Effects of Inorganic Salts and Polymers on the Foam Performance of 1-Tetradecyl-3-methylimidazolium Bromide Aqueous Solution

The foaming performance of 1-tetradecyl-3-methylimidazolium bromide (C₁₄mimBr) aqueous solution, in the presence of polymers (PEG or PVA) or inorganic salts (NaBr, MgCl₂, NaNO₃, Na₂SO₄ or Na₃PO₄), was investigated at 25.0?°C by using the self-made apparatus and the conductivity method. The experimental results show that the foaming ability and foam stability of the ternary aqueous systems of C₁₄mimBr coexisting with PEG or PVA are stronger than those of the C₁₄mimBr solutions in the absence of a polymer, and both the efficiency of foaming ability and foam stability of the surfactant solutions are evidently enhanced with an increase in polymer concentration. However, the addition of inorganic salts can decrease the foaming ability and foam stability of C₁₄mimBr solution. Especially, the inorganic salts, with high valence state of the anion (SO₄ ^2? and PO₄ ^3?), are good antifoam agents which can remove and inhibit foam quickly. For the aqueous solution of the surfactant, the effect of temperature on foaming properties was also examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions decrease with an increase in the temperature within the range from 25.0 to 45.0?°C.     

Surface active N-acylglutamate: II. Physicochemical properties of long chain N-acylglutamic acids and their sodium salts

The physicochemical properties of long chain N-acylglutamic acids (AGA) and their sodium salts (AGS_n) are described. The solubility, Krafft point, pH value, critical micelle concentration, surface tension and foaming power were measured. The properties of the optically active AGA or AGS_n differed from those of the corresponding racemates, especially in solubility. The monosodium salts generally had high Krafft points, but monosodium N-oleoylglutamate had a low Krafft point. The monosodium salts hydrolyzed in the diluted aqueous solution to liberate the AGA. The aqueous solutions of the monosodium salts had low surface tensions and good foaming properties. The disodium salts were highly soluble in water, while surface tensions and foaming properties were inferior to those of the corresponding monosodium salts.     

Rheological characteristics of foamed gel for mine fire control

Foamed gel as a new type of fire extinguishing material is used to prevent the spontaneous combustion of coal. In order to make a comprehensive study on rheological characteristics of foamed gel for mine fire control, by using type NDJ‐5s digital viscometer, the factors such as mass concentration of the mixture mixed by thickener and crosslinker, foaming multiple, added salts (NaCl, CaCl₂, AlCl₃), pH value and temperature having influences on the rheological properties of foamed gel have been investigated in this paper. It can be found that foamed gel shows the characteristic of non‐Newtonian fluids and has shear‐thinning properties. With increasing of mass concentration of the mixture, the thixotropy response becomes more significant. When the foaming multiple reaches 20, the apparent viscosity gets the maximum value. The obvious viscosity characteristic of ‘polyelectrolyte solution’ is observed in aqueous salt solutions when added salts are put into the solution. Under different conditions of pH values, foamed gel has higher sensitivity to acid than alkaline. Zero shear viscosity, depending on temperature, decreases with the temperature increasing. Meanwhile, the fire performances of foamed gel are studied experimentally and theoretically. Copyright © 2014 John Wiley & Sons, Ltd.     

Degradation of phenolic aqueous solutions by high frequency sono-Fenton systems (US–Fe2O3/SBA-15–H2O2)

The aim of this work is to establish the influence of different ultrasonic frequencies ranging from 20 to 1142 kHz on the efficiency of the US/Fe₂O₃/SBA-15/H₂O₂ (sono-Fenton) system. The frequency of 584 kHz has been established as the optimum ultrasonic irradiation for the degradation of aqueous phenol solutions by the sono-Fenton system and the effect of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6 g/L and hydrogen peroxide concentration, close to the stoichiometric amount, show high organic mineralization, accompanied by excellent catalyst stability in a wide range of concentrations of aqueous phenol solutions (0.625–10 mM). Additionally, the catalyst can be easily recovered by filtration for reuse in subsequent reactions without appreciable loss of activity. The coupling of US (584 kHz)/Fe–SBA-15/H₂O₂ at room temperature is revealed as a promising technique for wastewater treatment. Additionally, a new sono-Fenton variant, the so-called latent remediation has also been studied, using ultrasonic irradiation only as pretreatment for 15 min in an attempt at reducing the cost of the degradation process. It has been observed that latent remediation provides TOC degradation of around 21% after 15 min sonication followed by 6 h silent reaction while the typical sono-Fenton reaction affords 29% TOC reduction after 6 h sonication.     

