In situ Cs-133 and H-1 solution-phase NMR, thermoanalytical and X-ray diffraction studies of the adsorption of polyalkyleneglycol on Texas bentonite

The isotherms for the adsorption of a polyalkylene glycol (PAG1), of molecular weight <1000, onto Na+-, K+-, Cs+- and Mn2+-exchanged Texas bentonite are all of low affinity and the amount adsorbed increased in the sequence Cs<Na<Mn. X-ray diffraction studies showed that all exchange forms, except Cs, adsorbed two layers of PAG1 and the thermal stability of the PAG1/clay complexes paralleled the amount adsorbed. Washing the complexes once with water reduced the amount adsorbed by 50% and removed a layer of PAG1 from the interlamellar region, thus reducing the d-spacing to 14.5 Angstrom. Cs-133 NMR of clay suspensions, containing 2.5 wt.% bentonite, confirmed that PAG1 alone could not displace the resident Cs+-ions from the clay nor did the PAG1 interfere with the displacement of Cs+-ions by low molecular weight polycation. H-1 NMR shows PAG1 was incapable of displacing hydration-shell water molecules from the Mn2+-ions occupying the exchange sites on the clay. (C) 1998 Elsevier Science B.V.