Decolorising textile effluents

Amendments to the legislation on waste water are making the legal requirements for textile waste water more stringent. In addition to the limits on the metal content and the COD and AOX values, restrictions are also being placed on the colour of the effluent. Anionic dyes (e.g. reactive dyes and metal-complex acid dyes) are removed from spent dye liquors by means of ion pair extraction by long-chain amines. The effect of pH and the structure of the amine has been studied. In reactive dyeing such treatment reduces both the amount of colour and the AOX value. In the case of the metal-complex dyes the removal of the (chelated) metal is of prime importance. The metal-complex dyes can be recovered from the organic phase by extraction with caustic soda and then re-employed in dyeing. The amines that result at the end of dye recovery are practically colourless and may be reused.     

Effects of sewage treatment on textile effluent

Textile effluent is discharged to sewer with little or no destructive treatment. In investigating the effects of sewage treatment on textile effluent we aim to establish the biodegradability of the effluent and the reduction in toxicity exerted on aquatic organisms resulting from standard sewage treatment. Using three separate samples of effluent, the initial toxicity was tested using the aquatic invertebrate Daphnia magna. The samples were biodegraded following the Zahn-Wellens method and then retested. Results showed relatively good biodegradability but negligible toxicity reduction. The ‘hard COD’, or non-degradable, portion of the effluent, which appears to be responsible for exerting toxicity, is not altered by this treatment method.     

A Look at the Future of Bleaching,Dyeing and Finishing Polyester-Cotton

Held at The Post House Northenden Manchester, on 6 November 1974, the President of the Society, Mr J. Rigg, in the chair. The Canadian textile industry and market are discussed with special reference to consumer requirements. Modem plant for the continuous preparation, dyeing and finishing of polyester-cotton cloth is described. Energy and chemical conservation and effluent control are discussed briefly     

Use and Conservation of Water in Textile Processing

Meeting of the West Riding Region, held at the University of Bradford on 16 October 1969, Professor R. L. Elliot in the chair Information from an earlier survey showed that textile works used a wide range of quantities of water, from 0·5 to more than 50 gal/lb of textile material processed. There were indications that the more complex processes used more water than simple ones. In the present work this led to investigations of the usages in unit processes, rather than measurement of overall usage figures. Water usages have been determined under normal production conditions and the methods employed are described. Where possible the amounts of water used for processing and for washing were measured separately. The textile processes covered those where large quantities of water would be employed and included scouring, bleaching and dyeing, with the associated rinses at each stage. Machines observed were continuous ranges (both rope and open width), jig, winch and beam machines, and fixed vessels such as kiers and pits. The effects of different dyeing and bleaching processes have been studied where sufficient results were available. Possible methods of conservation of water are discussed, such as the re-use of ‘clean’ rinses, partial purification of effluent and purification of part of the effluent. Contra-flow washing is possible on continuous machines. The implications of the observations are discussed, covering the effects of changes in processing, the size, type and speed of machines and the effects of cloth weight and batch size.     

Environmental aspects of textile processing

The paper outlines some developments in ‘clean’ textile technology and discusses opportunities for effluent treatment with peroxy compounds. Particular aspects dealt with are elimination of organohalogen compounds (AOX) from cotton bleaching and wool shrinkproofing, energy and COD reduction in the continuous preparation of cotton and its blends, dye oxidation without chromium compounds, and the removal of colour from dyehouse effluent.     

Effect of EDTA on total dissolved copper concentration in textile effluents

The expected fate of copper in textile effluents has been examined in the context of an activated sludge waste treatment scenario, using experimental rate constants and results from previous sorption studies. The effect of EDTA on total dissolved copper concentrations, in effluent streams during waste treatment, is discussed in terms of competitive sorption and sequestration kinetics. For this purpose, rate constants for the reaction of EDTA with five reactive dyes were estimated spectrophotometrically. The results of these experiments show that the use of excess sequestrant can dramatically increase total dissolved copper concentrations in the effluent stream.     

碎煤加压气化废水的处理工艺及技术进展

概述了碎煤加压气化废水的特征以及我国碎煤加压气化炉装备及污水处理情况,对该废水的预处理,生物处理和深度处理的方法作了介绍,展望了几种最新的碎煤加压气化废水处理方法.     

Review on decolorisation of aqueous dye solutions by low cost adsorbents

Textile wastewater presents a challenge to conventional physico-chemical and biological treatment methods. Liquid-phase adsorption has been shown to be highly efficient for the removal of dyes and other organic matters from process or waste effluent. Many different types of adsorbent are used to remove colour from wastewater among which the most widely used material is activated carbon. Since activated carbon is expensive and necessitates regeneration, attempts have been made to substitute alternatives that are biodegradable, low cost and/or waste materials. This article presents the investigations carried out by numerous researchers on the use of different kinds of adsorbents and their adsorption capacities for the removal of specific dyes from textile wastewater.     

