Kinetics and equilibriums for adsorption of poly(vinyl alcohol) from aqueous solution onto natural bentonite

Kinetics and isotherms for the adsorption of poly(vinyl alcohol) (PVA) from aqueous solution onto natural bentonite were investigated systematically with respect to initial concentration, contact time and temperature. The kinetics of the adsorption process were discussed using three kinetic models, viz., pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic model. The experimental data fitted well with pseudo-second-order kinetic model. The adsorption isotherms were also described by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm model, respectively. It was found that the isotherms obeyed Langmuir model. FTIR results indicated the presence of PVA on the surface of bentonite/PVA complexes. XRD measurements showed that PVA molecules intercalated into the interlayers of bentonite. Zeta potential of bentonite particles decreased with increasing PVA concentration.

► Kinetics and isotherms for adsorption of PVA onto bentonite were investigated systematically. ► The adsorption process obeyed pseudo-second-order kinetic model. ► Langmuir isotherm model fitted well with the experimental equilibrium data. ► PVA molecules were adsorbed on the surfaces of bentonite particles with a certain degree of intercalation. ► Zeta potential of bentonite particles decreased with increasing PVA concentration.