Colloidal magnesium aluminum hydroxide and heterocoagulation with a clay mineral. II. Heterocoagulation with sodium montmorillonite

Abstract: Montmorillonite dispersions were completely coagulated ¶by magnesium aluminum hydroxide when the hydroxide mass fraction, χ, was 0.2 or greater. The hydroxide dispersion required only a montmorillonite mass fraction of 0.06 for total coagulation. Thus, heterocoagulates were formed for 0.2<χ>0.5, both properties decreased steeply, indicating the reduced mechanical stability of the network. Divalent anions at concentrations above 1 mmol/l acted as liquefying agents for the dispersed heterocoagulates. The specific surface area of the freeze-dried dispersions increased to a maximum value at χ = 0.65. The pore size distributions revealed that montmorillonite lamellae and hydroxide particles were not homogeneously distributed. </χ>