Water for the Dyehouse: Supply,Consumption, Recovery and Disposal

Factors which account for the almost universal choice of water as a medium for textile dyeing processes are outlined. Many of the dominant trends in the development of improved equipment and processes during the last decade have been associated with the control and treatment of this essential resource. Typical examples include the strong links between water conservation and most of the effective ways of saving energy, improvements in effluent treatment plants to minimise the impact of water-borne contaminants on the environment, exploitation of the possibilities for reuse of process water or treated effluent in further processing, as well as the direct objective of holding in check the rising contribution of water supply and effluent treatment to limit overall costs. This broad expanse of water, pure and impure, is surveyed from the viewpoint of the textile dye user, since, by virtue of the physical and chemical properties of textile dyes, he is also invariably a continual user of water.     

高吸油性树脂的合成、性能与应用

对高吸油性树脂的吸油机理、吸油特点及其常用的合成方法进行了综述，并对影响树脂性能的各因素进行了描述，介绍了高吸油性树脂在三废处理，芳香剂基材、渔网防污剂基材及合成树脂的改性添加剂等方面的应用。     

Removing colour from dyehouse waste waters — a critical review of technology available

Strict controls are being introduced on coloured effluents from UK dyehouses discharged to sewer. Failure to comply with these new regulations could result in prosecution. Yet in certain cases the technology to treat dyehouse waste waters adequately is either not available or prohibitively costly. This paper (originally given at a conference at the Manchester Conference Centre entitled ‘Waste water management for industry’) reviews the treatment technologies that can currently be used by the textile processor and discusses those newer techniques that may emerge in the near future.     

Recent developments of metal oxide semiconductors as photocatalysts in advanced oxidation processes (AOPs) for treatment of dye waste‐water

The textile industry presents a global pollution problem owing to the dumping or accidental discharge of dye waste‐water into waterways, which is having a major impact on the quality and aesthetics of water resources. The World Bank estimates that 17 to 20% of industrial water pollution comes from textile dyeing and treatment. This percentage represents an appalling environmental challenge for clothing designers and other textile manufacturers. Recently, the application of metal oxide semiconductors in the advanced oxidation process (AOP) has gained wide interest for the treatment of dye waste‐water owing to its good degradation efficiency, low toxicity and physical and chemical properties. AOP refers to a set of chemical treatment procedures designed to remove organic and inorganic materials from waste‐water by oxidation. In this paper, recently developed metal oxide semiconductors are discussed, in which the semiconductors are generally divided into three categories: (i) titanium dioxide; (ii) zinc oxide; and (iii) other metal oxides (such as vanadium oxide, tungsten oxide, molybdenum oxide, indium oxide and cerium oxide). The syntheses and modification methods as well as the efficiency of each category are discussed and analyzed. Copyright © 2011 Society of Chemical Industry     

Prospects for Radiation Techniques in Dyeing and Finishing

This paper evaluates the role, actual and potential, of high-energy and low-energy radiation in textile technology. Emphasis is placed on the cobalt-60 source and the electron accelerator as high-energy sources, and the glow discharge as a source of low-energy radiation. The effect of high-energy radiation on the structure and properties of fibres is reviewed. Two types of effect may be produced: crosslinking and degradation. The latter predominates with some polymers, whereas with others crosslinking of the polymer chains is the major effect. It is concluded that the direct effects of high-energy radiation are of insufficient value to justify its application to textiles without some simultaneous or subsequent chemical treatment of the fibre. The free radicals produced by the radiation serve as reactive sites at which the graft copolymerisation of monomers may be initiated within the fibre structure. Three methods are available for the radiation grafting of unsaturated monomers on to fibrous substrates: the ‘simultaneous’ method, the ‘post-irradiation’ method, and the ‘peroxide’ method. Most effort in this area has been devoted to the modification of synthetic-polymer fibres to make them more readily dyeable. Several examples of this are described. To achieve good penetration of the graft copolymer into the fibre, it is necessary that the fibre should be sufficiently swollen to permit penetration by the monomer molecules. Experiments on the swelling of polyester fibres in relation to grafting are described. The use of radiation-initiated grafting in the finishing of textiles is discussed next. The outstanding example of this, one that has achieved commercial exploitation, is the Deering Milliken Visa process for conferring durable-press properties on cotton and cotton–polyester fabrics. Flame-resistant cotton can also be produced by radiation-grafting techniques. The modification of the surfaces of textile fibres, for example, to confer soil-release and antistatic properties, is another potential application of radiation grafting in textile finishing. The deposition of coatings on solid surfaces by low-energy gas-discharge techniques has been the subject of many investigations. Recent work at the Shirley Institute, in collaboration with the Electricity Council Research Centre, has shown that several percent of vinyl monomers can be deposited on polyester fabric by means of the glow discharge. With hydrophilic monomers, the fabrics have improved antisoil and soil-release properties. Terylene (ICI) fabrics treated in a glow discharge with acrylic acid can be dyed to solid colours with basic dyes. The paper concludes with a brief assessment of the economics of radiation processes in relation to their use in textile technology.     

