Alkali Salt Solutions Research Articles

Fast fabricating superhydrophilic PVDF membrane via proanthocyanidins crosslinking at room temperature

Mussels in nature can adhere to the surface of hydrophobic substances by secreting adhesive substances, which has attracted wide attention by coating method for membrane modification. However, complicated processing procedures remain major problems. Here, we proposed a simple, mild and fast surface coating method. Proanthocyanidins (PC) react with 3-aminopropyl triethoxysilane (KH550) under the accelerated action of the oxidant ammonium persulfate (APS) at room temperature to form a polyphenol network. The hydrophilic network coating was constructed on PVDF membrane by surface co-deposition method for 1 h, which could effectively separate different emulsions. The water permeability of modified membrane was 18,271 L∙m−2∙h−1∙bar−1. The permeability for separating isooctane-in-water emulsion arrived at 14,223 L∙m−2∙h−1∙bar−1 and the oil rejection rate was 99.6 %. After ten cycles, the separation flux was 10,836 L∙m−2∙h−1∙bar−1 with the rejection rate of 98.8 %. Modified membranes were soaked in acid and alkali salt solutions of different pH values for 30 days, and maintained good underwater oleophobic performance (>156°). The developed membrane showed excellent separation performance, oleophobic property and acid-base stability. The proposed membrane modification strategy was prospective for efficient separation of oily wastewater.

Sepiolite@TiO2/Graphene oxide composite membrane for long-term Separation of oily wastewater

Microwave synthesis was taken to synthesis A-SEP@TiO2 which has a steady chemical property. The A-SEP@TiO2 composite materials and GO (with different proportion)were mixed and then pumped on commercial PVDF membranes to filter. Finally, the composite membrane A-SEP@TiO2/GO was obtained Under electrostatic self-assembly. Due to the superhydrophilicity and underwater super hydrophobicity of the surface of A-SEP@TiO2/GO membrane, A-SEP@TiO2/GO composite has shown great potential in the field of oil in water. The separation rates of four different emulsions (petroleum ether, toluene, Mesitylene, n-hexane) are all above 90%. With the steady chemical properties, A-SEP@TiO2/GO composite membrane is able to separate oil from water in harsh environment in long-run. After being immersed in 1 mol/L acid and alkali salt solution for one month respectively, all the sample membranes showed a better stability than commercial PVDF membranes. Also, the oil and water removal flux of A-SEP@TiO2/GO composite membrane only decreased by less than 10%, and that was why the composite membranecan can still maintain good cleaning performance even after ten times’ repetition of experiments,. Moreover, the membrane could efficiently remove dyes and heavy metal ions. Therefore, it has a great application prospect in complex water environment treatment.

Fluorine free TiO2/cyanate ester coated cotton fabric with low surface free energy and rough surface for durable oil–water separation

Low cost superhydrophobic cotton fabric was developed using TiO2/cyanate ester coating for the first time. The TiO2/cyanate ester coated cotton fabric displayed superhydrophobic behaviour with water contact angle of 158°, sliding contact angle of 8° and surface free energy of 18.0 mN/m2. Besides, the TiO2/cyanate ester coated cotton fabric also possesses excellent laundry durability as well as stability against acid, alkali salt solutions and mechanical abrasion. Consequently, the TiO2/cyanate ester coated cotton also delivered superior oil–water separation efficiency with different types of oil/water mixtures that includes engine oil/water, waste engine oil/water, petrol/water and diesel/water. The TiO2/cyanate ester coated cotton fabric shows separation efficiency as high as 98% with flux value of 7200 L/m2h for petrol/water mixture. Further, both cyanate ester and TiO2/cyanate ester coated cotton fabric delivers ultra-high UV-resistant ability with Ultraviolet Protection Factor value as high as 500 + . Hence, it is anticipated that the present approach of using cyanate ester can be widely explored further to construct multifunctional fabrics towards excellent self-cleaning as well as oil/water separation with UV and chemical robustness.

