), sulfonamidoethanol (R(F)SO2NRCH2CH2OH, R = -H, -CH3 or -C2H5) and sulfonamidoacetates (R(F)SO2NRCH2CO2H, R = -H, -CH3 or -C2H5) will be described. Many perfluorinated carboxylic acids and fluorotelomer alcohols are available from commercial sources. The review of the synthesis of these two classes of fluorinated compounds includes a review of their industrial synthesis and the synthesis of relevant degradation products.     

Recent trends and projections of primary NO2 emissions in Europe

An assessment of recent trends in primary NO₂ emissions has been carried out for ten case study locations across the European Union. Estimates of the percentage of NO_x from road traffic emitted as primary NO₂ (f-NO₂) have been derived for 1995, 2000 and 2005 by combining the results of a literature survey of primary NO₂ emission factors for different vehicle types and technologies with an emission inventory. Estimates of f-NO₂ have also been derived from ambient monitoring data at roadside sites in each case study location using a model.The results of the analysis of trends show that f-NO₂ has increased in recent years and that the rate of increase has been greatest since 2000. f-NO₂ has increased from 8.6% in 2000 to 12.4% in 2004 as an average across the monitoring sites and from an average of 6.3% in 2000 to 10.6% in 2005 as an average of the emission inventory based calculations for the case study countries. f-NO₂ is predicted to increase further to an average of 19.6% in 2010 and 32.0% in 2020 as a result of the further penetration of exhaust after treatment technologies for diesel vehicles in the fleets. This increase is expected to be offset by the large reduction in NO_x emissions over this period, resulting in an increase in NO₂ emissions from road traffic to 2015, followed by a decline to close to 2004 levels by 2020. Estimates of future ambient NO₂ concentrations have also been calculated for the roadside monitoring sites included in the study. At 29 out of 45 of these sites the annual mean NO₂ limit value is predicted to be exceeded in 2010. At 22 of these sites, the annual mean concentration is expected to remain above the limit value until 2020 and beyond.     

Heterogeneous photocatalytic degradation of picloram, dicamba, and floumeturon in aqueous suspensions of titanium dioxide

Heterogeneous photocatalytic degradation of three-selected herbicide derivatives: (1) picloram (4-Amino-3,5,6-trichloropyridine-2-carboxylic acid, (2) dicamba (2-Methoxy-3,6-dichlorobenzoic acid, and (3) floumeturon (N,N-Dimethyl-N-[3-(trifluoromethyl)phenyl]-urea) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique and decrease in total organic carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the herbicide was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2, and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3), and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts in the case of dicamba (2) and floumeturon (3), whereas Hombikat UV100 was found to be better for the degradation of picloram (1). The herbicide picloram (1) was found to degrade faster as compared to dicamba (2) and floumeturon (3). The degradation products were analyzed by gas chromatography-mass spectrometry (GC/MS) technique, and plausible mechanisms for the formation of products have been proposed.     

Heterogeneous photocatalysed reaction of three selected pesticide derivatives, propham, propachlor and tebuthiuron in aqueous suspensions of titanium dioxide

Heterogeneous photocatalysed reaction of three selected pesticide derivatives such as propham (1), propachlor (2) and tebuthiuron (3) has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing UV Spectroscopic analysis and depletion in Total Organic Carbon (TOC) content as a function of irradiation time. The degradation kinetics was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO(2) and in the presence of electron acceptors such as hydrogen peroxide (H(2)O(2)), potassium bromate (KBrO(3)) and ammonium persulphate (NH(4))(2)S(2)O(8) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The pesticide derivative propham (1) was found to degrade faster as compared to propachlor (2) and tebuthiuron (3). An attempt has also been made to identify the products formed during the photooxidation process through GC/MS analysis technique. All the model pollutants showed the formation of several intermediate products, which were identified on the basis of molecular ion and mass spectrometric fragmentation pattern. A probable mechanism for the formation of the products has been proposed.     

Effect of Oxidizing and Reducing Conditions on the Reaction of Water with Sulfur Bearing Blast Furnace Slags

The evolution of H₂S and SO₂ from hot blast furnace slags by reaction with H₂O has been found to be dependent upon the presence of O₂ or H₂ in the reaction zone as well as on the temperature. H₂ has been found to produce a small increase in H₂S and a small decrease in SO₂ emission, while O₂ has been found to produce a very great inhibiting effect on H₂S emission and only a small increase in SO₂ emission. The total emission of sulfur bearing gases is much less when H₂O + air is blown at the slag than when H₂O + Ar is blown at the slag, particularly at 1200°C and above. These effects may be useful in attempts to design systems for slag quenching which will produce less pollution.     

Cationic surfactant as a sensitizer for the spectrophotometric determination of hydrogen sulphide in air and evaluation of a new absorbing medium containing triethanolamine-zinc acetate-sodium hydroxide

An extractive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing the gas in triethanolamine (TEA)-zinc acetate-sodium hydroxide solution is described. The method is based on the reaction of iodate with hydrogen sulphide in the presence of acid and excess chloride ion leading to the formation of ICl2- species which is used to iodinate 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein. The iodinated product formed is extracted into an organic solvent and sensitized by equilibrating with a cationic surfactant, cetrimide, in the presence of acetate buffer (pH 5.9 +/- 0.1). The colour system obeys Beer's law over the range 0-1 microg of hydrogen sulphide and the relative standard deviation is 2.4% for 10 determinations at 0.75 microg of hydrogen sulphide. The effect of interfering gases on the determination is discussed. The proposed absorbing solution has been evaluated using a hydrogen sulphide permeation device. This absorbing solution has an absorption efficiency of > 93% at a flow rate of 1.5 litre min(-1) for a sampling period of 2 h. The fixed H2S is stable for 40 days. The method has been applied to determine residual H2S levels in a laboratory fume hood and in the vicinity of sewage pumping station. The method can be used to determine as little as 0.05 microg of hydrogen sulphide.