Obtaining cellulose nanocrystals from okra and cannabis plants

In this study, okra plant, which is an agricultural residue, was used as the source of cellulose to obtain nanocellulose. Okra plant was collected from the field and subjected to biological retting and okra bast fibers were obtained. Bast fibers were extracted from the hemp plant, a conventional textile plant, by the same digestion method for comparison. Mature fruits of the okra plant and the stem parts remaining from retting and the stem parts of the cannabis plant remaining from retting were also added to the study. First, different parts of okra and hemp plants were subjected to cellulose isolation processes separately. Cellulose isolation processes consist of alkalization, acidic bleaching and basic bleaching steps. H2O2, which is less burdensome on the environment, was used instead of chlorine-containing bleaches such as NaClO2 or NaOCl, which are harmful to the environment. The samples obtained at each processing step were subjected to Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) analysis, and the purification efficiency of cellulose and the quality of the resulting cellulose fibers were examined. The purified cellulose fibers were also subjected to X-ray Diffraction (XRD), Thermogravimetric (TGA) and Differential Scanning Calorimetry (DSC) analyses. These analyzes showed that the samples obtained as a result of cellulose isolation processes exhibited properties suitable for cellulose materials and had a high crystallinity index between 76.26% and 85.65%. SEM analysis showed that the cellulose obtained from okra bast and hemp bast fibers had more homogeneous morphological structure. These homogeneous cellulose fibers were subjected to nano-scale disintegration. Acidic hydrolysis with sulfuric acid was applied to break down cellulose at the nanoscale. After this process, the nanocellulose concentration was increased by centrifugation, purified from chemicals via dialysis, and dried by lyophilization. Afterwards, the particle dimensions obtained by Field Emission-Scanning Microcopy (FE-SEM) and nano-scale dimensions were determined.