Laboratory Investigations of Processing Highly Mineralized Alkali Solutions by Means of Electromembrane Technology

An analysis of water utilization systems at thermal power plants (TPPs) shows that highly mineralized effluent waters are mainly generated at these facilities by their water-treatment plants. Highly mineralized alkali liquid waste is presented by the products from continuous and periodic blowdowns of thermal demineralization systems and drum boilers, by spent anion exchange filter regeneration solutions, and by alkali concentrates from reverse osmosis plants. In view of the fact that the alkali used in technological processes has quite a high cost, it is economically expedient to subject alkali effluents to processing with the extraction of alkali for repeatedly using it in the production cycle. The article presents the results obtained at a TPP from experimental investigations into processing of highly mineralized alkali–salt solutions by means of electromembrane technology. The experimental investigations were carried out using the EMA-100 laboratory electromembrane apparatus and included two series of tests: a sequential diffusion–dialysis extraction with concentration by electrodialysis and a single-stage concentration by electrodialysis. As a result, a concentrated alkali solution and partially demineralized softened water were obtained. An analysis of the qualitative and quantitative compositions of the obtained products has shown the effectiveness of the proposed electromembrane processing arrangements, because an alkali solution suitable for its repeated use in the TPP water-treatment cycle was obtained in both series of tests. However, it should be borne in mind that single-stage concentration by electrodialysis is a more economically efficient and simple method, which provides high throughput and yields solutions containing satisfactorily separated alkali and salt components.

Engineering of Electron-Selective Contact for Perovskite Solar Cells with Efficiency Exceeding 15%

The past 5 years have witnessed the rise of highly efficient organometal halide perovskite-based solar cells. In conventional perovskite solar cells, compact n-type metal oxide film is always required as a blocking layer on the transparent conducting oxide (TCO) substrate for efficient electron-selective contact. In this work, an interface engineering approach is demonstrated to avoid the deposition of compact n-type metal oxide blocking film. Alkali salt solution was used to modify the TCO surface to achieve the optimized interface energy level alignment, resulting in efficient electron-selective contact. A remarkable power conversion efficiency of 15.1% was achieved under AM 1.5 G 100 mW · cm(-2) irradiation without the use of compact n-type metal oxide blocking layers.

Invited: Water Based AC/AC Supercapacitors Reaching the Performance of Systems in Organic Electrolyte

It has been long time accepted that capacitors with activated carbon (AC) electrodes in aqueous electrolytes do not deliver a high energy due to their low voltage, e.g., 0.7 – 0.8 V in KOH and H2SO4. Recently, we have demonstrated that the voltage window can be dramatically enhanced by using salt solutions with pH close to 7 [1,2]. In that case, the over-potential for di-hydrogen evolution at the negative electrode is very high [3], and the voltage window can be extended up to 1.5 V with stainless steel current collectors [4]. In this presentation, we introduce a number of strategies to optimize the performance of these systems.First, the corrosion of the positive current collector has been reduced by adding an inhibitor (sodium molybdate) to the electrolyte. Besides the capacitance of the positive electrode is slightly enhanced, allowing its maximum potential to be reduced. In these conditions, the system displays an excellent cyclability, up to 1.6 V, without remarkable oxidation of the positive AC electrode [4].The second improvement is based on using the advantages of the pseudo-capacitance provided by the carbon/iodine interface, while keeping the large potential window allowed by alkali salt solutions. An AC/AC capacitor in the KI – Li2SO4 mixture displays capacitance values up to 400 F g-1 at voltage of 1.6 V [5]. These values lead to an energy density which is comparable to the one reached with the same carbon in Et4NBF4/acetonitrile at 2.3 V.Finally, we have explored various routes to extend the operational temperature range to low values. We have designed a formulation of aqueous lithium sulfate electrolyte allowing the AC/AC capacitor system to operate down to -40°C with excellent charge propagation (Figure 1). At this temperature, the pseudo-faradic contribution due to hydrogen storage is kinetically blocked, and the system consequently works as a typical EDL one.In summary, AC/AC capacitors in aqueous alkali sulfate solutions with appropriate additives are now able to reach the performance of organic systems, while using environmental friendly and cost effective components. Acknowledgements: The Foundation for Polish Science is acknowledged for supporting the ECOLCAP Project realized within the WELCOME Program, co-financed from European Union Regional Development Fund.

