Micellar Enhanced Ultrafiltration as a Method of Removal of Chromium(III) Ions from Aqueous Solutions

This study was undertaken to check the possibility of using micellar enhanced ultrafiltration (MEUF) in the removal of chromium(III) ions from water systems. The influence of ion concentration in the feed, type of surfactant (SDS or Rofam 10), and the membrane material on separation efficiency were studied and discussed. The use of environmentally safer surfactants from renewable sources was proposed, that is, oxyethylated rape fatty acid methyl esters – trade name: Rofam 10. The results presented show the possibility of using MEUF as an effective method for removing chromium(III) ions from aqueous solutions, especially from solutions of low concentration.     

基于胶束强化超滤的金属离子去除技术研究进展

胶束强化超滤技术(MEUF)作为一种新兴的含金属废水处理技术,有着较好的应用前景.通过总结前人的研究结果,综合讨论了影响金属离子截留效果的各个因素,为优化MEUF提出了一些建议.并就当前采用胶束强化超滤法处理金属离子技术的最新发展与表面活性剂的循环再利用作了简要的介绍.     

Partition Coefficients of Alkyl Parabens and Ibuprofen in Micellar Systems

The partitioning of alkyl parabens and ibuprofen in aqueous solutions of nonionic and ionic surfactants is studied experimentally and via a priori predictions using the COSMO‐RS model. The effects of organic (Bu₄NBr) and inorganic (NaCl) electrolytes are examined. Addition of NaCl results in a slight increase in the partition coefficients of parabens in solutions of octylphenolpoly(ethyleneglycolether) and a more pronounced increase in the sodium dodecyl sulfate (SDS) system. The partition coefficients of ibuprofen increase on addition of NaCl to aqueous solutions of SDS and decrease if Bu₄NBr is added to dodecyl trimethyl ammonium bromide (DTAB) solutions. Good agreement between experimental and calculated data shows a high potential of COSMO‐RS in the prediction of micelle/water partition coefficients in the presence of electrolytes and makes it a valuable tool in drug and drug‐carrier design as well as in optimizing micellar reactions or micelle‐enhanced separation processes.     

Kinetic Model of Two‐Phase Epoxidation with Ionic Liquids as Micellar Catalysts

The biphasic catalytic epoxidation of cyclooctene using the ionic liquid (IL) 1,2‐dimethyl‐3‐octyl‐imidazolium perrhenate ([OMMIM]ReO₄) as micellar catalyst and H₂O₂ as oxidant was investigated. Kinetic experiments were carried out in the intrinsic kinetic regime as proved by variation of stirring rate and temperature. Variation of catalyst concentration allowed for determination of the critical micellar concentration (CMC) of the catalytic IL. The effect of substrate concentrations on the reaction rate was also assessed. Based on the experiments, a kinetic model adapted from enzyme catalysis was proposed to account for the micellar reaction environment. The model takes into account the onset of micelle formation at the CMC. The application of the kinetic model illustrated the good agreement with the experimental data. The model will be applied to other micellar epoxidation reactions and for the design of an appropriate reaction setup in the future.     

Colloid‐Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part V. Simultaneous Removal of a Chlorophenol and a Metal Ion

Abstract

Polyelectrolyte micellar‐enhanced ultrafiltration (PE‐MEUF) is a separation process to remove target solutes from water using a mixture of a surfactant and an oppositely charged polyelectrolyte as a colloid. An organic solute and a metal cation can simultaneously associate with the colloid, which is subsequently ultrafiltered from solution. An organic solute solubilizes in the surfactant micelle‐like aggregates whereas an inorganic cation binds onto the oppositely charged polyion chains. The solution is then passed through the membrane having pore sizes small enough to block the passage of the surfactant‐polymer aggregates. In this work, PE‐MEUF has been applied to mixtures containing dichlorophenol (DCP) and magnesium ion (Mg²⁺), using cetylpyridinium chloride (CPC) and sodium poly(styrenesulfonate) (PSS) mixtures. It was observed that the presence of Mg²⁺ does not affect DCP rejection. The [CPC] to [PSS] ratio and colloid concentration have a significant effect on both DCP and Mg²⁺ rejections. Increased ionic strength from added salt increases the gel point (colloid concentration at which flux is zero). The viscosity of the colloid solution is inversely related to the gel point.     

