Kinetics and Equilibrium Studies of the Adsoption of Methylene Blue Dye from Aqueous Solution on Carbonized Groundnut Shell

Abstract

This study investigated the adsorption of Methylene Blue dye present in aqueous solution
onto the activated carbon produced from groundnut shell. The dried groundnut shell was
carbonized at 300oC using a crucible in a muffle furnace for 20 minutes which was
characterized using Scanning Electron Microscope (SEM) and Fourier Transform Infrared
(FTIR) Spectrophotometry before and after adsorption. Batch adsorption was carried out to
study the various parameters influencing the adsorption such as the contact time, the
adsorbate concentration, adsorbent dosage, pH and the temperature. The highest percentage
removal of methylene blue dye was achieved with an adsorbent dosage of 1.0 g, an adsorbate
concentration of 15 mg/L methylene blue dye, pH of 7.0, the contact time of 90 minutes and
temperature of 30 °C. Generally, the removal of methylene blue dye decreased as temperature
increased from 30-50 °C except for an increase at temperatures of 40-45 °C. The variation of
contact time showed an increase from 30-90 minutes, after which a decrease occurred from
90-120 minutes. As pH increased from 3-11, adsorption reached a maximum at pH of 6.68
and then there was a decrease. There was a progressive increase with a variation of adsorbent
dosage from 0.2-1.0 g. A variation in adsorbate concentration from 1-15 mg/L also showed a
progressive increase in adsorption. The three most common adsorption equations, Temkin,
Freundlich and Langmuir adsorption isotherms were used in the study to verify the
adsorption performance. From the interpretation of the equations, the Freundlich adsorption
isotherm (R2=0.802) was found to fit the experimental data better than the other two.