Low Energy CO2 Capture Enabled by Biocatalyst Delivery System

This work presents research and development progress to improve biocatalysts, solvents, and system integration to reduce the cost of CO2 capture from flue gas. Laboratory data and field demonstration illustrate the potential of biocatalyst-enhanced CO2 capture from coal generated flue gas using non-volatile alkali salt solutions. The first generation biocatalyst system (coated packing) demonstrated 6 to 7-fold enhancement in the volumetric average mass transfer coefficient at 40°C with 3460hours on coal flue gas with 80% CO2 capture on average. The first 2800hours operated with an aqueous solution of 20% K2CO3, and the final 660hours demonstrated a new higher capacity non-volatile alkaline salt solution (AKM24). Lessons learned from the first generation biocatalyst delivery system (coated packing) demonstration are summarized. A second generation biocatalyst delivery system (biocatalyst microparticles) is introduced that shows a greater potential for rate enhancement in laboratory tests. This new biocatalyst system also provides a lower cost method of biocatalyst addition and replacement on-stream. Preliminary modeling estimates show a total equivalent work less than 220 kWh/t CO2 (including CO2 compression to 150bar) in two possible process configurations. Preliminary cost analysis demonstrates potential for more than 30% reduction in CO2 capture costs relative to NETL Case 12, version 2 (30% MEA with 75 psig cross over steam, bituminous coal power plant).

Mechanics of POPC Bilayers in Presence of Alkali Salts

Membranes mechanical properties are affected by solvent properties, i.e. the salt content. In this study, we use POPC GUVs (Giant Unilamellar Vesicles) as model membranes and we measure the membrane mechanical moduli by flickering analysis and micropipette technique for a series of alkali salt solutions. Salt concentration effects and ion specificity are investigated in these measurements. Membrane mechanical moduli are shown to display a complex dependence on the salt solution composition.

Cation specific binding with protein surface charges

Biological organization depends on a sensitive balance of noncovalent interactions, in particular also those involving interactions between ions. Ion-pairing is qualitatively described by the law of "matching water affinities." This law predicts that cations and anions (with equal valence) form stable contact ion pairs if their sizes match. We show that this simple physical model fails to describe the interaction of cations with (molecular) anions of weak carboxylic acids, which are present on the surfaces of many intra- and extracellular proteins. We performed molecular simulations with quantitatively accurate models and observed that the order K(+) < Na(+) < Li(+) of increasing binding affinity with carboxylate ions is caused by a stronger preference for forming weak solvent-shared ion pairs. The relative insignificance of contact pair interactions with protein surfaces indicates that thermodynamic stability and interactions between proteins in alkali salt solutions is governed by interactions mediated through hydration water molecules.

Precursor Luminescence near the Collapse of Laser-Induced Bubbles in Alkali-Salt Solutions

A precursor luminescence pulse consisting of atomic line emission is observed as much as 150 nanoseconds prior to the collapse point of laser-created bubbles in alkali-metal solutions. The timing of the emission from neutral Na, Li, and K atoms is strongly dependent on the salt concentration, which appears to result from resonant radiation trapping by the alkali atoms in the bubble. The alkali emission ends at the onset of the blackbody luminescence pulse at the bubble collapse point, and the duration of the blackbody pulse is found to be reduced by up to 30% as the alkali-salt concentration is increased.

