Micellization and Clouding Behavior of EO–PO Block Copolymer in Aqueous Salt Solutions

Aqueous solution properties of polyethylene oxide–block-polypropylene oxide–block-polyethylene oxide TBP [(PEO)₁₀₃(PPO)₃₉(PEO)₁₀₃] were studied in the presence of sodium salts with different anions (NaI, NaBr, NaCl, NaF, Na₂SO₄, Na₃PO₄) to investigate unimer-to-micelle transition [critical micelle concentration (CMC), critical micellization temperature (CMT)], micelle size and the phase separation (cloud point). This TBP, due to its very hydrophilic (80% PEO) nature does not form micelles at ambient temperatures. Micellization can be induced much below its CMT in water on addition of sodium salts having different anions. Analytical methods viz. fluorescence, FTIR and dynamic light scattering (DLS) were used to monitor the salt-induced micellization. The hydration of respective anion and resultant contribution to its salting-out effect was found to be the governing factor in promoting micellization. The presence of salt decreases the CMC, CMT and phase separation temperature. The salts affect the aggregation process in agreement with an order mentioned in Hofmeister series.     

Effect of Hofmeister Ions on Transport Properties of Aqueous Solutions of Sodium Hyaluronate

Tracer diffusion coefficients obtained from the Taylor dispersion technique at 25.0 °C were measured to study the influence of sodium, ammonium and magnesium salts at 0.01 and 0.1 mol dm⁻³ on the transport behavior of sodium hyaluronate (NaHy, 0.1%). The selection of these salts was based on their position in Hofmeister series, which describe the specific influence of different ions (cations and anions) on some physicochemical properties of a system that can be interpreted as a salting-in or salting-out effect. In our case, in general, an increase in the ionic strength (i.e., concentrations at 0.01 mol dm⁻³) led to a significant decrease in the limiting diffusion coefficient of the NaHy 0.1%, indicating, in those circumstances, the presence of salting-in effects. However, the opposite effect (salting-out) was verified with the increase in concentration of some salts, mainly for NH₄SCN at 0.1 mol dm⁻³. In this particular salt, the cation is weakly hydrated and, consequently, its presence does not favor interactions between NaHy and water molecules, promoting, in those circumstances, less resistance to the movement of NaHy and thus to the increase of its diffusion (19%). These data, complemented by viscosity measurements, permit us to have a better understanding about the effect of these salts on the transport behaviour of NaHy.     

Cathodic reduction and infrared reflectance spectroscopy of basic copper(II) salts on copper substrate

Infrared reflectance spectroscopy and cathodic reduction have been used for the characterization of copper corrosion products formed by atmospheric corrosion. The following basic copper(II) salts were synthesized: atacamite and paratacamite (Cu₂Cl(OH)₃), brochantite (Cu₄SO₄(OH)₆), posnjakite (Cu₄SO₄(OH)₆.H20), malachite (Cu₂CO₃(OH)₂), gerhardite (Cu₂NO₃(OH)₃). The samples for analysis were obtained by incrustation of submicron particles of the compound on the surface of OFHC copper coupons. Infrared reflectance spectroscopy shows that, unlike copper oxides, the reflection spectra of thin layers of basic copper(II) salts on copper are similar to those obtained by the usual KBr-pellet method for the location of the bands. However, some differences occur in the intensities of the bands between the two modes. Infrared reflectance spectroscopy allows an easy identification of basic copper(II) salts: chlorides can be identified by their Cu-O-H bending modes; sulfates, sulfite, nitrate and carbonate by the internal mode of the corresponding anion (v ₃ region). The cathodic reduction analyses of the salts on copper display only a wide peak in the range from –0.6 to –0.55 V vs SCE, indicating that one step is involved. The potential of this cathodic reduction peak is distinguishable from the one of copper(I) oxides (–0.9 V vs SCE). Thereby the relative proportions of copper(II)) salts and copper(I) oxides present in the corrosion layer can be determined.     

