Study On Polyester Fiber Degradation And Polyester/Cotton Separation By Ionic Liquid And Eutectic Solvent

With the development of the textile industry technology,the amount of waste textiles has increased dramatically and become one of the major sources of solid waste pollution in central cities in China,which is far greater than the amount of waste plastics.The recycling of waste textiles will have huge social and economic benefits in terms of environmental protection and resource conservation.As polyester and cotton being the main body of waste textiles,achieving effective separation of these two components and realizing high-value utilization of any component is the key to promote the process of recycling waste textiles.In this article,ionic liquids and deep eutectic solvents are used as catalysts in the process of polyester fibers hydrolysis and polyester/cotton separation,the specific contents are as follows:(1)Based on the previous research on the catalytic degradation of PET bottle flakes,in this work,a series of amino acid-based ionic liquids were first synthesized for polyester degradation.Based on the response value of conversion rate and yield,a four-factor three-level central combination experiment is designed.The optimal conditions for the degradation reaction are as follows:125 min,193.5 ^oC,8 wt%catalyst dosage and 15.7 g EG.Subsequently,experiments were conducted under this optimized condition,and the relative deviation of the model was 3.49%,which proved that the results were reliable.(2)In order to further improve the catalytic efficiency,a series of amino-acid based deep eutectic solvents were synthesized to catalyze polyester fibers degradation,which has achieved a good effect.The internal structure and physical properties of catalysts were characterized by FT-IR,¹H-NMR,TGA,DSC,etc.After a series of optimization of reaction conditions,we have obtained the optimized reaction conditions:under the condition of 190 ^oC for 45 min with 5%(w/w)catalyst of PET fibers and 25.0 g EG as the solvent,the conversion of PET fibers and yield of BHET are 100%and 87.2%,respectively.Meanwhile,the interaction mechanism among the catalyst,solvent and polymer was studied by means of ¹H-NMR,In-situ IR and other characterization methods.A possible reaction mechanism based Lewis-acid and hydrogen bond was proposed using density functional theory(DFT)simulation methods.(3)The optimized[Betaine]Zn(OAc)₂ catalyst was used in the PCBs separation experiment which avoid the strong acid solvents usually used in the most traditional methods.The surface morphology and internal structure of the recovered cotton were analyzed by SEM,XRD,FT-IR.This shows that the synthesized amino-acid ionic liquids and deep eutectic solvents not only have a good effect on the degradation of polyester,but also can further achieve the effective separation of polyester/cotton blends.