Optimization of Cellulose Extraction and TCF Bleaching from Olive Tree Pruning Residues by Box–Behnken Design

Abstract

ABSTRACT In this work, we successfully produced Totally Chlorine Free (TCF) Bleached pulp from olive tree pruning residues using the soda-anthraquinone pulping method. TCF pulp bleaching was carried out using a chelating–hydrogen peroxide bleaching sequence. Box–Behnken design (BBD), as an experimental design for response surface methodology (RSM), was used to study the effects of the different operating conditions on the cellulose extraction and bleaching pulp and to find an optimum for each process. After pulping under optimum conditions, we obtain a yield of 28.84% for leaves and 44.18% for stems, with a kappa number of 19.74 for leaves and 36.87 for stems. Soda-anthraquinone pulps from olive tree pruning residues were then bleached with a TCF sequence, reaching a value of brightness of about 82 and a kappa number of 10.13 for leaves and 13.69 for stems. A morphological study was investigated using scanning electron microscopy (SEM), showing the raw material structures and the fiber surfaces after delignification and bleaching processes. Isolated cellulose under optimum conditions was characterized using Fourier transform infrared spectroscopy (FTIR) confirmed that cellulose amolecules were not removed using several chemical treatments both of delignification and bleaching stages.