Mixture Of Aqueous Solution Research Articles

Effects of amine (APTES) and thiol (MPTMS) silanes-functionalized ZnO NPs on the structural, morphological and, selective sonophotocatalysis of mixed pollutants: Box–Behnken design (BBD)

The lack of selectivity of Zinc oxide nanoparticles (ZnO NPs) in the wastewater purification process is considered a severe limitation. This research aims to use surface-modified ZnO NPs with different surface charges for selective removal of methyl orange (MO) and methylene blue (MB) dyes from an aqueous mixture solution. The sonophotocatalyst process was investigated to improve the selective oxidation of the aqueous mixture. The surface of the ZnO NPs has been modified with a silane coupling agent (APTES and MPTMS) to get active surface functional groups. The synthesized modified ZnO NPs were characterized by XRD, FE-SEM, TEM and FTIR analysis. The surface charge and absorption spectrum were investigated using Zeta potential and UV-Vis spectrophotometer approaches, respectively. The selective sonophotocatalytic of anionic MO and cationic MB dyes was performed via APTES-ZnO and MPTMS-ZnO NPs, respectively. The selective removal was optimized using Response Surface Methodology (RSM) based on the Box–Behnken Design (BBD). To this end, the effects of catalyst dosage, dye concentration, and reaction time on selective removal were investigated under various experimental conditions. The results revealed that unmodified ZnO NPs have no selectivity in the decomposition of an MO and MB mixed, whiles the change in surface charges of ZnO NPs has been shown to change significantly the selectivity efficiency of ZnO NPs.

Microfluidic Preparation of Nanoparticles Using Poly(ethylene Glycol)-distearoylphosphatidylethanolamine for Solubilizing Poorly Soluble Drugs

Microfluidic systems have shown promise for the production of nanoparticles from mixtures of aqueous and organic solutions, including liposomes, oil-in-water nanoemulsions, and lipid nanoparticles. They offer important practical advantages, including low reagent consumption, parallelization, and automation, and are ideally suited to high-throughput optimization and scale-up. In this study, we developed a new method for the formulation of nanoparticles of poorly soluble drug compounds. The nanoparticles, prepared by microfluidic mixing using only poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE), were highly stable and uniform in size. By mixing an organic solution of poorly soluble cyclosporine A and PEG-DSPE with water in the microfluidic device, amorphous cyclosporine A nanoparticles (CsA-NPs), with an encapsulation efficiency of approximately 90% and a particle size of 100–200 nm, were obtained. Analysis of the microfluidic process parameters revealed that particle size distribution was significantly controlled by the flow rate ratio. The obtained CsA-NPs were stable for up to 150 days at room temperature, and the pharmacokinetic profile was similar to that of the commercial formulation containing Cremophor EL, which has been reported to induce serious adverse effects after intravenous administration. These findings provide a useful technical platform for the safe solubilization of poorly soluble compounds and their subsequent pharmaceutical development.

Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study.

The self-assembly behaviors of sodium oleate (NaOL), dodecylamine (DDA), and their mixtures in aqueous solution were systematically investigated by large-scale molecular dynamics simulations, respectively. The interaction mechanisms between the surfactants, as well as the surfactants and solvent, were revealed via the radial distribution function (RDF), cluster size, solvent-accessible surface area (SASA), hydrogen bond, and non-bond interaction energy. Results showed that the molecules more easily formed aggregates in mixed systems compared to pure systems, indicating higher surface activity. The SASA values of DDA and NaOL decreased significantly after mixing, indicating a tighter aggregation of the mixed surfactants. The RDF results indicated that DDA and NaOL strongly interacted with each other, especially in the mixed system with a 1:1 molar ratio. Compared to van der Waals interactions, electrostatic interactions between the surfactant molecules were the main contributors to the improved aggregation in the mixed systems. Besides, hydrogen bonds were found between NaOL and DDA in the mixed systems. Therefore, the aggregates in the mixed systems were much more compact in comparison with pure systems, which contributed to the reduction of the repulsive force between same molecules. These findings indicated that the mixed NaOL/DDA surfactants had a great potential in application of mineral flotation.

