Chemical recycling of cotton-based waste textiles by sulfuric acid hydrolysis

Sammanfattning: Large amounts of waste textiles are produced annually, of which only a small fraction is recycled currently. The purpose of this study was to develop a method to recycle cotton-based waste textiles chemically that can be coupled to the production of biofuels or green chemicals. Bedlinens, labeled 100% cotton, were dissolved and hydrolyzed in sulfuric acid to produce a glucose solution without the need of enzymes. One-step hydrolysis, where dissolution of raw material and hydrolysis occurred at the same conditions, and two-step hydrolysis, where the raw material was dissolved in concentrated sulfuric acid in a first step followed by hydrolysis in diluted sulfuric acid in a second step, were studied. The one-step procedure was not able to deliver high yields nor glucose concentrations due to the limitations of using only one particular concentration of acid. However, the two-step procedure was successful in producing pure, concentrated glucose solutions. When using 5wt% sulfuric acid in the second step, it was possible to obtain a 40 g/L solution and a yield of 84%, while increasing the concentration of sulfuric acid to 7.5% in the second step allowed to reach a higher glucose concentration of 50 g/L, but at a lower yield (68%). It could be expected that the solutions can be easily fermented to fuels or chemicals, as there are almost no impurities due to by-production formation. Further studies are needed to assess the economic viability of this process on a commercial scale, although it stands in a good position to compete with lignocellulose-based processes thanks to the cost savings in feedstock and enzymes.