THE EFFECT OF PHOTOIRRADIATION ON HIGH-YIELD PULPS - SPECTROSCOPY ANDKINETICS

Fluorescence, UV-visible reflectance and diffuse reflectance IR Fourie r transform spectroscopy were used to study the changes caused by phot oirradiation of unbleached, peroxide-bleached and ozone-bleached mecha nical and chemimechanical pulps. Irradiations were performed selective ly at 350 nm and emission spectra were obtained using the same excitat ion wavelength. Kinetic curves were obtained by plotting the integrate d emission intensity against the irradiation time. Different domains o f photochemical behaviour were observed for unbleached and ozone-bleac hed mechanical pulps. For peroxide-bleached samples, an exponential de cay of the emission intensity was observed on irradiation, accompanied by a shift in the emission maximum to longer wavelengths. The observe d emission spectra were deconvoluted into several components, and atte mpts were made to identify the chromophores causing the emission by co mparison with the fluorescence spectra of model compounds.