Adsorption of ions at the cellulose/aqueous electrolyte interface. Part 2.—Determination of the surface area of cellulose fibres

Abstract

The surface areas of the fibres studied in Part 1, obtained by the method of negative adsorption, are reported. Corrections were applied for low surface potential using Gouy–Chapman theory and the charge/pH isotherms. The fibres were oxidised to increase the charge and surface areas obtained for oxidised and non-oxidised fibres were in good agreement. The surface area was also obtained for unbleached sulphite pulp which has a high charge. The results were compared with surface areas determined by B.E.T. nitrogen adsorption. All the pulps were initially in a ‘never-dried’ state and for the B.E.T. work they were specially prepared using solvent-exchange techniques such that all the water was replaced by dry pentane. The negative adsorption results for the unbleached sulphate pulp clearly showed the effect of overlapping double layers, and this was treated theoretically. The effect of beating the fibres, as in paper-making, on the surface area was also investigated by both methods as was the effect of drying the fibres once.