Major Retailers Are Starting to Consider the Environmental Impact of the Fabric Dyeing and Finishing Processes Used by Their Manufacturers
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Textile manufacture A shade of green Major retailers are starting to consider the environmental impact of the fabric dyeing and finishing processes used by their manufacturers. Fiona Case reports In March this year researchers converted into other hazardous these goals are solutions which from the environmental activist In short substances, or accumulate in wastes progressively replace hazardous group Greenpeace completed Hazardous chemicals generated during the treatment chemicals with less hazardous, a project to collect wastewater were found in the process (such as sludges),’ explains and preferably ultimately non- samples from two Chinese textile wastewater of two Kevin Brigden, a scientist at the hazardous, alternatives.’ manufacturing facilities which Chinese textile Greenpeace Research Laboratories, produce clothing for a number of manufacturing plants based at the University of Exeter, UK. Hung out to dry international brands including earlier this year The Greenpeace Dirty Laundry The perfluorinated compounds Abercrombie & Fitch, Calvin Some international report, published in July, stirred (PFCs) probably came from water Klein and Lacoste. The facilities clothing retailers up interest. ‘A number of large repellent textile finishes. ‘PFOA – located on the Yangtze river and and brands are now textile brands are now making seems to be particularly problematic Pearl river deltas – had modern looking to improve commitments to eliminate the use and one solution is to switch to wastewater treatment plants, but gas their environmental of hazardous chemicals within the C6 material,’ says Martin Bide chromatography-mass spectrometry credentials their supply chains,’ says Brigden. from the department of textiles at analysis of their effluent revealed Research to eliminate ‘What is required to achieve the University of Rhode Island, US. the presence of undesirable bioaccumulative and compounds including a range of toxic compounds, perfluorinated compounds such and to improve the as perfluorooctanoic acid (PFOA: environmental footprint an environmentally persistent of textile dyeing and and bioaccumulative chemical finishing is of increasing with a range of toxic effects), interest nonylphenol (a persistent material considered to be an endocrine disruptor), toxic dichloroaniline, aminoanthraquinone and aromatic amines including 2-methoxyaniline (a known carcinogen). ‘Many persistent organic Water sampling from pollutants will either pass through the discharge pipe at the the conventional wastewater Youngor Textile Factory QUI BO/GREENPEACE QUI treatment plants unchanged, be on the Yangtze river delta 48 | Chemistry World | December 2011 www.chemistryworld.org SHUTTERSTOCK ‘In 2006 the US Environmental final coating is only nanometres Textile dyes in a range of photons with wavelengths between Protection Agency approached thick – and material that is not colours on a market stall 400 and 700nm. The charge on the the eight largest fluorocarbon coated onto the product is entirely molecule and its substituents define producers and requested a 95 per contained,’ Coulson explains. the type of dye and the materials on cent reduction in PFOA use by ‘Conventional chemistries such as which it will be used. 2010, and 100 per cent by 2015. The PFOA are not required and there are The first synthetic dye was major companies have responded no issues with waste.’ P2i are now discovered serendipitously in 1856 and have already transitioned their coating more than 1.5 million pairs of by the young William Perkin while textile finishing products to short- high-end shoes per year for brands he was trying to make quinine. chain chemistry.’ such as Timberland, Mizuno and Perkin’s mauve was a water- Use of these new materials would Teva, and are in discussions with soluble cationic dye. This class is reduce the PFOA in the effluent, but several clothing brands. still used for dying acrylic fibres Brigden is not satisfied. ‘The shorter Nonylphenol in the wastewater (the proposed mechanism is salt chain PFCs also have properties of almost certainly resulted from formation with anionic groups concern, and have already been found the degradation of nonylphenol on the fibres). Cellulosic fibres to bioaccumulate in the wild. The goal ethoxylate (NPE) surfactants. It such as cotton, viscose, or lyocell needs to be the elimination of PFCs.’ did not need to be there. ‘The use are often dyed using reactive P2i, a company focusing on liquid of NPEs in textile manufacture is dyes. As their name implies, the repelling nanocoating technology no longer permitted within the chromophore is attached to a group based in Abingdon, UK, is taking a EU, which clearly demonstrates such as a halogenated heterocycle step in that direction, according to the ability to manufacture textiles or an activated double bond which its chief technical officer Stephen without them,’ says Brigden. reacts with the hydroxide group Coulson. ‘We apply fluorinated ‘It is unfortunate that NPE use ‘Many on cellulose. Because they are acrylates to surfaces using plasma continues in other locations, and chemically bonded the reactive technology,’ he says. The technology that many brands allow their pollutants dyes have excellent colour fastness, was developed to provide maximum products to be manufactured using pass through however some of the older water and oil repellency for military these substances.’ materials can have fixation rates clothing. Acrylate monomers with wastewater as low as 50 per cent. Half of the fluorocarbon side chains are fed Dyeing to be green treatment dye ends up in the waste stream. A into the plasma. They deposit on the Dyes are typically large aromatic wide range of techniques including surface and polymerise. ‘We are only molecules with delocalised orbitals plants micro- and nano-filtration, using tiny amounts of material – the of appropriate energy to absorb unchanged’ photocatalytic oxidisation, sorption www.chemistryworld.org Chemistry World | December 2011 | 49 Textile manufacture methods and bioreactors have (the amount of dye that ends up ‘We abandoned using acid dyes, large multicyclic been used to remove the bright chemically bonded to the fibre). aromatic molecules with anionic colours from the effluent. ‘The last ‘In the past as much as 25 per cent chrome dyes a sulfonyl or amino functionalities, example I saw used plasma-treated of the physically absorbed dye did long time ago’ applied in an acidic dye bath. These onion skins,’ comments Bide. But a not chemically bond. This material materials are often mordanted with better approach is to optimise the ended up in the wash bath, six to chromium – which is of considerable chemistry. eight baths at high temperature concern in wastewaters. ‘We ‘We provide a range of dyes which were necessary to remove it. For abandoned chrome dyes a long have combinations of several, often our new dyes three or four baths time ago, although they may still be different, reactive groups on each at 60°C are sufficient. More than used in other parts of the world,’ chromophore,’ explains Patrice 90 per cent of the dye ends up says Carreau. ‘The new reactive Carreau, director of technology and chemically bonded to the fabric,’ dyes provide colours that are even project management at Huntsman explains Carreau. deeper than the chromes on wool or Textile Effects (headquartered Sulfur dyes used to be the main the sulfur dyes on cotton.’ in Singapore). ‘The dyes all have choice for dark black shades on Alenka Majcen Le Marechal is identical kinetics of absorption cotton. In a classic sulfur dyeing a professor at the University of and reaction – so that the final process the S–S bonds are reduced Maribor, Slovenia. She studies the colour created by a mixture is with Na2S producing soluble dye effluent from the textile industry as consistent throughout the fabric. anions which absorb into the fibre part of the European Aquafit4Use The light- and water-fastness must and are reoxidised to their insoluble project. She is still concerned also be consistent so that the colour form. While some dye suppliers about reactive dyes. ‘They are remains true as the fabric is worn have managed to greatly reduce not dangerous in themselves, and washed.’ the release of environmentally but their synthesis involves Huntsman aims to optimise both problematic sulfides in effluent, precursors and side products that the exhaustion rate of the dye (the others recommend moving to are toxic.’ The dichloroaniline amount of dye that is absorbed reactive dyes. Wool, silk, and nylon and aminoanthraquinone onto the fibre) and the fixation rate have traditionally been coloured observed by Greenpeace could have come from this source. ‘We are seeing increasing amounts of Catalytic clothing these toxic materials in the final Technologies are being product, particularly in recent developed to mitigate the years as the production of textile negative impact of textile dyes has moved from the EU to manufacture, but can our other countries,’ she says. ‘These clothes make a positive impact impurities can be released into on the environment? wastewater during textile finishing, Tony Ryan, pro-vice or even during home laundering.’ chancellor at the University of Cellulosic fibres are also dyed Sheffield, UK, believes they can. using vat dyes. The insoluble Working with artist and designer chromophore is reduced to its Helen Storey he hopes to colourless, but water-soluble form convince us all to wear clothing and absorbs into the fabric. Once coated with nanoparticles of the