Application of an exponential kinetic equation to the interaction of optical brighteners with pulp

A bleached softwood kraft pulp was treated with fluorescent whitening agent s Tinopal UP and Leucophor AP under different conditions. The kinetics of a dsorption-chemical interaction between optical brighteners and pulp was des cribed by an exponential kinetic equation. An entropy heterogeneity of the pulp surface related to the active sorption centers, their accessibility an d their spatial orientation was confirmed. The activation energy values obt ained were found independent of the brightener concentration and on the inc rease of pulp whiteness. A decisive role of the entropy factors was ascerta ined.