Aggregation in Organic Solutions of Malonamides: Consequences for Water Extraction

Effect of long-range interactions on ion equilibria in liquid–liquid extraction

“…The choice of the DIAMEX process as a numerical example is driven by the fact that recent experimental studies have been able to quantify the various aggregates of the organic phase [11,17], as represented in Figure 1 a. If the concentration of the malonamide extractant DMDOHEMA is low (typically less than 1 mol L −1 ), oligomeric aggregates are in the form of reverse micelles nucleated by water with four extractant molecules and i = 0, 1, 2 salt 'molecules' Eu(NO 3 ) 3 .…”

“…This general approach requires taking into account the presence of modifiers [10] or co-extracted water [11] or co-extracted acid. All these species are included in the polar core of the reverse micelles formed.…”

Solute‐Induced Microstructural Transition from Weak Aggregates towards a Curved Film of Surface‐Active Extractants

“…Diamide extractant aggregates have been accurately characterized experimentally using combined SAXS/ WAXS/osmometry analytical chemistry in "theta" solvents, that is, for intense quenching of liquid-liquid phase separation induced by the penetration of the outer layer of reverse micelles by solvent chains. [11,[16][17][18][19][20] We show here, using molecular dynamics (MD) simulations, that weak aggregation of oil-soluble surfactants, as detected by coupled SANS/SAXS experiments, [16,17] may already exist in the absence of complexed ionic species. The MD simulations herein have been performed in the gas phase in order to test [16,17] All the MD simulations-performed typically for a time of tens of nanoseconds-have been performed taking into account explicit polarization in order to be able to represent proper structures resulting both from 1) weak aliphatic chains interactions, or 2) strong interactions with the highly charged Eu 3 + cation.…”

“…[17] In this case, experimental standard thermodynamics of self-aggregation shows that roughly half of the extractant molecules are in monomeric state and probably all aggregation numbers up to twelve may coexist. [16] The Eu(NO 3 )(H 2 O) 4 DMDOHEMA 4 aggregate that we simulated is the one at the minimum of the lateral equation of state. [23] The molecular structures obtained show that the cohesion of this aggregate can clearly be related to the presence of the highly charged Eu 3 + cation that promotes electrostatic attraction and creates a well-defined polar core.…”

“…[16] Molecular dynamics simulations were performed in the gas phase, using this experimentally determined 1/4 ratio in order to test the intrinsic stability of this aggregate. Figure 1 a shows a characteristic structure (snapshot of MD simulations) for this weakly bonded aggregate involving the four extractants.…”