Aqueous Sulfate Solutions Research Articles

Acoustic and Viscometric Studies of Atropine Sulphate with Life Essential 3d- Transition Metal Ions in Aqueous Medium

In the present paper, the ultrasonic velocity u, density ρ and viscosity η measurements of the drug atropine sulphate in aqueous solutions of Cu(II) and Co(II) metal ions at  298.15 K/1atm at a wide range of concentrations (0.01M-0.1M) are reported. They constitute a valuable source of information viz. inter-relationship of system composition, intermolecular interactions and the physical properties of the solute and solvent investigated. The observed values of u, ρ and η were found in the range of 1500-1550 ms-1, 1000-1040 kgm-3 and 0.8900-1.300 Nsm-2 respectively. The effect of concentration on u, ρ and η in all ternary systems of metal ions were found to be positive. Acoustical parameters such as isentropic compressibility Ks, intermolecular free length Lf, specific acoustic impedance Z, relative association RA, free volume Vf, internal pressure πi, viscous relaxation time τ, Gibb’s free energy ΔG, attenuation coefficient α, Rao’s constant Rm, and Wada’s constant w were calculated from the experimental data. It was found that all the parameters increased with increasing concentration except Vf, Lf and Ks. On the basis of the Jones-Dole equation, viscosity data were analyzed and the values of the Falkenhagen coefficient A and Jones-Dole B coefficient were evaluated. The variations in these parameters are discussed in terms of hydrophilic-hydrophilic/hydrophilic-hydrophobic interactions in these systems along with the structure-making/breaking behaviour of the drug.

Chitin and chitin-cellulose composite hydrogels prepared by ionic liquid-based process as the novel electrolytes for electrochemical capacitors

This paper reports on the preparation and electrochemical performance of chitin- and chitin-cellulose-based hydrogel electrolytes. The materials were prepared by a casting solution technique using ionic liquid-based solvents. The method of chitin dissolution in ionic liquid with the assistance of dimethyl sulfoxide co-solvent was investigated. The obtained membranes were soaked with 1-M lithium sulfate aqueous solution. The prepared materials were preliminarily characterized in terms of structural and physicochemical properties. Further, the most promising biopolymer membranes were assembled with activated carbon cloth electrodes in symmetric electrochemical capacitor cells. The electrochemical performances of these devices were studied in a 2-electrode system by commonly known electrochemical techniques, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The devices operated at a maximum voltage of 0.8 V. All the investigated materials have shown high efficiency in terms of specific capacitance, power density, and cyclability. The studied capacitors exhibited specific capacitance values in the range of 92–98 F g−1, with excellent capacitance retention (ca. 97–98%) after 20,000 galvanostatic charge and discharge cycles. Taking into account the above information and the eco-friendly nature of the biopolymer, it appears that the prepared chitin- and chitin-cellulose-based hydrogel electrolytes can be promising components for green electrochemical capacitors.

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

Manganese oxide nanoflakes grown around cobalt oxide nanobundles with improved charge-storage performance for supercapacitors

Cobalt oxide nanobundle arrays (denoted as CoO) consisting of nanorods were homogeneously grown around the stainless steel wire mesh (SSWM) through a simple hydrothermal synthesis and subsequent heat treatment. The highly dispersed CoO can act as a supporting platform for the deposition of manganese oxide (MnO2) nanoflakes to engineer a CoO@MnO2 core-shell array structure. Without the CoO supports, the MnO2 was found to be prone to form aggregated nanoflakes on the SSWM substrate. CoO arrays with a one-dimensional nanorod skeleton can mitigate the aggregation of two-dimensional MnO2 nanoflakes. The CoO@MnO2 core-shell arrays integrate the advantages of abundant active edge sites, conductive networks for charge transfer, and pore channels for easy transport of electrolyte. The CoO@MnO2 electrode realizes a larger charge-storage capacity than the pristine MnO2 electrode in an aqueous sodium sulfate solution (1 M). The specific capacitances of CoO@MnO2 under 0.15 mA cm-2 and 7.50 mA cm-2 reach 79 mF cm-2 and 53 mF cm-2, respectively, much more than that of MnO2 (31 mF cm-2 and 20 mF cm-2). The CoO@MnO2 core-shell electrode shows a definite improvement in supercapacitive behavior compared to the pristine MnO2 electrode, resulting from reduced charge- and mass-transfer resistance during charge-storage process.

