Application of Terminalia arjuna as potential adsorbent for the removal of Pb(II) from aqueous solution: thermodynamics, kinetics and process design

Abstract

The present work explored the adsorption properties of Terminalia arjuna fruit powder for the removal of Pb(II) from aqueous solution. Effect of concentration, contact time, pH, adsorbent dose, and temperature were studied using batch process to optimize conditions for maximum adsorption of Pb(II). Kinetic data showed that the pseudo-second-order model was the best fit for the experimental data over a wide range of concentrations. Thermodynamic parameters (∆H° and ∆G°) suggested endothermic and spontaneous nature of adsorption. Mean free energies at different temperatures were in between 10.1 and 14.3 kJ mol⁻¹ indicating chemical nature of adsorption process. Equilibrium isotherm data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherms models at 30, 40, and 50°C. The breakthrough and exhaustive capacities were found to be 5 and 15 mg g⁻¹, respectively. Desorption studies were carried out by column method and 84% of Pb(II) ions were recovered when 0.05 N HCl was used. A single-stage batch adsorption design was proposed to predict the amount of adsorbent required for 98% removal of Pb(II) from different volumes of water.

Keywords:

• Terminalia arjuna
• Adsorption
• Thermodynamics
• Breakthrough capacity
• Desorption

Acknowledgments

Authors are thankful to the Chairman, Department of Applied Chemistry for providing research facilities. Support for this work through the Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India is also greatly acknowledged.