Abstract:
The possibility of using Raphia taedigera seed activated carbon as low cost adsorbent to remove methylene blue (MB) dye from aqueous solutions was investigated through batch experiment. For this purpose, activated carbons (ACs) were prepared via carbonization and chemical treatment of Raphia taedigera seed with sulphuric acid and sodium hydroxide to produce acid modified activated carbon (RTA) and base modified activated carbon (RTB), respectively. Both the ACs and raw Raphia taedigera seed (RRT) were characterized by Scanning Electron Microscopy (SEM), Thermo-gravimentry/Differential Thermal Analysis (TG/DTA) and Fourier Transform Infrared (FTIR) Spectroscopy. Dye adsorption studies with these ACs were carried out under different conditions. Desorption evaluation was carried out using different concentrations of hydrochloric acid and sodium hydroxide solution. The equilibrium data were modelled with adsorption isotherm and kinetic models and the thermodynamic parameters were calculated. SEM analysis revealed the surface morphologies, TGA/DTA revealed the thermal properties of the materials while FTIR results showed the presence of functional groups such as –C=O, –OH– and – C=C–. The results from performance evaluation showed the performances of the two ACs to be within 84.651% to 99.894%. Desorption analysis results gave the highest recoveries of MB dye to be 79% and 75% by RTA and RTB, respectively using 0.5 M HCl. Adsorption of MB dye onto RTA and RTB conformed to Langmuir isotherm and fit best to pseudo-second-order kinetic model. Thermodynamic studies revealed endothermic, feasible and physisorption nature of the two ACs while the adsorption of MB dye unto RTA was spontaneous and adsorption of MB unto RTB was non-spontaneous. The present study found ACs from Raphia taedigera seed to be a promising low cost adsorbent to remove MB dye from aqueous solutions.
