Abstract
The isolation of crystalline regions from fibers cellulose via the hydrolysis route generally requires corrosive chemicals, high-energy demands, and long reaction times, resulting in high economic costs and environmental impact. From this basis, this work seeks to develop environment-friendly processes for the production of Bacterial Cellulose Nanocrystals (BC-NC). To overcome the aforementioned issues, this study proposes a fast, highly-efficient and eco-friendly method for the isolation of cellulose nanocrystals from Bacterial Cellulose, BC. A two-step processes is considered: (1) partial depolymerization of Bacterial Cellulose (DP-BC) under ultrasonic conditions; (2) extraction of crystalline regions (BC-NC) by treatment with diluted HCl catalyzed by metal chlorides (MnCl2 and FeCl3.6H2O) under microwave irradiation. The effect of ultrasonic time and reactant and catalyst concentrations on the index crystallinity (CrI), chemical structure, thermal properties, and surface morphology of DP-BC and BC-NC were evaluated. The results indicated that the ultrasonic treatment induced depolymerization of BC characterized by an increase of the CrI. The microwave assisted by MnCl2-catalyzed mild acid hydrolysis enhanced the removal of the amorphous regions, yielding BC-NC. A chemical structure analysis demonstrated that the chemical structures of DP-BC and BC-NC remained unchanged after the ultrasonic treatment and MnCl2-catalyzed acid hydrolysis process.
Highlights
The most advantageous characteristics of the bio-based edible film are their edibility and inherent biodegradability [1]
Bacterial Cellulose Nanocrystals (BC-NC) was conveniently synthesized by sequential ultrasonic irradiation and microwave treatment
A simple and an eco-friendly approach was developed to control the degradation of bacterial cellulose at very low hydrochloric acid concentration
Summary
The most advantageous characteristics of the bio-based edible film are their edibility and inherent biodegradability [1]. Various biopolymers have been explored to reduce the use of non-degradable petroleum-based materials such as cellulose, chitosan, starch, collagen, pectin, etc. Problems of strong hydrophilic character, high degradation, and inadequate mechanical properties in moist environments still limit the applications of biopolymers [3,4]. For instance, the incorporation of reinforcement fillers [6,7] into the biopolymers matrix has shown to be an efficient strategy to overcome some critical issues [8] such as low mechanical resistance [9], hydrophilicity [10], and poor barrier to water vapor [11,12] compared to those of pure polymer or conventional (microscale) composites. The process is less expensive compared to the development of new synthetic polymeric materials [13]
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