Application of multi-walled carbon nanotubes as sorbents for the extraction of flavonoids from Grapefruit peel.

This study developed carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) as sorbents to extract flavonoids from grapefruit peel. The impact of solution pH and desorption conditions on extraction efficiency was investigated. In addition, Fourier transforms infrared spectroscopy, thermogravimetry, UVvisible spectroscopy, and scanning electron microscopy were used to characterize the carbon nanotubes. After five cycles, the desorption percentage of flavonoids was 82.7 %. HPLC analysis indicated that naringin was the dominant flavonoid in the grapefruit extracts, followed by rutin and quercetin. Insights into the adsorption mechanism of naringin to the MWCNT-COOH were obtained using the Freundlich isotherm equation to model the results. The carbon nanotubes developed in this study offer a cost-effective and straightforward method of extracting valueadded functional ingredients from food waste, thereby improving the sustainability and economic viability of the food supply. [ABSTRACT FROM AUTHOR]