Effect of Alkaline and Hot Water Treatments on the Structure and Morphology of Piassava Fibers

Abstract

The effect of alcaline and hot water surface treatments of piassava Attalea funifera fibers was investigated. The efficiency of each treatment was evaluated by Fourier transform infrared spectroscopy, X-ray diffractometry, optical microscopy, scanning electron microscopy and atomic force microscopy. The alkaline treatments were effective in removing the superficial lignin layer from the fiber, while the hot water treatment was not. Treatment with hot water and NaOH caused fiber defibrillation. NaOH was most effective in promoting both, a decrease in fiber diameter and an increase in fiber surface area. Treatment with Ca(OH) 2 led to the formation of a CaCO 3 layer deposited on the fiber, preventing defibrillation. The crystalline structure of the fiber was not altered by any of the treatments, maintaining type I cellulose.

Enhancement of the Amazonian Açaí Waste Fibers through Variations of Alkali Pretreatment Parameters

“…Possibly, some fibers will remain as bundles, while others will be partially or completely separated. Narrower size distributions, with small standard deviation, as observed in this work for fibers pretreated with 10 % of NaOH at 100 °C may be attributed to samples with more homogeneous fiber sizes …”

“…In the literature, it was verified that the pretreatment with NaOH also decreased piassava fiber diameters. This effect was attributed to the rupture of bundles of microfibrils, producing both defibrillation and fiber individualization . An investigation with kenaf fibers, reported declining patterns of fiber diameter and cross‐sectional area with the increasing level of alkali treatment parameters, such as the alkali concentration, immersion time, and immersion temperature .…”

“…An investigation of surface pretreatment of piassava fibers showed that hot‐water pretreatments removed impurities from fiber surface, while lignin was only removed by an alkaline one. In addition, comparing NaOH and Ca(OH) 2 pretreatments, the authors verified that the former was more effective in promoting defibrillation and increase of piassava fiber crystalline index …”

“…Narrower size distributions, with small standard deviation, as observed in this work for fibers pretreated with 10 % of NaOH at 100°C may be attributed to samples with more homogeneous fiber sizes. [14] In the literature, it was verified that the pretreatment with NaOH also decreased piassava fiber diameters. This effect was attributed to the rupture of bundles of microfibrils, producing both defibrillation and fiber individualization.…”

“…In addition, comparing NaOH and Ca(OH) 2 pretreatments, the authors verified that the former was more effective in promoting defibrillation and increase of piassava fiber crystalline index. [14] The efficiency of NaOH pretreatments depends considerably on the operating parameters such as temperature, NaOH concentration, reaction time, and the inbuilt characteristics of the biomass used. [15] The pretreatment of açaí fibers with NaOH solutions at 0.5 %, 1.0 %, and 2.0 % removed small amounts of hemicelluloses and lignin and only a portion of the superficial silicon structures inclusions that block the surface of the fiber cell walls.…”