TEMPO-mediated oxidation of lignocellulosic fibers from date palm leaves

The TEMPO-mediated oxidation of date palm lignocellulosic fibers (DPLF) from Phoenix dactylifera - i.e. cellulosic fibers still containing their initial lignin and hemicellulose components - was performed under conditions leading to a high degree of oxidation. The resulting carboxylated fibers were shown to still contain high residual contents of lignin (12%, w/w) and hemicelluloses (34%, w/w). The ultrastructure of the oxidized DPLF was revealed by scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. These techniques not only confirmed the surface carboxylation of the DPLF, but also gave some insight on the oxidation heterogeneity when going from the surface to the core of the fibers. Finally, in relation with the chemical data and the morphology of the substrate, it has been possible to propose a heterogeneous oxidation kinetic model, which was applied with success not only to DPLF but also to the cellulose whiskers extracted from the rachis of the palm from P. dactylifera. (C) 2011 Elsevier Ltd. All rights reserved.