Physico-Chemical Properties of Nicotine and Nicotine-Bitterness Inhibitor Mixtures in Aqueous Solution and the Role of Water in their Taste

Physico-Chemical Properties of Nicotine and Nicotine-Bitterness Inhibitor Mixtures in Aqueous Solution and the Role of Water in their Taste

Controllable superlubricity achieved with mixtures of green ionic liquid and glycerol aqueous solution via humidity

In this work, superlubricity between steel surfaces lubricated by mixtures of [Choline][Proline] ([Cho][Pro]) ionic liquid and glycerol aqueous solution has been reached by using a rotating tribometer. Stable superlubricity could be obtained even under the humidity between 7 and 9% RH. The lowest friction is observed when the lubricant contains 3 wt% ionic liquid. It is found that adding 3 wt% [Cho][Pro] is helpful to maintain enough water in the steady period to retain a low viscosity. According to the calculation, the superlubricity achieved in thin film lubrication region, which is attributed to the stern layer formed by [Cho][Pro] and hydrogen-bond network that enabled a thin water layer at the interface. Interestingly, it is observed that humidity can be used to control lubrication state between superlubricity and non-superlubricity. This study provides a new method to accomplish switchable superlubricity under low humidity.

Effect of fluorocarbon surfactants on the adsorption of hydrocarbon surfactants mixture at the water-air interface

Taking into account the great practical importance of the surface tension of the aqueous solution of multicomponent surfactant mixtures their adsorption at the water-air interface and the composition of the adsorbed monolayer were considered. For this consideration the mixture of the p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycol) Triton X-165 (TX165) and hexadecyltrimethylammonium bromide (CTAB) with FC6EO14 as well as with FC5EO10 was applied. The surface tension of the studied solution at the constant CTAB and TX165 binary mixture concentration corresponding to its solution surface tension equal to 60 and 50 mN/m and changing fluorocarbon surfactant concentration was measured. The obtained results were described by the exponential function of the second order and predicted by the modified Fainerman and Miller equation. To solve the Fainerman and Miller equation the fraction of adsorbed mixed monolayer at the water-air interface occupied by particular surfactants was determined. For its determination, the contribution of particular surfactants in the mixture to reduction of water surface tension was taken into account. The fraction occupied by the given surfactant in the mixed monolayer was compared to that determined using the Hua and Rosen equation obtaining good agreement between them. The fraction of the mixed monolayer occupied by a given surfactant was also successfully used to solve the Gibbs and Frumkin equations for determination of surface concentration of a particular surfactant in the mixed monolayer. Based on the isotherms of the surface excess concentration as well as the Hua and Rosen theory the packing of the mixed monolayer and the presence of the synergetic effect in the reduction of water surface tension were deduced. This effect was also reflected in the standard Gibbs free energy of adsorption of surfactant mixtures at the water-air interface. It was found that this energy can be predicted based on this energy for particular surfactants of the mixture and Gibbs free energy of mixing.

Mutual influence of ethanol and surfactin on their wetting and adhesion properties

The measurements of the contact angle of aqueous solution of ethanol and surfactin mixture in the whole range of ethanol concentration on PTFE, PMMA and quartz were made at changing ethanol concentration and constant of surfactin and vice versa. Based on the obtained results, the Young-Dupre and van Oss et al. equations, the intermolecular interactions parameter between the solution and solid phases was determined and used to explain the possibility to form the ethanol and surfactin mixed layer beyond the solution drop settled on the PMMA and/or quartz surface. This layer pressure and that at the PMMA-solution, the quartz-solution interface was determined using the Young-Dupre and van Oss et al. equations and applied for the ethanol and surfactin Frumkin isotherm adsorption determination. The Gibbs adsorption isotherm was also determined. The ethanol and surfactin Gibbs and Frumkin isotherms at the solid-solution, solid-air interfaces were compared to those at the solution-air one. From these isotherms of surfactin and ethanol adsorption at three interfaces, the slope of the linear dependence between the adhesion and surface tension was explained. The Gibbs isotherm was applied for determination of the Gibbs standard free energy of ethanol and surfactin adsorption at the solid-air and solid-water interfaces.

