Factors Affecting the Droplet Size of Water‐in‐Oil Emulsions (W/O) and the Oil Globule Size in Water‐in‐Oil‐in‐Water Emulsions (W/O/W)

Multiple emulsions of the W₁/O/W₂ type are promising tools for encapsulating bioactive ingredients in the inner aqueous droplets. It is necessary, however, to control the factors influencing their encapsulation efficiency. One important factor is the particle size because it determines the surface area available for mass transport. Because of the coexistence of water and oil droplets in multiple emulsions, there are numerous factors that have an impact on particle size, for example, oil phase composition, interfacial properties, and viscosity of the phases. The purpose of this study was to systematically investigate the effect of these factors on particle sizes in multiple emulsions.     

Water‐in‐oil Emulsions Stabilized by Hydrophobized Microfibrillated Cellulose

The properties of water‐in‐toluene emulsions stabilized solely by hydrophobized microfibrillated cellulose (MFC) were investigated. By varying the degree of surface substitution (DSS), the wettability of the MFC was altered. All emulsions prepared with MFC displayed excellent stability to coalescence. The stability to gravity‐induced sedimentation increased with increasing MFC concentration, the highest stability being obtained with MFC of moderate hydrophobicity. Drop sizes increased with increasing DSS, with a corresponding decrease in stability to sedimentation. An increase in the toluene:water ratio at constant MFC concentration resulted in a decrease in the average drop size. For all emulsions, the polydispersity in drop size decreased with decreasing average drop diameter.     

Stereoselective Synthesis of cis‐1‐Aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes in Water

The highly stereoselective preparation of cis‐1‐aryl‐2‐benzoyl‐3,3‐dicyanocyclopropanes with arsonium salt and olefin in water is described. It is simple, efficient, and environmentally benign.     

Spectrophotometric Determination of Gold in Water and Ore with 2‐Carboxyl‐1‐Naphthalthiorhodanine

Abstract

This paper reports on the synthesis of a new chromogenic reagent, 2‐carboxyl‐1‐naphthalthiorhodanine (CNTR). A high sensitive, selective, and rapid method for the determination of gold based on the rapid reaction of gold with CNTR and the solid phase extraction of the colored chelate with a reversed phase polymer‐based C₁₈ cartridge was developed. In the presence of 0.05–0.5 mol L^?1 of phosphoric acid solution and emulsifier‐OP medium, CNTR reacts with gold to form a red chelate of a molar ratio 1∶3 (gold to CNTR). This chelate was enriched by the solid phase extraction with a polymer‐based C₁₈ cartridge and the retained chelate was eluted from the cartridge with dimethyl formamide (DMF). The enrichment factor of 100 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.35×10⁵ L · mol^?1 · cm^?1 at 540 nm. Beer's law is obeyed in the range of 0.01～2 µg mL^?1 in the measured solution. The relative standard deviation for 11 replicates sample of 0.5 µg L^?1 level is 2.05%. The detection limit, based on three times the standard deviation is 0.02 µg L^?1 in the original sample. This method was applied to the determination of gold in water and ore with good results.     

Salt‐Induced Micellization of Pluronic F88 in Water

The effect of potassium chloride on the micellization of a poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymer (Pluronic F88: EO₁₀₃PO₃₉EO₁₀₃.) in water was studied by fluorescence, FTIR, ¹H NMR, dynamic light scattering, and dye solubilization. The critical micellization temperature (CMT) values of the copolymer decreased with an increase of KCl concentration while micellar core gets progressively dehydrated. The results reveal the leading role of salt‐water interaction in promoting the micellization of PEO‐PPO‐PEO copolymer by the addition of salt. No significant micellar growth was seen even at temperatures close to cloud point.     

Phase Transition of Acrylamide‐Based Polyampholyte Gels in Water

The swelling behavior of acrylamide (AAm)–based polyampholyte hydrogels in water and in aqueous salt (NaCl) solutions was investigated. [(Methacrylamido)propyl]trimethyl‐ammonium chloride (MAPTAC) and acrylic acid (AAc) were used as the ionic comonomer in the hydrogel preparation. Three sets of hydrogels containing 70 mol% AAm and 30 mol% ionic comonomers of varying mole ratios were prepared. The variations of the hydrogel volume in response to changes in pH, and salt concentration were measured. As pH increases from 1, the hydrogel volume V _eq in water first increases and reaches a maximum value at a certain pH. Then, it decreases again with a further increase in pH and attains a minimum value around the isoelectric point (IEP). After passing the collapsed plateau region, the gel reswells again up to pH=7.1. The reswelling of the collapsed gels containing 10 and 4% MAPTAC occurs as a first‐order phase transition at pH=5.85 and 4.35, respectively, while the hydrogel with 1% MAPTAC reswells continuously beyond its IEP. Depending on pH of the solution, the hydrogels immersed in salt solutions exhibit typical polyelectrolyte or antipolyelectrolye behavior. The experimental swelling data were compared with the predictions of the Flory‐Rehner theory of swelling equilibrium including the ideal Donnan equilibria. It was shown that the equilibrium swelling theory qualitatively predicts the experimental behavior of polyampholyte hydrogels.     

