Bentonite and double hydroxides as emulsifying agents

Abstract

The use of solid-laden emulsions (Pickering emulsions) provides an interesting alternative to normal emulsions because the need for organic surfactants is removed or reduced. Combination of a bentonite with a layered double hydroxide represents an effective emulsifying system and provides high stability against coalescence. Solid contents as low as 0.1% (w/w, related to the total mass of the emulsion) are sufficient to prepare very stable O/W emulsions; the mass ratio of hydroxide/bentonite is not critical but should vary between 0.25 and 4 (corresponding to mass fractions of the hydroxide between χ = 0.2 and 0.8). With large hydroxide contents, stabilization is mainly caused by the envelope of hydroxide particles around the oil droplets. This shell provides a mechanical barrier against coalescence, typical of Pickering emulsions described so far. Addition of increasing amounts of bentonite provides an additional stabilization by building-up a threedimensional network consisting of both types of particles spanning the coherent phase. A high storage modulus at mass fractions of the hydroxide between 0.2 and 0.8 indicates high flexibility for the inorganic framework which is considered to be an important factor in the high stability of these emulsions.

Rearrangement of layered double hydroxide nanoplatelets during hollow colloidosome preparation

“…We infer that LDH particles should also lie flat on the emulsion droplet surface. This inference is supported by the studies of Bon and co-workers and Lagaly and co-workers, in which plate-like clay particles were showed to lie flat on the o/w emulsion droplet surface [40][41][42][43].…”

Natural food-grade solid particles for emulsion stabilization

“…Numerous studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have demonstrated that solid particles provide highly stabile emulsions and foams compared with emulsions and foams stabilized using classical surfactant molecules. Such systems, particularly foams, uniquely remain stable for months (more than a year).…”

Evaluation of the exfoliation and stability of Na-montmorillonite in aqueous dispersions

“…The swelling and exfoliation behaviors of these tactoids in aqueous medium have invoked scientific curiosity for a long time (Norrish, 1954;Anderson et al, 2010), (Swartzen-Allen and Matijevic, 1974). The understanding of the exfoliation kinetics of these clay minerals in dispersion is very important due to their wide use as fillers in clay-polymer nanocomposites (Ray and Okamoto, 2003;Pavlidou and Papaspyrides, 2008;Lambert and Bergaya, 2013), as adsorbents for the treatment of contaminated water and radio-active waste (Abollino et al, 2003;Bradl, 2004;Boufatit et al, 2007), as thickeners in paints and drilling fluids (Murray, 2000), as an emulsifying agent that results in high stability against coalescence (Abend and Lagaly, 2001), as an adsorber of RNA and DNA molecules (Franchi et al, 2003;Taki et al, 2013), as an active green catalyst (Zhou, 2011) and in bio-sensing applications (Chen et al, 1999), (Mousty, 2010).…”