A mixture of calcium chloride, ethanol and water was developed for the separation and recovery of polyamide for further usage.
The ‘circular economy’ concept envisages deriving the maximum value out of resources and reducing waste to a minimum. In textiles, that includes the recovery of fiber materials out of used clothing and reusing them in the construction of new clothes. . We investigate the approach of selective non-destructive dissolution and recovery of polyamide fiber from mixed textile waste by using the solvent system CaCl2/Ethanol/Water (CEW) based on complexation and decomplexation of polyamide (PA). The results show that PA is precipitated and de-complexed by simple addition of water and substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide.
Initial results – Laboratory experiments
Initial investigation on textile waste models demonstrates that CEW treatment can successfully separate different fiber materials. The non-destructive approach in dissolving PA using CEW, clearly shows the benefit, that PA fiber can be separated by controlled complexation/ decomplexation without degradation, thus avoiding the re-polymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations.
Figure 1 . polyamide/wool fibre mix before (a) and after CEW treatment: (b) 30/70, (c) 50/50, and (d) 70/30 of polyamide/wool mixtures (Copyright Univ. Innsbruck).
As shown in Figure 1, the second component of the model mixture – in this case wool – retains intact after the separation from the dissolved polyamide.
These results suggest a potential advantage of selective non-destructive dissolution and recovery of PA fibres. Thus, the concept will make significant contribution to a green textile recycling approach.
Transfer to different materials systems and process optimisation
The potential of the separation technology is being tested in further textile fibre mixture system such as polyamide/elastan, polyamide/cellulose. Figure 2 demonstrates the feasibility of the technology on an elastic knitwear.
Figure 2. Separation of dyed polyamide from an elastic knitwear: (a) before and (b) after treatment (Copyright, Univ. Innsbruck).
Furthermore, process conditions, e.g. temperature and agitation speed are under investigation to optimise the dissolution efficiency of the systems.
Strategic project 3.2 Solutions toward textile circularity
WP2: Development of separation and recovery technology for PA mixed textiles
The COMET Project “Textile Competence Center Vorarlberg 2 – FFG 882502” is funded within COMET – Competence Centers for Excellent Technologies – by BMK, BMDW as well as by the co-financing federal province Vorarlberg. The COMET programme is managed by FFG.