Efficient Extraction of Cellulose Nanocrystals through Hydrochloric Acid Hydrolysis Catalyzed by Inorganic Chlorides under Hydrothermal Conditions

Abstract

Four inorganic chlorides were introduced into hydrochloric acid hydrolysis to extract cellulose nanocrystals (CNCs) from microcrystalline celluloses (MCC) under hydrothermal conditions. The as-prepared CNCs were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT–IR), and thermogravimetric analysis (TGA). The role of inorganic chlorides including ferric chloride hexahydrate (FeCl3·6H2O), copper chloride dihydrate (CuCl2·2H2O), aluminum chloride (AlCl3), and manganese chloride tetrahydrate (MnCl2·4H2O) in the extraction and properties of high quality CNCs was determined. It is observed that the introduction of inorganic chlorides obviously enhanced the hydrolysis process through faster degradation of the disordered region of cellulose. Compared with those for pure hydrochloric acid hydrolysis, smaller diameter and a larger length to diameter ratio of CNCs could be obtained through salt-catalyzed hydrolysis, which could contribute to greater enhancement on the mechanical properties of polylactic acid (PLA) nanocomposite films. Moreover, it is found that the highest reinforcing effects for the PLA matrix as well as the best transparency among all the nanocomposites were achieved in the presence of ferric chlorides, benifiting from the largest length to diameter ratio and most white of the corresponding CNCs. These results show that the use of salt-catalyzed hydrolysis especially ferric chloride has a significant improvement in achieving the energy-efficient and cost-effective conversion of cellulose starting materials into high quality CNCs.

Influence of Hydrolysis Conditions on Characteristics of Nanocrystalline Cellulose Extracted from Ramie Fibers by Hydrochloric Acid Hydrolysis

“…This is due to the lack of an electrostatic repulsion charge between crystal particles because chlorite ions are easily removed during the dialysis process[Lima and Borsali 2004;Roman and Winter 2004;Wang et al 2007]. In addition, NCC particles hydrolyzed by HCl have a strong hydrogen bonding at the surface of NCC particles resulting in agglomeration[Cheng et al 2017]. Similar observations were also reported by previous researchers[Corrêa et al 2010] where NCCs particles hydrolyzed with hydrochloric acid was in agglomeration.…”

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

“…The crystallinity index was 86.5% ± 0.3% and the maximum thermal decomposition temperature was 344 ∘ C. The hydrolysis system of Cr(NO 3 ) 3 -H 2 SO 4 was also investigated by Chen and coworkers [127]. In this work, the maximum yield and highest crystallinity of CNCs were obtained under hydrolysis conditions of 0.22 M Cr(NO 3 ) 3 , 0.80 M H 2 SO 4 , and 82.2 ∘ C within 1 h. Other transition metals were examined as well for catalyzing the hydrolysis of raw cellulose materials to prepare CNCs, such as Fe(III), Al(III), Ni(II), Co(II), and Mn(II) [68,128,129], and they will not be elaborated in detail.…”

“…Cheng et al reported an inorganic chloride/hydrochloric acid system for extracting CNCs from microcrystalline cellulose (MCC) under hydrothermal conditions [68]. Four inorganic chlorides including FeCl 3 ⋅6H 2 O, CuCl 2 ⋅2H 2 O, AlCl 3 , and MnCl 2 ⋅4H 2 O were investigated in this work.…”

Preparation of Chitosan-Cellulose Composite Beads Using Cellulose Isolated From Sugarcane Bagasse

“…Therefore, in order to increase the economic value of sugarcane bagasse, in this work we used cellulose isolated from sugarcane bagasse as a filler of chitosan polymer. Some methods to obtain pure cellulose from a materials has been developed, including chemical [4], mechanical [5], and biological [6] methods. This research employed chemical extraction method, which was acid hydrolysis.…”

“…This research employed chemical extraction method, which was acid hydrolysis. Cellulose extraction through hydrolysis with strong acid is the most common used method [2,4]. This process include the hydrolysis of the amorphous parts of cellulose and hemicellulose fibers [7,8].…”