Hydrolytic-Assisted Fractionation of Textile Waste Containing Cotton and Polyester

Abstract

Resulting properties of cotton and polyester blends make polycotton the most common fabric in textile industry. Separation technologies are key for the chemical processing of the massive amount of polycotton waste produced worldwide. The very different chemical nature of cellulose and polyethylene terephthalate determines the fractionation strategies to obtain two valuable monomaterial streams. In this work, we propose separation pathways seeking the conversion both polymers. First, polyester was depolymerised into its monomeric units through catalytic alkaline hydrolysis. The combined effect of alkali concentration and the catalyst was analysed to overcome the hydrophobic nature of polyester and optimise its conversion rate minimising the damaged caused to the cellulose chains. Conversion rates up to 80% were reached in a single separation stage with a limited effect of the polymer chain distribution of cellulose which remains a fiber-grade feedstock. Alternatively, cellulose was fully removed by selective dissolution in ionic solvent and subsequent filtration resulting in a spinnable mixture. Finally, enzymatic treatments for the conversion of cellulose into fermentable sugars were studied. Single stage conversions of 65% were achieved after maximizing the enzymatic activity. Structural and spectroscopic analysis showed that crystalline domains of textile-grade cotton limit the enzymatic activity. Optimal fractionation process is, in our view, highly context dependent what conveys to seek a variety of alternatives seeking for chemical processes driven by the ulterior up-cycling of the monomaterial streams