pH-responsive oil-in-water Pickering emulsions were prepared simply by using negatively charged silica nanoparticles in combination with a trace amount of a zwitterionic carboxyl betaine surfactant as stabilizer. Emulsions are stable to coalescence at pH ≤ 5 but phase separate completely at pH > 8.5. In acidic solution, the carboxyl betaine molecules become cationic, allowing them to adsorb on silica nanoparticles via electrostatic interactions, thus hydrophobizing and flocculating them and enhancing their surface activity. Upon increasing the pH, surfactant molecules are converted to zwitterionic form and significantly desorb from particles’ surfaces, triggering dehydrophobization and coalescence of oil droplets within the emulsion. The pH-responsive emulsion can be cycled between stable and unstable many times upon alternating the pH of the aqueous phase. The average droplet size in restabilized emulsions at low pH, however, increases gradually after four cycles due to the accumulation of NaCl. Experime...

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pH-Responsive Pickering Emulsions Stabilized by Silica Nanoparticles in Combination with a Conventional Zwitterionic Surfactant.

The extraction of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from nitric acid solutions into an organic phase containing N,N′-bis(diphenylphosphinyl-methylcarbonyl)diaza-18-crown-6 and ionic liquid (IL) 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMImTf2N) has been studied. The effect of HNO3 concentration in the aqueous phase and that of the extractant and IL concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. A considerable synergistic effect was observed in the presence of IL in the organic phase containing a neutral organophosphorus ligand. This effect is connected with the hydrophobic nature of the IL anion. The partition of IL between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of lanthanide (III) ions in the extraction system. The potentialities of polymeric resin impregnated with compound I and ...

Extraction of Lanthanides(III) with N,N′-Bis(Diphenylphosphinyl-Methylcarbonyl)Diaza-18-Crown-6 in the Presence of Ionic Liquids

Hydrophobic interactions are one of the main thermodynamic driving forces in self-assembly, folding, and association processes. To understand the dehydration-driven solvent exposure of hydrophobic surfaces, the micellization of functionalized decyldimethylammonium chlorides, XC10Me2N+Cl-, with a polar functional group, X = C2OH, C2OMe, C2OC2OMe, C2OOEt, together with the "reference" compound decyltrimethylammonium chloride, C10Me3N+Cl-, was investigated in aqueous solution by density measurements, isothermal titration calorimetry (ITC), and dielectric relaxation spectroscopy (DRS). From the density data, the apparent molar volumes of monomers and micelles were estimated, whereas the ITC data were analyzed with the help of a model equation, yielding the thermodynamic parameters and aggregation number. From the DRS spectra, effective hydration numbers of the free monomers and micelles were deduced. The comprehensive analysis of the obtained results shows that the thermodynamics of micellization are strongly affected by the nature of the functional group. Surprisingly, the hydration of micelles formed by surfactant cations with a single alkyl chain on quaternary ammonium is approximately the same, regardless of the alkyl chain length or functionalization of the headgroup. However, notable differences were found for the free monomers where increasing polarity lowers the effective hydration number.

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Insight into the Hydration of Cationic Surfactants: A Thermodynamic and Dielectric Study of Functionalized Quaternary Ammonium Chlorides

Novel polyfunctional neutral organophosphorus compounds, namely bis(diphenylphosphoryl-methylcarbamoyl)alkanes of general formula [Ph2P(O)CH2C(O)NH]2(CH2)n (I-III; n = 3, 5, 8), were synthesized and studied as extractants for La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from perchloric acid solutions. The influence of both of HClO4 concentration in the aqueous phase and that of the extractant in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. Bis(diphenylphosphorylmethylcarbamoyl)alkanes II and III possess a higher extraction efficiency towards Ln(III) than their monoanalogue Ph2P(O)CH2C(O)NHC9H19. The potentialities of polymeric resin impregnated with bis(diphenylphosphorylmethylcarbamoyl)pentane II for the preconcentration of lanthanides(III) from perchloric acid solutions are demonstrated.

Extraction of Lanthanides(III) from HClO4 Solutions with Bis(diphenylphosphorylmethylcarbamoyl)alkanes

Sorption methods for the concentration and separation of rare earth elements are reviewed. Sorbents based on organic polymers, specifically strongly and weakly acidic cation exchangers, anion exchangers, and complexing sorbents, are successively considered. Data on the use of inorganic sorbents and solid phase extractants in the rare earth chemistry are also given. Considerable attention is paid to hybrid organomineral materials constituting a promising class of sorbents. Advantages and disadvantages of using biosorbents, molecularly imprinted sorbents, and nanosorbents for the concentration and separation of rare earths are discussed.