Determination of pK a Values of Oxocholanoic Acids by Potentiometric Titration

The pK _a and the maximum solubility values of cholic, deoxycholic salts and their oxo-derivatives have been measured by the method of potentiometric titration. In the monomer phase (under the critical micellar concentration, CMC), the bile salts have different pK _a values, as a result of their structural differences (the number of hydroxyl and oxo groups in the steroid skeleton) and different hydration properties of the acid anions. In the micellar phase (above the CMC), the bile salts have higher pK _a values than in the monomer phase (under the CMC). This increase in the pK _a values is greater in more hydrophobic bile salts (cholate and deoxycholate), than in less hydrophobic oxo derivatives, which can be explained by the different aggregation numbers of these bile salts. The oxo-derivatives are more likely to form dimeric micelles, where the carboxylic groups are situated on the two sides of the micelle, not causing any electrostatic repulsion. In the more hydrophobic bile salts, aggregation numbers are higher, which causes electrostatic repulsion of the nearby situated carboxylic anions and consequential protonation of these anions (which leads to the stabilization of the micelle). The maximum solubility values are higher for the oxo-derivatives. If the steroid skeleton of the bile salt is more hydrophobic, the capacity to solubilize the unionized bile acid is higher, i.e. a smaller amount of the bile acid anion is needed for the solubilization of the bile acid monomer. The oxo-derivatives are less hydrophobic, but alongside their hydrophobicity, the structure of the micelle determines the solubilization capacities.     

The solubilities of phosphate and sulfate salts in supercritical water

Inorganic compounds are regularly present in aqueous streams. To understand their influence and behavior on these streams at supercritical conditions, little to no property data is available, which can be used as starting point for further research or application design. Since inorganic compounds tend to precipitate at these conditions, scaling, blocking and erosion can occur as a consequence. Furthermore, a separation of (precious) compounds from the bulk stream due to the precipitation is possible. Here, phosphate compounds are regarded as interesting for further investigation since resources are assumed to be depleted in future. As phosphate is present in many waste streams, these could be used as sources for recoverable phosphate. Resulting from these facts and options, a proper understanding and knowledge of these systems is important for later industrial applications. Therefore, the authors have investigated the behavior of salts (e.g. NaCl, NaNO₃ and MgCl₂) in supercritical water in previous works.To extend this knowledge, the solubilities of the sulfate salts MgSO₄ and CaSO₄ in a range of 18.8-23.2 MPa and 655-675 K as well as of the phosphate salts Na₂HPO₄, NaH₂PO₄ and CaHPO₄ in a range of 20.5-24.2 MPa and 665-690 K were investigated in this work with a continuous flow method in continuation of former work of the authors. The solubilities were compared with existing data available from open literature. A quantitative correlation on base of a phase equilibrium between the present phases was used to describe the behavior and to compare it with previous results. For the investigated calcium salts, CaSO₄ and CaHPO₄, it was found that a significant solubility decrease already happens at subcritical conditions resulting in precipitation in unwanted locations. For the remaining compounds, a parallel hydrolysis reaction was found as could be seen from a change in pH in the effluent stream.     

Mixed Micellization and Mixed Monolayer Formation of Sodium Cholate and Sodium Deoxycholate in Presence of Hydrophobic Salts Under Physiological Conditions

Mixed micellization and mixed monolayer formation of two bile salts namely sodium cholate (NaC) and sodium deoxycholate (NaDC), in the presence of sodium chloride (NaCl) and three hydrophobic salts including sodium acetate (NaAc), sodium butanoate (NaBu) and sodium hexanoate (NaHx) in 10 mM phosphate buffer (pH 6.5) at 37 °C were investigated by means of surface tension measurements. The experimental results were utilized to evaluate various parameters like critical micellar concentration (CMC), micellar and monolayer interaction parameter (β and β ^σ), micellar and monolayer mole fractions (X and Z), activity coefficients of two bile salts in mixed micelles and monolayer (f and f _(σ)), surface excess (Γ_max) and minimum surface area per molecule of bile salt (A _min). Mixed micelles and mixed monolayer were found to show slight non-ideality and both these phenomena have been found to be affected differently in the presence of various additive salts with NaHx showing larger effects. Higher efficiency of NaHx in affecting both phenomena has been attributed to its appreciable hydrophobicity and surface activity, thus showing stronger interactions with bile salt molecules.     

