水中微量汞的原子吸收光谱分析

由于有机汞的毒害比无机汞大,环境保护中要求测知水中有机汞的含量。水中有机汞化合物的测定,目前多采用薄层分离原子吸收测定,或用有机溶剂抽提水中的有机汞化合物,抽出液用带有电子捕获鉴测器的气相色谱测定。操作手续繁复,且受设备条件的限制。近年梅崎芳美等利用强碱性介质和酸性介质还原气化水中的汞离子用原子吸收法分别测定总汞和无机汞含量,从总汞量扣除无机汞量简接地测知有机汞的含量。R.J.Baltisberger 则在过氯酸介质中还原汞测定无机汞含量,用过氧化氢加少量的锡预氧化后再用原子吸收测知     

化工环保

含汞废液及其治理新方法含汞废液的来源是多方而。例如:制造氯碱的化工厂的废水中含有元素汞和氯化汞,生产农药的废水中含有汞;造纸工业用汞做杀菌剂和粘絮去除剂;仪表厂用汞作温度计:压力计的填充液;金矿的选矿场用“汞板”捕集颗粒金;用汞的化合物制造炸药,生产药剂、防腐剂、印染、照相等行业的废水中都含有汞及其化合物。这些废液排入水体后会造成水体的汞污染。汞是剧毒     

GB 11198.9-89《工业硫酸 汞含量的测定 双硫腙光度法》

本方法为工业硫酸中汞含菅测定的仲裁法。1 主题内容与适用范围本标准规定了用双硫腙光度法测定工业硫酸中的汞含量。本标准适用于工业硫酸中汞含量大于0.000005%的测定。2 方法原理试样中的汞,用高锰酸钾氧化成二价汞离子。用盐酸羟胺还原过量的氧化剂,加入盐酸羟胺和乙二胺四乙酸二钠消除铜和铁的干扰。     

水泥工业汞的排放现状及展望(Ⅱ)——汞排放的机理及监测方法分析

<正>上篇文章[1]中介绍了国内外水泥汞排放的现状,认识到了水泥用原燃料材料汞含量差别巨大及生产的复杂性是水泥生产汞排放控制的困难之一。本文对水泥厂汞循环进行分析,并对几种常用的汞排放监测方法进行对比分析,为汞排放的监控提供参考。1汞循环特征及其工艺影响因素1.1汞循环特征分析在水泥生产中,影响汞排放的因素存在较大的不确定性。对汞排放量的估计应基于水泥生产中汞的质     

宁夏金海创科化工顺利通过低汞触媒生产企业审核认证

<正>为规范聚氯乙烯行业生产用汞触媒市场,加强低汞触媒的推广,积极推动中国汞公约履约工作,有效降低电石法聚氯乙烯行业汞的消耗,减少对环境的污染,环保部汞公约履约处委托中绿环保实业有限公司组织专家对低汞触媒生产     

华东地区印染企业废水中汞污染现状评估及原因分析

对华东地区20家印染企业生产用新鲜水和处理前废水抽样检测,发现其废水中存在汞污染。对这些企业的生产特点、污染现状及污染源进行分析,结果表明:华东地区印染企业的废水中存在汞污染,检出的汞浓度范围为0.12～4.27μg/L;染料、含汞试剂、含汞危险废弃物和生产用新鲜水是华东地区印染企业废水中汞污染的主要原因。     

国内外简讯

正宁夏金海创科化工顺利通过低汞触媒生产企业审核认证为规范氯乙烯行业生产用汞触媒市场,加强低汞触媒的推广,积极推动中国汞公约履约工作,有效降低电石法PVC行业汞的消耗,减少对环境的污染,环保部汞公约履约处委托中绿环保实业有限公司组织专家对低汞触媒生产企业进行了审核认证。     

乙炔氢氯化反应用无汞催化剂的研究进展

综述了国内外乙炔氢氯化反应用无汞催化剂的研究情况，介绍了目前实验室中无汞催化剂的开发进展，展望了无汞催化剂的发展前景。     

水中微量汞的分光光度测定研究

为克服双硫腙光度法测定水样中汞的选择性差和条件要求苛刻等缺点 ,研究合成了新三氮烯类试剂——— 6 -硝基苯并噻唑重氮氨基 - 4-硝基苯 (NBTDAPNP)及试剂与汞的显色反应 ,提出了用分光光度测定汞的新方法。在弱碱介质中 ,汞与试剂形成 1∶2的黄色络合物 ,用双波长法测定 ,表观摩尔吸光系数为 2 .18× 10 5L/ (mol·cm) ,汞量在 0～ 10 μg/ 2 5mL范围内符合比尔定律。应用于工业废水和环境水样中汞的测定 ,获得了满意的结果。     

