Application of the trickle tower to problems of pollution control. III. Heavy-metal cyanide solutions

The destruction of CN^– and co-deposition of copper, cadmium, nickel, zinc and lead, both as simple solutions and as mixtures, have been investigated in a number of trickle towers with from 8 to 49 layers of cells. Specific chemical effects due to the formation of cyano-complexes of some of the metals are evident, and it has been found that copper, nickel and cadmium accelerate the destruction of CN^–, at least initially. For simple solutions a previously proposed scaling law is adequate.Nomenclature a length of bipolar element (cm) - c concentration (ppm) - c ⁰ initial concentration (ppm) - K mass transfer coefficient (cm s^–1) - K=K _L effective mass transfer coefficient (cm s^–1) - L wetted perimeter per layer of packing (cm) - p number of layers of cells - t time (s) - v _o volumetric flow rate (cm³ s^–1) - V inventory of solution (cm³) - _L fractional active length - _s reversible potential with respect to main counter reaction (V) - _s ^T potential applied across an element with respect to main counter reaction (V)     

Application of the trickle tower to problems of pollution control. I. The scavenging of metal ions

The theory of metal deposition in a bipolar trickle tower is reviewed briefly and applied to the scavenging of copper, silver, lead and calcium from dilute streams. Measurements of reference potential and mass-transfer coefficients for the copper system in one tower allow estimates ofθ _L, the fractional active length, to be made and subsequently allow data from different towers to be collapsed into a universal plot, thus substantiating the theory at least to a first approximation. In the co-deposition of copper, lead and cadmium, the data for copper and lead can be collapsed, but for cadmium cannot, probably because cadmium's reference potential is very negative under the conditions of the experiments. A scaling law is proposed which can be used in the design of practical systems.     

The indirect electrochemical epoxldation of butenes and ethylene in a bipolar trickle tower

1-Butene,cis-2-butene,trans-2-butene and ethylene have been epoxidized under conditions which give reasonable results for propylene. In all cases the selectivities are high, but the current efficiencies are low (< 65%) due to the bulk phase chemical reactions being slower than the electrochemical generation of oxidant. Under conditions where the rates of the chemical and electrochemical reactions match, the figures of merit would be comparable to those for propylene. In the epoxidation the conformation of each butene isomer is preserved.     

The effect of operational parameters on the performance of a bipolar trickle tower reactor

A bipolar trickle tower reactor (BTTR) (of 7.9 cm internal diameter and 75 cm length containing 57 layers, each layer having 30 carbon Raschig rings, each of 1.25 cm outside diameter) has been studied under a range of operational conditions. The batch recycle mode of operation has been used for the removal of Cu(II) ions (at an initial concentration of 50–200 ppm) from an acid sulfate solution (typically 3000 cm³) at 295 K. Non‐ideal flow and Peclet number values have been considered to establish the degree of deviation from ideal reactor flow models. Operational variables included the potential difference per layer (1.0–3.0 V), volumetric flow rate (8.3–50 cm³ s^?1) and the effect of H₂SO₄ concentration (which increased conductivity and lowered pH) in the electrolyte. The reactor has been shown to be best suited to the treatment of a moderately high reactant concentration (eg 100–200 ppm) and low electrolyte conductivity. The final concentration can be as low as a few parts per million but the performance of the reactor (as judged by the current efficiency and the rate of concentration decay) markedly decreased as the dissolved metal ion concentration fell. Copyright © 2004 Society of Chemical Industry     

高级氧化技术在对氯硝基苯污染控制中的应用研究

对氯硝基苯(p-CNB)的污染控制问题受到研究者的广泛关注,高级氧化技术(AOPs)是一种能有效降解难降解有机污染物的水处理技术。阐述了化学催化氧化、光催化氧化、电催化氧化等典型AOPs的原理,总结了AOPs处理p-CNB的研究现状与进展,探讨各种技术在降解p-CNB过程中的一些不足,提出AOPs技术在今后的发展趋势。     

Voltammetric study of the cyanide complexes of osmium—II. The behaviour of lower oxidation state cyanide complexes of osmium on a platinum rde

