Influence of Cations on Flocculation of Clay Minerals by Microbial Metabolites as Determined by the Electrical Sensing Zone Particle Analyzer
1967
Santoro, T. | Stotzky, G.
Flocculation of clay minerals by microbial metabolites was determined by measuring changes in particle-size distribution. No floculation occurred when clay and metabolite mixtures were analyzed in sodium metaphosphate as the suspending electrolyte. When the mixtures were analyzed in electrolytes containing the chloride salt of the cation to which montmorillonite was made homoionic, all metabolites caused flocculation in the presence of trivalent cations, some with divalent cations, but none with monovalent cations. Similar results were obtained with purified rhizobial polysaccharides, which, however, also flocculated kaolinite homoionic to Na. The degree of flocculation of the clays differed with the source of the metabolites. A nonionic polyacrylamide (Separan) flocculated both montmorillonite and kaolinite, regardless of the type of cation present. The possible implications of these results in the aggregation of soil by microorganisms are discussed.
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