Experimental study of the influence of sodium salts as additive to NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>OUT process

An experimental study of the SNCR process with urea as reducing agent and sodium salts as additive has been carried out, and detailed analysis of the reaction mechanism has been given here. In the temperature range of 800–975 °C, NO concentration decreases at first and then increases while the concentration of N₂O increases at first and then decreases with the increasing of temperature, and the turning point is 900 °C. With increasing of normalized stoichiometric ratio of reduction nitrogen to NO _x (NSR), NO removal efficiency increases, while the concentration of N₂O also increases, which decreases overall NO _x removal efficiency. With sodium salts as additive, the concentration of N₂O decreases with increasing of sodium salts addition at all temperatures, while the concentration of NO decreases at first and then increases at low-temperature side of the temperature window and increases at high-temperature side with additional increasing, whose changing extent is smaller than N₂O. Since sodium salts as additive can remove N₂O effectively and have no large influence on the removal of NO, the effect of sodium salts as additive is the combined effect of the production of active radicals and the removal of HNCO produced by the decomposition of urea through neutralization reactions, which is more important. To achieve the same effect under each condition, the needed addition of NaOH and CH₃COONa is less than that of Na₂CO₃ counting as Na atom. For the decomposition of CH₃COONa can produce CH₃COO, its addition can promote the reduction of NO more obviously at the lower temperature than Na₂CO₃ or NaOH. Overall NO _x removal efficiency at 900 ‡C with NSR=1.5 had been improved from about 30% to 70.45% through the addition of sodium salts. Sodium salts as additive caused the flue gas to become alkaline gas, but it was not serious for sodium salts existing as NaNCO.     

Extraction of Actinides from a Chloride Medium Using Pentaalkylpropanediamides

Abstract

Pyrometallurgical processes for the purification of plutonium for defense create waste solutions containing actinides, mainly americium, in chloride medium. Studies have been undertaken to study the extraction of actinides in a chloride medium (hydrochloric acid mixed with concentrated salts such as LiCl, CaCl₂, MgCl₂, KCl) using pentaalkylpropanediamides as extractants. Plutonium(IV) is very easily extracted, but Am(III) needs a salting-out agent such as LiCl. Back extraction of trivalent cations is easy in HCl <5 M . Plutonium(IV) and (VI) can be stripped by reduction either with ascorbic acid or hydroxylammonium salts in a weak-acid medium. Several diluents can be used (aromatic, chlorinated, or even aliphatic) with addition of decanol to prevent third-phase formation. In conclusion, diamides can be used for declassification of various wastes, they are potentially completely incinerable, and, as the synthesis has been optimized, they appear to be promising extractants.     

Effect of Inorganic Salts on the Aggregation Behavior of AOT at the Air/Water Interface

The aggregation behavior of sodium bis-(2-ethylhexyl)-sulfosuccinate (AOT) at the air/water interface in the absence and presence of inorganic salts was investigated by molecular dynamics simulation. Both monovalent and divalent ions were studied, such as LiCl, NaCl, KCl, MgCl₂ and CaCl₂. It has been proved that these inorganic ions have great influence on the structure of the AOT monolayer and water molecules around its headgroup. In the presence of inorganic salts, AOT molecules are relatively ordered at the interface and water around the headgroups of AOT shows a lower diffusion coefficient compared with the situation without inorganic salts. All the counterions are prone to move toward the headgroups and locate at the interface. Divalent ions have a strong interaction with AOT, thus they affect the aggregation behavior of AOT remarkably.     