Pharmacokinetic comparison between Tanreqing Capsules Substitute and Tanreqing Capsules in rats by LC-MS/MS

Due to the limited resource of bear bile powder, the major raw material of Tanreqing Capsules(TRQ), cultured bear bile powder is used as a replacement to develop the Tanreqing Capsules Substitute(TRQS). An LC-MS/MS method was established in this study for simultaneous quantitation of 8 compounds from TRQS in rat plasma: tauroursodeoxycholic acid(TUDCA), taurocheno-deoxycholic acid(TCDCA), ursodeoxycholic acid(UDCA), chenodeoxycholic acid(CDCA), ferulic acid, wogonoside, baicalin, and forsythoside A. Thereby, the pharmacokinetic behaviors of TRQ and TRQS were evaluated. Concentration of endogenous compounds TUDCA, TCDCA, UDCA, and CDCA was determined with the stable isotope surrogate analytes: D4-TUDCA, D4-TCDCA, D4-UDCA, and D4-CDCA. Plasma samples were extracted by acetonitrile-induced protein precipitation. The LC conditions are as follows: Waters BEH C_(18) column(2.1 mm×100 mm, 1.7 μm), mobile phase of 10 mmol·L~(-1) ammonium formate aqueous solution(containing 0.01% formic acid) and acetonitrile-methanol mixture(1∶5). MS conditions are as below: multiple reaction monitoring(MRM), ESI~(+/-). Concentration of UDCA, CDCA, TUDCA, and TCDCA was corrected with a response factor, which is the ratio between the responses recorded for the surrogate and the authentic analyte at the equal concentration. Each of the plasma components showed good linearity(r > 0.995 1). Accuracy and precision met the criteria(inter-day RSD<7.0%, RE 89.98%-112.0%; intra-day RSD<12%, RE 90.41%-111.2%). The recovery was 64.83%-119.9% and matrix effect was 87.15%-113.8%. The validated method was applied for pharmacokinetic study of TRQS and TRQ(po, 0.94 g·kg~(-1)). There was no significant difference in C_(max) and AUC_(0-24 h) of baicalin, UDCA, TUDCA, and TCDCA between the two groups, indicating similar pharmacokinetic behaviors between TRQS and TRQ in rats.

Study of thermo-acoustical properties of Liquid mixtures of Aqueous solution of Lithium Chloride and Lithium Hydroxide at Different Temperatures

Density, viscosity and ultrasonic velocity of the various compositions of liquid mixtures of aqueous solutions of Lithium chloride (LiCl) and Lithium hydroxide (LiOH) have been experimentally measured at 303,308,313 and 318K and at atmospheric pressure. From these experimental measurements the acoustic impedance (Z) and adiabatic compressibility (ad) have been calculated. The variations in these parameters have been correlated to derive the intermolecular interactions taking place between the mixtures of present study.

Aqueous solution thickening of amino acid‐based surfactant by alkylpyrrolidone

AbstractThe thickening behaviors in aqueous solution of mixed surfactant mixtures containing an amino acid‐based surfactant, sodium lauroyl sarcosinate (SLSar), and a nonionic surfactant, N‐dodecylpyrrolidone (C12P) were investigated using the rheological methods of steady‐shear and frequency sweep. The results varying the added C12P concentration and the mass ratio of SLSar and C12P indicate that the addition of C12P can promote the formation of wormlike micelles and hydrogels, resulting in viscosity enhancement in the mixed aqueous solution of SLSar and C12P. Viscosity maxima in SLSar/water/C12P systems are sensitive to pH, temperature, the concentration of added C12P, and the mass ratio of SLSar and C12P. In the high concentration of total surfactant (30–39 wt%), the enhancement of viscosity obviously occurs by adding 6 wt% C12P, whereas in the low concentration of total surfactant (15 wt%), the C12P must be added more than 9 wt% in 15 wt% mixtures of SLSar and C12P. Moreover, during the solution pH lowered from SLSar' natural pH of 7.2 to the mixture's pKa 5.2, the intermolecular forces between SLSar acid, SLSar anionic salt, and C12P gradually reduce the overall headgroups areas and contribute to the formation of wormlike micelles, hydrogels, and the thickening behaviors.

