ABSTRACT
The adsorption of water-soluble polymers, predominately of the polysaccharide type, on attapulgite, bentonite and berea sand/bentonite (15 wt,%) agglomerated substrates and on deflocculated bentonite suspensions has been conducted. In the agglomerated substrate studies the molecular weight of derivatied polysaccharides was an important factor; the lower the molecular weight the greater the adsorption. Molecular weight was not important in adsorption on deflocculated bentonite substrates.
In the adsorption of underivatized, non-ionic polysaccharides, chain rigidity influenced by the positional bonding between repeating pyranosyl units was important. The greater the rigidity of the chain, the higher the adsorption, which occurred on the exterior of the bentonite particles. Ether linkages either in a totally synthetic polymer (PEO) or appendaged to a polysaccharide to facilitate aqueous solubility promote penetration of the bentonite interlayer sites and increase interplanar spacings. Despite high adsorption values, poly (ethylene oxide) (PEO) exhibits the greatest regularity along the clay axis. Polysaccharides (PS) with a critical molar substitution of ether linkages adsorb less than PEO but significantly increase the interplanar spacing. The difference in behavior between PEO and PS ethers is presumably due to the inability of ether linkages appendaged to a PS chain to assume, or bring the PS chain into, an interfacially flat configuration in the matrix.
Several interesting observations on the adsorption of anionic W-SPs from high salinity solutions have been made and indicate the need for additional studies.
