Glucose and Valuable Chemicals Production from Cotton Waste Using Hydrothermal Method

Direct hydrolysis of a towel to glucose was investigated using steam explosion and microwave-assisted treatment to find effective uses for cotton waste. The maximum glucose yield by direct hydrolysis (based on an untreated towel) was 18.8%, obtained at a steam pressure of 5.5 MPa (at 271 °C) and steaming time of 5 min using steam explosion. For the microwave-assisted treatment, with a 1.0 (w/w)% sulfuric acid catalyst, the maximum glucose yield by direct hydrolysis was 28.9%, obtained at a microwave heating temperature of 200 °C for 7 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 78.0%, attained at a microwave heating temperature of 200 °C for 7 min with 0.5 (w/w)% sulfuric acid catalyst. Furthermore, the maximum total glucose and valuable water soluble chemicals (cellobiose, 5-hydroxymethylfurfural, formic acid, and levulinic acid), 94.1%, were achieved at heating temperature of 200 °C for 10 min with 0.5 (w/w)% sulfuric acid catalyst. Finally, ethanol, 84.5% of conversion rate, could be produced using supernatant (it contained glucose) and microwave treated residue (200 °C for 7 min with 0.25 (w/w)% sulfuric acid catalyst) as carbon source for Saccharomyces cerevisiae with less fermentation inhibition.