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, UV-visible 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 value-added functional ingredients from food waste, thereby improving the sustainability and economic viability of the food supply.