Development of carbon dots from lignocellulose oil palm wastes: A potential CO2 adsorbent

Abstract

This paper explores the utilisation of oil palm wastes, specifically palm kernel shells (PKS), mesocarp fibres (MF), and empty fruit bunches (EFB), into valuable carbon dots (CDs) through hydrothermal synthesis. Through comprehensive chemical techniques, including alkaline bleaching treatment, cellulose was successfully isolated from oil palm waste, yielding 59.28%, 57.64%, and 55.98% from EFB, MF, and PKS, respectively. Morphological analysis revealed separated fibrils with pits and holes, indicating successful impurity removal during delignification. Fourier-transform infrared spectroscopy (FTIR) confirmed the removal of wax, lignin, and hemicelluloses, while thermogravimetric analysis (TGA) indicated cellulose's thermal stability at 360°C. Elemental analysis showed carbon as the predominant element. The novel aspect of this research lies in the subsequent hydrothermal synthesis of CDs from the extracted cellulose at 180°C for 24 hours, using a 1:1:3 weight ratio of cellulose, thiourea, and potassium hydroxide (KOH) as doping agents. Results indicated that MF-derived CDs exhibited the highest quantum yield (64.14%), followed by EFB (62.36%) and PKS (58.99%). Surface characterisation revealed functional groups enhancing CDs' hydrophobicity, with nitrogen and sulfur doping significantly improving their CO2 adsorption properties. These findings highlight the potential of CDs derived from oil palm waste as a novel and efficient CO2 adsorbent, contributing to sustainable waste management and environmental efforts for CO2 capture applications. This research stands out by showcasing an innovative approach to waste valorisation, turning abundant oil palm wastes into high-value functional materials with environmental benefits, and demonstrating the practical applications and sustainability of CDs technology in CO2 capture.