Japanese researchers develop decolourisation process for textiles

This method will adopt sustainable techniques to limit the environmental impact of textile waste. The researchers optimised a decolourisation process known as supercritical fluid dyeing, in which supercritical carbon dioxide effectively penetrates fabric fibres to remove the dyes. The extracted dyes can be reused, and the fabrics can be redyed.

The research was led by Professor Kazumasa Hirogaki, and visiting professor Teruo Hori achieved successful optimisation of the decolourisation process, enabling the dye removal from clothes with minimal environmental impact. This study builds on outcomes from the NEDO feasibility study programme/feasibility study programme on new technology and was further developed under the JST COI-NEXT programme on open innovation platforms for industry-academia co-creation (COI-NEXT), as per a press release by the University.

The researchers first created supercritical carbon dioxide (CO2) fluid inside a specialised heated and pressurised vessel and mixed it with a decolourising agent before adding it to the dyed fabric. The idea was that by adding a decolourising agent with a solubility parameter between those of the dye and the fabric, efficient decolourisation could be achieved, stated the release.

The research claims to develop three decolourisation methods—to be used depending on the characteristics of the textile, the dyes, and the decolourising agent. The first method is called solvent trapping, in which supercritical CO2 dissolves and then traps the dye in a solvent phase at the bottom of the vessel. In contrast, the solid trapping method involves re-treating a processing body with a decolourising agent or placing an adsorbent in the vessel. The supercritical fluid extracts the dye and then traps it onto the processing body or adsorbent. Finally, in the homogenous method, the decolourising agent is completely dissolved in the supercritical fluid, and the extracted dye also dissolves in the supercritical fluid.

Using these techniques, an astounding decolourisation rate of over 90-100 per cent was achieved. Notably, this strategy was found to be effective for polyester fabrics. Moreover, the processing liquids, extracted dyes, and decolourising agents can also be repurposed and reused effectively, added the press statement.

Owing to its tremendous potential in terms of sustainability, the team of researchers from University of Fukui is actively seeking to commercialise this technology, with hopes of transforming the ‘make, use, and dispose’ model of the textile industry into a truly circular and sustainable ‘make, use, and reuse’ model, according to the release.

Fibre2Fashion News Desk (SG)