Photochemical bleaching of paper webs

Effects of exposure time and environment (concentration of H2O2, pH and amo unt of additives) on brightness and fiber strength of samples treated with photoenhanced peroxide bleaching were studied. Effects of UV, and H2O2 resp ectively, were proved. It has been found out that a fibre strength fall dep ends on the radiation periods for all studied pulps. Further on, the effect of additional agents on photochemical bleaching was examined. EDTA was chosen for unbleached sulphate and sulphite pulps. The a pplication of EDTA resulted in a brightness growth which was increasing wit h delaying the time of exposition to UV-irradiation. Ethanol was used as an additional agent for groundwood, and partial colour reversion was proved.