It was found that the product of the reduction of the cyanide complex of hexavalent osmium, OsO₂(OH)₂(CN)^2?₂ is the Os(OH)₄(CN)^3?₄ complex and the product of the reduction of the OsO₂(CN)^2?₄ complex is the Os(OH)₂(CN)^2?₂ complex. Further reduction of the Os(OH)₄(CN)^3?₄ complex of trivalent osmium is complicated by a follow-up chemical reaction and the stable reduction product is a complex of divalent osmium, Os(OH)₂(CN)^4?₄ which forms a reversible redox system with the Os(OH)₂(CN)^3?₂ complex with a formal redox protential (1 M KOH, 0.1 M KCN) of ?760 mV/sce. The Os(OH)₄(CN)^3?₂ and Os(OH)₂(CN)^4?₄ complexes are stable only in solutions with at least a ten-fold excess of OH^? ions over the concentration of CN^t- ions. At greater cyanide concentrations, the chemical reactioins, Os(OH)₄(CN)^3?₂ → Os(OH)₂(CN)^3?₄ and Os(OH)₂(CN)^4?₄ → Os(CN)^4?₆, occur. The reaction rate for the latter reaction was found to be ?₄ = 1.87 × 10^t-4 l mol^?1 s^?1 in solutions with pH = 11.8. The characteristics of the individual forms of the cyanide complexes of osmium are also discussed.     

The behaviour of a trickle tower electrolytic cell for the production of cobalt(III) acetate from cobalt(II) acetate

The production of Co(III) acetate from Co(II) acetate using a bipolar trickle tower of graphite Raschig rings was investigated. Space time yields up to 18 kg m^–3 h^–1 were obtained, which showed no improvement over those achievable in a conventional plate and frame cell. A mathematical model of the system indicated that the electrode reactions occurred almost entirely at the opposing annular surfaces between consecutive layers of Raschig rings and that the unexpectedly low performance of the device was most probably due to the unfavourable mass transport conditions which existed in the intervening gaps.Nomenclature a annular cross sectional area of one Raschig ring (m²) - b _C kinetic exponential constant for reduction of Co(III) (V^–1) - b _A kinetic exponential constant for oxidation of Co(II) (V^–1) - b _H kinetic exponential constant for hydrogen evolution (V^–1) - b ₀ kinetic exponential constant for oxygen evolution (V^–1) - [Co(II)] concentration of Co(II) (mol m^–3) - [Co(III)] concentration of Co(III) (mol m^–3) - F Faraday constant (96 487 C mol^–1) - f fraction of total flow by-passing the annular gap between adjacent Raschig rings in a vertical row - I current per vertical column of rings (A) - k _C rate constant for reduction of Co(III) (A m mol^–1) - k _A rate constant for oxidation of Co(II) (A m mol^–1) - k _H rate constant for hydrogen evolution (A m^–2) - k _O rate constant for oxygen evolution (A m^–2) - k _L mass transfer coefficient (m s^–1) - Q flow rate per vertical row of Raschig rings (m³s^–1) - v volume of annular gap between adjacent Raschig rings in a vertical row (m³) - V superficial velocity of electrolyte (m s^–1) - _A anodic potential (V) - _C cathodic potential (V)     

PROFACE触摸屏在汽提塔控制系统中的应用

简要说明了汽提塔的工作原理,重点介绍了PROFACE触摸屏和西门子200 PLC系统的通讯参数设置,PROFACE触摸屏变量设置,数据采样,画面开发,安全设置等功能的应用。     

Dynamics of direct and indirect channels to dissociative adsorption

Two limiting dynamic processes leading to dissociative adsorption of hydrogen on W(100) are described. An indirect channel to dissociation is evident at low incident translational energies, and the probability that the precursor will go on to dissociate depends in a complex fashion on the coverage of atomic hydrogen. In addition to the indirect route, a direct channel to dissociation also contributes on the clean surface. Pre-adsorbed nitrogen in the c(2 × 2) structure is shown to block the direct channel to dissociation at low incident translational energies. However, the indirect channel to dissociative adsorption remains intact, and leads to a significantly high initial dissociation probability at low energies (60% at 3.4 meV) to conclude that the precursor must be formed at the W(100)-c(2 × 2)N unit cell.     

盐酸绝热吸收塔存在的问题及解决方法

介绍了盐酸绝热吸收塔的反应原理、特性及在工艺、设备方面等存在的问题,并提出了解决方法。     

Composition control in emulsion copolymerization. II. Application to binary and ternary systems

The optimal monomer feed policy for producing in a semibatch reactor a given amount of polymer with constant instantaneous composition, in the minimum reaction time and complete monomer depletion, as developed in Part I of this work, has been implemented experimentally. Conversion has been monitored on-line using a densitometer suitably connected to the laboratory reactor. The procedure has been applied to two binary and one ternary systems. The composition of the polymer produced has been characterized through various experimental techniques. The composition control procedure is insensitive to most types of irreproducibilities that arise in batch reactions performed in industrial appli-fjcations. © 1994 John Wiley & Sons, Inc.     