Observation of the matrix effect due to the electron transfer in laser ablation plasma

We investigate the so-called “matrix effect” on the relative intensities of ions in mixed solutions of alkali salts by using femtosecond laser ablation time-of-flight mass spectrometry (fsLA-TOFMS). For the 1:1 mixed solution of sodium and potassium salts, the intensity ratio of cations (Na+/K+) decreases as the total concentration increases. From the measurement for the mixed solution of lithium, sodium, potassium, rubidium, and cesium solutions, we find out significant dependence of each ion intensity on the total concentration. The results suggest that the electron transfer from neutral atoms to cations coexistent in the ablation plasma affects the relative ion intensities observed with TOFMS when the total ion concentration is high.

Development of Enteric Coated Flurbiprofen Tablets using Opadry/acryl-eze System—A Technical Note

Tablet coating is perhaps one of the oldest pharmaceutical processes still in existence (1). It offers many benefits namely: improving the aesthetic qualities of the dosage form, masking unpleasant odour or taste, easing ingestion, improving product stability and modifying the release characteristics of the drug. It is widely used in enteric coating, controlled release system and osmotic pump systems (2). Enteric coated dosage forms are designed to resist the destructive action of the gastric fluid and to disintegrate in the higher pH environment of the intestinal fluid. Polymer for enteric coating can be applied to solid dosage forms (i.e. granules, pellets, or tablets) from aqueous solutions of alkali salts, or organic solvent solutions. The most commonly used pH-sensitive enteric coating polymers today include: cellulose acetate phthalate (CAP), cellulose acetate trimellitate (CAT), hydroxypropyl methyl cellulose phthalate (HPMCP) and methacrylic acid copolymers (3). In recent years, acrylic copolymers have evolved as the most preferred materials for designing enteric coating formulations in terms of performance and global acceptability (1). Aqueous enteric film coatings have been used widely in recent years. Many of these systems are pseudolatex dispersions of polymers such as CAP, latex dispersions of methacrylic acid copolymers and aqueous solutions of alkali salts (4).The advantages of an aqueous based coating system have been recognized. This is derived from the drawbacks of organic solvents including pollution, explosion hazards, and solvent toxicity. Especially there are risks for operators (5). Almost all nonsteroidal anti-inflammatory drugs irritate gastric mucosa and enhance ulceration by blocking protective action of the prostaglandins on gastric mucosa, causing ulcer formation not only in stomach but also in lower part of oesophagus and in duodenum too (6). The most important side effects of flurbiprofen include peptic ulceration, hemorrhage and perforation (7).The aim of current investigation was to develop an enteric coated flurbiprofen tablet formulation to minimize the gastric intolerance caused by flurbiprofen on long term use and to improve patient compliance by utilizing Acryl-Eze. Acryl-Eze is an optimized, one-step, pigmented, aqueous acrylic system for the application of an enteric film coating for oral solid dosage forms. Acryl-Eze combines the benefits and performance of a globally accepted enteric polymer (Eudragit® L100-55) with a fully formulated coating system, providing significant time savings in both development and production. Acryl-Eze has further been optimized for either tablet or multiparticulate applications (8). Eudragit® L100-55 is a copolymer of methacrylic acid and ethyl acrylate (1:1 ratio) which meets the USP definition for Methacrylic Acid Copolymer Type C. L100-55 is a re-dispersible powder produced by spray drying Eudragit® L30-D. Film coatings prepared from such dispersions are resistant to gastric juice but readily dissolve at a pH above 5.5 (9). EudragitL100-55 has been used as a coating polymer in several studies (10,11,12).

Light Emission from Porous Silicon Photoetched in Aqueous Alkali Salt Solutions

An interband-transition model was applied to explain the emission mechanism in porous silicon (PSi) fabricated by photoetching in aqueous HF and salt (NaF and KF) solutions. The HF-formed samples show a yellow photoluminescence band at ∼2 eV. The salt-formed samples, on the other hand, show an ultraviolet (UV) emission peak at ∼3.3 eV with a spectral width of ∼0.1 eV, together with a broad emission band at ∼2.7 eV. The broad emission bands at ∼2 and ∼2.7 eV can be explained by the quantum-mechanical confinement effect, i.e., a relaxation of the momentum conservation at and above the indirect-absorption edge (supra-EgID emission). This effect may also lead to a change in the E1 critical point (CP) from the two-dimensional M0 to the zero-dimensional CP with decreasing nanocrystalline size. The change in the E1-CP dimensionality makes possible an emission in the UV region with a narrow spectral width.

