Demonstration of cyclodextrin techniques in treatm.. (LIFE DYES4EVER)
Demonstration of cyclodextrin techniques in treatment of waste water in textil industry to recover and reuse textil dyes
Start date: Jul 1, 2013,
End date: Dec 31, 2015
Textile industries commonly create wastewater containing potentially hazardous contaminants for the environment. Dye compounds are one of the wastewater contaminants that often need special treatment. T
he percentages of unfixed dyes remaining in wastewater can range from approximately 1% in pigments to as much as 50% for reactives. The reactive dye used on cotton is that which displays the lowest fixation ratio. Given that cotton represents half the textile output on the worldâs markets, the problem of effluent coloured with reactive dyes greatly increases the contamination problem.
Standards laid down in water legislation state that the admitted levels of dye are such that the colour will be inappreciable in a dilution of 1/40. Currently, several treatments are performed, some separated, others combined to meet the standard: either by mixing and blending with wastewater from other processes that do not use dyes to reduce the overall value obtained; or through a chemical treatment of the dye to destroy the colour group, which involves additional chemicals and new costs.
The LIFE DYES4EVER project aims to demonstrate and validate the ability of cyclodextrins (CDs â a compound made of sugar molecules obtained from starch) as encapsulation agents for dyes. The advantage of encapsulating the dye with CDs over current techniques of purification is that apart from reducing residual water coloration, the process allows for recovery of the dye compounds in a reusable form that can be applied in subsequent dyeing process. In addition, the water it is possible to reuse the water in the new process as it is not polluted with dyes.
A semi-industrial scale pilot will be set up to recover CDs and dyes in wastewater. This process is relatively complex for two reasons: firstly, the variety of dyes used to obtain the range of colours demanded by the fashion industry; and secondly, the differing specific requirements of dyes depending upon the textile substrate used.
The prototype will be installed in a typical Spanish textile company in order to provide representative results.
The project expects to achieve the following results:
A considerable reduction in the use of chemicals (dye-stuffs), which will in turn mean that these are not released into the environment;
A 70-80% reduction in the purifying costs of dye removal of wastewater between 70% and 80%;
The ability to use up to 95% of recovered CDs in subsequent dying processes; and
The recovery, in one single treatment, of at least 90% of the unfixed dye that remains in the effluent. Greater accuracy is not possible because this value will also depend on the type of dye and fibre used in the process as well as any auxiliary products and processes involved. In addition to the quantity of dye recovered, the project expects to achieve the legislated dilution of 1/40 without the need for any further purification. The project will also reduce CO2 emissions from the savings in dyes manufacturing and transport.
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