Kinetic, Equilibrium and Thermodynamic Studies of the Adsorption of Methylene Blue from Synthetic Wastewater Using Cow Hooves

Abstract

Aims: To investigate the feasibility and the kinetic of using cow hooves (CH) as a low-cost adsorbent for the removal of methylene blue (MB) from synthetic wastewater. Place and Duration of Study: Chemistry Laboratory, Afe Babalola University, Ado-Ekiti, Nigeria, from October 2012 to January 2013. Methodology: This study was conducted through batch process. The influence of initial pH, contact time, CH dosage and temperature on the adsorption property of CH was investigated using pH ranging from 2.0–11.0, contact time of 5-180 minutes, CH dosage of 0.15–1.0 g and temperature of 298–318 K. All experiments were carried out using 0.25 g of CH per 100 mL of MB solution except for effect of CH dosage. The equilibrium studies were carried out using MB concentration ranging from 10–100 mgL-1 at 298, 308 and 318 K and the experimental data obtained were analysed and modelled using Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Results: Our results indicated that a time of 90 minutes was required for equilibrium to be attained for 25 mgL-1 MB. The percentage removal of MB was found to increase with increase in pH. The isotherm data were best fitted by Temkin isotherm model. The kinetics modelling of the experimental data agreed with the pseudo-second-order model suggesting that chemisorption was the rate determining step. The values of the thermodynamic parameters (∆G0, ∆H0 and ∆S0) revealed that the adsorption process was spontaneous at very low temperature, feasible and exothermic. Conclusion: Cow hoof could be a promising low-cost adsorbent for the removal of methylene blue from wastewater and this could be best achieved at high MB pH and within a period of one and half hours.