Stabilization of emulsions by heterocoagulation of clay minerals and layered double hydroxides |
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Authors: | S Abend N Bonnke U Gutschner G Lagaly |
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Institution: | Christian-Albrechts-Universit?t Institut für Anorganische Chemie D-24098 Kiel Germany E-mail: h.mittag@email.uni-kiel.de, DE
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Abstract: | Paraffin/water emulsions were stabilized by colloidal particles without surface active agents. Mixtures of two types of particles
with opposite signs of charge were used: a layered double hydroxide (the hydroxide layers carry positive charges) and the
clay mineral montmorillonite (the silicate layers carry negative charges). The emulsions were very stable and did not separate
a coherent oil phase. The stability of the emulsion (no oil coalescence after centrifugation) was independent of the mixing
ratio of both the compounds when the total solid content was >0.5%. Solid contents up to 2.0% were optimal. In contrast to
stability, flow behavior of the emulsion was dependent on the mass fraction χ of the hydroxide. The maxima of viscosity and
yield value were observed at χ≈0.2–0.3; the emulsion showed pronounced antithixotropic behavior. Weak thixotropic properties,
smaller viscosities and yield values were observed at χ≤0.2 and ≥0.5. In the absence of the clay mineral, the double hydroxide
particles stabilize by forming envelopes around the oil droplets. Addition of bentonites creates a three-dimensional network
of particles with high elasticity which impedes coalescence of the oil droplets.
Received: 9 March 1998 Accepted: 6 April 1998 |
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Keywords: | Aluminum magnesium hydroxide antithixotropy bentonite emulsions montmorillonite Pickering emulsions layered double hydroxide solid stabilized emulsions |
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