Enhanced removal capability of kaolin toward methylene blue by mussel-inspired functionalization

Adsorption is an effective and commonly adopted method for removal of organic pollutants from environment. In this work, we described the synthesis and the adsorption behavior of poly(sodium p-styrenesulfonate hydrate) (PSPSH)-modified kaolin, which was obtained by combination of mussel-inspired chemistry and Michael addition reaction. The amino-terminated PSPSH was synthesized by free radical polymerization using cysteamine hydrochloride as the chain transfer agent and sodium p-styrenesulfonate hydrate as the monomer. Raw kaolin and PSPSH-modified kaolin were characterized using several techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X-ray photoelectron spectroscopy in detail. The adsorption of methylene blue onto modified kaolin from aqueous solution was investigated, in which the effects of contact time, temperature, solution pH, and initial methylene blue concentration were studied. The experiment data were analyzed using two common adsorption models: Langmuir and Freundlich isotherm models. The kinetic adsorption data were analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion model. The values of thermodynamics constants such as entropy change (Delta S-0), enthalpy change (Delta H-0) and Gibbs free energy (Delta G(0)) were also determined. The modified kaolin showed favorable dispersibility and convenient separation, high efficiency, and good regeneration capability in the removal of methylene blue from solution.