Chemical Reaction-Driven Spreading of an Organic Extractant on the Gas–Water Interface: Insight into the Controllable Formation of a Gas Bubble-Supported Organic Extractant Liquid Membrane

Abstract

The extraction and recovery of low-concentration valuable metals from various complex aqueous solutions or industrial waste waters have attracted extensive interests in recent years. In our previous works, we suggested a novel technique called bubbling organic liquid membrane extraction by spreading and covering an organic extractant with extremely small volume on the surface of gas bubbles to form a layer of the gas bubble-supported organic liquid membrane for selective extraction and enrichment of low-concentration targets from dilute aqueous solutions. It was found that for successfully performing the bubbling organic liquid membrane extraction, a prerequisite is knowing how to control the formation of a stable organic liquid membrane covered on the surface of gas bubbles. However, once the organic extractant starts to spread on the surface of gas bubbles, the extraction chemical reaction at the interface between the organic extractant liquid membrane and the rare-earth aqueous solution will occur. In the present work, the spreading behavior of the organic extractant P507 on the surface of rare-earth aqueous solutions was investigated and was compared with the behaviors on the surface of deionized water. It was revealed that the spreading of the organic extractant P507 on the surface of aqueous solutions containing rare-earth ions was accelerated because of the occurrence of the chemical reactions at the gas–water interface. The difference in the spreading rate of organic extractant P507 liquid droplets on the surface of deionized water and on that of Er­(III) aqueous solutions with an increase in the P507 concentration, the saponification degrees of the P507 extractant, and the preloading amount of Er­(III) in the P507 extractant revealed that the chemical reaction at the interface between the spreading P507 thin liquid membrane and the Er­(III) aqueous solution would result in the Marangoni convection along the interface, which is in favor of overcoming the resistance from the viscous force when the surface tension gradient replaces gravity as a dominant driving force for the spreading. The present work provides an experimental foundation toward understanding the effect of the interfacial chemical reaction on the spreading behavior of an organic oil droplet on the gas–water interface. It is beneficial for the development of our suggested new technique of bubbling organic liquid membrane extraction and to achieve a controllable generation of a stable gas bubble-supported organic liquid membrane for performing solvent extraction at large aqueous-to-oil phase ratios.

Specific Ion Effects of Trivalent Cations on the Structure and Charging State of β-Lactoglobulin Adsorption Layers

“…Nd 3+ or La 3+ ions to interface-adsorbed proteins in foams and emulsions is also interesting for ion extraction from liquids and may evolve as an important strategy to recycle rare earth elements. [10][11][12] In fact, proteins are known to adsorb at fluid interfaces that are ubiquitous in aqueous foams and emulsions where the proteins form viscoelastic adsorbate layers. [13][14][15] The surface activity of proteins, their surface rheology and interfacial charging state are strongly linked to the solvent conditions and significantly vary with pH and ionic strength.…”

“…Different from biochemical aspects, the interaction of trivalent ions with proteins and surfactants has gained considerable attention in the case of protein crystallization − but also for sensing purposes that are able to detect trace amounts of rare earth elements or for ion flotation. , Efficient binding of, e.g., Nd 3+ or La 3+ ions to interface-adsorbed proteins in foams and emulsions is also interesting for ion extraction from liquids and may evolve as an important strategy to recycle rare earth elements. − …”

Bubble dynamics and mass transfer characteristics from an immersed orifice plate

“…Bubbling behavior of gas–liquid two‐phase flow widely exists in chemical, biological, environmental industries, etc . Especially for various multiphase reactor applications, such as gas–liquid bubble column reactor, gas–liquid–solid fluidized reactor, and sieve‐plate column reactor, the initial detachment state of the bubbles is critical to the shape, size, oscillation, interaction, dissolution of bubbles during the subsequent migration.…”