Facile and Efficient Deoxygenation of Amine‐N‐oxides with Gallium in Water

Abstract

A facile and efficient procedure for the deoxygenation of amine‐N‐oxides with gallium metal in water is described. The experimental procedure is quite simple and the products are obtained in high yields without any activating agent.     

Relationship Between the Polymer Structures and Destabilization of Polymer‐Containing Water‐in‐Oil Emulsions

The viscous properties, scanning electronic microscopy (SEM), and water/oil interfacial tension (IFT) of partially hydrolyzed polyacryamide (HPAM) and hydrophobically associating hydrolyzed polyacryamides modified with N‐dodecylacrylamide were studied with the objective of investigating the influence on destabilization of emulsions. As expected, the copolymers exhibit significant viscosity enhancing capacity and three‐dimensional network structures due to intermolecular hydrophobic associations, and also present high interfacial activities as the IFT decrease with increasing polymer concentration. As a result, the existences of copolymers increased both the viscosity of emulsions and the intensity of interfacial film, in which case slow down the diffusion of demulsifier molecules and enhance the stability of emulsions, finally, the separation of water from oil becomes more difficult.     

Halogenation of Pyrazoles Using N‐Halosuccinimides in CCl4 and in Water

Reaction of pyrazoles with N‐halosuccinimides (NXS, X=Br, Cl) in either CCl₄ or water gave 4‐halopyrazoles in excellent yields. The reaction was carried out under mild conditions and did not require any catalysts or special precautions. The reaction provides an efficient method for 4‐C halogenation of pyrazoles.     

Spectrophotometric Determination of Nitrite in Water Samples with 4‐(1‐Methyl‐1‐Mesitylcyclobutane‐3‐yl)‐2‐Aminothiazole

Abstract

A simple, sensitive, and specific spectrophotometric method for the measurement of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. The azo dye, 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐(p‐N,N‐dimethylazobenzene)‐1,3‐thiazole was synthesized with the reaction of 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐aminothiazole and N,N‐dimethyl aniline in acidic medium. Obtained azo dye has been characterized by infrared (IR), ¹H nuclear magnetic resonance (NMR), and microanalysis methods. The dye shows an absorption maximum at 482 nm. The method is optimized for acid concentration, pH, amount of reagents required, time, and interfering species. All the determinations were carried out at this wavelength throughout the work. At an analytical wavelength of 482 nm, Beer's law is obeyed over the concentration range 0.05 to 2.00 µg nitrite per mL analyte. The molar absorptivity, Sandell's sensitivity, and relative standard deviation are 2.03×10⁴ L mol^?1 cm^?1±251.3 (95%), 2.28×10^?3 µg cm^?2, and 2.74% (n=10), respectively. The detection limit of the method is 0.012 µg ml^?1 of nitrite ion. The method was succesfully applied to the determination of nitrite in tap water and lake water.     

Stereo‐ and Regioselective Thiolysis of 1,2‐Epoxides in Water

A simple, efficient, stereoselective, and highly regioselective procedure for the synthesis of β‐hydroxy sulfides by thiolysis of various 1,2‐epoxides in water as a solvent, using no catalyst and under very mild conditions, is described.     

Effect of Emulsification Method on the Properties of Lecithin‐ and PGPR‐Stabilized Water‐in‐Oil‐Emulsions

Water‐in‐oil (w/o) emulsions were prepared with phosphatidylcholine‐depleted lecithin or polyglycerol polyricinoleate (PGPR) as emulsifying agents. The effect of different laboratory emulsification devices and the effect of sodium chloride on particle size distribution, coalescence stability, and water droplet sedimentation were investigated. The properties of lecithin‐stabilized w/o emulsions were found to depend more strongly on the emulsifying method than those prepared with PGPR. The rotor‐stator system was not suitable for preparing stable w/o emulsions with lecithin. Whereas the addition of salt was essential to achieve coalescence‐stable emulsions prepared with PGPR, the presence of NaCl favored the coalescence of water droplets and phase separation in emulsions containing lecithin.     

Studies on Separation of Liquid‐Liquid Dispersions: Diesel‐Water System in Batch Settler

In this article, batch settling of liquid‐liquid dispersion in a vertical batch settler was comprehensively studied. The experiment results of the investigation on liquid‐liquid batch settler phase separation were compared with a well predefined physical model proposed by Jeelani and Hartland [1998, Ind. Eng. Chem. Res. 37: 547–554] using a semi theoretical approach. The effect of initial dispersion height, initial hold‐up volume, settler diameter, and mixing time on separation of batch liquid‐liquid dispersions were experimentally investigated in terms of variation in the final settling time and coalescing interfaces with time. From the present work it was found that, final separation time varied as polynomial function of degree 2 with respect to initial dispersion height and was constant with respect to initial hold‐up volume. Final separation time also varied according to the completeness of dispersion achieved with respect to the mixing time. The experimental data obtained showed a good correlation with the theoretically predicated values. Results allow the use of experimental procedure with the mathematical model as a tool in monitoring the dispersion behavior in commercial units on industrial importance.     

