Kinetics and thermodynamics of the organic dye adsorption on the mesoporous hybrid xerogel

We investigate the kinetics and thermodynamics of brilliant blue FCF (BBF) adsorption on a mesoporous hybrid xerogel derived from tetraethoxysilane (TEOS) and propyltriethoxysilane (PTES) with cetyltrimethylammonium bromide (CTAB) as a templating agent. We study the effect of initial BBF concentration, temperature, pH, and ionic strength on the adsorption of BBF from aqueous solution. Kinetic studies show that the kinetic data are well described by the pseudo second-order kinetic model. Initial adsorption rate increases with the increase in initial BBF concentration and temperature. The internal diffusion appears to be the rate-limiting step for the adsorption process. The equilibrium adsorption amount increases with the increase in initial BBF concentration, temperature, solution acidity, and ionic strength. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic. Electrostatic attraction and hydrophobic interaction are suggested to be the dominant interactions between dye and the xerogel surface.