Separation of azeotropic mixtures of alcohols and water with FricDiff

FricDiff is an energy efficient separation process based on a difference in transport velocities of the components of a gas or vapor mixture when they diffuse through a sweep gas (‘enhancer’). The separation process takes place inside the pores of a non-selective macro-porous barrier. In this paper the separation of a 2-propanol–water mixture with the FricDiff-principle is studied, using CO₂ as the enhancer. A detailed numerical model is developed that describes the separation process that takes place inside a cylindrical FricDiff-unit. In this unit the vapor mixture to be separated and the sweep gas flow at opposite sides of a porous barrier in a counter current mode. Through the porous barrier selective mass transport of components of the feed mixture through the sweep gas takes place resulting in a separation. The model takes into account axial velocity profiles as a result of laminar flow of the gas and vapor mixtures through the flow channels, radial concentration gradients and radial velocities. The transport through the porous barrier is described with the Binary Friction Model. The influences of process conditions and the characteristics of the porous barrier on the separation process are studied.     

Ion—solvent interactions in acetonitrile + water mixtures

Standard Gibbs energies of transfer, ΔG°_t of alkali metal chlorides (M = Li, Na, K, Rb and Cs) and potassium bromide and iodide from water to the aqueous mixtures of 20, 40, 60 and 80 mass per cents of acetonitrile (ACN) have been determined at 25°C from emf measurements performed on the double cell comprising AgAg X and M (Hg) electrodes. The individual ionic contributions to ΔG°_t have also been evaluated using the reference electrolyte (RE = Ph₄AsBPh₄) method, the required ΔG°_t's of the RE being obtained from the measured solubilities of salts viz. Ph₄AsPic, KBPh₄ and KPic (Pic = picrate and Ph = phenyl). The observed increasing ΔG°_t values of the halide ions X^? and their order Cl^? ? Br^? ? I^? furnish the thermodynamic evvidence for the effect of the well known decreased H-bonding and the anion destabilizing propensities of dipolar aprotic cosolvent ACN. But the observed shallow minima in ΔG°_t-composition profiles for M⁺ and H⁺ are indicative of the result of the oppositg effects of water structure breaking propensities and the protophobic character of ACN and their relative order is the combined effects of acid—base, Born-type and soft—soft interactions. Moreover, while the distinctly pronounced stabilization of large tetraphenyl ionshas been ascribed as the combined effects of dispersion and cavity-forming interactions, the less pronounced solvation of Pic^? has been attributed to the combined effects of increased dispersion interactions of benzene nucleus and of decreased H-bonding interactions of O-atoms of the substituents. These contentions have been further substantiated by comparing ΔG°_t(i) values of some selected ions in ethylene glycol—water mixtures.     

Polymers with upper critical solution temperature behavior in alcohol/water solvent mixtures

Thermoresponsive polymers are of great importance in numerous nanotechnological and biomedical applications. Compared to polymers that undergo a lower critical solution temperature (LCST) phase transition in aqueous solution, i.e., demixing occurs upon heating, polymers exhibiting the reversed upper critical solution temperature (UCST) behavior in aqueous solution have been much less documented as it is more challenging to achieve this behavior in aqueous solutions. Furthermore, the high sensitivity of UCST behavior to minor variation in polymer structure and solution composition hampered the development of applications based on these polymers [18]. However, polymers with UCST transition in alcohol/water solvent mixtures are more commonly reported and exhibit promising properties for the preparation of ‘smart’ materials. This review will focus on the theory and development of such polymers with UCST behavior in alcohol/water solvent mixtures. By highlighting reported examples of UCST polymers in alcohol/water solvent mixtures, we aim to demonstrate the versatility and potential that such UCST polymers possess as biomedical and ‘smart’ materials.     

