Abstract
The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical volume fraction of water where phase inversion from W/O to O/W emulsion took place was determined through conductivity measurements. Cetyltrimethyl ammonium bromide (CTAB) was used as a surfactant to modify the nanoclay. The adsorption of CTAB onto nanoclay had a strong influence on the contact angle and the critical volume fraction of water where phase inversion took place. The modification of the nanoclay brought about by the adsorption of CTAB increased the three-phase contact angle (measured through the aqueous phase), thereby making it more hydrophobic, and prolonged the phase inversion point. CTAB alone and CTAB-modified nanoclay delayed the phase inversion process in a similar manner, showing a strong dependence on the CTAB concentration.
Highlights
Various types of solid materials have been used as particulate stabilizers for water-in-oil (W/O) or oil-in-water (O/W) emulsions, including clays, silica, iron oxides, barium sulfate, alumina, and calcium carbonate [1]
Further sequential addition of the aqueous phase to the resulting O/W emulsion after the phase inversion occurred, which led to higher conductivity values that became more prominent with an increase in the weight % of Cetyltrimethyl ammonium bromide (CTAB) at a constant concentration of nanoclay
The emulsifying nature of hydrophilic bentonite nanoclay can be enhanced by modification with surfactants such as cationic CTAB
Summary
Various types of solid materials have been used as particulate stabilizers for water-in-oil (W/O) or oil-in-water (O/W) emulsions, including clays, silica, iron oxides, barium sulfate, alumina, and calcium carbonate [1]. One of the crucial characteristics of these particles that impacts their effectiveness in stabilizing emulsions is their wettability [2,3]. Particles with contact angles slightly greater or smaller than 90◦ tend to stabilize W/O or O/W emulsions, respectively [4]. The particle experiences a potential energy minimum, which is directly related to the contact angle. The fluid into which the particle is removed dictates the sign on the cosθow. It is negative when the particle is removed into water.
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