Textile industry has always been a significant part of human civilizations for as long as the recorded history goes back. While it holds the record of being the second largest industry after food industry in the world, it is also one of the most polluting industries. Naturally occurring traditional textile fibres like cotton and silk are generally white in colour. To make it more attractive to the consumers it is often dyed to obtain coloured fabric. But this chemical process of dying involves all sort of synthetic organic dyes that produce large volumes of toxic waste water as by- product. Hence, a greener solution to this enormous problem was long expected.
Scientists in National Chemical Laboratory, Pune, India have developed the much needed green solution. In a paper published in ACS Publications, they report that when the mulberry silkworms were fed with a diet modified with a dye formulation, They naturally produced coloured silk cocoon of the same colour. More specifically, the silkworms were fed mulberry leaves sprayed/coated with azo dyes of different colours. The azo dyes are the most common dyes used in textile/food industry, which are cheaply available as well as proved to be harmless to the silkworm. Of the seven dyes, that were sprayed on to the mulberry leaves, two ended up in the cocoons produced by the silkworms.
The successful diffusion of the dyes from the silkworms’s alimentary canal to its silk glands can be done by controlling some of the parameters of the dye used. For the diffusion to take place, parameters like molecular weight, partition coefficient and the ratio of hydrophilic to hydrophobic character, lipophillicity etc. has to be controlled. The intensity of the colour can be however, easily controlled by controlling the dye’s concentration in the feed of the worm. The method thus successfully produces colourful silk, without producing any toxic by-product. Now, this solution had been studied before too, but with the dye called Rhodamine, which is quite expensive, making its use impossible for commercial purposes. Azo dye on the other hand, which the scientists in NCL, Pune used in their studies, is cheaply available and harmless to the worms.
Feeding the silkworms naturally occurring dyes to produce coloured silk is a solution that is as green as it can get. And the solution coming from India, one of the largest producer and consumer of silken garments, makes the event more worthy of celebration and satisfaction.