Particle aggregation in complex aquatic systems

The influence of humate, gallate and salicylate on the surface charge chara cter and particle aggregation of permanently and/or conditionally charged c lay and oxide minerals (montmorillonite, kaolinite and aluminium-oxide) was investigated at pH 7-8 in the presence of an indifferent electrolyte. pH-d ependent surface charging of minerals were determined by acid-base titratio n. The pH- and ionic strength dependent particle aggregation was measured i n both the absence and presence of organic anions by means of dynamic light scattering (DLS). Relatively small amount of organic anions, less than one species per nm(2), adsorbed on the AI-OH surface sites of minerals induces a significant increase in the colloidal stability of dilute suspensions. B ound organic anions smear out the heterogeneity of surface charge and the d ifferences between the clay and oxide minerals. (C) 1999 Elsevier Science B .V. All rights reserved.