Processing of dyed cotton-based waste garments for re-use through the lyocell processing technology

The world’s population growth together with the change in lifestyle and fashion culture
has led to an increased demand for textile fibres. Fuelling this growth is the increasing
number of short fashion seasons in the clothing retail markets, which has led to the overall
decreased lifespans of clothing in developed countries such as the United Kingdom,
which in turn has resulted in a significant increase in waste textile. The current disposal
routes for the generated waste textile is through reuse or recycling, with up to 30% of the
waste being landfilled or incinerated. Both landfill and incineration of waste textile are
associated with environmental pollution, while reuse of waste garment as second-hand
clothing is associated with the decline of the textile industries in developing countries due
to the lower cost of the imported second-hand garments undercutting the local products.
Moreover the common mechanical recycling of the waste textile back to the component
fibre is also compromised by the presence of colour and mixed fibre blends which in turn
results in low value non-woven products.
This study investigated the potential methods to chemically recycle waste cotton
garments and reuse the recycled materials as feedstock for producing regenerated
cellulosic fibres through the Lyocell process. Methods to chemically ‘strip’ colorants and
finishing agents from waste cotton garments were first established and their efficiency
evaluated. Acid and alkali hydrolysis, dithionite reduction and oxidative bleaching were
evaluated as potential methods for delivering cheap, efficient and environmental-friendly
colour removal from cotton substrates. It was established that, the sequential
acid/dithionite/peroxide treatment could strip a wide range of colorants from cotton
fabrics, while the sequential acid/alkali/peroxide treatment could only strip relatively few
colorants from the cotton substrates.
The recycled waste cotton garments were successfully used to generate Lyocell fibres
from both 100% recycled cotton pulp and a blend of recycled cotton pulp (20%) and wood
pulp (80%). Both the fibre’s mechanical and structural properties were assessed using
tensile parameters, X-ray diffraction spectroscopy (XRD), Fourier Transform Infrared
(FTIR) and scanning electron microscopy (SEM) and were compared to the conventional
Lyocell fibres from wood pulp. The overall findings of this study demonstrated the
potential of reusing waste cotton garments through the Lyocell process and producing
fibres with properties similar to conventional Lyocell fibres.