Experimental Demonstration of the Stabilization of Colloids by Addition of Salt

Abstract

We demonstrate a general non-Derjaguin-Landau-Verwey-Overbeek method to stabilize colloids in liquids. By this method, colloidal particles that initially form unstable suspension and sediment from the liquid are stabilized by the addition of salt to the suspending liquid. Yet, the salt is not expected to adsorb or directly interact with the surface of the colloids. For the method to work, the liquid should be a mixture, and the salt needs to be antagonistic such that each ion is preferentially solvated by a different component of the mixture. The stabilization may depend on the salt content, mixture composition, or distance from the mixture's coexistence line.

Reversible pore gating in aqueous mixtures via external potential

“…The pore filling described below is promoted by the preferential solvation of ions in water, which has previously been shown to modify bulk coexistence [11][12][13], solvent and ion adsorption on surfaces [11][12][13], and the inter-particle potential in colloidal suspensions [14][15][16][17][18][19][20]. Here, a purely solvation induced transition in confinement is quantified for the first time, and it is shown that its magnitude is comparable to that of capillary condensation.…”

Membrane Formation in Liquids by Adding an Antagonistic Salt

“…According to the theoretical study by Onuki and Kitamura in 2004 [8], it is suggested that a semi-micro-scale long-range periodic structure is formed as the CDW structure due to strong coupling between the concentration fluctuation of solvents and the preferential solvation of ions. Formation of the CDW structure was also observed in the mixtures of water/3MP/PPh 4 Cl [23], water/2,6-dimethylpyridine/polystyrene/NaBPh 4 [27], water/ethanol/1-octane/antagonistic salts (NaBPh 4 and sodium thiocyanate) [28], water/2,6-dimethylpyridine/tetraheptylammonium bromide [30], and water/acetonitrile/NaBPh 4 [31] by means of smallangle X-ray scattering (SAXS). Figure 10 shows the example of the SAXS profiles for the H 2 O/acetonitrile/NaBPh 4 mixtures [31].…”

Solvo-osmotic flow in electrolytic mixtures

“…Although the cations are indifferent to the local composition, they also adsorb at the surface due to electrostatics, but are distributed more broadly. The result is an electric double layer at an uncharged surface (Samin & Tsori 2013;Samin et al 2014), even though this layer is overall charge neutral. figure 2 shows a good agreement between the full numerical solutions and the linear theory.…”

“…The preferential wetting of one liquid at a solid surface or the presence of a liquid-liquid interface therefore also affects the electrostatics of the mixture. It leads to a modification of colloid-colloid (Law et al 1998;Bonn et al 2009;Hertlein et al 2008;Nellen et al 2011;Samin et al 2014) as well as colloid-interface interactions (Leunissen et al 2007a,b;Elbers et al 2016;Banerjee et al 2016;Everts et al 2016). The strength of preferential solvation is measured by the Gibbs transfer energy k B T g α of an ion species α between two solvents, where k B T is the thermal energy, and |g α | ∼ 1 − 10 for aqueous mixtures of relatively polar organic solvents (Kalidas et al 2000;Marcus 2007), but can be as large as 15 in less polar solvents containing antagonistic salts (Onuki et al 2016).…”