Removal of Ni(II) from aqueous solution using chemically modified cellulose nanofibers derived from orange peels

Abstract

Abstract Orange peel waste is generally of low economic value even though it contains components such as cellulose which can be utilised to produce nanocellulose adsorbents for wastewater remediation. This study was aimed at improving the chemical and physical properties of cellulose nanofibers derived from modified orange peel (OP) biosorbent. The OP was chemically modified using Phosphoric acid (POP) and Sodium hydroxide (NaOP) and applied for the removal of Ni(II) contained in wastewater. Biosorbent characterisation using Fourier transform infrared spectrometer revealed the presence of acidic carboxyl groups, the principal ligands responsible for metal binding. Increased crystallinity due to chemical treatment was confirmed by X-ray diffraction, while Transmission Electron microscopy and Scanning electron microscopy analyses confirmed the formation of nanofibers. The raw and modified orange peel fibres had surface areas of 0.948 m 2 /g and 1.428 m 2 /g, respectively, obtained from the Brunauer–Emmett–Teller analyser. From the batch adsorption studies, the optimum pH values were between 5 and 6, equilibrium was reached within one hour and thirty minutes for all the biosorbents, and the optimum adsorbent mass was 4 g/L. The Langmuir equation provided the best fit with maximum uptake capacities of 37.5, 21.08 and 8.4 mg/g for POP, NaOP, and OP, respectively. Compared to the raw orange peel, the adsorption capacities of the chemically modified orange peels were higher, with POP having the highest adsorption capacity of 37.5 mg/g.