Microwave-Assisted Hydrolysis of Cellulose in Towel and Wheat Straw Using Freeze-Thawing with NaOH

Abstract

The aim of this study was to produce a high yield of direct hydrolysis of glucose from a cotton towel and wheat straw by microwave-assisted (MW) treatment. To this effect, a freeze-thawing with 3% NaOH was added before MW treatment. Multiple MW parameters were tested. For the towel, the highest glucose yield of 42.4% based on freeze-thawing with 3% NaOH-treated sample was observed after MW treatment at 200 °C for 30 s with 2% sulfuric acid as a catalyst. This corresponded to a 44.4% yield based on the cellulose content of treated samples, which was 1.3-fold higher than that of samples treated only by MW at 200 °C for 7 min with 1% sulfuric acid as a catalyst (maximum glucose yield in our previous report). For wheat straw, the highest glucose yield of 27.0% based on freeze-thawing with 3% NaOH-treated sample, and 41.9% based on the treated sample cellulose content were observed after MW treatment at 200 °C for 3 min with 0.5% sulfuric acid as a catalyst. Under the optimum conditions, the glucose yield was 40.5% from raw towel and 14.7% from wheat straw. Combined severity parameter analysis revealed that the addition of freeze-thawing with NaOH before the MW treatment increased the glucose yield and reduced the severity of the treatment conditions. In conclusion, freeze-thawing using 3% NaOH before MW treatment is effective for the direct hydrolysis of glucose from towels and wheat straw.