Technical Bulletin No. 0212: Surface Properties of Hydrogels Resulting from the Treatment of Pulp and Papermill Effluents

This is the first report on the basic studies underway on hydro gels, the purpose of which is to find new approaches leading to the development of improved methods for thickening and de-watering the extremely hydrous sludges obtained in treatment of pulp and paper mill wastes. Included are those containing ground wood and other fines, biological sludges and residues precipitated on removing color bodies from pulping and bleaching effluents. The objective of the research reported herein was to relate the nature of the fiber/liquid interface and the water adsorption-desorption properties of wood fibers to their dewatering characteristics. The problem is attacked entirely from the point of view of the surface chemist. The gas adsorption experiments are designed to determine the specific surface area of the fibers, the degree of hydrophilicity of the surface, and the ability of the fibers to adsorb and absorb water irreversibly. The electro-kinetic experiments were designed to study the electrical properties of the fiber/liquid interface as a function of pH in order to predict the interaction between particles in different ionic environments. The theory of gas adsorption and the electrical double-layer is briefly presented in order to expose the theoretical assumptions, how they apply to the present system under investigation, and the reliability of interpretation of the experimental data.