The kinetics of DPKSH (di-2-pyridylketone salicyloylhydrazone) adsorption onto silica gel has been investigated at (25 +/- 1) degrees C and pH 1 and 4.7. The kinetics of adsorption of DPKSH is discussed using three kinetic models, the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. The adsorption of DPKSH, at pH 1 and 4.7, onto silica gel proceeds according to the pseudosecond-order model and the correlation coefficients were very close to 1. The intraparticle diffusion of DPKSH molecules within the silica gel particles was identified as the rate-limiting step. The parameters of the pseudo-second-order model are q(max,calc) = 1.02 x 10(-4) and 1.5 x 10(-4) g DPKSH/g silica; k(2) = 3.01 x 10(4) and 9.67 x 10(4) h(-1) g silica/g DPKSH, respectively, for pH I and 4.7. (c) 2006 Elsevier Inc. All rights reserved.