Interaction of m-Dinitrobenzene (DNB) with Calcium and Potassium saturated reference smectites in aqueous suspensions

Smectites are the most commonly found clay mineral in many temperate region soils.It exhibits variability in shrink – swell behavior and sorption of organic molecules. Previousresearch has established the relationship between extent of swelling and sorption of organiccompounds by smectites. The effect of the interlayer cation on sorption of organiccompounds and the inter-relationship between cation exchange selectivity and extent ofswelling has also been demonstrated. We investigated the effect of sorption of an organiccompound on cation exchange selectivity and the interaction between organic sorption,cation exchange, and clay swelling. Our hypothesis was that adsorption of organic moleculesin the interlayers of smectite influences the affinity of the clay for inorganic cations inaqueous systems. Caand Ksaturated SPV (bentonite) and SAz-1 were equilibrated withmixed salt solutions containing 0.01 M KCl and 0.005 M CaCl2 in the presence or absence of200 ppm m-dinitrobenzene (DNB). Concentrations of Ca and K in solution and on the clayand concentrations of m-DNB were measured. The clay suspensions, both with and withoutthe m-DNB, were also analyzed on the x-ray diffractometer to study the clay structure andthe d-spacing. In general, SPV that was initially saturated with Ca sorbed more m-DNB thanthe SPV that was initially saturated with K. In general, the SPV sorbed more m-DNB than theSAz-1. Sorption of m-DNB on SPV increased preference for K relative to Ca for samplesinitially saturated with Ca, but it had little effect on exchange selectivity for samples that