Enhancement of kinetic rates of CO2 in aqueous solutions of piperazine and methyldiethanolamine with addition of sulfolane

AbstractMeasurements of kinetics rates of CO2 in aqueous solutions of methyldiethanolamine (MDEA), piperazine (PZ), and mixtures of (MDEA + PZ), (PZ + sulfolane) and (MDEA + sulfolane) were carried out using the stopped flow technique, and reported in terms of pseudo‐first‐order rate constants (k0). When possible, the second‐order reaction rate constants (k2) were regressed from the data. Experiments were performed over new concentration ranges of (10–60), (200–800), (200–800, 10–40), (10–40, 10–200), and (200–800, 10–200) mol/m3 for the above‐mentioned five systems, respectively, and at temperatures varying from (298.15–313.15 K). When sulfolane was added to the amine solution, pseudo‐first‐order rate constants in the mixed solvents were higher than in aqueous MDEA and PZ solutions at all temperatures. The kinetic rates were highest at 298.15 K and decreased at higher temperatures for aqueous (MDEA + sulfolane) solutions but increased with temperature for aqueous (PZ + sulfolane) systems. Reaction orders for both PZ and MDEA were practically one at all sulfolane concentrations and temperatures. The base catalysis mechanism was used to regress very well data for aqueous MDEA and (MDEA + sulfolane + water) and the termolecular mechanism was used for (PZ + sulfolane + water) system. Both the zwitterion and termolecular models were able to fit the experimental data for the aqueous PZ system well. Finally, the termolecular and a hybrid model based on the combination of the Zwitterion and base catalysis mechanisms were able to successfully correlate the experimental data for the mixed aqueous (MDEA + PZ) systems.

Effect of composition of mono/di-hydroxy organic compounds and temperature on the aggregation behavior and physico-chemical properties of polyvinyl alcohol + TTAB mixture

Herein, the aggregation manners of polyvinyl alcohol (PVA) with tetradecyltrimethylammonium bromide (TTAB) in alcohols/diols media containing various concentrations and at several temperatures were performed using the conductivity measurement technique. Different physico-chemical parameters, such as critical micelle concentration (CMC), fraction of bound counter ions (β) and thermodynamic properties (ΔGo m, ΔHo m, ΔSo m, and ΔCo m) for the TTAB + PVA mixture in aqueous solutions of EtOH (EtOH), 1-propanol (1-PrOH), ethylene glycol (EG), and propylene glycol (PrG), have been determined. The CMC values were found to undergo a decrease in 1-PrOH in comparison to the values obtained in aqueous media, but in EtOH, the CMC value firstly decreases, touches the lowest point, and then exhibits an upsurge with further increase of the percentage of EtOH. The observed greater CMC values in diols media disclose that the micelle formation of TTAB + PVA mixture is delayed in the manifestation of diols. The CMC values of TTAB + PVA mixture have also been observed to vary with the change of study temperature. The negative values of ΔG0 m were obtained for all circumstances suggesting a spontaneous aggregation phenomenon of TTAB + PVA system. The values of ΔH 0 m and ΔS0 m dictate that the PVA molecule interacts exclusively with TTAB through the formation of hydrogen bonding, ion-dipole, and hydrophobic interaction. Furthermore, the standard molar heat capacity (ΔC 0 m), compensation temperature (T c), intrinsic enthalpy gain (ΔH 0,* m), and the thermodynamic properties of transfer (ΔG 0 m.tr, ΔH 0 m.tr. and ΔS 0 m.tr.) for the studied system were assessed and demonstrated with appropriate explanations.

Results of experimental studies of integrated physico-chemical impact in carbonate reservoirs

The article highlights the experimental studies results of carbonate rock dissolution kinetics in order to develop effective methods of slowing down the acid reaction rate in the heterogeneous structures. It was found that the intensity of carbonate reservoirs leaching process with the addition of hydrocarbon solvents such as dioxanes increases due to the acetals transition to the oil phase, dissolution of highly active oil components and more intense penetration of an aqueous solution of hydrochloric acid to the carbonate matrix of the reservoir rock, which intensifies the process of leaching. The technology of complex physico-chemical impact on carbonate reservoirs has been developed. It is shown that the use of a aqueous hydrochloric acid solutions mixture and an organic solvent leads to an increase in the dissolution efficiency to 88% and the reaction rate increases by a factor of 3.5.