A new method for the direct flame calibration of nebulized additive concentrations

A new technique is described to calibrate the flame delivery flux of an aerosol-producing nebulizer. The method is based on flame deposition. It centers on the nature of deposition onto a cooled surface immersed in the burned flame gases that contain an alkali salt (Na, K, Rb, or Cs) that has been nebulized into the flame. This deposition process has been shown to be controlled solely by the alkali concentration in the flame and for the same alkali flux the rates of deposition are invariant being independent of the nature of the alkali flame speciation, the fuel, equivalence ratio, flame or probe temperature (in the 350-800 K range for the latter), probe material, or the deposit’s molecular composition. In flames containing, for example, sodium and sulfur or chlorine, there is a pronounced preferential ranking of Na 2SO 4 > NaCl > Na 2CO 3 > NaOH for the resulting composition of the deposit. This dominance of sulfate formation is so pronounced that it produces a linear titration method for the alkali, and fractional addition of sulfur reflects into a corresponding fractional formation of Na 2SO 4. In flames containing solely sodium and sulfur additives, insufficient sulfur for a Na 2SO 4 formulation will result in a fractional mixture of the sulfate, with the remaining sodium forming carbonate. Collecting a deposit from a flame containing a nebulized alkali salt solution aerosol and a known trace addition of SO 2, and then analyzing the deposit using an inductively coupled plasma/atomic emission spectrometer (ICP/AES) for its alkali to S ratio, provides a measure of the extent of sulfate formation. This then translates into an absolute calibration of the nebulizer delivery flux of alkali in the burned gases. A variation of the method is to use instead a Raman scattering spectrometer to measure the ratio of sulfate to carbonate in a deposit, in this case for flames free of halogens. The method has the advantage that it can be used in any flame, turbulent or laminar, requires only a trace of deposit for ICP analysis, and is accurate. Moreover, the probe can intercept any partial part of the flame gases. A limited number of other techniques currently are available for nebulizer calibration. However, other than the curve of growth method, these have not been discussed in combustion texts. Their various limitations and accuracies are outlined together with that of the presently suggested method.

Electrochemical Degradation of Polychlorinated Biphenyls

The feasibility of electrochemical conversion of polychlorinated biphenyls to the parent hydrocarbon in N,N-dimethylformamide was studied with respect to the charge and mass efficiency of the process. The process was conducted in two variants, viz. as indirect conversion through pre-electrolysis of an alkali salt solution, and as direct electroreducing splitting of the carbon-chlorine bonds. Mercury served as the working electrode; the suitability of other metals as cathode materials was also examined by slow cyclic voltammetry.

Tunable Selectivity of an Alkali Aerosol Flame Ionization Detector Towards Organobromine and Organoiodide Species for Gas Chromatography

Abstract The performance of a halogen selective aerosol alkali flame ionization detector (AFID) is presented. A constant delivery of desolvated alkali salt aerosol is introduced into the detector in the form of dual hydrogen gas flames. The problems of enhancement-source vaporization and contamination, which occur in fixed alkali salt versions, do not occur with the presented aerosol design. Detection limits range from 321 pgI/sec to 450 pgI/sec and 6.7 ngBr/sec to 15 ngBr/sec. Selectivity ratios were 103 gI/gC and 102 gBr/gC using an 100 ppm potassium chloride as the alkali salt solution.

