Recent Progress in Production Methods for Cellulose Nanocrystals: Leading to More Sustainable Processes

Abstract

202100100polymers, hemicelluloses and lignin, further assembling into cellulose fibers. Cellulose microfibrils are semicrystalline as the tight packing of cellulose chains at the biosynthesis site leads to the formation of crystalline regions which are stabilized by intra-and intermolecular hydrogen bonds as well as dispersion forces. [4] These crystalline regions are periodically separated by very short areas (a few nanometers) where the molecules are disordered but still aligned along the fiber axis. [5,6] These disordered regions are crucial to CNCs preparation and determines the length of resulting CNCs upon chemical treatments. Recent studies suggest such defects are artificially formed during processing, such as drying, rather than inherent to the native microfibril structures. [7,8] CNCs, also known as nanowhiskers, are colloidal rodshaped particles characterized by high crystallinity. [9] They can be extracted from various cellulose sources from plants such as wood pulp, cotton, and ramie, to tunicate and bacteria. [10] Due to their low densities (about 1.6 g cm −3 [11] ) and impressive mechanical strengths (Young's modulus above 100 GPa in the axial direction, similar to that of Kevlar [12,13] ), CNCs have found applications as reinforcement agents in polymer nanocomposites, [14] oxygen and moisture barriers, [14] and for smart coatings in photonic applications, [15] electronic materials, [16] biodegradable packing and food ingredients. [17] The growing interest in such a novel biomaterial has resulted in accelerated industrial production of CNCs, with several companies active in the sector. [18][19][20] As an example, Celluforce is a fully functioning industrial plant in Canada that uses wood pulp as a raw material to produce up to 300 tons of CNCs annually. Melodea Ltd is currently operating a pilot-scale production line that produces sulfated CNCs in Israel (producing 100 kg per day), which, once fully scaled-up, should ultimately be able to produce 200 tons of CNCs per year in Sweden. The University of Maine Process Development Center, based in the US, can produce 90 kg of sulfated CNCs a week from dissolving wood pulp. GranBio (formerly American Process) exploits agricultural residues to produce CNCs using sulfur dioxide/ethanol mixtures with a production capacity of 0.5 ton per day. Blue Goose Biorefineries and Anomera (both in Canada) are producing carboxylated CNCs from viscose grade dissolving pulp with a capacity of about 100-150 kg per week.However, so far, the production of CNCs on an industrial scale mainly relies on sulfuric acid hydrolysis. The first successful preparation of an aqueous colloidal cellulose solution was by Rånby in 1949 using 2.5 N sulfuric acid. [21,22] Since then,

Role of Nanocellulose in Tailoring Electroanalytical Performance of Hybrid Nanocellulose / Multiwalled Carbon Nanotube Electrodes

“…where α is the transfer coefficient (usually approximated to 0.5), n ′ is the number of electrons transferred before rate determining step (n ′ = 1 and n = 2 for dopamine, assuming that the second electron transfer is the rate determining step) and the remaining parameters are same as eqn (1). Table 2 lists the ECSA values estimated from the main oxidation peak currents of 100 mV/s CV measurements with 1 mM Ru(NH 3 ) 6 2+/3+ (Fig.…”

“…Cellulose, being the most abundant biopolymer on the planet, offers a sustainable alternative to petroleum-based synthetic polymers in various applications ranging from packaging to biotechnology. The successful extraction of nanoscale structures from plant-based cellulosic materials [1,2] has further augmented their applicability in the development of various high-value functional hybrid materials. [3][4][5][6] Plant-based nanocellulosic materials can be primarily classified into cellulose nanocrystals (CNC) composed of predominantly highly crystalline regions of cellulose units, and cellulose nanofibrils (CNF) containing both crystalline and disordered regions.…”

“…[3][4][5][6] Plant-based nanocellulosic materials can be primarily classified into cellulose nanocrystals (CNC) composed of predominantly highly crystalline regions of cellulose units, and cellulose nanofibrils (CNF) containing both crystalline and disordered regions. [1,5,7] The dimensions and surface chemistry of the nanocellulosic materials are heavily dependent upon their plant source as well as the type of mechanical and chemical extraction processes used. [8,9] In addition, the highly reactive surface hydroxyl groups on the cellulose units can be further functionalized using several different chemical reactions.…”

Aqueous Dispersion of Carbon Nanomaterials with Cellulose Nanocrystals: An Investigation of Molecular Interactions

“…[35] Despite different manufacturing methods such as mechanical, acid hydrolysis, and enzyme hydrolysis, [35] the main industrial route for isolation of CNCs is acid hydrolysis (e.g., sulfuric acid). [37] This enables to attach sulfate ester groups on CNC's surface, resulting in a negative electrostatic layer around the nanocrystal in aqueous solvents. [37,38] As a result, CNC can Dispersing carbon nanomaterials in solvents is effective in transferring their significant mechanical and functional properties to polymers and nanocomposites.…”

“…[37] This enables to attach sulfate ester groups on CNC's surface, resulting in a negative electrostatic layer around the nanocrystal in aqueous solvents. [37,38] As a result, CNC can Dispersing carbon nanomaterials in solvents is effective in transferring their significant mechanical and functional properties to polymers and nanocomposites. However, poor dispersion of carbon nanomaterials impedes exploiting their full potential in nanocomposites.…”