Investigation of the decomplexation of polyamide/CaCl2 complex toward a green, nondestructive recovery of polyamide from textile waste

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. Processes such as mechanical separation, depolymerization treatment, and selective dissolutions of individual polymers are applied. We investigate the approach of selective nondestructive 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 decomplexed by simple addition of water and a substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide. Investigation on a mixed textile waste model of polyamide/wool demonstrates that CEW treatment can successfully separate different fiber materials. The nondestructive 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 repolymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations. Thus, the concept will make significant contribution to a green textile recycling approach.