Isolation and characterization of cellulose from cashew (Anacardium occidentale L.) nut shells

Abstract

Cashew nut shells are agro-waste after the flesh and oil have been extracted from edible cashew nut. In this study, cashew nut shells (CNS) were utilized as the raw material for obtaining purified cellulose. The modified acid hydrolysis method was used to isolate cellulose from dewaxed CNS using 7% (w/v) nitric acid, alkaline treatment (17.5% w/v NaOH) and bleaching with 3.5% (v/v) sodium hypochlorite solution (NaOCl). Micromophologies, chemical functional groups and thermal stabilities of the obtained crystalline cellulose samples were obtained via Scanning Electron Microscopy (SEM), Fourier Transforms Infrared Spectroscopy (FTIR) and Thermogravimetry Analysis (TGA) respectively. The presence of inherent elements such as C, Ca, Mg and Fe were obtained in the distinct rod-like shaped cellulose. Structural changes revealed via FTIR and XRD show that, after undergoing a temperature range of 300–400 ​°C ​± ​10%, a yield of 20.8% of highly crystalline cellulose whose crystallinity index of 77.7%. This implies that the CNS can be repurposed as raw material for the production of cellulose fibres that are used for packaging, reinforcement and binders for some industrial products.

Keywords

• Cellulose
• Cashew
• Nut
• Shells
• Crystalline
• Acid hydrolysis