Morphological properties of nanofibrillated cellulose produced using wet grinding as an ultimate fibrillation process

Abstract

Nanofibrillated cellulose (NFC) aqueous suspensions were produced from once-dried bisulfite softwood pulp using enzymatic or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation pretreatments, followed by wet grinding, as an ultimate fibrillation technique. Two commercial enzyme solutions: cellulase, with the major activity of endoglucanase and exoglucanase, and monocomponent endoglucanase, were compared to facilitate the nanofibrils isolation from cellulose fibers. The influence of their concentrations, as well as the other processing conditions, was analyzed. The morphology of the produced NFC was characterized using optical microscopy, atomic force microscopy (AFM), field emission gun-scanning electron microscopy (FEG-SEM), and morphological fiber analyzer (MorFi). Nanofibrils with a wide size distribution were produced. The average lateral dimensions of 12 ± 7 nm for the most disintegrated enzymatically hydrolyzed NFC and 4 ± 2 nm for TEMPO-oxidized NFC were determined from the AFM height images. The degree of polymerization (DP) decreased and the crystallinity index (CI) increased with an increase of the concentration of both enzyme solutions. TEMPO-oxidation did not have a significant impact on the cellulose CI; however, the DP was strongly affected. The monocomponent endoglucanase solution was found to have a better effect on the nanofibrils isolation rather than their depolymerization.

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

“…Taniguchi and Okamura used Masuko's colloider grinder for the first time to grind 5-10 wt.% cellulose materials for 10 times and successfully prepared CNFs with diameter of 20-90 nm [164]. Since then, this method has attracted wide attention [165][166][167][168][169][170]. Gane et al determined that adding kaolin or calcium carbonate is helpful for accelerating grinding in the grinding operation and will provide composite of CNFs and a mineral [171,172].…”

“…The enzyme pretreatment has a mild condition and a high selectivity and can make fibers produce holes, peeling, and fine fibrosis, which is conducive to the nanofibrillation of cellulose in subsequent mechanical processes and reduces the probability of blocking the homogeneous valve by cellulose slurry. The enzyme system could be multicomponent enzyme mixture [192][193][194] or the monocomponent [157,170,193,[195][196][197][198]. According to the reports, the monocomponent endoglucanase seems to give a better pretreatment effect [170,199,200].…”

Current Progress in Rheology of Cellulose Nanofibril Suspensions

“…The production of CNFs using only mechanical treatment is highly energy consuming. Thus, the development of pretreatment techniques, e.g., enzymatic hydrolysis 6-8 , carboxymethylation 9 , carboxylation [10][11][12] , quaternization 13,14 (with quaternary ammonium compounds) and sulfonation 15,16 , has increased the interest in CNFs greatly, as summarized recently by Nechyporchuk et al 4 [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Thickness, nm − no /enzymatic pretreatment 10-100 7,[17][18][19] − chemical pretreatment 3−10 10,11,20 Length, nm − no /enzymatic pretreatment 1000-5000 18,21 − chemical pretreatment 500−2000 11,22 Crystallinity, % 40-80 12,[18][19][20] Degree of polymerization 200-1000 11,18,19,23 Production yield, % 90...…”

Effect of the oxidation treatment on the production of cellulose nanofiber suspensions from Posidonia oceanica : The rheological aspect

“…Since the 1980s, when Turbak et al (1983) and Herrick et al (1983) reported the preparation of nanofibrillar cellulose from wood fibers in water suspension using high pressure homogenization, an exponential number of scientific works were performed on the isolation and characterization of CNF using high-pressure homogenizer (Alila et al, 2013;Andresen et al, 2006;Andresen and Stenius, 2007;Bettaieb et al, 2015;Djafari Petroudy et al, 2014;Erkisen et al, 2008;Nakagaito and Yano, 2004;Rezayati Charani et al, 2013;Stenstad et al, 2008;Syverud and Stenius, 2009;Winuprasith and Suphantharika, 2013;Zhang et al, 2012), micro-fluidizer (Bendahou et al, 2010), ultrafine friction grinder (Abe et al, 2007 Abe andYano, 2009;Hassan et al, 2012;Iwamoto et al, 2005Iwamoto et al, , 2008Jang et al, 2013;Nechyporchuk et al, 2015a;Subramanian et al, 2008), cryo-crushing (Chakraborty et al, 2005;Janardhnan and Sain, 2006), and ultrasonic method (Zhao et al, 2007). For all those processes, high energy consumption is required.…”