Bulk nanobubbles in aqueous salt solution

Abstract

We have investigated the nanobubble generation, characterization, and their stability in monovalent and multivalent salt solution. The solubility of gases in aqueous salt solution decreases with salt concentration and this effect is the so-called “salting out effects” of dissolved gases. The dissolution of salt in water leads to dissociation of salt into ions and presence of water molecules results in solvation of ions. The solvation weakens the affinity of non-polar oxygen molecules in water and thus tends to out the dissolved oxygen from the water molecules. We have experimentally observed that dissolved gas releases in the form of nanobubbles in the bulk liquid. Nanoparticle tracking analysis (NTA) have been used to characterize the size and bubble number density of nanobubbles. The surface charge of the nanobubbles is characterized in terms of zeta potential of the nanobubbles releasing during salting out of the dissolved gases. The effect of the mono and multivalent salts has been investigated. The stability of nanobubbles is reported by measuring the bubble size distribution over the period of time. The nanobubbles are observed to stable for more than 3 days.