Textile Waste Waters: Treatment and Environmental Effects

The paper considers the use of water and chemicals in the textile industry and the volume, nature and composition of process effluents, the effect they have on the environment and the limitations they pose on the reuse of water. An outline is given of the methods available for treatment of waste waters from the industry, on site or at a Water Authority's works and the effects that chemical constituents of the effluents have on the treatment processes and on disposal of water and sludge. The assessment and significance of biodegradability and the extent of present-day knowledge on the biodegradability of the main classes of chemicals used in textile processing are discussed. The paper concludes with a section dealing with the removal of colour from waste waters.     

Electrochemical oxidation of reactive dyes: method validation and application

Electrochemical oxidation is a very effective technique for wastewater processing and, in the textile industry, it can be employed to remove colour from residual dyeing and washing liquors. In previous studies, the main factors were established for the control of the electrochemical removal of reactive dyes from textile wastewater. Mathematical models were proposed for the decolorisation of these dyes and for the electrical consumption. In the present work, these models are analysed and a three-step methodology is established in order to determine whether a dye can be removed from wastewater by electrochemical treatment. This methodology is applied and verified on a further four reactive dyes. The mathematical models are also employed to evaluate the colour removal from textile wastewater samples containing reactive dyes.     

Safety and Health in Industry,with Special Reference to Toxicity

The terms ‘toxicity hazard’, ‘acute toxic effect’ and ‘chronic toxic effect’ are defined. Toxic substances are classified into five groups, which are discussed. The mode of entry of toxic substances into the body is described. The threshold limit and ceiling values are the concentrations of toxic substances in the atmosphere which decide the extent of the hazard that may be present. These factors are discussed. Methods of detection are then described briefly, as are the steps that may be taken if a toxic substance must be used. Finally, the legislation governing the use of toxic substances is outlined.     

Investigation of the decomplexation of polyamide/CaCl2 complex toward a green,nondestructive recovery of polyamide from textile waste

The ‘circular economy’ concept envisages deriving the maximum value out of resources and reducing waste to a minimum. In textiles, that includes the recovery of fiber materials out of used clothing and reusing them in the construction of new clothes. Processes such as mechanical separation, depolymerization treatment, and selective dissolutions of individual polymers are applied. We investigate the approach of selective nondestructive dissolution and recovery of polyamide fiber from mixed textile waste by using the solvent system CaCl₂/ethanol/water (CEW) based on complexation and decomplexation of polyamide (PA). The results show that PA is precipitated and decomplexed by simple addition of water and a substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide. Investigation on a mixed textile waste model of polyamide/wool demonstrates that CEW treatment can successfully separate different fiber materials. The nondestructive approach in dissolving PA using CEW, clearly shows the benefit, that PA fiber can be separated by controlled complexation/decomplexation without degradation, thus avoiding the repolymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations. Thus, the concept will make significant contribution to a green textile recycling approach.     

The rotating cylinder electrode: a review of development

Recent developments in the theory and applications of rotating cylinder electrodes are reviewed. Particular attention is paid to the mass transfer behaviour and the development of turbulent flow patterns, and its exploitation in electrochemical reactors for a variety of applications including metal deposition from waste and effluent liquors.     

An Eco-Benign Approach for Unhairing Goat Skin Using Ozone

Unhairing or hair removal is an important step in leather processing. The conventional lime-sulfide process used for unhairing operation generates considerable waste and toxic hydrogen sulfide in the effluent when mixed with acidic effluent. Oxidative chemicals offer an alternative to the use of sodium sulfide in a rapid unhairing reaction. Oxidative unhairing was investigated using hydrogen peroxide, chlorine dioxide, and calcium peroxide, with unsatisfactory results. Ozone being a good oxidative agent was tried in this work in unhairing goat skin. Experiments on the use of ozone with oxygen/air as feed gas were carried out to study the unhairing effect on different regions of a goat skin. Unhairing was done in a static reactor. The wet blue produced from the skin underwent physical testing and was compared with the conventional operation. COD of the spent liquors were tested for comparison. The experimental results indicate that ozone as an oxidative agent could be used for depilation without affecting the physical and chemical characteristics of the resulting leather. The use of ozone for unhairing operation in place of sodium sulfide results in hair recovery and reduction of pollution loads.     

含氟织物整理剂概况

综述了国内外含氟织物整理剂的现状及结构分类，简述了其合成方法。对织物整理剂的防水性防油性的测试方法也作了简要的叙述。