Near‐infrared probe for in situ characterization of nafion thin films

AbstractA near‐infrared (NIR)‐absorbing cyanine dye was used as a probe for in situ characterization of Nafion thin films. This NIR dye was very sensitive to changes in the hydrophobicity of the environment and proved to be very suitable for probing the Nafion coatings, which involve a two‐Phase structure of hydrophobic and hydrophilic zones. Sorption phenomena of water and aqueous alkali salt solutions by Nafion were investigated. For our study systems of thin‐coating films prepared from 5% wt alcoholic solution of Nafion 117, the absorption spectrum was dominated by higher‐order aggregates when in dry form. In pure water, the absorption maximum of the monomer dye appears at 773 nm and can be used as an indication of the swelling process of the film. The water uptake reaches saturation in only a few seconds. After the swelling process, an additional absorption band with a maximum at 555 nm appears primarily at the expense of the NIR monomer dye absorption band. The peak transition process, which is a very slow process and is a strong function of the water content inside the matrix, can be used as an indication of the establishment of equilibrium between the two‐phase structure due to the water uptake. Since the absorption maximum of the study system is around 800 nm, semiconductor lasers can be used. This technique shows high potential in other applications where polymers are used as support material, e.g., in situ thin‐film thickness measurements. In the study, the feasibility of this approach was illustrated.

Measurement of acid dissociation constants of weak acids by cation exchange and conductometry

A simple strategy is presented for the determination of acid dissociation constants based on the measurement of conductance of a known concentration of the acid and/or the conductance of a solution of its fully or partially neutralized alkali-metal salts. For an n-protic acid, 2n conductance measurements are minimally necessary. In the simplest case of a typical monoprotic acid, the conductance of its alkali salt solution is measured before and after passage through an H{sup +}-form exchanger. From these data both the pK{sub a} of the acid and the equivalent conductance of the anion can be computed. The underlying equations are rigorously solved for monoprotic acids and some diprotic acid systems. For other diprotic and multiprotic acid systems, initial estimates are obtained by making approximations; the complete data set is then subjected to multiparametric fitting. The method does not require pH measurements; conductance can generally be measured accurately at low enough ionic strengths to obviate the need for major activity correction. Several experimental measurements are presented and excellent agreement with literature pK{sub a} values is observed. The reliability of the equivalent conductance values computed in this fashion is limited, however.

Studies of alkali-silica reaction. Part 4. Effect of different alkali salt solutions on expansion

It has been shown that the extent of expansion due to alkali-silica reaction depends on the type of alkali compound and its concentration in the sorrounding liquid phase. It is of particular interest to note that a 3N alkali hydroxide solution causes less expansion than a 3N alkali salt solution. The result also showed that the expansion due to alkali-silica reaction is not directly proportional to the degree of chemical reaction. These results, though at variance to a generally held belief, are consistent with a recently proposed mechanism of alkali-silica reaction. The results indicate that in an accelerated alkali-silica test the use of an alkali salt is preferable to an alkali hydroxide.

Optimization of an industrial chemical cleaning process for glass lenses

AbstractThe chemical cleaning of glass constitutes an extremely complicated problem, since its exposure to chemical attack by either water, acid, alkali salt solutions or even gases in the atmosphere may result in corrosion. In reality, corrosion generally occurs in a combination of ways simultaneously. This is particularly true with respect to industrial chemical cleaning of glass lenses, in which the absolute cleanliness (and spotlessness) of the surface of the lenses is the primary condition for further processing and/or fitness to the ultimate use. This paper presents data of a selected industrial field study (in vivo conditions) in which an application, optimization, and assessment of the chemical cleaning process (and its results) of glass lenses involving various surfactant‐based formulations has been carried out. With a high level content of polyphosphates (i.e., sodium tripolyphosphates), the phosphate ester‐based formulations were found to perform better than formulations based on other classes of surfactants (i.e., anionics and nonionics). The best results were achieved with 2.5–3.5% solutions of the formulation that contained ca. 3% of surface active agent. The optimal ratio of alkali‐phosphate in the formulations was found to be in the range of 1:1.7–1:2.4. The results are discussed and conclusions with regard to the “real world” of such industrial processes have been drawn.