Efficient recycle of waste poly-cotton and preparation of cellulose and polyester fibers using the system of ionic liquid and dimethyl sulfoxide

Efficient recycling of waste textiles is beneficial to the utilization of waste resources and environmental protection. In order to selectively dissolve the cotton from the waste poly-cotton fabrics, 1-allyl-3-methylimidazole chloride ([Amim]Cl)/Dimethyl sulfoxide (DMSO) and 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP)/DMSO system were used as solvents to dissolve the cotton from the waste poly-cotton fabrics. The influence of dissolved parameters, such as the mass ratio of ionic liquids (ILs) to DMSO, the size and amount of waste poly-cotton fabrics, and the dissolution temperature and time on the dissolution performance were investigated systematically in this work. The results showed that when the mass ratio of [Emim]DEP/DMSO was 5:5, the size of 1.0 × 1.0 cm, the cotton content of 1.4 wt%, the dissolved temperature of 80 °C, and the dissolved time of 60 min, the dissolution rate of cotton from the waste poly-cotton fabrics was 99.9%. The solubilization ability of the [Emim]DEP/DMSO system was higher than that of the [Amim]Cl/DMSO system for cotton, and the viscosity of the obtained cellulose solution was 0.1 Pa·s, which was more favorable for the separation of polyester from the cellulose solution. Furthermore, the degradation of regenerated cellulose obtained in [Emim]DEP/DMSO system was 5.0%, which was much lower than that of the [Amim]Cl/DMSO system. After five recycles, the dissolution rates of each time on cotton were all above 98%, which was basically the consistency with fresh [Emim]DEP/DMSO. In addition, the separated cellulose solution was used to prepare regenerated cellulose fibers by wet spinning, and polyester was used to prepare regenerated polyester fibers by melt spinning, and both of these fibers had smooth and dense surfaces. This strategy may provide a new approach to efficiently recycling waste poly-cotton fabrics.