新型减水剂中间大分子单体的合成工艺

通过衣康酸与甲氧基聚乙二醇进行直接酯化反应,生成了一种具有反应活性的新型聚羧酸盐减水剂中间大分子单体—甲氧基聚乙二醇衣康酸单酯。探讨了酸醇比、催化剂用量、阻聚剂用量、带水剂用量等实验条件对酯化反应的影响,并对酯化产物进行了红外光谱分析和凝胶色谱分析,得出了合成甲氧基聚乙二醇衣康酸单酯的最佳合成工艺。     

Enhanced Solvent Extraction with Water-in-Ok Microemulsions

Abstract

This paper examines theoretically the conditions which favor enhanced extraction when a microemulsion phase containing a surfactant and a chelating agent is used as the solvent extraction organic phase. A general thermodynamic model of liquid-liquid distribution in reversed micellar systems is presented. The model treats the reversed micellar aggregates of the surfactant HA as a pseudophase and considers (a) the partition of a chelating extractant (HL) between the continuous organic phase and the reversed micellar pseudophase, (b) transfer of the metal ion M^z+ into the continuous organic phase via reaction with HA monomers, (c) partition of the M^z+-HA complex between the continuous organic phase and the reversed micellar pseudophase, (d) reaction of the M^z+ -HA complex with HL in the reversed micellar pseudophase, and (e) partition of the HL-containing complex between the reversed micellar pseudophase and the continuous organic phase. Quantitative expressions are derived that permit one to identify the chemical parameters that influence the liquid-liquid transfer process and therefore permit one to undertake the rational design of microemulsion formulations for specific applications.     

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

An efficient multi‐gram scale synthesis protocol of a variety of P,N ligands is described. The synthesis is achieved in a two‐step reaction. First, the amine is deprotonated and subsequently the chlorophosphine is added to yield the corresponding P,N ligand. Deprotonation of the amine is normally achieved with n‐BuLi at low temperature, but for the preparation of ligands with a 2,2′‐dipyridylamino backbone and phosphines with a high steric demand KH has to be employed in combination with reaction temperatures of 110 °C for the salt metathesis step. The reaction of two equivalents of a selected P,N ligand with one equivalent of the iridium complex [IrCl(cod)]₂ (cod=1,5‐cyclooctadiene) affords P,N ligand‐coordinated iridium complexes in quantitative yield. X‐Ray single crystal structure analysis of one of these complexes reveals a monomeric five‐coordinated structure in the solid state. The iridium complexes were used to form catalysts for the N‐alkylation of aromatic amines with alcohols. The catalyst system was optimized by studying 8 different P,N ligands, 9 different solvents and 14 different bases. Systematic variation of the substrate to base and the amine to alcohol ratios as well as the catalyst loading led to optimized catalytic reaction conditions. The substrate scope of the developed catalytic protocol was shown by synthesizing 20 different amines of which 12 could be obtained in isolated yields higher than 90%. A new efficient catalyst system for the selective monoalkylation of primary aromatic and heteroaromatic amines with primary aromatic, heteroaromatic as well as aliphatic alcohols has been established. The reaction proceeds with rather moderate catalyst loadings.     

Rhodium‐Catalyzed Asymmetric 1,4‐Additions,in Water at Room Temperature,with In‐Flask Catalyst Recycling

Using the newly introduced designer surfactant polyethylene glycol ubiquinol sebacate (PQS), as the platform for micellar catalysis, non‐racemic BINAP has been covalently attached and rhodium(I) inserted to form PQS‐BINAP‐Rh. This species, the first example of a non‐racemically‐ligated transition metal catalyst‐tethered amphiphile, can be utilized for Rh‐catalyzed asymmetric conjugate addition reactions of arylboronic acids to acyclic and cyclic enones. These are performed in water at room temperature, while the catalyst can be recycled without its removal from water in the reaction vessel.     

