Valorization of polycotton waste textiles: An acidic solution

This thesis investigates the valorization of polycotton waste textiles, the most common and difficult-to-recycle textile blend, through an innovative hydrochloric acid-based recycling process. The research addresses the growing environmental burden of textile waste, of which the vast majority is still landfilled or incinerated, despite increasing demand for circular solutions. The study focuses on converting the cotton fraction of polycotton into valuable chemical building blocks while simultaneously preserving the polyester fraction for further recycling. A comprehensive review of existing recycling technologies revealed that concentrated acid hydrolysis offers a robust alternative to enzymatic recycling. Experimental work demonstrated that treatment with 42–43 wt% hydrochloric acid enables complete separation of cotton and polyester at room temperature. Cotton is hydrolyzed into glucose and oligomeric saccharides with yields up to 90–95%, while the recovered polyester can be chemically recycled into high purity bis(2-hydroxyethyl) terephthalate. The process was successfully scaled from laboratory experiments to a 230 L pilot plant, confirming its industrial potential. Additionally, the thesis further optimized the conversion of cotton-derived sugars into 5-(chloromethyl)furfural (CMF), a valuable platform chemical that can be used for the production of renewable polymers, fuels and specialty chemicals. Through process optimization and evaluation of different reactor configurations, CMF yields up to 73.3% were achieved. Additional studies on non-polycotton fibers and textile dyes demonstrated that cellulose-based contaminants are compatible with the process, while animal fibers and certain synthetic fibers require consideration during feedstock selection. Dye molecules had limited impact on process performance. Show more