Interactions of a water-soluble polymeric detergent additive (polycarboxylate) with clay minerals from soil

Abstract

Acrylic/maleic acid (PAA-PMLA) copolymer is a low biodegradable dispersing agent. Its interfacial behaviour is investigated at clay minerals which control the transport of organic compounds in the soil compartment. Adsorption affinities and surface coverage results indicate that binding sites are located on edge faces of clay minerals. contributions of long-range electrostatic (anion exchange reaction) and of short-range chemical interactions (ligand exchange reaction) to the adsorption/desorption process are discussed. Thus, the roles played by protonated aluminol binding sites at kaolinite surface and by the ionization degree of the copolymer are studied from variations of pH and ionic strength and from binding competitions of phosphate compounds. a dependence of the PAA-PMLA copolymer desorption on the adsorbed layer structure can be concluded. Furthermore, investigations concerning the interactions with kaolinite components, Al and Si, show that only the non-crystalline form of the adsorbed aluminium on the akolinite can be solubilized.