Effect of combined dilute-alkaline and green pretreatments on corncob fractionation: Pretreated biomass characterization and regenerated cellulose film production

Abstract

Pretreatment is an essential step prior to the effective valorization of lignocellulosic biomass. However, depending on the pretreatment method, it can be costly and originate potential environmental threats. In this study, green pretreatments, namely Liquid Hot Water (LHW) and 1-butyl-3-methylimidazolium chloride (BmimCl), as well as low concentrated sodium hydroxide solution (NaOH), were applied individually and in combination to pretreat corncob, and their effects on physicochemical properties of fibers were analyzed. The pretreated samples were dissolved in ionic liquid and attempts to prepare regenerated cellulose films have been made. While NaOH was efficient to removal lignin, LHW presented higher solubilization hemicellulose. By combining these treatments, the biomass was fractionated in a complementary way, and a solid enrich-cellulose fraction with high thermal stability and crystallinity was obtained. The BmimCl did not significantly change the chemical composition of biomass and, independent of the treatment applied in combination, samples were regenerated as amorphous cellulose coexisting with lesser amount of cellulose crystalline I. This structural conversion was also confirmed through thermogravimetric analysis, from which a decrease in thermal stability was verified. This latter property was markedly affected by the presence of hemicellulose remained after some pretreatments. The obtained results indicate that each pretreatment performed can meet different application requirements. The LHW-NaOH pretreated sample was the only one suitable to produce regenerated films, which exhibited good mechanical properties to be used in value-added applications, such as packaging.