Separation of organic solvent from dilute aqueous solutions and from organic solvent mixtures through crosslinked acrylate copolymer membranes by pervaporation

The composite membranes of acrylate polymers and porous substrate were prepared. The separation of the organic solvent–water mixtures and the organic solvent–organic solvent mixtures through these membranes by pervaporation was investigated. The acrylate copolymer membrane showed the organic solvent permselectivity for the separation of the organic solvent–water mixture, especially for the chlorinated hydrocarbon–water mixture separation. The high organic solvent permselectivity should be governed by solubility selectivity. The influence of the ester residue of acrylate on the phenol–water mixture separation was observed. The copolymerization of the macromonomers containing the polystyrene, poly(methyl methacrylate), and polydimethylsiloxane chain had a small effect on the separation of the chlorinated hydrocarbon–water mixture. High flux and low selectivity of organic solvent were observed in the case of the organic solvent mixture separation through the n-butylacrylate membrane. The difference of permeability of organic solvent was observed for the acrylate copolymer which has various structures of ester residue. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1483–1494, 1998     

Dehydration of glycerin/water mixtures by pervaporation using homo and copolymer membranes

Separation characteristics of glycerol/water mixtures were studied using hydrophilic poly(acrylonitrile-comethacrylic acid) (PANMAC), poly(acrylonitrile-co-hydroxyethyl methacrylate) (PANHEMA), Poly(vinyl alcohol) GFT-1001, and poly(vinyl alcohol) (PVA) crosslinked with maleic anhydride (PVAManh) membranes. All membranes were found to be highly water selective. PVAManh membrane yielded the highest permeation flux for water over the entire range of water concentration studied. Homopolymers (PVAManh and GFT-1001) gave better permeation rates than copolymer membranes (PANHEMA and PANMAC). But the swelling of homopolymers is nuch greater than that of copolymers, which is why PVA membranes have poor longevity. No effect on selectivity of the membrane was observed with a change in operating parameters. No decomposition/polymerization of glycerin was observed, as there was no involvement of high temperatures as there is with distillation. A comparison of pervaporation with vapor-liquid equilibrium data showed that pervaporation of glycerin/water mixtures yielded better selectivity than vapor-liquid equilibrium, particularly for glycerol concentrations above 90 wt%.     

Solubility of piperonal in different pure solvents and binary isopropanol+water solvent mixtures

Using a laser monitoring observation technique, the solubilities of piperonal in different pure solvents and binary isopropanol+water solvent mixtures were determined by synthetic method from 273.15 K to 293.15 K. Results of these measurements were correlated by Apelbat equation and the combined nearly ideal binary solvent (CNIBS)/Redlich-Kister equation. The results find that Apelbat equation and the combined ideal binary solvent (CNIBS)/Redlich-Kister equation provided accurate mathematical representations of the experimental data, respectively.     

Characteristics of cellulase modified with amphiphilic copolymer in organic solvent

Characteristics of modified cellulases in organic solvents were studied. Cellulases modified with amphiphilic copolymer of polyoxyalkylene (POA)-derivative and maleic acid anhydride (MAA). Amino groups of the cellulase molecule were easily coupled with the MAA functional group of the copolymer. At the maximum degree of modification (DM) of 55%, the activity of modified cellulase retained more than 80% of the unmodified native cellulase activity. The modified cellulase using AKM-1511 with DM greater than 40% was found to be more than 90% soluble in aqueous solution of acetone and ethanol, leaving the native cellulase and impurities in the fermentation broth with the residue. Modified cellulase showed excellent stability against water-insoluble solvent. Moreover, cellulase modified with hydrophobic copolymer, which consists of ethylene oxide (EO) and propylene oxide (PO), could be dissolved in these solvents.     

Pervaporation of ethanol–water mixtures through styrene-substituted N-phenylmaleimide copolymer membranes

A number of copolymers of styrene with substituted N-phenylmaleimides were synthesized and their solutions in chloroform were used in the casting of homogeneous membranes. The latter were applied in the separation of variously concentrated ethanol—water mixtures by pervaporation at 35°C. The membranes were characterized by the separation factor related to preferentially transported water and by the flux of the permeate. In contrast to membranes made from copolymers of styrene with N-phenylmaleimide, the separation factor of membranes containing substituted N-phenylmaleimides increased with increasing amount of ethanol in the feed solution. The effect of incorporated imide units on the properties of the membranes under investigation is discussed. © 1992 John Wiley & Sons, Inc.     