Removal of Ni(II) ions from wastewater by micellar enhanced ultrafiltration using mixed surfactants

Ni(II) ions were removed from aqueous waste using micellar enhanced ultrafiltration (MEUF) with a mixture of surfactants. The surfactant mixture was the nonionic surfactant Tween 80 (TW80) mixed with the anionic surfactant sodium dodecyl sulfate (SDS) in different molar ratios ranging from 0.1–1.5. The operational variables of the MEUF process such as pH, applied pressure, surfactant to metal ion ratio and nonionic to ionic surfactant molar ratio (α) were evaluated. Rejection of Ni and TW80 was 99% and 98% respectively whereas that for SDS was 65%. The flux and all resistances (fouling resistance, resistance due to concentration polarization) were measured and calculated for entire range of α respectively. A calculated flux was found to be declined with time, which was mainly attributed to concentration polarization rather than resistance from membrane fouling.     

Prediction of Equilibrium Partitioning of Nonpolar Organic Solutes in Water‐ Surfactant Systems by UNIFAC and COSMO‐RS Models

In the present study the potential of two thermodynamic‐based models (the group‐contribution UNIFAC model and the a priori predictive COSMO‐RS model) to predict solute partitioning in aqueous surfactant solutions is evaluated. In order to take into account the small size of micelles, the UNIFAC model was extended by the interfacial contribution based on the Gibbs‐Thompson equation. The applicability of the approach was successfully proved for the partitioning of nonpolar solutes (toluene, p‐xylene) in aqueous solutions of nonionic surfactants. The original COSMO‐RS model underestimates the concentration of the solute in the aqueous phase in the case of micellar systems since it does not account for the small size of micelles. At the same time, this model gives quantitative results for the octanol/water partition coefficients of both solutes under study leading to the conclusion that the affinity of both solutes to a certain solvent is well described. Thus, extending the COSMO‐RS by the interfacial term seems to be promising.     

Amphipathic polymers with stimuli‐responsive microdomains for water remediation: Binding studies with p‐cresol

Amphipathic, stimuli‐responsive water‐soluble polymers have been investigated as potential remediation agents for micellar enhanced ultrafiltration (MEUF). The systems represent divergent architectural types, a triblock ABA copolymer of PEO‐PPO‐PEO, an n‐octylamide modified poly(sodium maleate‐alt‐ethyl vinyl ether), and the transport protein, bovine serum albumin. Each type exhibits stimuli‐dependent microphase separation or domain formation in response to temperature, pH, and/or ionic strength changes. Segmental associations result in hydrophobic clusters resembling those present in small molecule surfactant micelles. The effects of such segmental aggregation on sequestration of a model hydrophobic foulant, p‐cresol, have been investigated using equilibrium dialysis. The favorable molar binding values, the large hydrodynamic dimensions of the stable polymer aggregates, and potential reversibility of foulant loading could have commercial utility in high flow rate, multiple‐pass remediation processes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2290–2300, 1999     

Micellar enhanced ultrafiltration: A comparative study

A pilot plant study was carried out to evaluate the performance of continuous cross flow micellar enhanced ultrafiltration (MEUF) method for the simultaneous separation of phenol and ortho‐cresol from the aqueous phase using a cationic surfactant, cetyltrimethyl ammonium bromide. The membranes used in this study are polysulfone tubular hollow fibre membrane with 6 kDa and a ceramic membrane having pore diameter 50 nm with an active layer of microporous zirconia (ZrO₂) supported on α‐alumina, respectively. The work includes comparing the effectiveness of membranes based on pollutants structural parameters, membrane properties and membrane modules. The characteristic parameters such as the distribution coefficient (D), micelle binding constant (K_p) and micelle loading (L_m) were obtained at optimal experimental conditions. High initial rejections were observed (above 95%) for both the membranes and the permeate flux remained almost constant at 17 LMH. It was found that the polysulfone material membrane suited better for MEUF with higher and steady rejections over a period of time. High micelle leakage was observed in ceramic membrane. The energy consumption for hollow fibre polysulfone membrane was less than the ceramic membrane. © 2011 Canadian Society for Chemical Engineering     