Contribution of Different Molecules and Moieties to the Surface Tension in Aqueous Surfactant Solutions. II: Role of the Size and Charge Sign of the Counterions.

Understanding the role of the counterion species in surfactant solutions is a complicated task, made harder by the fact that, experimentally, it is not possible to vary independently bulk and surface quantities. Here, we perform molecular dynamics simulations at constant surface coverage of the liquid/vapor interface of lithium, sodium, potassium, rubidium, and cesium dodecyl sulfate aqueous solutions. We investigate the effect of counterion type and charge sign on the surface tension of the solution, analyzing the contribution of different species and moieties to the lateral pressure profile. The observed trends are qualitatively compatible with the Hofmeister series, with the notable exception of sodium. We point out a possible shortcoming of what is at the moment, in our experience, the most realistic nonpolarizable force field (CHARMM36) that includes the parametrization for the whole series of alkali counterions. In the artificial system where the counterion and surfactant charges are inverted in sign, the counterions become considerably harder. This charge inversion changes considerably the surface tension contributions of the counterions, surfactant headgroups, and water molecules, stressing the key role of the hardness of the counterions in this respect. However, the hydration free energy gain of the counterions, occurring upon charge inversion, is compensated by the concomitant free energy loss of the headgroups and water molecules, leading to a negligible change in the surface tension of the entire system.

Image analysis based mass transfer measurement in droplet breakage phenomenon

The effect of droplet breakage on mass transfer in copper solvent extraction was studied by measuring concentrations directly inside a droplet. Single organic phase droplet was rising through the aqueous copper sulphate solution. Organic phase consisted of hydroxyoxime type copper extractant dissolved into hydrocarbon diluent. The droplet collided with steel blade and was cut as it elongates and eventually breaks up. Droplet breakage was recorded on the video. Droplet sizes, velocities and concentrations were determined using image analysis of video frames. Results indicate that droplet breakup enhances mass transfer. Breakage and mass transfer times are short and mass transfer due to pure diffusion alone does not explain excess mass transfer. This is proposed to be due to extractant absorption on newly forming interface, which leads to increased extraction. Although measured droplet sizes are much larger than those formed in mixed tanks, the results provide insights for industrial copper extraction intensification.

Separation and structural elucidation of cefsulodin and its impurities in both positive and negative ion mode in cefsulodin sodium bulk material using liquid chromatography/tandem mass spectrometry

The structure identification of impurities in cephalosporins was reported. However, to the best of our knowledge, there was no report on impurities of cefsulodin sodium, which is necessary for the quality control. Thus, the aim of this study was to separate and characterize the impurities in cefsulodin sodium raw material using LC-MS/MS. The analytes were separated on a Kromasil 100-5C18 column (4.6 mm ×250 mm, 5 μm) by a gradient elution with a mobile phase consisting of 1% ammonium sulphate aqueous solution and acetonitrile in the first dimension. The separation in the second dimension was carried on a Shimadzu Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm) with a mobile phase consisting of 10 mM ammonium formate solution and methanol. The fragmentation behaviors of cefsulodin and its impurities were studied and the structures of impurities were deduced based on the MSn data. The structures of ten unknown impurities were proposed based on the work carried out in this study. The degradation behaviors of cefsulodin sodium were also studied. It revealed that the storage environment of cefsulodin sodium should be preserved in a dry, cool and dark closed container. Based on the characterization of impurities, this study not only revealed the mechanism of impurity production, thus providing guidance to pharmaceutical companies for manufacturing process improvement and impurity control, but also provided a scientific basis for further improvement of official monographs in pharmacopoeias.