Study of Interaction of Glycerol Cryoprotectant and Its Derivatives with Dimethylacetamide in Aqueous Solution Using Fluorescent Probes

In this paper we have studied the interaction of the mixtures of glycerol (GL) and its oxyethylated derivatives (OEG) with polymerization degree n = 3, 25 and 30 with dimethylacetamide (DMAc) in aqueous solution using 3-hydroxy-4´-(N, N dimethylaminoflavone) fluorescent probe. The combination of GL and its oxyethylated derivatives with DMAc was found to reduce the membranotropy of certain cryoprotective agents, forming a mixture. The combination of both GL and its low molecular weight derivative (OEGn=3) with DMAc reduced the membranotropy of the latter. At the same time, combining GL derivatives of high molecular weight (OEGn=25 and OEGn=30) with DMAc diminished the membranotropy of OEG. The OEGn=30 at concentrations above 1 wt.% was shown to form the micellar-type structures or micellar associates in aqueous solution. This enabled suggesting the membranotropic ability of high molecular weight OEG associates to be stipulated by possible interaction of their nonpolar segments with nonpolar sites on biomembrane surface. Structural rearrangements of molecular associates in aqueous solutions of low and high molecular weight cryoprotectant mixtures were designated as the experimentally established mechanism of cytotoxicity reduction in combined cryoprotective media.

High impact of thiol capped ZnS nanocrystals on the degradation of single and binary aqueous solutions of industrial azo dyes under sunlight

Sulfur zinc (ZnS) nanocrystals were prepared using an aqueous colloidal route with thioglycolic acid (TGA) as a stabilizer. These ZnS-TGA nanocrystals were used as a low-cost and environmental friendly alternative for the photodegradation of methylene blue (MB) and methyl orange (MO) from aqueous solutions using sunlight irradiation. Structural and optical properties of nanocrystals were determined via X-ray diffraction, Fourier transform infrared spectroscopy, Transmission electron microscopic, UV–Visible and photoluminescence spectroscopy. Results showed a blue shift of absorbance band and higher energy band gap values than bulk ZnS materials, which was in agreement with the quantum confinement effect. X-ray diffraction confirmed the formation of cubic phase of ZnS-TGA containing also a slight wurtzite phase. Calculated average size of ZnS nanocrystals by the Debye Scherrer relation was 3.5 nm. Characterization results showed the fixation of TGA on ZnS-NCs via sulphur and carboxylic functionalities on catalyst surface. Photoluminescence spectra obtained under excitation wavelength at 325 nm showed three emission bands (416, 441 and 484 nm), which were mainly related to band edge and defect-activated emissions. The photocatalytic activity of ZnS-TGA nanocrystals under sunlight irradiation to degrade tested MB and MO dyes and their mixture in aqueous solutions was evaluated. High dye degradation efficiency was achieved at a very short time (27 min) and this performance was attributed to the negative surface charge, surface area, surface defects and high dispersion of ZnS-TGA nanocrystals on the aquatic medium. Overall, this study demonstrates that these nanocrystals could be employed as low-cost nanocatalyst for the degradation of organic dyes in wastewater treatment.

Critical Micelle Concentrations in Surfactant Mixtures and Blends by Simulation.

We explore the use of coarse-grained dissipative particle dynamics simulations to predict critical micelle concentrations (CMCs) in polydisperse surfactant mixtures and blends. By fitting pseudo-phase separation models (PSMs) to aqueous solutions of binary surfactant mixtures at selected compositions above the CMC, we avoid the need for expensive simulations of more complex multicomponent mixtures performed as a function of dilution. The approach is demonstrated for sodium laureth sulfate (SLES) surfactants with polydispersity in the ethoxylate spacer. For this system, we find a modest degree of cooperativity in micelle formation, which we attribute to the reduced repulsion between charged headgroups for surfactants with dissimilar ethoxylate spacer lengths. However, this is insufficient to explain the lowered CMC often observed in commercial SLES samples, which we attribute to the presence of small amounts of unsulfated alkyl ethoxylates and/or traces of salt.