Evolutionary Catalyst Screening: Iridium‐Catalyzed Imine Hydrogenation

A high throughput catalyst screening is presented employing an evolutionary approach. The method comprises the optimization of initial leads by subjecting the catalysts to iterative rounds of optimization, including structural elaboration of the ligands by creating new focused libraries. Highly modular supramolecular ligands, robotized synthesis combined by high throughput experimentation creates a platform for fast catalyst development. An illustrative example for the asymmetric hydrogenation of cyclic 2,3,3‐trimethyl‐3H‐indole using iridium catalysts is presented. The kinetic investigation of the best catalyst yields an unusual second order in iridium, first order in hydrogen and zeroth order in substrate. Under optimized reaction conditions a TOF of 100 mol mol⁻¹ h⁻¹ with 96% ee could be obtained with the best catalyst. A full catalyst screening and kinetic study was conducted within a three‐week time‐frame.     

Photo‐Induced Sonogashira C?C Coupling Reaction Catalyzed by Simple Copper(I) Chloride Salt at Room Temperature

The conventional thermal Sonogashira C C coupling reaction requires the use of a palladium catalyst and a large amount of ligands. Although there were a few reports describing the use of inexpensive metal catalysts, such as, copper (Cu), iron (Fe), and nickel (Ni), for replacement of palladium (Pd) in the Sonogashira reactions, it was later questioned that the observed effects were due to ppb levels contamination of Pd present in the reagents used in the reactions. Herein, we report that simple copper(I) chloride (CuCl) salt, in the absence of Pd and ligands, can catalyze the Sonogashira reaction with high yields (80–99%) under blue LED light irradiation at room temperature. Control experiments show that no cross‐coupling product was formed, when palladium(II) chloride (PdCl₂) was used to replace CuCl as a catalyst. A series of electron‐rich and electron‐poor substituted aryl halides (bromides and iodides) as well as aryl‐ and alkylacetylenes are examined and the reaction mechanism is discussed.     

The Complex Synergy of Water in Metal/Bromide Autoxidations. Part II. Effect of Water and Catalyst on the Aerobic Oxidation of Benzaldehydes and the Effect of Water on the Elementary Catalytic Pathways

All of the rates of the elementary steps in the Co/Br and Co/Mn/Br homogeneous, liquid‐phase catalyzed reactions decrease with increasing water concentration in acetic acid. The step‐wise replacement of the acetic acid ligands by water ligands in the coordination sphere of the catalyst metals may be responsible for this behavior. The non‐catalyzed and metal‐catalyzed (Co, Co/Mn/Br and Co/Mn) aerobic oxidations of benzaldehyde and 4‐methylbenzaldehyde are reported. The non‐catalyzed autoxidations are quite vigorous reactions in acetic acid/water mixtures but by‐products from the Baeyer–Villiger reaction, the thermal decomposition of the peroxy acid, and over‐oxidation to carbon dioxide limit the yield to the aromatic carboxylic acids. As the concentration of a Co or Co/Mn/Br catalyst increases these by‐products are first reduced and then eliminated probably due to the very fast, selective reaction of [Co(II)]₂ with the peroxy acid. A Co/Mn catalyst completely inhibits the autoxidation of the benzaldehydes. There is a gradual change in the yield of terephthaldicarboxaldehyde from 4‐methylbenzaldehyde with increasing Co/Mn/Br concentration suggesting that the non‐catalyzed steps are being replaced by catalyzed ones. The autoxidation of heptaldehyde generates about 500 times more carbon monoxide than does benzaldehyde using a Co/Mn/Br catalyst and gives only a 50% yield to heptanoic acid consistent with excessive amounts of decarbonylation with aliphatic aldehydes.     