英国石油公司发展氯碱厂废汞回收新技术

英国石油公司为了减少采用汞齐电解槽的氯碱工厂汞的损失,发展了新的次氯酸盐洗气方法,它适用于处理损失汞的氯碱厂的各种气体。这些气体中汞的损失,仅仅反映汞电解槽生产氯过程中废汞问题的一部分。用放射性示踪物和其他技术测定表明,一个比较现代化的汞齐电解槽的氯碱厂,在管理好的情况下生产,总的汞损失,认为大约是75～100克/吨氯;在管理不好的情况下,这个数字可达250克/吨氯;在操     

Vapour Pressures and Heats of Sublimation of Some Disperse Dyes

The vapour pressures, latent heats of sublimation and associated entropy changes of anthraquinone and monoazo disperse dyes have been obtained by the transpiration method. These compounds have vapour pressures of 0.0005-0.193 mm Hg over the temperature range of 120–215°C. The heats of sublimation are discussed in terms of their molecular structure.     

Development of a method for the determination of ultra-trace level mercury in adipose tissue by cold vapour atomic fluorescence spectrometry

A method for the determination of total mercury in rat adipose tissue by cold vapour atomic fluorescence spectrometry (CVAFS) has been developed. Adipose samples were initially subjected to a lyophilization procedure in order to facilitate the homogenization and accurate weighing of small tissue aliquots (~50 mg). A closed vessel microwave digestion procedure using a mixture of sulphuric and nitric acids was used to liberate mercury from the adipose matrix. All mercury species were quantitatively oxidized to Hg(II) by a potassium bromate/bromide oxidation, then reduced to Hg(0) vapour by stannous chloride prior to fluorescence detection. The CVAFS exhibited a linear range of 10 pg Hg/ml to 120 pg Hg/ml. The method detection limit in solution was 2 pg Hg/ml, or 1 ng Hg/g adipose tissue, based on a nominal 50 mg sample and a final volume of 25 ml. A reference material from the National Research Council of Canada (DOLT-2, trace metals in dogfish liver) was prepared in quadruplicate in order to assess the accuracy and precision of the method. Mercury in this material was recovered at 2.22 +/- 0.08 mu g/g, which is 104% of the certified level (2.14 +/- 0.10 mu g/g).     

Metal sorbents for high temperature mercury capture from fuel gas

We have determined the Hg removal capacities of Pt and Pd supported on alumina at a range of different metal loadings from 2 to 9 wt% using Hg vapour in a simulated fuel gas feed. In the temperature range studied (204-388 °C) Pd proved far superior to Pt for Hg removal. The Hg removal capacity for both Pt and Pd increased with metal loading, though decreased with sorbent temperature. A shift in the 2θ position of the Pd XRD diffraction peak from 82.1 to 79.5 after Hg adsorption at 204 °C was consistent with the formation of a solid solution of Hg in Pd.     

Association effects in ternary vapour—liquid equilibria

A thermodynamic model is proposed for the analysis of multicomponent systems capable of homo and heteroassociation between all the chemical species present. Detailed equations have been developed for ternary systems. The method has been applied to the experimental vapour—liquid data obtained for the system formic acid—acetic acid—propionic acid at 760 mm Hg. The calculated activity coefficients were thermodynamically consistent and were correlated using the Redlich—Kister equation. Boiling points, compositions and activity coefficients can be predicted from the vapour—liquid equilibrium data of the three binary systems.     

Vapour-liquid equilibria in associating solutions

Isobaric vapour—liquid equilibria data were measured for the binary mixtures of acetic acid—propionic acid and formic acid—propionic acid at 760 mm Hg. The data were tested against a new thermodynamic model which extends the one proposed by Marek in that it is suitable for the case of binary mixtures containing two associating species and takes into account hetero-dimerization in the vapour phase. The proposed model converts into that of Christian for the particular case of an ideal liquid solution. The model fits well the system acetic acid—propionic acid with regard to the thermodynamic consistency of the overall activity coefficients, but does not fit the second mixture so well, probably because higher degrees of polymerization have to be included in it.     