Agent distribution and water remaining of polyester nonwoven fabrics after‐treated with polyurethane–citric acid

Polyester nonwoven fabric samples were used to treat with aqueous solutions of water‐soluble polyurethane (PU) containing the foaming agent, citric acid, or the mixtures of foaming agent and citric acid to examine the water remaining and the degradation of PU under the simulative condition of under ground. The results reveal that the viscosity of PU solutions could affect the values of pickup and add‐on. The water remaining values for PU containing citric acid are higher than those for PU containing the foaming agent and PU containing the foaming agent and citric acid. The pore structures, nonwoven construction, and the pores caused by the aggregation of PU within/on the treated nonwoven fabrics can affect the water remaining. From the observation of SEM and the comparison of FTIR, the degradation of water‐soluble PU resin is proved, which could form the rough porous surface of PU resin on the fiber surface as a factor improving the water remaining. The value of water remaining for PU containing citric after 60 weeks' treatment is significantly higher than the pristine nonwoven fabric (control). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 47–56, 2006     

Foamability of Detergent Solutions Prepared with Different Types of Surfactants and Waters

In the development of new detergent products, it is important to test the foaming behavior of different types of surfactants. Different types and concentrations of surfactant solutions prepared with three types of water are expected to present differences in their foamability. In this study, foam volumes produced by cetyl trimethyl ammonium bromide (CTAB; C₁₉H₄₂BrN), Tween 80^® (T80; C₆₄H₁₂₄O₂₆) and sodium dodecylsulfate (SDS; C₁₂H₂₅NaO₄S) aqueous solutions (0.5, 1.0 and 1.5%, w/v) were compared using a stirring system, rotating at 8,000, 9,500 and 13,500 rpm. The foamability produced by CTAB, SDS and T80 solutions, in a concentration range between 0.2 and 1.0% (w/v), prepared using deionized, hard and hypersaline water were also compared. Foam volumes were higher at a stirring speed of 9,500 rpm than at 8,000 rpm. However, the results obtained at 9,500 and 13,500 rpm were not significantly different. In general, SDS solutions produced higher foam volumes than CTAB and T80 solutions. Water characteristics did not seem to influence significantly the foamability of the three types of surfactants in the studied concentrations. These studies related with foaming behavior appear to be an important step in the pre-formulation of detergent products, particularly in cosmetics and pharmaceutics.     

Synergism in binary mixtures of surfactants. 7. Synergism in foaming and its relation to other types of synergism

The relationship between synergism in Ross-Miles foaming and the existence of other types of synergism in binary mixtures of surfactants has been investigated. All studies were conducted in solutions of constant ionic strength (0.1 M NaCl) at 25 and/or 60 C. Six anionic-zwitterionic or anionic-nonionic mixtures and a sodium dodecylbenzenesulfonate (LAS)-soap mixture, all consisting of commercial surfactants, were studied. Synergism in foaming effectiveness, measured by initial foam heights, appears to be related to synergism in surface tension (γ) reduction effectiveness, but not to synergism in γ reduction efficiency or in mixed micelle formation. The LAS-soap system showed negative synergism in foaming effectiveness, correlated with negative synergism in γ reduction effectiveness, the conditions for which are defined. There appears to be no correlation between synergism in foaming efficiency and synergism in either γ reduction efficiency or mixed micelle formation. There also appears to be no unambiguous relationship between foam stability, measured by the ratio of the 5-minute to the initial foam height, and the average area per surfactant molecule at the aqueous solution/air interface. Presented in part at the American Oil Chemists’ Society meeting in New Orleans in May 1987.     

