Effect of ozone and sodium hydroxide treatments on some chemical characteristics of cotton straw

Abstract

AbstractCotton straw (CS) was treated with ozone or sodium hydroxide, and the effect of treatments on the organic acid and monosaccharide composition and on the chromat‐ographic characteristics of alkali lignin was studied. The concentrations of formic and acetic acids in the ozonised CS were 3.98 and 1.36 g 100 g−1 organic matter (OM) respectively. Oxalic acid was not detected. A high content of uronic acids (9.78 g 100 g−1 OM) was found in CS. The overall decrease in total monosaccharides in the ozonated CS was very small (5%) with the matrix constituents being principally affected. The 8% sodium hydroxide treatment exerted a very limited effect on the composition of CS cell walls. Ozonation increased the content of soluble carbohydrates from 9.2 to 21.8%; this was contributed mainly by the hemicellulose fraction. Alkali lignin was extracted from CS and was fractionated by gel chromatography. The elution pattern of alkali lignin was very similar for the treated and untreated materials. The three peaks coincided at an average mol. wt of 40 000, as judged from the use of dextran standards.