Competitive biosorptive removal of a basic dye from ternary dye mixture using sawdust

Abstract

Adsorption equilibrium isotherm, kinetics and thermodynamics of the removal of Methylene blue dye by biosorption onto sawdust of Parkia biglobosa from aqueous solutions of binary and ternary dye mixtures was investigated. The sawdust was characterized and adsorption experiments were conducted in batch mode to determine the effects of adsorbent dose, initial concentration and pH of the dye solution, temperature and contact time, on the adsorption process. Experimental data obtained were subjected to various equilibrium isotherm and kinetics models, and the results validated using R2 and χ2 goodness-of-fit functions. The results showed the biosorption processes in single and binary systems fitted well to Freundlich isotherm while the ternary system followed Langmuir model. The processes were better described by pseudo-second order kinetics; they were all endothermic and increasingly thermodynamically spontaneous with rise in temperature as G values are -9.33, -10.68, -11.17 and -11.87 kJ/mol at 303, 313, 323 and 333 K respectively