Inkjet printing of photocatalytically active TiO2 thin films from water based precursor solutions

In this work, aqueous chemical solution deposition route suited for inkjet printing is used for the synthesis of photocatalytically active TiO₂ coatings. Environmentally friendly precursor solutions with electromagnetic ink-jet printing, allows cheap and simple processing of TiO₂ films on glass. The hydrolysis reaction of water sensitive titanium alkoxide (Ti-alkoxide) precursor is controlled by adding complexing agents as citric acid and triethanolamine prior to water addition, and aqueous stable solutions are achieved. The pH of the solutions is brought to neutral to guarantee flexible processing, avoid damage to substrates and equipment. Solution parameters are adapted to obtain optimal gelation conditions and good jettability. The influence of processing parameters on the phase formation and surface morphology is studied by thermogravimetric analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The photocatalytic activity of the films is evaluated by the degradation of methyl orange.     

Solvent extraction of gold by LIX 79: experimental equilibrium study

The extraction of gold(I) from aurocyanide aqueous solutions using LIX 79 has been studied. Different variables that could affect the extraction system were evaluated: equilibration time, aqueous pH, metal and extractant concentrations, organic phase diluent and aqueous ionic strength. The extraction of the aurocyanide complex with respect to other metal‐cyano complexes has also been studied on both synthetic and real leach solutions. Gold experimental data have been analysed numerically to determine the stoichiometry of extracted species and its equilibrium constant. It was found that gold(I) was extracted into the organic phase by the formation of the species RHAu(CN)₂ (LIX 79=R). Stripping of gold from loaded organic phases was carried out using NaOH or NaCN solutions. © 1999 Society of Chemical Industry     

Studies of activated charcoal cloth. II. Influence of boron-containing impregnants on the rate of activation in carbon dioxide gas

The influence of aqueous solutions of boron-containing compounds as impregnants of viscose rayon cloths on the subsequent activation of the derived carbonised materials in CO₂ gas at 850°C has been studied. The presence of Na⁺ (or other alkali metal ions) is essential for the enhancement of the rate of activation above that observed for the untreated cloth or for the cloth initially impregnated with aqueous boric acid solutions. However, in terms of the activation rate generated, borax is more effective as an additive to boric acid solutions than sodium chloride.The results are interpreted in terms of the catalytic abilities of various alkali metal ions in the systems studied and the complexity of the borate species generated at different pH values in the aqueous impregnant solutions employed.     

Kinetic study of photodegradation of water soluble polymers

The kinetic models of the photo-oxidative degradation of water-soluble polymers, as the main component of water-soluble composite films in aqueous solutions, by ultraviolet radiation and hydrogen peroxide (UV/H₂O₂) are developed. The rate expressions of the photochemical degradation of soluble polymers are developed based on the mass balance of the main chemical species in water. Continuous-distribution kinetics is applied for the kinetic modeling of the photo-oxidative degradation of polymers in aqueous solutions based on the population balance equations (PBEs). It is assumed that the random chain scission is the mechanism of the chain cleavage. The PBEs are solved by the moment operation which transforms the integro-differential equations into ordinary differential equations that could be readily solved to obtain the rate coefficients of the polymer photodegradation. The model predictions for the number average molecular weight and the number of chain scissions per molecules are in good agreement with the experimental data obtained from the open literature for the photodegradation of poly(ethylene glycol) by the UV/H₂O₂ process in aqueous solution. The results confirmed the random chain scission assumption. The sequential quadratic programming was used as an optimization technique to find the kinetic parameters that could be used for scaling-up purposes.     

Batch foaming of SAN/clay nanocomposites with scCO2: A very tunable way of controlling the cellular morphology

This paper aims at elucidating some important parameters affecting the cellular morphology of poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposite foams prepared with the supercritical CO₂ technology. Prior to foaming experiments, the SAN/CO₂ system has first been studied. The effect of nanoclay on CO₂ sorption/desorption rate into/from SAN is assessed with a gravimetric method. Ideal saturation conditions are then deduced in view of the foaming process. Nanocomposites foaming has first been performed with the one-step foaming process, also called depressurization foaming. Foams with different cellular morphology have been obtained depending on nanoclay dispersion level and foaming conditions. While foaming at low temperature (40 °C) leads to foams with the highest cell density (∼10¹²-10¹⁴ cells/cm³), the foam expansion is restricted (d∼0.7-0.8 g/cm³). This drawback has been overcome with the use of the two-step foaming process, also called solid-state foaming, where foam expansion occurs during sample dipping in a hot oil bath (d∼0.1-0.5 g/cm³). Different foaming parameters have been varied, and some schemes have been drawn to summarize the characteristics of the foams prepared - cell size, cell density, foam density - depending on both the foaming conditions and nanoclay addition. This result thus illustrates the huge flexibility of the supercritical CO₂ batch foaming process for tuning the foam cellular morphology.     

