Chemical pretreatment of corncob for the selective dissolution of hemicellulose and lignin: influence of pretreatment on the chemical, morphological and thermal features

Abstract

The aim of this work was to remove the hemicellulose and lignin fraction from corncob using chemical pretreatments, and to stablish the effect of that on the composition, microstructure, and thermal properties of corncob. The biomass was pretreated with H2SO4 and NaOH solution to dissolve hemicellulose and lignin portion. Likewise, the biomass pretreated was characterized by scanning electron microscope, IR spectroscopy and TGA methods. It was found that the acid pretreatment disrupt the hemicellulose structure by hydrolysis of glycoside bonds. Moreover, the corncob morphology becomes flaky after acid pretreatment due to dissolution of hemicellulose. The lignin is removed during alkaline pretreatment by solvation of aryl groups. In addition, the crystalline morphology of cellulose fibers was disrupted, increasing the surface area. The pretreatment of corncob with 1.0% H2SO4 and 0.1 M NaOH solubilized ∼42.6% and ∼20.9% of the biomass, respectively. The soluble products were analyzed by FTIR, Fehling test, and calorimetric analysis, to stablish their composition and heat content. The hydrolysis of hemicellulose leads to the release of the monomeric sugars and soluble oligomers. Moreover, the lignin of corncob releases more energy per unit of mass, making it an energy-denser component of corncob.