Polyacrylamide polymers are widely used in aggregates quarries as flocculants for water recycling, to facilitate suspended solid decantation.  Polyacrylamide is produced from the toxic acrylamide monomer. Even if the toxicity of polyacrylamide has not yet been investigated, research is needed to determine its fate and transport in soil, from decantation lagoon.  In this research, we were interested to study the role of clays in preventing migration of polyacrylamide and acrylamide through the soil.   Sludge from a quarry site was characterized with XRD to determine the phyllosilicate phase. The predominant clays from the sludge sample (kaolinite and illite) as well as the sludge sample were used for batch experiments (sorption isotherms) with acrylamide and polyacrylamide according to EPA protocol1. Z�ta potential, BET surface area and granulometry analyses were conducted on these solids.   Adsorption isotherms obtained for acrylamide indicate a weak affinity of acrylamide to clays (kaolinite and illite) and to soil samples. This low affinity can be explained by the high solubility and hydrophily of acrylamide, its small size and the negative charges of both acrylamide and the surfaces of the solids. Unlike acrylamide, polyacrylamide showed a rapid and a strong affinity to clays and sludge samples. Polyacrylamide adsorption isotherm was well correlated with the Freundlich isotherm. The amount of polyacrylamide adsorption increased with ionic strength. This can be explained by the screening of electrostatic repulsions between the anionic polyacrylamide and the negatively charged surface of solids (clays and sludge) when cation concentration increases2.   From our results, we can conclude that clays can be an effective barrier to limit the migration and the mobility of polyacrylamide, but not for acrylamide.

Adsorption of anionic polyacrylamide flocculants and acrylamide on clays and clayey sludge

248th National Meeting (2014)

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