Wood Adhesives Based on Alkaline Extracts from Wastewater Biosolids and Mustard Protein

This work reports on the dry adhesion strength of wood adhesives formulated with fractions of an alkaline extract obtained from wastewater activated sludge, a renewable and abundant resource. The extract was fractionated and desalted using ultrafiltration techniques. The effect of molecular weight and composition (protein and carbohydrate content) on the extract’s adhesion strength was assessed, as well as the effect of crosslinking using glutaraldehyde. The dry adhesion strength of adhesives formulated with soluble mustard seed protein isolate, a protein-rich alkaline extract, is also reported. In the presence of glutaraldehyde, an extract fraction with high protein content and low salt and hydroxide content showed adhesion strength close to that of the mustard protein adhesive and a commercial wood adhesive. It was further determined that the adhesion strength of the extract and its fractions was strongly correlated with their protein content.