Synthesis of Functionalized Pyrroles by Reaction of 3,4‐Diacetylhexane‐2,5‐dione with Primary Amines in Water

3,4‐Diacetylhexane‐2,5‐dione (tetra‐acetylethane) undergoes a complex reaction with primary amines in boiling water to produce N‐alkyl‐3‐acetyl‐2,5‐dimethylpyrroles, together with small quantities of N‐alkyl‐3,4‐diacetyl‐2,5‐dimethylpyrroles and 2,5‐dimethyl‐1H‐pyrrol‐3‐yl‐vinyl‐acetamides. When the reaction was carried out in methanol at room temperature, the yields of the latter products increased.     

Synthesis of Substituted 1,4‐Dihydropyridines in Water Using Phase‐Transfer Catalyst Under Microwave Irradiation

Abstract

The synthesis of various substituted 1,4‐dihydropyridines has been achieved by the reaction of aldehydes, ethyl/methyl acetoacetates, and ammonium acetate in water using phase‐transfer catalyst under microwave irradiation. Compared to the classical Hantzsch's reaction conditions, this new method consistently has the advantage of good yields and short reaction times. Bifunctional compounds containing two units have been synthesized using dialdehyde as precursor in good yields.     

Separation of Water‐in‐Oil Emulsions Using Glass Fiber Media Augmented with Polymer Nanofibers

Water‐in‐oil emulsion separations are important to the petrochemical industry for product quality, safety, environmental, and economic reasons. Glass fiber filter media are often used to remove water droplets out of water‐in‐oil emulsions. The experimental results in this work show that 1% by mass of polyamide nanofibers with diameters of about 150 nm added to conventional micron‐sized glass fiber filter media improves the separation efficiency of the filter media from 71 to 84%. The addition of similar amounts of micron‐sized polyamide fibers to the glass fiber media do not improve filter capture efficiency.     

Molecular Dimension and Interaction Parameters of Polyacrylamide in Water‐N,N‐Dimethylformamide Mixtures

The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights are measured in various mixtures of water (good solvent) and N, N dimethyl formamide (DMF, nonsolvent) at different temperatures. The observed results show a significant variation of cosolvency as a function of solvent composition (?_DMF). The nature of curves in [η] vs. ?_DMF plot at different temperatures indicates the existence of two antagonistic effects. The unperturbed dimensions (K_θ) of the polymer are determined by a number of methods, which agree well with each other. The temperature coefficient of unperturbed dimension (K′), molecular extension factors (α_n), characteristic ratio (C_α) and chain rigidity (σ) are evaluated and the effects of temperature, solvent composition are discussed. The volume related parameter V_E and shape factor ν were also computed, which shows the shape of polymer molecules to be more or less spherical in solution.     

Diffusion Mechanism of As‐spun Polyacrylonitrile Fiber in a Dimethyl Sulfoxide‐Water Coagulation Bath

In this paper, the diffusion mechanism of as‐spun PAN fiber was investigated in dimethyl sulfoxide‐water by determining the dynamic compositions of the fibers and the diffusion coefficients of solvent and nonsolvent during coagulation. The diffusion process could be divided into two stages. Results showed that the first stage of the diffusion process was the most important during the whole process, which was fundamental to further study on the formation mechanism. Also, compared with wet spinning, the dry‐jet wet spinning method had the advantage of mild coagulating at a high jet‐stretch. At high concentrations, the diffusion coefficients increased and the ratio of solvent diffusion coefficient to nonsolvent diffusion coefficient decreased; an increasing temperature resulted in the increase of both diffusion coefficients with a decrease in their ratios. To some extent, for the PAN‐DMSO‐water system, the more the ratios D_s*/D_n* tended to 1, the more the cross‐section shapes of as‐spun PAN fiber tended to be circular.     

Novel Procedure for Highly Stereoselective Synthesis of Bicyclic Cyclopropane‐lactam with cis‐2‐Aryl‐1‐benzoyl‐3,3‐dicyanocyclopropane and 2‐Cyanomethyl‐1,3‐benzothiazole in Water

The novel procedure for synthesis of cyclopropyl lactams incorporating benzothiazole structure units from cis‐2‐aryl‐1‐benzoyl‐3,3‐dicynocyclopropane and 2‐cyanomethyl‐1,3‐benzothiazole has been achieved. This method is highly stereoselective and environmentally friendly.     

Studies of Kinetics of Coalescence of Water‐in‐Furrial Crude Oil Emulsions by Confocal Microscopy

The kinetic of coalescence of water in Furrial crude oil emulsions (W/O) during the initial stage of demulsification process is showed through of high‐resolution image micrographics by using a confocal microscope. Furrial crude oil from Monagas state is a crude oil extra heavy with severe flocculation/aggregation problems. The kinetic of the initial stage in the coalescence process is critical and of great importance in the definition of the foreword behavior. This information allowed us to characterize the demulsification rate process in a Furrial crude oil. Total W/O emulsion separation was achieved about of 2 hours at 80ºC. The initial fast coalescence is characterized by a short binary coalescence time, which is followed by a large binary coalescence time. Our results demonstrate that the initial coalescence rate determinate the time necessary to achieve a total separation.