Adsorption of polyacrylamide on smectite, illite, and kaolinite

Interactions between polyacrylamides (PAMs) and clay minerals are the primary reactions in most applications of the water-soluble polymers. Our main objectives were to study (i) the effects of charge of PAM on the flocculation/dispersion or clay suspensions and on the adsorption of the polymers on clays, and (ii) the surface properties of PAM-clay complexes. Three PAMs-an anionic PAM 836A, a nonionic PAM 903N, and a cationic PAM 494C-were used to react with three common clay minerals -smectite, kaolinite, and illite. In the polymer concentration range tested (04.2 g L-1) the anionic PAM 836A increased the dispersion of the clay suspensions but the cationic PAM 494C promoted the flocculation. The strong flocculation function of cationic PAM 494C made trapped clay particles inaccessible for adsorption despite its highest affinity for clay surfaces. The adsorption of the polymers was irreversible. Nonionic PAM 903N and cationic PAM 494C intercalated smectite but anionic PAM 836A did not. The adsorbed polymer moderately altered the charge properties: the cation exchange capacity (CEC) and the abilities to remove heavy metal Cu and Cr had the following order: anionic PAM 836A-clay > nonionic PAM 903N-clay approximate to clay > cationic PAM 494C-clay. The PAM-clay complexes did not show distinct adsorption for hydrophobic chlorophenols, indicating that the adsorbed polymers did not increase the hydrophobicity of the clay surfaces.