Preparation and characterization of cellulose gels from corn cobs

Aqueous cellulose gels were prepared by extraction of ground corn cobs with hot aqueous sodium hydroxide/sodium hypochlorite and shearing. Initial shearing in a blender broke up cob tissue structure into individual cells and resulted in a gel. Subsequent shearing in a high pressure homogenizer increased viscosity by 50–100×. Rheological studies showed all samples were gel-like from 0.5 to 2.0% and that G′ increased following a power law with exponents of 3.7 and 3.2 for blended and homogenized samples, respectively. G′ and G″ were maximal after two passes through the homogenizer and were about ten times larger than typical literature values for microfibrillar cellulose suspensions. SEM and AFM of two-pass sample showed networks of microfibrils and larger expanded fibrillar aggregates while bundles of more separate microfibrils were observed after eight passes. These results should improve understanding of the relationships between processing, morphology and properties of cellulose from corn stover and lead to new applications.