Unusual Compatibility of N‐Reacetylated Oligochitosan with Sodium Dodecyl Sulfate in Aqueous Solution with a Wide Range of the Solution pH

AbstractN‐reacetylated oligochitosan (RA‐oligoCHI) with molecular weight ≤ 12 kDa and a random‐type distribution of acetyl groups can form soluble RA‐CHI/SDS (SDS; sodium dodecyl sulfate) complexes and transparent solutions both in acidic, where RA‐oligoCHI is soluble, and alkaline aqueous media, where RA‐oligoCHI is soluble too, at SDS concentration above its critical micellar concentration. AN antibacterial activity test shows that RA‐CHIs preserve a high bacteriostatic activity toward S. aureus and E. coli in the presence of SDS both in acidic and alkaline aqueous solutions. The discovered compatibility and preservation of antibacterial activity can make promising the application of RA‐CHIs as artificial biocides for the preparation of microbiologically stable pharmaceutical hydrocolloids and cosmetic compositions containing strong anionic surfactants designed for topical applications.

Degradation of trichloroethene by citric acid chelated Fe(II) catalyzing sodium percarbonate in the environment of sodium dodecyl sulfate aqueous solution

In this study, the common chlorinated solvent trichloroethene (TCE) was selected as the target contaminant. The aqueous solution after solubilization treatment (containing TCE and sodium dodecyl sulfate (SDS)) was used as the research object to carry out the remediation technology research of citric acid (CA) enhanced Fe(II) activation in sodium percarbonate (SPC) system. In 0.15 mM TCE and 1 critical micelle concentration (CMC) SDS solution, CA chelating Fe(II) activated SPC could effectively promote 93.2% degradation of TCE when the dosages of SPC, Fe(II) and CA were 3.0, 6.0 and 3.0 mM, respectively. SDS had a significant inhibitory effect on the degradation of TCE, and the surface tension changed after the reaction. The addition of CA greatly increased the generation of hydroxyl radicals (HO) in the system, while the removal of TCE was mainly attributed to HO, and the removed TCE was almost completely dechlorinated. The pH range from 3 to 7 could keep the TCE degradation above 80.0%. In the actual groundwater remediation, this technique could also efficiently degrade TCE (including SDS), showing a great application potential and development prospective in practice.

Concentration-Dependent Solvation Structure and Dynamics of Aqueous Sulfuric Acid Using Multinuclear NMR and DFT.

Sulfuric acid is a ubiquitous compound for industrial processes, and aqueous sulfate solutions also play a critical role as electrolytes for many prominent battery chemistries. While the thermodynamic literature on it is quite well-developed, comprehensive studies of the solvation structure, particularly molecular-scale dynamical and transport properties, are less available. This study applies a multinuclear nuclear magnetic resonance (NMR) approach to the elucidation of the solvation structure and dynamics over wide temperature (-10 to 50 °C) and concentration (0-18 M) ranges, combining the 17O shift, line width, and T1 relaxation measurements, 33S shift and line width measurements, and 1H pulsed-field gradient NMR measurements of proton self-diffusivity. In conjunction, these results indicate a crossover between two regimes of solvation structure and dynamics, occurring above the concentration associated with the deep eutectic point (∼4.5 M), with the high-concentration regime dominated by a strong water-sulfate correlation. This description was borne out in detail by the activation energy trends with increasing concentration derived from the relaxation of both the H2O/H3O+ and H2SO4/HSO4-/SO42- 17O resonances and the 1H self-diffusivity. However, the 17O chemical shift difference between the H2O/H3O+ and H2SO4/HSO4-/SO42- resonances across the entire temperature range is nevertheless strikingly linear. A computational approach coupling molecular dynamics simulations and density functional theory NMR shift calculations to reproduce this trend is presented, which will be the subject of further development. This combination of multinuclear, dynamical NMR, and computational methods, and the results furnished by this study, will provide a platform for future studies on battery electrolytes where aqueous sulfate chemistry plays a central role in the solution structure.

