ELECTROCHEMICAL BLEACHING OF KRAFT PULP

In situ single-stage electrochemical bleaching of kraft softwood pulp was studied on a laboratory scale. The electrolytic cell consisted of a cylindrical steel cathode and a platinized mesh titanium anode. The application of a dc voltage to an alkaline chloride solution produced hypochlorite ClO- necessary for bleaching. The effects of current dens ity, pH, sodium chloride concentration, electrolysis time, and tempera ture were studied. The electrolysis solution can be reused several tim es for different bleaching series. Viscosity measurements were used to verify the degradation level of the products. ISO brightness increase s with increasing current density and sodium chloride concentration. B rightness is optimum at 35-degrees-C and reaches a maximum at pH 8. Th e electrochemical bleaching produces semibleached kraft pulp equivalen t to that obtained from the semibleached sequential CEH bleaching proc ess.