Study of the Removal of Pb(II) Using a Weak Acidic Cation Resin: Kinetics, Thermodynamics, Equilibrium, and Breakthrough Curves

Abstract

This study presents a method for the removal of Pb(II) from aqueous solution in batch and column modes using a commercial weak acidic cation (WAC) resin (Lewatit CNP80). Batch experiments carried out under different conditions yielded optimum conditions of pH = 5, t = 360 min, and m = 0.05 g (1 g L-1). The mechanism of ion exchange was studied using isotherm, kinetic, and thermodynamic models. The good fit of the Koble-Corrigan isotherm model indicates both heterogeneous and homogeneous sorption of Pb(II) on the resin. The concentration of Pb(II) in the solution had a strong influence on both the diffusion kinetics and the mechanism controlling the kinetic coefficient The fit of the experimental data to the pseudo-second-order model indicated that the reaction is affected fundamentally by Pb(II) concentration, whereas temperature did not result in a significant change. The Gibbs free energy change (Delta G degrees) values were negative, corresponding to a spontaneous process of Pb(II) ion sorption onto the WAC resin. The S-shaped breakthrough curves from the column studies show that most of the resin capacity was used up to the breakthrough point. Clean and Pb(II)-loaded WAC resins were characterized on the basis of zeta-potential measurements, Fourier transform infrared spectrum (FTIR) spectral study, thermogravimetric analysis (TGA), and environmental scanning election microscopy (ESEM) images. The O-H and C-O stretching of the carboxylic acid groups and the C-O-C stretching groups were the main functional groups of the WAC resin participating in the Pb(II) binding. A visible change in the surface morphology observed from the ESEM images showed some fouling, an indicator of the 28% irreversible loss of capacity after regeneration It can be concluded that ion exchange with WAC resin is a satisfactory process for Pb(II) removal especially for low concentrations.