Facile fabrication of tough and biocompatible hydrogels from polyvinyl alcohol and agarose

AbstractA polyvinyl alcohol (PVA)‐agarose (agar) composite hydrogel (M‐PVA‐agar‐60) was developed by simple three cycles of freeze‐thawing, followed by successively soaking in ammonium sulfate aqueous solution to induce phase separation and dialyzing against deionized water to remove residual sulfate salts. Due to the synergy of crystalline regions, hydrogen bonding and phase separation domains, the obtained M‐PVA‐agar‐60 hydrogel exhibits excellent mechanical properties (tensile strength = 1.1 MPa, tensile strain = 324% and compressive stress = 12.5 MPa), combined with a high water content of 87.0%. Moreover, the hydrogel hardly expands after immersing in the phosphate‐buffered saline aqueous solution at 37°C for a week, and the tensile stress and toughness remain almost the same as their initial values, superior to most reported non‐swellable hydrogels. Because of the biocompatible starting materials, absence of toxic chemicals, and dialysis in advance to remove ammonium sulfate, the hydrogel also shows excellent cell compatibility, making it an ideal candidate for tissue engineering materials.

Energetically efficient and electrochemically tuneable exfoliation of graphite: process monitoring and product characterization

In this work, graphene oxide was prepared by electrochemical exfoliation of graphite in sodium dodecyl sulphate and sodium dodecylbenzene sulphonate aqueous solution. Two different working electrodes were investigated: an electrode prepared from natural graphite flakes and a commercial natural graphite rod. The working electrode was polarized in a two-electrode system by using platinum counter electrode and by a multistep change of polarity or by single anodic and cathodic polarization. The voltage value ranged from 2.5 to 3.2 V. By monitoring the current transients and the colour of the resultant solutions, it was shown that the exfoliation process depends on the type of working electrode, surfactants and applied voltage value. The multistep change of polarity was more effective compared to single polarization. The ultraviolet–visible spectrophotometry and Raman spectroscopy indicated the presence of defects within the graphene structure, while FTIR spectroscopy indicated the presence of oxygen functional groups, which is characteristic of graphene oxide (GO). Dynamic light scattering revealed that the solutions obtained in this work contained GO sheets within the size of 10–600 nm. Atomic force microscopy measurements proved that the obtained product contains multilayer sheets. The energy consumption for the process carried out in this work ranges from 0.084–0.038 kWh g−1, and therefore this process is considered to be a low-energy and cost-effective process.

Removal of Zinc(II) Ions from Wastewater Using Natural Zeolites

The kinetics of the adsorption of zinc(II) ions by natural zeolites was studied using pseudo-first and pseudo-second-order kinetic models. The objects of study were zeolites mined in East Transbaikalia. The X-ray phase analysis and IR spectroscopy data confirmed that natural zeolite-containing rock samples have the following composition: calcium heulandite Ca[Al2Si7O18]⋅6H2O and impurity rocks, namely, sanidine KAlSi3O8 and cristobalite SiO2. The dependence of the adsorption value on zeolite grain size was studied. It was shown that the adsorption value increases 3.8 times and reaches 0.075 mol/g as the grain size decreases from 5 to 0.1 mm. The kinetic study of zinc(II) ions adsorption was performed at pH 5.0–5.4 in the temperature range of 298–318 K. In a zeolite–zinc sulfate aqueous solution system, the adsorption equilibrium time was 120 min. It was shown that the zinc(II) ions adsorption rate decreases under the temperature increase. It was established that the kinetics of zinc(II) ions adsorption is best described by a pseudo-second-order model, the correlation coefficient values varying in the range of 0.998–0.999. The highest adsorption rate constant value of 0.446 g/(mmol⋅mm) corresponds to the temperature of 298 K. It was shown that zeolites demonstrate the highest adsorption value towards heavy metal ions at the temperature of wastewater. The proof-of-principle studies were performed to establish the feasibility of the recovery of copper(II), nickel(II), and zinc(II) ions from wastewater produced by galvanic manufacture using the studied minerals. The treatment process was performed under the conditions determined as optimal for model solutions. The efficiency of heavy metal ions removal was 85–89%.

