Selective recognition of 2,4-dichlorophenol from aqueous solution by uniformly sized molecularly imprinted microspheres with β-cyclodextrin/attapulgite composites as support

Abstract

In this study, uniformly sized molecularly imprinted microspheres (MIP) using β-cyclodextrin/attapulgite composites as support were prepared for recognitive adsorption of 2,4-dichlorophenol (2,4-DCP) from aqueous solution. Characterization of MIP were achieved by FT-IR spectra, SEM micrographs, nitrogen adsorption–desorption analysis, EDX measurement and elemental analysis. Equilibrium data, at various temperatures, were described by the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The thermodynamics parameters (positive values of Δ H° and Δ S°, negative values of Δ G°) indicated that binding system for MIP was endothermic, entropy gained and spontaneous. Kinetic properties were successfully investigated by pseudo-first-order model, pseudo-second-order model, intraparticle diffusion equation, initial adsorption rate, half-adsorption time and activation energy. A diffusion-controlled process as the essential adsorption rate-controlling step was also proposed. MIP could be reused four times without significant loss in adsorption capacity. The selectivity of MIP also demonstrated higher affinity for target 2,4-DCP over competitive phenolic compounds than that of non-imprinted polymers (NIP).