Tiger nut residue as a renewable adsorbent for methylene blue removal from solution: adsorption kinetics, isotherm, and thermodynamic studies
Alexander Nti Kani, Evans Dovi, Farid Mzee Mpatani, Zhaohui Li, Runping Han, Lingbo Qu
Abstract
ABSTRACT Tiger nut residue (TNR), an agricultural waste, was investigated as a cheap and eco-friendly adsorbent to remove methylene blue (MB) from solution. The surface characteristics of TNR were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that increasing dose resulted in increased percentage removal. TNR had a pH zpc of 5.5. The presence of salt in the system did not significantly affect MB removal. Higher temperatures were not beneficial to the adsorption process. The adsorption mechanism is predicted by the pseudo-second-order kinetic model while Langmuir and Freundlich’s equations describe best the adsorption isotherm. The maximum adsorption capacity by Langmuir isotherm is 146 mg/g. Thermodynamic analyses suggested that MB adsorption onto TNR was a physisorption process that was spontaneous and exothermic and that no remarkable change in entropy occurred during the adsorption process. Finally, the cost analysis was presented. The potential of TNR to be used as the future of green and sustainable adsorbent has been further demonstrated by its potent reusability.