Vapour–liquid equilibrium data for n-butyl acetate–1,2-propylene glycol

Vapour–liquid equilibrium data for the binary system n-butyl acetate–1,2-propylene glycol have been obtained at pressures between 725 and 735 mm Hg. The activity coefficient data were correlated by Chao's modified Redlich Kister equation and van Laar's equation. The vapour composition was also correlated by the equations of Nagata and Hirata. Thermodynamic consistency was confirmed by Herington's area test.     

The role of H2O in the photocatalytic oxidation of toluene in vapour phase on anatase TiO2 catalyst: A FTIR study

Photocatalytic oxidation of toluene has been carried out in a gas–solid regime by using polycrystalline anatase TiO₂ in a fixed-bed continuous reactor. Air containing toluene and water vapours in various molar ratios was fed to the photoreactor irradiated by a medium pressure Hg lamp. Toluene was mainly photo-oxidised to benzaldehyde, and small amount of benzene, benzyl alcohol and traces of benzoic acid and phenol were also detected. In the presence of water, no decrease of photoreactivity was observed at steady-state conditions. By removing water vapour from the feed, the conversion of toluene to benzaldehyde was almost completely inhibited, and an irreversible deactivation of the catalyst occurred. FTIR investigations indicated that benzaldehyde is photoproduced on the TiO₂ surface even in the absence of water vapour, but exposure of the catalyst to the UV light in a dry atmosphere results in an irreversible consumption of surface hydroxyl groups. As these species play a key role in the photoreactive process, this dehydroxylation should be the reason of the catalyst deactivation observed in the catalytic runs carried out in the absence of water vapour.     

Kinetics of the calcination of calcium sulphate dihydrate

The kinetics of calcination of calcium sulphate dihydrate were studied at 100° at air pressures from 760 to less than 10^?5 mm Hg. Any reduction in air pressure below atmospheric caused an increase in reaction rate. Water vapour removal initially facilitated the dehydration at higher pressures, but began to impede the reaction at low pressures.     

Classification of carbon in Canadian fly ashes and their implications in the capture of mercury

Fly ashes produced from Canadian power plants using pulverized coal and fluidized bed combustors were examined for their carbon content to determine their ability to capture mercury. The feed coal used in these power plants were lignite, subbituminous, high and medium volatile bituminous, their blends, and also blends of coal with petroleum coke (Petcoke). The carbon and mercury content of the coals and fly ashes were determined using the ASTM standard method and by the cold vapour atomic absorption spectrometry method. The carbon content of the fly ash was concentrated by strong acid digestion using HCl and HF. The quantitative and qualitative analyses of the carbon concentrate were made by using a reflected light microscope. The results show that the carbon content of fly ash appears to be partially related to depositional environment during coalification and to the rank of the coal. The Hg captured by the fly ash depends on the rank and blend of the feed coals and the type of carbon in the fly ash. The isotropic vitrinitic char is mostly responsible for the capture of most Hg in fly ash. The inadvertent increase in carbon content due to the blending of coal with petroleum coke did not increase the amount Hg captured by the fly ash. The fly ash collected by the hot side electrostatic precipitator has a low Hg content and no relation between the Hg and carbon content of the ash was observed. These results indicate that the quantity of carbon in the fly ash alone does not determine the amount Hg captured. The types of carbon present (isotropic and anisotropic vitrinitic, isotropic inertinitic and anisotropic Petcoke), the halogen content, the types of fly ash control devices, and the temperatures of the fly ash control devices all play major roles in the capture of Hg.     

Thermal decomposition of zinc oxalate dihydrate: Kinetics of dehydration and pyrolysis in various atmospheres

Thermogravimetric analysis has indicated that a convenient range for the study of Zn(COO)₂.2H₂O dehydration is 120–300 °C, while for pyrolysis it is 320–400 °C. Kinetics of isothermal dehydration and pyrolysis were studied as two consecutive steps in various atmospheres, namely in constant water vapour pressure of 4.8 and 8 mm Hg, in air saturated with water vapour at 25 °C and in vacuo. The kinetic data indicated that dehydration is a pseudo-first order reaction, which is highly dependent on the surrounding atmosphere. The mechanism of dehydration is either activated diffusion (alternatively surface diffusion) for dehydration in vacuo or in low water vapour pressures, or activated desorption for dehydration in presence of high water vapour pressure. On the other hand pyrolysis is independent of the prevailing atmosphere, and the energy of activation is of the order of the enthalpy change of the reaction. Earlier studies have involved contact of the dehydrated oxalate with air, or have obscured the influence of the prevailing atmosphere, by dehydrating the sample material at the pyrolysis temperature. These conditions are considered in the present investigation.