二恶英对环境的污染及其控制技术进展

简述了二恶英的公害性及有关特性;二恶英毒性表示法及二恶英的传播途径。重点介绍了二恶英的形成条件和二恶英的控制技术进展。     

先进控制系统在PX氧化反应过程中的应用

洛阳石化PTA装置应用DMC plus先进控制技术,在PX氧化反应过程中成功建立多变量预测系统,先进控制投用率达到99.5%以上,该系统优化了TA产品品质控制和原辅料消耗,使关键被控变量标准偏差下降20%以上,同时也使装置的乙酸单耗下降0.9 kg。     

多变量先进控制系统在PX氧化反应过程中的应用

在Honeywell的集散控制系统TDC3000的基础上,结合多变量预测控制和软测量技术,建立了氧化反应先进控制系统和TA品质先进控制系统。在2个系统的联合控制下,氧化反应中的强耦合和多约束难题得到了很好地解决,稳定并优化了氧化反应器的操作条件,提高了TA产品品质。     

Electrocatalytic oxidation of aliphatic alcohols: Application to the direct alcohol fuel cell (DAFC)

The electrooxidation of some low molecular weight alcohols, such as ethanol, ethylene glycol and n-propanol, is discussed in terms of reaction mechanisms and catalytic activity of the anode material. Some examples of a single cell, using a proton exchange membrane (PEM) as electrolyte, are given to illustrate interesting results, particularly for the direct electrooxidation of ethanol. This alcohol may replace methanol in a direct alcohol fuel cell.     

Gold catalysts for the direct oxidation of aminoalcohols to aminoacids

Gold catalysts on different supports, prepared by sol immobilization and deposition–precipitation, were tested in aminoalcohol oxidation for the direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40 °C) represent a good compromise for enhancing selectivity to aminoacids. TiO₂ represents the most versatile support.     

Electrochemical oxidation of organic pollutants in water at metal oxide electrodes: A simple theoretical model including direct and indirect oxidation processes at the anodic surface

The electrochemical oxidation of organics in water at metal oxide electrodes was investigated with the aim to discuss the correlations between the instantaneous current efficiency ICE and operative conditions by considering both the hypothesis of a direct oxidation process and of an indirect process mediated by adsorbed hydroxyl radicals or chemisorbed “oxygen”, in order to explicit the main differences expected between these cases. Thus, a simple theoretical model was discussed, as an extension of previous studies of Comnnellis and co-workers which were focused on indirect oxidation paths [C. Comninellis, Electrochim. Acta 39 (1994) 1857; O. Simond, V. Schaller, Ch. Comninellis, Electrochim. Acta, 42 (1997) 2009], concerning both the cases of mass transfer control and oxidation reaction control and mixed kinetic regimes. A very good agreement, between theoretical predictions and experimental data pertaining to the electrochemical oxidation of oxalic and formic acid at IrO₂–Ta₂O₅, was observed.     

Wet-air oxidation of sewage sludge. Part II: The oxidation of real sludges

Experiments on the oxidation of real sludges of different origins and compositions were carried out which lead to a mathematical model which described the results obtained. On basis of this model large scale reactors can be calculated. The conversion of the Chicago installation is predicted to be 81% under conditions where the really obtained conversion is reported to be 80%.     

ORP在水环境污染防控方面的应用

氧化还原电位(ORP)是判断液相体系氧化还原能力的综合参数,反映了液相体系的氧化还原倾向。探讨了温度、时间、pH、溶解氧等因素对ORP的影响,总结了ORP指标在水环境污染防控中的应用,指出了ORP应用过程中应注意的事项。就目前应用而言,ORP在给水处理、循环水处理、脱硫废水处理、水处理设备防腐等方面具有很好的应用前景。此外,ORP在湿地保护方面的应用也是新的发展方向。     

Legislation and the control of dyehouse pollution

The aim of this paper is to briefly review the law as it relates to the cost and prevention of water pollution, with particular reference to the textile and dyeing industries in Scotland. It examines how the statutes affect the industrialist. The procedures adopted for the control and prevention of pollution are described, and the rationale behind current practices is explained. Finally, a few thoughts are offered on options to avoid pollution and meet the requirements of the pollution control authorities.