The Use of C-Near Edge X-Ray Absorption Fine Structure Spectroscopy for the Elaboration of Chemistry in Lignocellulosics

摘要

The research presented elucidates the oxidation chemistry occurring in hydrogen peroxide bleached kraft pulp fibers by employing carbon near edge x-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft x-ray technique that selectively interrogates atomic moieties using photoelectrons (X-rays) of variable energies. The X1A beam line at the National Synchrotron Light Source (NSLS) was employed to probe carboxylic acid groups that display a signature absorption band at 289 eV. This study is the capstone to a larger effort to support the mechanistic basis for lignocellulosic fiber chemical degradation induced by the disproportionation of hydrogen peroxide during fiber bleaching. We present X-ray absorption spectra obtained using a scanning transmission X-ray microscope (STXM) at the end of a 2.5 GeV electron synchrotron that provided 1s → π~* contrast-enhanced micrographs illustrating random distributions of carboxylic acids that were principally located on fiber surfaces. Control studies using non bleached fibers demonstrated that very little signature carboxylic acid absorption patterns were present in the fibers suggesting that these groups are a fingerprint for macroscopic fiber strength damage during non radical suppressed hydrogen peroxide bleaching.