Biosorption of copper from aqueous solution by chemically activated pine cone: A kinetic study

The effect of different chemical activating agents (NaOH, KOH and Ca(OH)(2)) on external and internal diffusion of copper(II) onto pine cone has been studied. Base treatment favored the formation of new pores with mesopore predominating in the order of raw < Ca(OH)(2) < KOH < NaOH treatment. The approach to equilibrium was enhanced by base treatment, while surface area and surface negative charge were found to influence the external mass transfer, boundary layer thickness and intraparticle diffusion to varying degrees. Initial solution pH affected the Cu(II) removal to a greater extent for the base treated samples than for the raw pine cone. The pseudo-first order rate constant calculated using the intrinsic adsorption rate, k(a), had a linear relationship with initial concentration, hence it is proposed that diffusion of copper(II) ions across the liquid film at the surface of the absorbent particle control the adsorption process at the initial stage. The values of mass transfer parameters, KD, were higher than K-D2 indicating that the adsorption differences within the samples are due to mass transfer in the fast step. External mass transfer was favored by increased magnitude of pore volume of the sample. (C) 2011 Elsevier B.V. All rights reserved.