Extraction of cellulose nano-crystals from Polyalthia longifolia and Terminalia catappa leaf litter and the synthesis of low-cost CNC-based hydrogel for articular cartilage

Drathi U K Drathi U K,Pushpa Agrawal Pushpa Agrawal

doi:10.30574/gscbps.2021.16.1.0197

Abstract

Due to the rise in demand for biodegradable and renewable materials, the synthesis of CNCs from lignocellulosic biomass opens up a new avenue for the creation and application of novel materials in nanotechnology. The CNC-based hydrogels appear to be a favorable material in various applications due to their excellent mechanical strength, biodegradability, biocompatibility, and low toxicity. This work aimed to utilize the fallen leaves for the extraction of Cellulose Nano-crystals (CNC) from Polyalthia longifolia and Terminalia catappa leaf litter. Leaves mainly consist of cellulose hence used for the extraction of nanocellulose. Alkali treatment was performed with aqueous sodium hydroxide, followed by bleaching with aqueous sodium chlorite. Sulphuric acid hydrolysis was used for the extraction of CNC. The morphology, structure, functional groups, and crystallinity of the retrieved CNC were studied using a Transmission Electron Microscope (TEM), Fourier Transformed Infrared spectroscopy (FTIR), and X-Ray Diffraction (XRD). The shape was rod-like for both P. longifolia and T. catappa and the CNC’s crystallinity index was enhanced to 72.40% and 73.95%, respectively. The TEM micrographs revealed that the impurities present on the leaf fibres were successfully removed by alkali treatment and subsequent bleaching further purified the fibres, leaving behind mostly cellulose while the hemicellulose and lignin were removed, which was revealed in FTIR spectra. The obtained CNC was used in the preparation of hydrogel by cross-linking with natural polymers like sodium alginate and gelatin. A Freeze-thawing process was carried out for the fabrication of hydrogel. The resulting hydrogel can be used as a substitute for cartilage applications.

Highlights

Over recent decades, fossil fuels have been increasingly scarce, green renewable resources arose wide attention, especially cellulose; the most abundant natural polymer [1]
Transmission Electron Microscope The characteristic size and shape of cellulose nano-crystals hydrolysed by acid hydrolysis is shown in Figure 7 for (a) Polyalthia longifolia and (b) Terminalia catappa
In this study, Cellulose nano-crystals were successfully extracted from Polyalthia longifolia and Terminalia catappa leaf litter via sulphuric acid hydrolysis

Summary

Introduction

Fossil fuels have been increasingly scarce, green renewable resources arose wide attention, especially cellulose; the most abundant natural polymer [1]. Both rural and urban areas are burdened by the wastes that are generated from plants. In urban settings the degradation process is difficult because the majority of soil is capped with concrete and results in the clogging of the drainage system The disposal of this precious resource for making compost is generally done through burning which leads to air pollution or by dumping the litters into landfills [2, 3].

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