Adsorption of Rhodamine B Dye from Aqueous Solution on <i>Irvingia gabonensis</i> Biomass: Kinetics and Thermodynamics Studies

Abstract

Raw Irvingia gabonenses (dika nut) (DN) and its acid-treated form(ADN) were used for the uptake of rhodamineB(RhB) dye from aqueous solution. The adsorbents were characterized by Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett– Teller (BET) surface area analysis and scanning electron microscopy (SEM). The adsorbents were found to have characteristic functional groups such as –OH, C-N and C=O. SEM revealed that acid treatment resulted in the development of several pore sizes. Sorption data fitted the Freundlich adsorption isothermbetter than the Langmuir isotherm.The maximum sorption capacities, q_max, obtained from the Langmuir adsorption isotherm were 212.77 and 232 mg g^–1 for DN and ADN, respectively. The pseudosecond- order kinetics model was observed to fit the adsorption data. Solution pH and temperature significantly influenced the adsorption process and negative values of ΔG° suggest that the sorption process was spontaneous and feasible. Intraparticle diffusion mainly controlled the uptake of RhB onto DN and ADN; however, boundary layer diffusion also occurred in the RhB-ADN system. The desorption efficiency of RhB from the adsorbents was tested with a number of eluents. The eluents were found to follow the order: H₂O>CH₃COOH>HCl and CH3COOH>HCl>H₂O for DN and ADN, respectively.

KEYWORDS Irvingia gabonenses, adsorption, rhodamine B, thermodynamics, kinetics, biomass.