Effect of blended inorganic salts containing negative hydration ions on hydration and properties of alkali-activated slag cement

Water glass (WG) is generally considered to be the most effective activator to prepare alkali-activated slag (AAS) cement in terms of strength and durability. However, the rapid setting and hardening of WG activated slag results in rapid loss of fluidity of AAS concrete mixture, which limits its engineering application. In the paper, the effect of blended inorganic salts containing negative hydration ions on the fluidity, setting time and mechanical strength of AAS cement was studied. The hydration process and hydration products were used to explore the action mechanism. Ba(NO₃)₂ greatly delayed the hydration of AAS cement. The four inorganic salts (KCl, KNO₃, KBr and NaCl) blended with a small amount of Ba(NO₃)₂ can improve both the initial fluidity and fluidity retention, and a wide setting time range can be obtained to meet engineering requirements. The compressive strength decreased with the increase of inorganic salts. The incorporation of inorganic salt did not change the composition of the main hydration products. Considering the fluidity required by construction, mechanical properties and the durability of structure, it is recommended to add 4%–5% KBr or KNO₃ blended with no more than 0.2% Ba(NO₃)₂ into AAS cement.     

Mode of action of ferric and ferrous iron salts in activated sludge

BACKGROUND: Both ferric iron Fe(III) and ferrous iron Fe(II) salts are commonly used for chemical phosphorus removal (CPR) in the activated sludge (AS) process but only a few studies have compared Fe(III) and Fe(II) salts regarding their effect on the physical and biological properties of AS. In this research, the units of a continuous flow laboratory‐scale AS plant were dosed with Fe(III) and Fe(II) salts at a concentration of 25 mg Fe dm^?3 feed and changes in the AS properties were measured as Fe accumulated or washed out during startup, normal operation and withdrawal of dosing. RESULTS: The morphological characteristics of the flocs showed marked differences depending on the type of ion used. Fe(II) dosed flocs were more compact, less filamentous and smaller in size than Fe(III) dosed flocs. The settleability index of the Fe(II) dosed sludge was lower than that of the Fe(III) dosed sludge. The activity of ammonium (NH₄⁺‐N) and nitrite (NO₂^?‐N) oxidizing bacteria was found to be affected by the accumulation of Fe relating products into the sludge. CONCLUSIONS: Fe(II) was a more effective flocculent than Fe(III) and this was attributed to its ability to form stronger ionic bonds with the flocs prior to its oxidation to Fe(III). A hypothesis explaining the mode of action of Fe(II) is proposed. Floc surface properties were enhanced, this being beneficial to the morphological characteristics and settleability with further implications for the operation of AS. However, the effect may be reversed at high Fe contents. Copyright © 2010 Society of Chemical Industry     

Quaternary salts as solubilization site modifiers of organic compounds in anionic micellar solutions

The effects of the addition of different salts (quaternary bromides or NaBr) on the viscosity (measured under Newtonian flow conditions) of sodium dodecylbenzenesulfonate (SDBS) micellar solutions were studied at 30°C. Tetra-n-butylammonium bromide (Bu₄NBr) was found most effective in increasing the viscosity (due to possible change in micellar shape) at fairly low SDBS concentration (50 mM). The effectiveness of Bu₄NBr may be due to the presence of four butyl chains and to the positive charge on its counterion (Bu₄N⁺) which can subsequently interact with anionic SDBS micelles electrostatically as well as hydrophobically; owing to solubility/steric problems, other salts were ineffective. Organic additives such as cyclohexylamine and cyclohexanol had marginal effects on viscosity when added to 50 mM SDBS solutions having no Bu₄NBr. However, in the presence of Bu₄NBr, the effect was dependent on salt concentration and the nature of the additive. The overall effect is discussed on the basis of change in the solubilization site of the additive in the presence of Bu₄NBr.     

Ionic Liquids and Salts from Ibuprofen as Promising Innovative Formulations of an Old Drug

Herein we report the synthesis of novel ionic liquids (ILs) and organic salts by combining ibuprofen as anion with ammonium, imidazolium, or pyridinium cations. The methodology consists of an acid–base reaction of neutral ibuprofen with cation hydroxides, which were previously prepared by anion exchange from the corresponding halide salts with Amberlyst A-26(OH). In comparison with the parent drug, these organic salts display higher solubility in water and biological fluids and a smaller degree of polymorphism, which in some cases was completely eliminated. With the exception of [C₁₆Pyr][Ibu] and [N_1,1,2,2OH1][Ibu], the prepared salts did not affect the viability of normal human dermal fibroblasts or ovarian carcinoma (A2780) cells. Therefore, these ibuprofen-based ionic liquids may be very promising lead candidates for the development of effective formulations of this drug.     

