Delignification Kinetics and Characterization of Kraft Pulp Containing Varying Lignin Content With Sodium Perborate and Sodium Metaperiodate

The study examined the use of chlorine free bleaching agents consisting of sodium perborate for removal of lignin found in kraft pulp under various process conditions, including temperature (ranging from 30 °C to 50 °C), sodium perborate dosage (ranging from 1 g to 3 g), and pulp consistency (ranging from 2% to 4%). The optimal kappa reduction occurred between 40 °C and 45 °C and a pulp consistency of 3% to 3.5%. Scanning electron microscopy images confirmed the lignin removal in the bleached pulp samples. FT-Raman spectroscopic analysis was employed to identify the blueprint of different molecules. Raman spectra indicated the Raman shift at 10 cm-1, which resulted from the polymorphic transfer of cellulose I to II. The absence of significant peaks in the bleached pulp, compared to the unbleached pulp, confirmed the lignin removal. Fourier transform infrared spectroscopy provided information on the unbleached and bleached pulp functional groups. The reaction rate constant determined for the sodium perborate bleaching process is 0.00833 min-1. The reaction constant calculated using sodium metaperiodate bleaching is 0.0083 min-1, and the value of activation energy is 28.73 KJ/mol.