Evaluation of thermodynamic parameters via reaction stoichiometry and the corrected Langmuir parameter for sorption of Cu(II) on chitosan and chitosan blended PVA films

Abstract

Natural Chitosan (C) and Chitosan blended with Poly vinyl Alcohol (PVA) C + P film was prepared by solution casting method for the sorption of Cu(II) from aqueous solution. The FTIR studies revealed that the amino group of chitosan played key roles in the copper uptake and FE-SEM and EDAX studies confirmed the formation of Cu-amino complex in 1:1 ratio of metal to ligand. The prime objective of present studies is the evaluation of thermodynamic parameters (ΔG0, ΔH0 and ΔS0) via reaction stoichiometry and the corrected Langmuir parameter for sorption of Cu(II) on chitosan (C) and (C + P) films. The surface morphology, stability and Cu(II) adsorption efficiency of the films were investigated. The C + P film showed enhanced chemical and mechanical endurance over the C film. The batch adsorption studies exhibited that the adsorption capacity of both the films was pH dependant and the maximum adsorption obtained was 55.56 mg g−1 for C film and 35.71 mg g−1 for C + P film at pH 5.5. The adsorption process was described by Langmuir adsorption model and was found to follow pseudo first order kinetics. The Gibbs free energies calculated using the formation constant Kn and the corrected dimensionless Langmuir constant KL(C) were in good agreement with each other thereby confirming the formation of pendant complex [Cu-NH2]2+. The C + P film could be reused till 5 desorption cycles using EDTA as the desorbing agent and could recover around 169.16 mg of Cu(II) per g of the material.