Isothermal and nonisothermal crystallization kinetics of isotactic polypropylene nucleated with substituted aromatic heterocyclic phosphate salts

The crystallization kinetics of isotactic polypropylene (iPP) and nucleated iPP with substituted aromatic heterocyclic phosphate salts were investigated by means of a differential scanning calorimeter under isothermal and nonisothermal conditions. During isothermal crystallization, Avrami equation was used to describe the crystallization kinetics. Moreover, kinetics parameters such as the Avrami exponent n, crystallization rate constant Z_t, and crystallization half‐time t_1/2 were compared. The results showed that a remarkable decrease in t_1/2 as well as a significant increase in overall crystallization rate was observed in the presence of monovalent salts of substituted aromatic heterocyclic phosphate, while bivalent and trivalent salts have little effect on crystallization rate of iPP. The addition of monovalent metal salts could decrease the interfacial free energy per unit area perpendicular to PP chains σ_e value of iPP so that the nucleation rate of iPP was increased. During nonisothermal crystallization, Caze method was used to analyze the crystallization kinetics. It also showed that monovalent metal salts had better nucleation effects than bivalent and trivalent metal salts. From the obtained Avrami exponents of iPP and nucleated iPP it could be concluded that the addition of different nucleating agents changed the crystal growth pattern of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3307–3316, 2006     

Amphiphilic microblock tough cationic hydrogels with reduced permeability of the fluid channels: synthesis and properties

The high permeability channels would reduce the ultimate oil production resulting from excess water flooding. The objective of this paper is to prepare and evaluate a novel tough gel that can be used to significantly reduce the permeability of the fluid channels. We synthesized the hydrophobic associated hydrogel composed of poly(acrylamide-co-diacryl quaternary ammonium salts) (G(AM/DiAC)) by simple aqueous solution copolymerization method. Here, three diacryl quaternary ammonium salts are cation surfmer with different alkyl lengths (DiAC, carbon chain length?=?6, 8, 10, respectively). The gel properties, including the mechanical performance and swelling property, as well as its influencing factors were investigated. The results showed that G(AM/DiAC) hydrogel has excellent mechanical properties. It was found that its mechanical properties were dependent on the alkyl length and dosage of surfmer. When carbon chain of DiAC was C₈ and the dosage of DiAC₈ reached 0.5 mol%, G(AM/DiAC₈) hydrogel showed the most excellent mechanical performance (tensile strengths?=?58.97 kPa, elongation-at-break?=?3712% and compressive strengths?=?100.01 kPa). The toughness mechanism derived from the increase in the sequence length and number of hydrophobic micro-blocks in the molecular chains of hydrogels. Furthermore, the hydrogels exhibited slow swelling property, in favor of deep migration and plugging high permeable layer. The swelling equilibrium time of hydrogels was prolonged by 10 days when the dosage of DiAC₁₀ reached 0.9 mol%, by reason of the intermolecular dissociation between hydrophobic micro-blocks.     

Reverse osmosis separation of inorganic salts using polyvinylalcohol membranes

Permeabilities and fluxes of fifty-four mono-, divalent anions and cations of sodium and chloride salts have been tested under experimental conditions of 50 bar and room temperature through asymmetric polyvinylalcohol membranes crosslinked with formaldehyde. The following percent rejections among these salts are given: sodium salts of divalent anions (70–80%), chloride salts of divalent cations (30–40%), H₂ SO₄ (30%), sodium salts of monovalent monoatomic anions, chloride salts of monovalent cations (15– 30%) and HCl, HNO₃, NaOH, KOH (10–20%). Sodium salts of monovalent polyatomic anions gave higher rejections than those of monovalent monoatomic anions. Higher rejection of divalent anions than that of divalent cations of chloride salts suggests that the membrane surface is negatively charged.     

