Title
Alfa fiber: alkaline extraction together with structural and morphological characterization
Authors
KHALED LABIDI MONTASSAR ZRIDA OONA KORHONEN MARYAM BORGHEI and AHMED HICHEM HAMZAOUI

Received February 8, 2018
Published Volume 52 Issue 9-10 October-December
Keywords Alfa fibers, Stipa tenacissima, Esparto grass, alkaline extraction, single fibers

Abstract
Cellulosic fibers were extracted from Alfa stems (Stipa tenaccissima L.) using alkaline methods only and without any fiber pretreatment in order to reduce the environmental impact and the extraction costs. A simple post-treatment that consisted of subsequent manual fiber disintegration was studied. The extraction quality was improved according to a two-step investigation. Firstly, the processing temperature, duration and the sodium hydroxide (NaOH) concentration, together with the usefulness of the post-treatment, were studied based on visual examinations. Then, a second set of NaOH concentrations was selected and their effect on the non-cellulosic components removal and on the crystallinity degree of the native crystalline cellulose I was studied. Fibers were characterized by means of Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), High Performance Anion Exchange Chromatography equipped with Pulse Amperometric Detection (HPAEC-PAD), together with optical microscopy and Scanning Electron Microscopy (SEM). It was shown that the best pulp was obtained by treating the stems in a NaOH solution with a concentration of 3.25 M at 100 °C during 2.5 hours, together with applying the post-treatment. The resulting pulp consisted mainly of single fibers with a smaller amount of bundles and nano-fibrillated cellulose (NFC). Besides, the crystallinity of cellulose I was of 88% and the fibers had an average diameter and length of 10.19 µm and 1082 µm, respectively. Furthermore, the XRD study showed that treating the fibers with NaOH concentrations beyond 3.25 M resulted in a significant drop in the cellulose I crystallinity.