Green acid-free hydrolysis of wasted pomelo peel to produce carboxylated cellulose nanofibers with super absorption/flocculation ability for environmental remediation materials

Abstract

Carboxylated nanocellulose hold great application potential and research value in environmental remediation owing to its eco-friendly nature, high specific surface area, high density of functional groups and abundant reserves properties. In present work, a new type of cellulose nanofibers (CNF) with high aspect ratio and high density of carboxyl groups were prepared by directly thermo-oxidizing natural wasted pomelo peel with H2O2. The effects of reaction time on the content of carboxyl groups, morphology, and thermal stability of CNF were investigated. It is found that pomelo-CNF (POCNF) with larger aspect ratio of 169 and carboxyl group contents of 1.711 ± 0.173 mmol/g was fabricated by reacting at 60 °C for 6 h. Furthermore, the high density of carboxyl groups of POCNF allowed it to graft functional polyetherimide (PEI) on the surface of nanocellulose, and the resulting PNOCNF-PEI showed excellent adsorption performance to pollutants, such as malachite green (MG) and Cu(II), with adsorption capacity of 530 mg/g to MG and 74.2 mg/g to Cu(II). Moreover, the adsorbent showed excellent reusability. Besides, the possible adsorption kinetics/mechanism of nanocelluloses to various pollutants has been provided. The simple preparation process and excellent properties of POCNF made it become a viable candidate as environmental remediation material.