Improving Valorization of Waste Textiles: Assessing Separation Efficiency of Cotton–PET Blends via Alkaline and Enzymatic Hydrolysis

Recycling cotton–PET textile blends using alkaline solutions has gained increasing attention, with studies showing promising treatment pathways with diverse process setups. However, these separation processes use various input materials and focus on a small number of treatment parameter values which render the comparison of results over a large parameter range difficult. This study presents the feasibility of recovering cotton or PET at fabric level from cotton–PET blends across a wide range of temperatures (from −30 °C to 95 °C) and alkaline concentrations (from 0 to 40% (w/w)). The focus of this study is centered on the share of separation and recoverable fiber mass after hydrolyzing one component using alkaline hydrolysis or alkaline pre-treatment followed by enzymatic hydrolysis. A comparison of purity and material loss of the recovered polymers for all parameter sets is given. Experiments were performed on two distinct textiles while process parameters were selected in a straightforward manner, excluding catalysts, co-solvents and defibration. The results map temperature and alkaline concentration areas where these cotton–PET separation processes are feasible regarding recoverable fiber mass. Based on these results, separation efficiency could be optimized to design economic and environmentally friendlier process conditions.