Phosphate adsorption by Na−, Mg− and Ca−saturated soil clays

摘要

AbstractPhosphate adsorption by the homoionic clay (Na, Ca, Mg) of three soils with widely varying mineralogy obeyed theLangmuirisotherm. The Langmuir constants b and k were a function both of the nature of the dominant clay mineral present and of the saturating cations following the order: Ca++≫ Mg++≫ Na+. This order was in agreement with those predicted by the diffuse double layer theory. The sample having montmorillonite when saturated with sodium, exhibited a negative adsorption of phosphorus which changed to a large positive adsorption in the presence of 0.1 N NaCl; It was concluded that the exchangeable cations influenced the extent of P adsorption by controlling the accessibility of the edge clay surfaces to phosphate i