Application of an Exponential Kinetic Equation to the Interaction of Optical Brighteners with Pulp

A bleached softwood kraft pulp was treated with fluorescent whitening agentsTinopal UP and Leucophor AP under different conditions. The kinetics ofadsorption-chemical interaction between optical brighteners and pulp wasdescribed by an exponential kinetic equation. An entropy heterogeneity of thepulp surface related to the active sorption centers, their accessibility and theirspatial orientation was confirmed. The activation energy values obtained werefound independent of the brightener concentration and on the increase of pulpwhiteness. A decisive role of the entropy factors was ascertained.