AN EXPERIMENTAL STUDY OF GAS HOLDUP IN TWO-PHASE BUBBLE COLUMNS WITH FOAMING LIQUIDS

Gas-liquid upward flow experiments have been performed in two bubble columns of different diameters (0.10 and 0.29 m,) using air as gas phase and several liquids: water, aqueous solutions of ethanol and glycerine, kerosene, and a solution of a surfactant in kerosene. The main goal of the study is the analysis of foaming systems, including the comparison of their behavior with respect to non-foaming systems. The gas holdup was determined experimentally as a function of the gas and liquid superficial velocities in bubbling, churn-turbulent and foaming regimes. It was found that, for foaming systems, semi-batch operation enhances foam formation, yielding higher holdups than those obtained in continuous operation at very low liquid velocities. Opposite to what is observed in non-foaming systems, the liquid superficial velocity affects the gas holdup appreciably in foaming systems. An increase in column diameter results in a decrease in gas holdup for all the systems studied. In aqueous foaming systems, this trend is more drastic since foam is inhibited as the column diameter increases.     

Solvent extraction of silver by LIX® 79: experimental equilibrium study

The extraction of silver(I) from argentocyanide aqueous cyanide solutions using LIX^® 79 has been studied. Different variables that could affect the extraction system were evaluated: equilibration time, aqueous pH, metal and extractant concentrations, and organic phase diluent. The extraction of the Ag(CN)₂^? complex with respect to other metal‐cyano complexes has also been studied on both synthetic and real leach solutions. Experimental data relating to silver have been analysed numerically to determine the stoichiometry of the extracted species and its equilibrium constant. It was found that silver(I) was extracted into the organic phase by the formation of the species RHAg(CN)₂ (LIX 79 = R). Copyright © 2004 Society of Chemical Industry     

Prolonged degradation of end-capped polyelectrolyte multilayer films

Cationic chitosan (CT) and anionic dextran sulfate (Dex) were layer-by-layer (LbL) assembled from aqueous solutions containing 1 M NaCl on a quartz crystal microbalance (QCM) substrate, and the original films ((CT-Dex)₃-CT)) were end-capped with LbL assembly from CT solutions containing 1 M NaCl and Dex solutions without NaCl. The enzymatic degradation of films by chitosanase was quantitatively analyzed by QCM in terms of numbers of end-capping steps. The degradation of films end-capped with (Dex-CT)₃ was considerably prolonged when compared to those end-capped with other end-capping steps. A mechanism for the prolonged degradation was proposed by quantitative QCM data and zeta potential results.     

Degradations‐ und Energieverhalten reaktiver Amin‐Lösungen bei der CO2‐Absorption/Desorption

Reactive absorption using aqueous amine solutions is the technically most feasible retrofit option for the separation of CO₂ from flue gases. Frequently discussed issues are the realization of a cost‐effective increase in efficiency in the sophisticated overall absorption process and the minimization of the energy demand for solvent regeneration under operating conditions. However, the influence of degradation phenomena on capacity and energy efficiency during the absorption‐regeneration cycles using blended monoethanolamine solutions has been less considered so far. The decrease in capacity depends in particular on time, temperature, O₂‐ and SO₂ concentration in the flue gas and has to be considered in plant design. Addition of degradation inhibitors decreases the energy requirements.     

Photocatalytic Cyanide Oxidation from Aqueous Copper Cyanide Solutions over TiO2 and ZnO

The elimination of cyanide from aqueous copper cyanide solutions by oxidation under UV illumination using titanium oxide (TiO₂) and zinc oxide (ZnO) as catalyst has been investigated. The study has been carried out by determining the yield of cyanide elimination at different irradiation times, initial cyanide concentrations and pH. It has been observed that cyanide is photo-oxidised with higher yields in presence than in absence of copper in solution when TiO₂ is used as photocatalyst, while the opposite behaviour is reported when ZnO is the photocatalyst employed. This fact is related with the feasibility in which copper species are able to react with photogenerated electrons in the conduction band of the TiO₂ particles. Finally, the elimination of cyanide, both free and complexed, from a sample of an electroplating bath has also been studied. The results show that the photocatalytic method is very efficient in the elimination of cyanide in aqueous dilute solutions.     