Optimal Performance of Thin-Film Composite Nanofiltration-Like Forward Osmosis Membranes Set Off by Changing the Chemical Structure of Diamine Reacted with Trimesoyl Chloride through Interfacial Polymerization.

Thin-film composite (TFC) polyamide membranes formed through interfacial polymerization can function more efficiently by tuning the chemical structure of participating monomers. Accordingly, three kinds of diamine monomers were considered to take part in interfacial polymerization. Each diamine was reacted with trimesoyl chloride (TMC) to manufacture TFC polyamide nanofiltration (NF)-like forward osmosis (FO) membranes. The diamines differed in chemical structure; the functional group present between the terminal amines was classified as follows: aliphatic group of 1,3-diaminopropane (DAPE); cyclohexane in 1,3-cyclohexanediamine (CHDA); and aromatic or benzene ring in m-phenylenediamine (MPD). For FO tests, deionized water and 1 M aqueous sodium sulfate solution were used as feed and draw solution, respectively. Interfacial polymerization conditions were also varied: concentrations of water and oil phases, time of contact between the water-phase solution and the membrane substrate, and polymerization reaction time. The resultant membranes were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy, field emission scanning electron microscopy, atomic force microscopy, and surface contact angle measurement to identify the chemical structure, morphology, roughness, and hydrophilicity of the polyamide layer, respectively. The results of FO experiments revealed that among the three diamine monomers, CHDA turned out to be the most effective, as it led to the production of TFC NF-like FO membrane with optimal performance. Then, the following optimum conditions were established for the CHDA-based membrane: contact between 2.5 wt.% aqueous CHDA solution and polysulfone (PSf) substrate for 2 min, and polymerization reaction between 1 wt.% TMC solution and 2.5 wt.% CHDA solution for 30 s. The composite CHDA-TMC/PSf membrane delivered a water flux (Jw) of 18.24 ± 1.33 LMH and a reverse salt flux (Js) of 5.75 ± 1.12 gMH; therefore, Js/Jw was evaluated to be 0.32 ± 0.07 (g/L).

Model development for estimating calcium sulfate dihydrate, hemihydrate, and anhydrite solubilities in multicomponent acid and salt containing aqueous solutions over wide temperature ranges

