Currently accounting for around 10 per cent of global carbon emissions, the clothing sector sees almost 90 per cent of post-consumer fibre waste being disposed of through incineration or in landfills. Synthetic fibre especially has become a major threat to the environment since it is not biodegradable in nature. Polyester accounts for more than half of all fabrics produced annually and is the most widely used synthetic fibre in the world due to its low cost and durability.
Now a new ‘chemical sorting’ process has been developed by a research team from the Korea Research Institute of Chemical Technology (KRICT). This process separates polyester from waste textiles which are disposed of in a mixed or contaminated form. In the process, a unique chemical compound, which selectively disrupts the chemical interaction between polyester and the dye used for its colour, is used for the separation.
A new chemical recycling technology has also been developed by the researchers, which converts polyester into valuable monomers while consuming less energy than conventional methods. These monomers can then be used to create new polymer materials.
Currently, clothes recycling relies on unreliable, low accuracy and labour-intensive processes to manny sort waste textiles into material types, which often fails to process homogenous materials.
This new process chemically discriminates polyester from waste fabrics using a non-toxic and biodegradable compound. When the compound is applied to textiles, colourants only present in polyester are completely extracted while no significant changes occur in other materials. Clean polyester can then be separated from the mixture of fabrics.
This method can also be used to separate polyester from uncoloured fabric mixtures as well. When the waste colourants extracted from the sorting process come into contact with the fabric, only polyester accepts the colorants which can then be separated and used as clean feedstock for chemical recycling.
The researchers believe that converting polymer waste into the original building blocks, like in chemical recycling, has the potential to achieve circular recycling for waste polyester.
Team leader, Dr Joungmo Cho, said, “Recently, the garment industry has utilised transparent and clean post-consumer PET bottles to produce recycled polyester clothes.”
“However, this method is not sustainable because the material cannot be repeatedly recycled. In contrast, our current technology would not be limited by the complexity of the constituent materials or the initial level of impurity in the waste,” he added.
“Whether the targeted materials are derived from petroleum directly or recycled from waste, the technology can repeatedly process most post-consumer textile streams. Thus it will help reduce waste in landfills and substantially achieve a circular economy in the plastic and textile industries.”