Reentrant conformational transition of polyelectrolyte network in water alcohol mixtures in the presence of oppositely charged surfactant

Summary Reentrant conformational transitions are observed in polyelectrolyte networks of sodium methacrylate-acrylamide copolymers in water-alcohol mixtures in the presence of cetylpyridinium bromide. At low alcohol content, gel shrinking is induced by complex formation between charged network and oppositely charged surfactant. In media with high alcohol content the complex dissociates and the collapse comes as a result of volume interactions between charged network and the solvent. At intermediate alcohol concentration, hydrophobic interactions between hydrocarbon groups of surfactant ions are suppressed and the gel swelling is observed.     

Polymeric micelles formed by polypeptide graft copolymer and its mixtures with polypeptide block copolymer

Polymeric micelles based on poly(γ-benzyl-l-glutamate)-poly(ethylene glycol) graft copolymer (PBLG-g-PEG) with various degrees of grafting and the mixtures composed of PBLG-g-PEG and poly(γ-benzyl-l-glutamate)-poly(ethylene glycol) block copolymer (PBLG-b-PEG) were prepared by the dialysis method in deionized water. Fluorescence spectroscopy and transmission electron microscope (TEM) have been used to study the self-assembly behavior. The experimental results revealed that the degree of grafting exerts marked effect on the critical micelle concentration (CMC) and the morphology of the micelle formed by PBLG-g-PEG. With increasing the degree of grafting, the CMC value becomes larger and the morphology of formed micelle changes from irregular shape to spindle. It was also found that mixtures of PBLG-g-PEG/PBLG-b-PEG can associate into hybrid polymeric micelle with various shapes.     

Sorption and permeation of acetic acid–water mixtures by pervaporation using copolymer membrane

Poly (acrylonitrile‐co‐methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid–water mixtures over the concentration range of 80–99.5 wt% acetic acid in water. Interaction parameters based on Flory–Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory–Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution–diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30°C temperature 1–20 wt% water in feed was concentrated to 82–84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg m^?2 h^?1 mμ and 409, respectively. OLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Dielectric relaxation of binary mixtures of alcohols with acrylic esters

A dielectric relaxation study on alcohol–acrylic ester binary mixtures has been carried out at different concentrations using time domain reflectometry (TDR). The least‐squares fit method has been used to obtain the dielectric parameters (the static dielectric constant ?₀ and the relaxation time τ). By using these parameters, the Bruggeman factor, the Kirkwood correlation factor, and excess inverse relaxation time were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The ?₀ and τ values decreased with an increase in the percent of acrylic ester in alcohol for all the systems. The value of t increased with an increase in chain length of both the alcohol and acrylic ester, whereas the reverse trend is observed for ?₀. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrochemical determination of acidity level and dissociation of formic acid/water mixtures as solvent

The autoprotolysis constant K_HS of formic acid/water mixtures as solvent has been calculated from acid-base potentiometric titration curves. A correlation of the acidity scale pK_HS of each medium versus pure water has been implemented owing to the Strehlow R⁰(H⁺) electrochemical redox function. The results show that formic acid/water mixtures are much more dissociated than pure water; such media are sufficiently dissociated to allow electrochemical measures without addition of an electrolyte. It has also been shown that for a same H⁺ concentration the activity of protons increases with formic acid concentration. For more than 80 wt.% of formic acid the acidity is sufficiently increased to locate the whole acidity scale pK_HS in the super acid medium of the generalized acidity scale pHH₂O.     