Preparation and characterization of gel polymer electrolyte based on PVA-K2CO3

ABSTRACT

In this study, electrolyte materials were synthesized by mixing a highly conducting salt (K₂CO₃) with the poly(vinyl alcohol) (PVA) in different proportions (from 10 to 50 wt.%). The synthesized electrolyte was characterized using Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) for their functional groups, morphology, thermal stability, glass transition temperature (T_g ), ionic conductivity, and potential window, respectively. Characterization results show that the complex formation between PVA and K₂CO₃ salt has been established by FTIR spectroscopic study, which indicates the detailed interaction between PVA and the salts in PVA-K₂CO₃ composites while the amorphous nature of the electrolyte after incorporation of the salts has been confirmed by FESEM analysis. Similarly, TGA and DSC analysis revealed that both decomposition temperature and T_g of the synthesized electrolytes decrease with the addition of K₂CO₃ due to the strong plasticizing effect of the salt. The results confirm that the electrolytes have sufficient thermal stability for supercapacitor operation, as well as an amorphous phase to effectively deliver high ionic conductivity. The highest ionic conductivity of 4.53 × 10^?3 S cm^?1 at 373 K and potential window of 2.7 V was exhibited by PK30 (30 wt.% K₂CO₃), which can be considered as high value for solid-state electrolytes which are superior to those electrolytes from PVA salts earlier reported. The results similarly show that the prepared electrolyte is temperature-dependent as conductivity increase with increase in temperature. Based on these properties, it can be imply that the PVA-K₂CO₃ gel polymer electrolyte (GPE) could be a promising electrolyte candidate for EDLC applications. The results indicate that the PVA-K₂CO₃ as a new electrolyte material has great potential in practical applications of portable energy-storage devices.     

Zur Acylierbarkeit des Phosphorylsauerstoffs. I. Acyloxyphosphoniumsalze aus Hexamethylphosphorsäuretriamid und Carbonsäurederivaten

On the Acylation of the Phosphoryl Oxygen. I. Acyloxyphosphonium Salts from HMPT and Carboxylic Acid Derivates Acylation equilibria with participation of acyloxyphosphonium ions exist in solutions of HMPT and carboxylic chlorides, or anhydrides, respectively, as can be shown by ³¹P-n.m.r. after trapping the counter ion with SbCl₅. Moderately stable acyloxyphosphonium salts have been isolated for the first time by acylation of HMPT. In the alternative reaction of (Me₂N)₃P with CCl₄ and carboxylic acids, acyloxyphosphonium salts are formed only after prolonged reaction times, due to the stability of the intermediate chlorotris-(dimethylamino)-phosphonium ion.     

Measurement and prediction of gas hydrate and hydrated salt equilibria in aqueous ethylene glycol and electrolyte solutions

A recently developed method in modelling electrolyte solutions is extended to include phase behaviour of aqueous solutions containing hydrated salts (e.g., calcium chloride) and organic hydrate inhibitors (e.g., ethylene glycol). A novel salt precipitation model applicable to various hydrated salts is presented. The precipitation model takes into account various precipitates of hydrated salts over a wide range of temperature (i.e., -20-120 ^°C). Due to lack of the required experimental data in the literature, new experimental data have been generated. These data, which have been used in determining the binary interaction parameters between salts and organic inhibitors, include; freezing point depression, boiling point elevation, and salt solubility in the aqueous solutions containing salts and organic inhibitors. The extended thermodynamic model is capable of predicting complex vapour-liquid-solid equilibria (VLSE) for aqueous electrolytes and/or organic inhibitor solutions over a wide range of pressure, temperature and inhibitor concentration.In addition, in order to establish the effect of a combination of salts and organic inhibitors on the locus of incipient hydrate-liquid water-vapour (H-L_W-V) curve, reliable equilibrium data have been generated for one quaternary system, methane/water/calcium chloride/ ethylene glycol at pressures up to 50 MPa. These data along with various independent literature data are used to validate the predictive capabilities of the model for phase behaviour and hydrate equilibria. Good agreement between experimental data and predictions is observed, demonstrating the reliability of the developed model.