Thermodynamic solubility of calcium sulfate in multicomponent electrolyte aqueous solutions is of significant importance in many disciplines in science and engineering. A knowledge of environmental chemistry and aqueous solubility of calcium sulfate and several of its hydrates; anhydrite (CaSO4), hemihydrate (CaSO4.0.5H2O), and dihydrate (CaSO4.2H2O); in acid and salt-containing media is of huge practical and theoretical importance. In this study, a solubility calculation model was developed based on coupling of Least Squares Support Vector Machine and Coupled Simulated Annealing (CSA-LSSVM) to model the solubility of various forms of calcium sulfate in aqueous solutions over wide temperature ranges. Comparing the model results to 3079 experimental data gathered from the literature yields a correlation coefficient of 0.9897 and RMSE of 0.0068. The model is able to present accurate solubility results for calcium sulfate dihydrate (CaSO4.2H2O) in aqueous solutions containing H2SO4, ZnSO4, CuSO4, NiSO4, MnSO4, H3PO4, NaCl, CaCl2, MgCl2, KCl, FeCl2, Na2SO4, HNO3, Ca(NO3)2, HCl, AlCl3, Ca(HCO3)2, NaNO3, LiNO3, Li2SO4, MgSO4, Al2(SO4)3, NaClO4, NaOH, KOH at temperatures up to 100 °C, calcium sulfate hemihydrate (CaSO4.0.5H2O) in solutions containing NaCl, CaCl2, MgCl2, KCl, FeCl2, HCl at temperatures up to 125 °C, and calcium sulfate anhydrite (CaSO4) in solutions containing H2SO4, NaCl, CaCl2, MgCl2, Na2SO4, HNO3, HCl, NaNO3, LiNO3, NiSO4, MgSO4, Al2(SO4)3, Mg(NO3)2 at temperatures up to 350 °C. Comparison of the CSA-LSSVM model results to those of Pitzer ion interaction model as well as BR-ANN model in binary, ternary, and multicomponent mixtures reveals the superiority of the CSA-LSSVM model developed in this study in all cases.

Effect of Sodium Lauryl Sulfate (SLS) Applied as a Patch on Human Skin Physiology and Its Microbiota

In this study, we assessed the change in skin microbiota composition, relative abundance, and diversity with skin physiology disruption induced by SLS patch. Healthy women declaring to have a reactive skin were submitted to a 0.5% aqueous sodium lauryl sulfate solution application under occlusive patch condition for 24 h. Skin properties were characterized by tewametry, corneometry, and colorimetry and bacterial diversity was assessed by 16S rRNA sequencing. Analysis before and one day after SLS patch removal revealed an increase of skin redness and a decrease of stratum corneum hydration and skin barrier function. The relative abundance of taxa containing potential pathogens increase (Firmicutes: Staphylococcaceae; Proteobacteria: Enterobacteriaceae, Pantoea) while some of the most occurring Actinobacteria with valuable skin protection and repair capacities decreased (Micrococcus, Kocuria, and Corynebacterium). We observed an impaired skin barrier function and dehydration induced by SLS patch disturb the subtle balance of skin microbiota towards skin bacterial community dysbiosis. This study provides new insights on the skin bacterial composition and skin physiology simultaneously impaired by a SLS patch.

Zinc Borate Chemical Garden and Zinc Borate Powders from Tincal Mineral and Zinc Sulfate Heptahydrate

The formation of the first membrane, the swelling of the crystal by incoming water from the semipermeable membrane and the formation of irregular shaped branches were observed by optical microscopy, when zinc sulfate heptahydrate crystals were immersed in saturated borax solution. The powders obtained by mixing dilute aqueous borax and zinc sulfate solutions had B, O, Na, S and Zn elements. Presence of Na Zn 1/2B4O7.xH2O was indicated by EDX analysis. The molar ratio of B 2O3/ZnO in powders was around 2. FTIR analysis indicated the ratio of absorbance values of asymmetric stretching vibrations of B(3)-O at 1351 cm-1 to that of B (4)-O at 1026 cm-1 increased with their heating time at 90ºC during their preparation. X-ray diffraction patterns indicated the presence of Zn(OH)2 and Zn 4(OH)6(SO4)·4H2O. The zinc borate compounds in the powders were not crystalline since no sharp peaks related to zinc borates were present in x-ray diffraction diagram. There were two mass loss steps in TG curves of the powders. The first step at 150-350ºC and the second step at 700-950ºC were due to elimination of water and due to decomposition of sulfate ions respectively. The submicron powders were a mixture of zinc borate, Zn(OH)2, Zn4(OH)6(SO4)·4H2O and Na Zn 1/2B4O7.xH2O and they could be used as lubricant additive due to their small particle size of 600 nm.

Synergistic Action of Temperature and pH Factors in the Cleaning of Fatty Acids Soils; Analyzed by Probability Density Functional Method.