Reversible selectivity of water/organic solvent mixtures in poly(lactic acid) film

The separation properties of water/organic solvent mixtures in poly(lactic acid) (PLA) films were investigated. The organic solvent flux increased linearly as the feed concentration increased, whereas the water flux was almost constant up to a feed concentration of 30 wt %. Interestingly, the permselectivity of PLA films was reversed from organic solvent selectivity to high water selectivity depending on the type of organic solvent. The permselectivity was strongly correlated with the solution concentration at which the solvent‐induced crystallization of the PLA films occurred. The selectivity of permeation, solution, and diffusion in water/organic solvent mixtures was determined by the expanded free volume of the PLA films as a result of the interaction between PLA and the water/organic solvent mixture. The permeability behavior of water/organic solvent mixtures in PLA films was very complex. However, it was found that this behavior could be predicted through immersion tests. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43822.     

含8-羟基喹啉侧基二嵌段共聚物的合成

以8-羟基喹啉和甲基丙烯酸羟乙酯为原料,经一系列反应得到含8-羟基喹啉配体结构的甲基丙烯酸甲酯类单体（HQMA）,再利用可逆加成-断裂链转移（RAFT）法实现该单体的活性可控聚合,然后以此聚合产物为大分子RAFT试剂,与苯乙烯实现活性可控聚合得二嵌段共聚物,并用1H NMR和GPC对其进行了表征,确定了其组成和结构;研究了所得共聚物在四氢呋喃（THF）（作共溶剂）和甲苯（Tol）（作选择性溶剂）混合溶剂中的自组装行为,结果表明,当共溶剂（THF)和选择性溶剂(甲苯)的体积比为V(THF):V（甲苯）=5:5和V(THF):V（甲苯）=4:6时,形成的胶束是球形的,当V(THF):V（甲苯）=2:8形成的胶束是蠕虫状的。     

Stabilization of oils by microencapsulation with heated protein-glucose syrup mixtures

The use of proteins [whey protein isolate (WPI) or soy protein isolate (SPI) in combination with dried glucose syrup (DGS) for stabilization of microencapsulated spray-dried emulsions containing tuna oil, palm stearin, or a tuna oil-palm stearin blend was investigated. Pre-emulsions containing heated (100°C/30 min) protein-DGS mixtures and oils at oil/protein ratios of 0.75∶1 to 4.5∶1 were homogenized at two passes (35+10 or 18+8 MPa) and spray-dried to produce 20–60% oil powders. Microencapsulation efficiency decreased at lower homogenization pressure and as the oil load in the powder was increased beyond 50% but was independent of the type of oil encapsulated and the total solids (TS) content of the emulsions (24–33% TS) prior to drying. Oxidative stabilities of the powders, as indicated by headspace propanal values and PV after 4 wk of storage at 23°C, generally decreased with increasing oil content and homogenization pressure but increased with increasing TS of the emulsion prior to drying. Powder containing palm stearin was more stable to oxidation than powders containing a 1∶1 ratio of palm stearin and tuna oil or only tuna oil. Heated WPI-DGS formulations were superior to corresponding formulations stabilized by heated SPI-DGS, producing spray-dried powders with higher microencapsulation efficiency and superior oxidative stability.     

Stabilization of unstable detonation waves in mixtures of nitromethane with inert diluents

Mass velocity profiles of detonation waves in mixtures of nitromethane with acetone and methanol with added diethylenetriamine sensitizer were measured using a VISAR laser interferometer. It was found that even small, about 1%, concentrations of acetone and methanol, inert diluents, led to instability of the one-dimensional detonation front in nitromethane. The results of the experiment show that the use of the sensitizer is an effective method of flow stabilization and if the concentration of the inert diluent does not exceed 10%, the detonation front becomes stable with the addition of 1% diethylenetriamine. At a higher diluent concentration, the sensitizer does not suppress the instability but decreases the oscillation amplitude by several times. The addition of diethylenetriamine to the mixture has been found to increase the detonation velocity.     

Electroosmotic transport of water in polyelectrolyte networks

Summary The phenomenon of contraction of polyelectrolyte gels under the influence of direct current is studied experimentally. It is shown that the number of water molecules per one ion of the electric current is very large N 10³. This effect can be explained as electroosmotic transport of water molecules through the gel, which can be represented as an effective fine-porous medium with the diameter of pores equal to the mesh size of a network.