Isolation and characterization of cellulose from spent ground coffee (Coffea Arabica L.): A comparative study

Abstract

This study compares several methods, such as sodium chlorite, nitric acid, and hydrogen peroxide treatments with alkali pre-treatments, for efficiency of extracting cellulose from spent ground coffee. The extracted cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD), thermogravimetric analysis (TGA), colour analysis, chemical composition, and particle size analysis. FTIR confirmed the removal of non-cellulosic components from coffee, which correlates with chemical composition and colour analysis results. The highest cellulose content (96.7 %) and the highest whiteness index (71.24) were obtained for the cellulose materials extracted using nitric acid-sodium chlorite and sodium chlorite with alkali pre-treatments, respectively. XRD data reveals that the treated coffee presented exhibited a higher crystallinity index compared to the untreated one. The highest increase in crystallinity index (from 54.9 % to 66.3 %) was achieved for the cellulose extracted using a 20 % hydrogen peroxide treatment with alkali pre-treatment. The maximum degradation temperature of the spent ground coffee increased from 292.0 to 310.5 °C after treatment with 10 wt% hydrogen peroxide and alkali pre-treatment. In summary, these findings highlight the great potential of spent ground coffee as a source of cellulose.