Adsorption of poly(vinylpyrrolidone) on sodium, calcium and aluminium montmorillonite

The adsorption of three different molecular weight samples of polyvinyl pyrrolidone (PVP) (Mw = 10,000, 44,000 and 360,000 g mol−1) from water onto montmorillonite saturated with sodium, calcium and aluminium chloride has been studied at different temperatures (25, 30, 35, 40 and 60 °C). The results of the adsorption isotherms were compared with the extension of the electrokinetic layer thickness of montmorillonite and X-ray diffraction (XRD) patterns.The amount of the polymer adsorbed was independent of both the adsorption temperature and the molecular weight of the polymer. All isotherms were Langmuir type. The electrokinetic layer of montmorillonite extended with decreasing the valence of the saturated cation and increasing the adsorption temperature for Na-montmorillonite but not for Al-montmorillonite. The extension was calculated only at room temperature for Ca-montmorillonite. Interlammellar adsorption was detected according to XRD patterns of polymer adsorbed Na- and Ca-montmorillonite but not for Al-montmorillonite.