Lewis acid mediated polymerization of poly(dimethylsiloxane) polymers: Investigating reaction kinetics using both NMR spectroscopy and cyclic voltammetry

Bulk condensation polymerization of (dimethylmethoxy)‐m‐carborane and (dichlorodimethyl)silane occurs in the presence of an M^x+Cl_x Lewis acid catalyst. In the literature, FeCl₃ is commonly used as the catalyst of choice but little is known about the activation energy and entropy of this polymerization. By monitoring using ¹H‐NMR the reaction of a methoxy‐terminated poly(dimethylsiloxane) and (dichlorodimethyl)silane the rate determining step in the FeCl₃ catalyzed system is determined. The activation energy was calculated to be +43.6 kJ mol^?1 and the entropy of the reaction was also calculated. The calculated large entropy of reaction indicates that the transition step is highly ordered. The formation of the electrophile intermediate species in the first step of the reaction has also been investigated using cyclic voltammetry. To the cyclic voltammetry data Randles‐Sevcik fits have been applied to the oxidation peaks to determine the diffusion coefficients for the oxidation of Fe²⁺ to Fe³⁺. Also, the initial prediction of a reversible reaction Step 1 was shown to be incorrect as the normalized reduction peak maxima increase with scan rate, indicative of an electron transfer‐chemical reaction mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Solubilization of selected polycyclic aromatic compounds by nonionic surfactants

Solubilization of selected polycyclic aromatic compounds (PAC) by biodegradable nonionic surfactants, Tergitol 15-S-X (X=7 or 9) and Neodol 25–7, was investigated and correlated with micellar properties of these surfactants. These PAC include dibenzofuran, phenanthrene, acenaphthene, fluoranthene, and 9-chloroanthracene. Tergitol surfactants are mixtures of secondary ethoxylated alcohols, and Neodol 25–7 is a mixture of similar species but has the alcohol group in the primary position. These surfactants have the same chain length of hydrophobic tails and similar numbers of ethylene oxides. The results show that the Neodol surfactant yields micelles having larger hydrophobic core volume and renders a higher solubilization capacity for the PAC solubilizates in comparison with Tergitol surfactants. In general, aggregation numbers and micellar sizes both increase at elevated temperatures still below the cloud point. The micellewater partition coefficients of these PAC by the nonionic surfactants were well correlated to their octanol-water partition coefficients. Moreover, an estimated log K _ow value of 9-chloanthracene is 4.78.     

Ionic Liquid Effect on the Reversal of Configuration for the Magnesium(II) and Copper(II) Bis(oxazoline)‐Catalysed Enantioselective Diels–Alder Reaction

Ionic liquids have been used to support a range of magnesium‐ and copper‐based bis(oxazoline) complexes for the enantioselective Diels–Alder reaction between N‐acryloyloxazolidinone and cyclopentadiene. Compared with reaction performed in dichloromethane or diethyl ether, an enhancement in ee is observed with a large increase in reaction rate. In addition, for non‐sterically hindered bis(oxazoline) ligands, that is, phenyl functionalised ligands, a reversal in configuration is found in the ionic liquid, 1‐ethyl‐3‐methylimidazolium bis[(trifluoromethanesulfonyl)imide], compared with molecular solvents. Supported ionic liquid phase catalysts have also been developed using surface‐modified silica which show good reactivity and enantioselectivity for the case of the magnesium‐based bis(oxazoline) complexes. Poor ees and conversion were observed for the analogous copper‐based systems. Some drop in ee was found on supporting the catalyst due a drop in the rate of reaction and, therefore, an increase in the contribution from the uncatalysed achiral reaction.     

Mono‐ and Bidentate Phosphine Ligands in the Palladium‐Catalyzed Methyl Acrylate Dimerization

The influence of several phosphine ligands on the activity, selectivity and stability of the catalytic system Pd(acac)₂, ligand, [HOEt₂][BF₄] was studied in the dimerization of methyl acrylate (MA). It was found that the catalyst's activity increased with increasing the basicity of the monodentate ligands used, whereas bulky phosphines lowered the linearity of the dimers and the reaction rates. With chelating P N‐, P P‐, and P As‐ligands the Pd‐catalyst could be efficiently stabilized during the reaction. The use of 1‐dibutylphosphino‐2‐dimethylaminoethane as ammonium tetrafluoroborate salt allowed the highest overall activity.