SYNERGISTIC EFFECT OF A COMBINATION OF COLLECTORS IN ADSORPTION AT GAS-LIQUID INTERFACE

The promising nature of flotation with a combination of collecting agents is well known. The synergetic effect of combinations of collectors develops as hydrophobization of a mineral surface during adsorption and as reduction in surface tension at gas-liquid interface. The earlier proved mechanism of physisorption of an agent is based on the connection of its surface characteristics (surface pressure, spreading rate) and their collectability. It is assumed that the ratio of agents in their combination for flotation can be selected from the maximum synergistic effect achieved. This study focuses on adsorption at the gas-liquid interface in aqueous solutions of binary mixtures of sodium lauroyl sarcosinate and hexadecyltrimethylammonium bromide. The interaction parameters and the ratio of the components in the solution so that the maximum synergistic effect is achieved are determined.

Pressure-swing distillation process for separating ternary azeotropic mixture of acidic aqueous solution

The separation of ternary mixture of acidic aqueous solution is difficult due to presence of both binary and ternary azeotropes that generate distillation boundaries. In this work, a pressure-swing distillation process for separating the mixture was investigated. Three variants of pressure swing distillation process were therefore proposed. The operating pressure of each distillation column was chosen on the basis of the location of the feed composition in the distillation regions. The sensitivity analysis of the operating parameters of each separation process was carried out to determine the best operating conditions to reach higher purity for the three products (i.e., 99.9 mol.%). It has been found that formic acid and water present in the ternary mixture with high content can be separated twice as a distillate product with total molar recovery ratio of about 90%. In addition, the energy consumed to separate water was higher than that required to recover formic acid.

Effect of heat treatment on corrosion of laser-textured aluminum alloy surfaces

The kinetics of electrochemical corrosion of aluminum alloy (AlMg6) surfaces with different wettability was analyzed. The surfaces were processed by three different methods, in particular, polishing, laser texturing, the combination of laser texturing and low-temperature heating. After laser processing, the dimple-like texture was formed on the surface, and the wettability significantly enhanced. Low-temperature heating of laser-textured AlMg6 alloy surfaces led to the wettability inversion from strongly hydrophilicity to superhydrophobicity. Microscopic and profilometric methods were used to estimate the surface degradation due to corrosion when aggressive solution droplets (a mixture of NaCl and hydrogen peroxide aqueous solutions) evaporated. The potentiodynamic polarization measurements of AlMg6 alloy surfaces were conducted. The typical modes of corrosion and evaporation of aggressive solution droplets were detected. The kinetics of corrosion was estimated by the behavior of the corrosion area evolution. In addition, when immersing laser-textured sample with strongly hydrophilic properties into aggressive solution, the higher corrosion rate was found in the liquid meniscus region (aggressive mixture / alloy / air interface) compared to the textured site immersed in the mixture. This was explained by convection increasing the rate of reaction products removal and promoting a stronger deviation from the equilibrium state in the aggressive mixture. Experimental results of the potentiodynamic polarization measurements revealed that laser-textured samples exhibit enhanced corrosion protective properties compared to polished samples.

One-Pot Synthesis of CeO2 Modified SBA-15 With No Pore Clogging for NO Reduction by CO

CeO2 modified SBA-15 composites have been prepared by adding cerium precursor (Ce(NO3)3·6H2O) directly into the mixture of soft template (P123), silica precursor (TEOS) and urea aqueous solution but without mineral acid. The products were characterized by X-ray fluorescence (XRF), powder X-ray diffraction (XRD), N2 physisorption and transmission electron microscopy (TEM). Results indicated that ceria were successfully grafted onto mesoporous silica matrix and no pore clogging was observed. Both ceria content and mesoporous ordering of the final products were found to depend on urea amount. Compared to CeO2/SBA-15 from conventional impregnation method, the one-pot synthesis not only showed simple and green operation, but also superior catalytic performance in NO+CO reaction after loaded with CuO. It was revealed that both the presence and location of ceria had great influence on the reducibility of CuO, and the catalytic performances were intimately related to the redox properties of crystalline CuO. That is, higher NO conversion and N2 selectivity were achieved over catalyst with easier reduction of crystalline CuO.