In this study, the interaction between the temperature and the pH of soil containing fatty acids with sodium dodecyl sulfate (SDS) aqueous solution was investigated to elucidate their synergistic effect in cleaning. A tergotometer was used for the cleaning test, and the cleaning results were analyzed by the probability density functional method, using the calculated parameter, µ rl , as an index of the cleaning power. The increase in µ rl by one of the factors was defined as ΔX or ΔY and the increase in µ rl by the both factors was defined as Δ(X + Y). It is assumed that there is a synergistic effect when Δ(X + Y) > ΔX + ΔY. The cleaning of fatty acid stains followed the addition rule pertaining to mechanical force and the pH effect. However, synergy was observed between the temperature and the pH effect. This was also supported by the plot of µ rl vs 1/T and observations using a phase-contrast microscope.

In-situ investigation of wetting patterns in polymeric multibore membranes via magnetic resonance imaging

Wetting of the membrane to displace air or conditioning liquids is important to exploit the complex porosity of a filtration membrane. This study reveals the details of wetting in multibore membrane-based filtration modules. Using magnetic resonance imaging (MRI), we quantify the fluid distribution patterns during initial membrane wetting in dead-end permeation mode. The spatio-temporal evolution of aqueous copper sulfate solution wetting the membrane fibers was investigated as a function of the applied flux, packing density, and position along the membrane module length.Three initial wetting conditions were examined: delivery-state membranes, ethanol-washed and dried (air-filled) membranes, and ethanol-filled membranes. Significant changes in wetting patterns were observed due to interfacial and polymer swelling effects. This in-situ investigation reveals a slow wetting progression over six hours and more to obtain complete wetting, even at high fluxes of 200 LMH. However, an increased flux leads to faster wetting kinetics as the evolving wetting patterns are flux dependent. The packing density of the multibore fibers additionally impacts the wetting kinetics by shifting the prevalent pressure conditions. Although in dead-end mode, the wetting progression is non-uniform along the membrane module length.In addition to this parameter study, different pre-wetting agents’ effect on the displacement behavior was investigated in depth. This study helps to understand (a) complex wetting phenomena inside multibore membranes in dead-end filtration, (b) the membranes’ interaction with their surroundings due to neighboring membranes, and (c) the effect of the used fluid system for displacement on the resulting wetting patterns.

SLES/CMEA mixed surfactant system: Effect of electrolyte on interfacial behavior and microstructures in aqueous media

In aqueous anionic sodium lauryl ether sulfate (SLES) solution, presence of nonionic cocamide monoethanolamine (CMEA) depicts intriguing interfacial and bulk properties. CMEA has poor water solubility but can be readily solubilized in SLES solution to form mixed micellar aggregates as revealed by surface tension measurements. Sphere-to-rod micellar transition in aqueous SLES-CMEA binary mixtures occurs at higher surfactant concentration (total surfactant concentration beyond 15 wt%), inducing a sharp growth in the viscosity (>1000 cP). Nevertheless, adding NaCl in SLES-CMEA mixtures, substantial growth in viscosity is perceived at much lower surfactant concentration (~5–10 wt%) attributed to the formation of intertwined worm-like micelles. Micellar sizes were obtained by dynamic light scattering (DLS) measurements and small-angle neutron scattering (SANS) investigations is used to determine micellar shapes and aggregation number for SLES-CMEA mixtures. Furthermore, it is observed that foaming behavior of SLES can be modulated by CMEA ascribed to the change in foam film rigidity. Corresponding experiments were also performed with nonethoxylated counterpart sodium lauryl sulfate (SLS) under analogous condition for comparison. The study reported here may prove to be an appropriate tactic to alter not only the rheology or foaming behavior of SLES-CMEA mixed surfactant system but also provide pre-solubilized composition of CMEA which could be highly beneficial for personal care products enabling CMEA blending at room temperature, which otherwise needs high temperature mixing.