Absorption of CO2 and H2S in aqueous alkanolamine solutions using a fixed-bed reactor with cocurrent downflow operation in the pulsing flow regime: Absorption von CO2 und H2S in wäßrigen alkanolamin-lösungen in einem Festbettreaktor bei abwärtsfließendem Gleichstrombetrieb und pulsierendem Arbeiten

Absorption rates of H₂S and CO₂ in several aqueous alkanolamines in a cocurrent downflow fixed-bed reactor operated in the pulse flow regime have been measured in order to obtain information on the potential selectivity and on the mass transfer parameters. From these experiments it can be concluded that this type of reactor seems to be very suitable for the selective removal of H₂S from acid gases.It was not possible to derive correlations which are always valid for the calculation of the mass transfer parameters in laboratory-scale contactors. The results of the present study in combination with the data published in the literature were correlated with only one unknown parameter in which the influence of the physical properties of the system and the shape and material of the packing were combined. This parameter has to be determined empirically.Small amounts of acid gases in aqueous alkanolamine solutions have a pronounced effect on the properties, such as the foaming behaviour, of the liquid phase. The pressure drops measured in the cocurrently operated fixed-bed reactor were affected substantially by small amounts of acid gases present in the aqueous alkanolamine solutions and up to now this effect could not be explained satisfactorily.For the design of contactors for industrial purposes, detailed scale-up rules are required. In the present study this aspect is not investigated.     

Photocatalytic degradation of ethidium bromide over titania in aqueous solutions

The photocatalytic degradation of ethidium bromide (EtBr), a DNA intercalating pollutant, by TiO₂-based catalysts has been analyzed. Three different titanium dioxide samples synthesized by sol–gel within reverse microemulsions at different pH and thermal treatments were characterized and studied for the photocatalytic degradation of EtBr by oxygen in aqueous solutions. A commercial titania, Degussa P25, was also examined as a reference material for comparative purposes. Appreciable differences in the final structural and surface properties of these titania samples are observed which include disparities in the anatase/rutile proportions, optical absorption characteristics, EtBr chemisorption and acid–base properties. EtBr photodegradation results suggest that catalytic acid–base properties are the most relevant to explain EtBr chemisorption and play an important role in their final photocatalytic behaviour. It is stressed that photocatalysis can be an interesting alternative to other chemical or biological methods for mineralization of EtBr diluted in aqueous solutions.     

Properties of biodegradable hydrogels prepared by γ irradiation of microbial poly(ϵ-lysine) aqueous solutions

Poly(?-lysine) (PL) hydrogels have been prepared by means of γ irradiation of PL produced by Streptomyces albulus in aqueous solutions. When the dosage of γ irradiation was 70 kGy or more and the concentration of PL in water was 1–7 wt %, transparent hydrogels (opaque hydrogels for 1–3 wt % PL concentration) could be produced. In the case of 70 kGy of γ irradiation and 5 wt % PL concentration, the specific water content (wt of absorbed water/wt of dry hydrogel) of the PL hydrogel was approximately 160. Specific water contents of PL hydrogels decreased markedly with an increase in the dosage of γ irradiation. The specific water contents were increased with an increase in PL concentration in the irradiated solution. This result indicates the presence of a radical scavenger in the PL solution. Swelling equilibria of PL hydrogels were measured in water or in aqueous solutions of various pHs or concentrations of NaCl, Na₂SO₄, and CaCl₂. Under acid conditions, the PL hydrogel swelled due to the ionic repulsion of the protonated amino groups in the PL molecules. The degree of deswelling in electrolyte solution was smaller than that of other ionic hydrogels [poly(γ-glutamic acid), poly(acrylic acid) etc.]. In addition, the enzymatic degradations of PL hydrogel were studied at 40°C and pH 7.0 in an aqueous solution of the neutral protease [Protease A (Amano)] produced from Aspergillus oryzae. The rate of enzymatic degradation of the respective PL hydrogels was much faster than the rate of simple hydrolytic degradation. The rate of enzymatic degradation decreased with the increase in γ-irradiation dose during preparation of the PL hydrogel. © 1995 John Wiley & Sons, Inc.