Use of TOF-SIMS for the analysis of surface metals in H2O2-bleached lignocellulosic fibers*

Abstract: Oxidation of cellulose, caused by metal-catalyzed hydrogen peroxide decomposi-tion, is one of the main potential reactions that can occur during the alkaline peroxide bleach-ing of pulp. This oxidation decreases the individual fiber strength and thus the sheet strength. The bleaching reaction should be controlled to limit cellulose degradation. The goal of this project was to characterize the fiber surface metal distribution using time-of-flight secondary ion mass spectrometry (TOF-SIMS) on laboratory-generated hydrogen peroxide-bleached pulps. For this study, a single black spruce was chosen and kraft pulped. Peroxide bleaching was conducted via benchtop polyethylene bag bleaching in a temperature-controlled water-bath. The overall metals content was determined using inductively coupled plasma (ICP), whereas the surface metals were determined with TOF-SIMS. Many fundamental approach-es to study metal identity and content in fibers have been undertaken, including ICP, electron spectroscopy for chemical analysis (ESCA), X-ray fluorescence, and UV–vis. None of these methods can provide the localized density distribution and metal-mapping ability that is available through TOF-SIMS. It has spectacular imaging capabilities that were exploited for evaluating metals on the fiber sheets used in this work. The samples were subjected to other sheet and fiber testing. Tests conducted on select samples included brightness and viscosity. Factors in this experiment included metal addi-tion, chelation, and peroxide charge