Kinetic, equilibrium, and thermodynamic studies of the biosorption of cadmium (II) from solution by Stereophyllum radiculosum

Abstract

Biosorption of heavy metal ions can be an effective process for the removal of Cd(II) from wastewater. In this study, the batch removal of Cd(II) from dilute aqueous solution using Stereophyllum radiculosum as the biosorbent has been investigated. The Cd(II) uptake was dependent on the initial pH, contact time, initial metal ion concentration, and temperature. The residual Cd(II) in the solution was determined using Atomic Absorption Spectrophotometer. The optimum pH for the biosorption was pH 6. Maximum biosorption was obtained after 60 min of the process. Kinetic study showed that the pseudo-second-order rate equation best described the biosorption process. The adsorption isotherms obtained fitted well into the Freundlich and Langmuir isotherm. The Freundlich equation obtained was log Ⲅ = 2.6924 logC _e + 0.1131, while the Langmuir equation obtained was 1/Ⲅ = 0.0008/C _e + 17.41. The correlation factors obtained were 0.0995 and 0.9904, respectively. The free energy change obtained for the biosorption of Cd(II) at 300 K, initial Cd(II) concentration of 100 mg L^-1 and pH 6 was -20.894 kJ mol^-1. The thermodynamic study showed that the increase in temperature led to increase in the amount of the metal ion biosorbed. These results indicate that S. radiculosum has potential for the uptake of Cd(II) from industrial effluents.

Keywords:

• Stereophyllum radiculosum
• cadmium
• biosorption
• equilibrium
• thermodynamics

Acknowledgment

The authors are grateful for the technical assistance rendered by Mr J.O. Adegoke of the Department of Chemical Sciences, Olabisi Onabanjo University, Ago-Iwoye, Nigeria.