Sorption in the chemistry of rare earth elements

GRAPHICAL ABSTRACT ABSTRACT Bis(3-aminophenyl)phosphinic acid was synthesized as bis(3-ammoniophenyl)phosphinic acid dichloride with sequential converting of bis(3-nitrophenyl)phosphinic acid to the corresponding O-butyl-bis(3-nitrophenyl)phosphinate, and then reducing it with hydrogen under pressure and hydrolyzing of the resulting O-butyl-bis(3-aminophenyl)phosphinate with conc. HCl. Homo- and heteronuclear NMR (COSY, HSQC, and HMBC) experiments were used for the unambiguous attribution of the proton and carbon atom signals in the 1H and 13C NMR spectra of synthesized compounds.

Synthetic routes to bis(3-aminophenyl) phosphinic acid

Partition of trace amounts of metal (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc) perchlorates was studied between aqueous HClO4 solutions and dichloroethane solutions of phosphorus podands bearing two Ph2P(O)CH2C(O)NH-terminal groups linked via di-and triethylene glycol spacers. The stoichiometry of extracted complexes was determined. The efficiency of metal ion recovery to the organic phase was studied as a function of aqueous HClO4 concentration and nature of the organic solvent. The compounds synthesized have higher metal extraction capacities in HClO4 solutions than (dibutylcarbamoyl)diphenylphoshine oxide. The utility of macroporous polymer sorbents impregnated by these podands for extracting and concentrating rare earth(III) and scandium(III) ions from aqueous perchlorate solutions was demonstrated.

Extraction of rare-earth, yttrium, and scandium perchlorates by podands bearing diphenylphosphorylacetamide terminal groups

A series of acyclic symmetrical and asymmetrical quaternary ammonium chlorides of the general formula R1R2R3N+AR4Cl– (R1 = Me, Bu; R2 = n-C12H25, PhCH2, C
 n
 H2n+1(OCH2CH2)
 m
 , n = 9 and 12, m = 1 and 2; R3 = n-C12H25, PhCH2, HOCH2CH2,–OOCCH2; R4 = n-C12H25, PhCH2; A = (CH2CH2O)1,2, CH2C(O)O) was synthesized by the alkylation of tertiary amines in a two-phase system containing water. A convenient method for the synthesis of the initial symmetrical and asymmetrical tertiary amines of the general formula MeNR1R2 (R1 = Me, Bu; R2 = n-C12H25, PhCH2, CnH2n+1(OCH2CH2)
 m
 , n = 9 and 12, m = 1 and 2) in an organic phase-aqueous phase heterogeneous system, which allows the use of aqueous solutions of alkali and amines, was developed. The improved method for the preparation of intermediate ethylene glycol and diethylene glycol monoethers is monoalkylation of glycols in dioxane using solid KOH in a two-phase system.

Synthesis of some acyclic quaternary ammonium compounds. Alkylation of secondary and tertiary amines in a two-phase system

Extraction of micro amounts of U(VI), Th(IV), and REE(III) from HNO3 solutions with solutions of diphenyl{[N-(2-diphenylphosphinylethyl)-N-alkyl]carbamoylmethyl}phosphine oxides in organic solvents has been studied. Extracted complexes stoichiometry has been determined, effect of extractant structure, organic solvent nature, and aqueous phase composition on the efficiency of U(VI), Th(IV), and REE(III) recovery into organic phase have been considered. It has been shown that the modification of diphenyl(dialkylcarbamoylmethyl)phosphine oxide by the introduction of additional phosphoryl group into the amide moiety leads to increase in extraction ability toward Th(IV) and slight change in the recovery degree of U(VI) from nitric acid solutions. The efficiency of U(VI), Th(IV), and REE(III) recovery into organic phase increases considerably in the presence of ionic liquid: 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide.

N. A. Bondarenko

Papers

Synthetic routes to bis(3-aminophenyl) phosphinic acid

Extraction of rare-earth, yttrium, and scandium perchlorates by podands bearing diphenylphosphorylacetamide terminal groups

Synthesis of some acyclic quaternary ammonium compounds. Alkylation of secondary and tertiary amines in a two-phase system

Extraction Properties of Diphenyl{[N-(2-diphenylphosphinylethyl)-N-alkyl]carbamoylmethyl}phosphine Oxides in Nitric Acid Solutions

Extraction properties of phosphoryl-containing aza podand in hydrochloric acid media