KINETIC, ISOTHERM AND THERMODYNAMIC STUDIES OF THE ADSORPTION OF CRESOL RED DYE USING AGRICULTURAL WASTES

Agricultural wastes and plant biomass are alternative low-cost adsorbents because they can be used without or with a minimum processing. In the present study, batch experiments were carried out to study the adsorption of cresol red (CR) unto mango leaf (ML) and orange peel (OP). Several parameters that affect adsorption process such as pH, adsorbent dosage, contact time, initial dye concentration and temperature were investigated. FTIR and SEM were used to determine the functional group responsible for adsorption. The results revealed that the highest adsorption efficiency was at pH 5 for the two adsorbents. It was also discovered that CR removal efficiency increased with the increase in contact time and adsorbent dosage while adsorption capacity was higher with increase in initial dye concentration but removal efficiency was lowered. The kinetics conform with the pseudofirst-order kinetic model for mango leaf but conform with the pseudo-second-order kinetic for orange mesocarp due to the value of the correlation coefficient (R2). Based on the value of correlation coefficient, the experimental results for the removal by mango leaf best fitted the Langmuir isotherm model with monolayer adsorption capacity of 70.64 mg. g-1, while Freundlich isotherm model was best fitted to the experimental results for the adsorption of CR by Orange peel. The thermodynamic results revealed that the process is spontaneous and endothermic.