Na2SO4 Medium Research Articles

Efficient photo-electrochemical performance using CuO-based electrodes in aqua medium

Copper oxide impregnated with different amounts of PbO and selenium layer were synthesized by electrodeposition, followed by anodization and heat treatment. The photocurrent performance of the cathodes was determined using DC (linear sweep photo-voltammetry and chronopotentiometry) and AC (electrochemical impedance spectroscopy) techniques. The photocurrent response was maximal for the CuO electrode with 13 % Pb (Cu32.06Pb12.84O54.25Se0.85). High photo-conversion efficiency (2 %) was achieved for the sample with a band gap of 1.6 eV in 0.5 M Na2SO4 medium at −0.2 V (vs. SCE) bias potential under illumination. The photocurrent stability of the samples was tested at 0 V (vs. SCE) in the flip-flop light condition for 50 min. Physical characterizations such as field emission scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–visible spectroscopy were performed to gather information about the morphology, elemental compositions, crystallinity, binding energy and band gap of the thin film.

Brine solution-driven synthesis of porous polyaniline for supercapacitor electrode application

Increasing environmental and economic impacts has driven the need for development of inexpensive methodology for polymer nanostructure synthesis using non-toxic reagents. Herein, we report synthesis of porous polyaniline (PANI) by polymerization of aniline in brine (saturated sodium chloride) solution. The resulting polyaniline is highly porous, thus providing large surface area, which is a vital parameter for the significant improvement of supercapacitor performance. Brine solution acted as a pseudo-template for the formation of porous PANI, eliminating the need of organic solvents/acids and hard/soft templates. The porous PANI electrodes showed a high specific capacitance of 662 F/g, which is 2.5 times greater than that of conventional PANI. X-ray diffraction studies revealed an ordered nature of porous PANI chains as compared to conventional one, whereas their chemical nature is similar as confirmed by FTIR, and UV–visible spectroscopy. Polymerization reaction carried out at various concentration of NaCl solution helped to understand the evolution of porous morphology, based on which a plausible mechanism is proposed for formation of the porous polymer. Polymerization was also carried out in brine in the presence of other commercial acids like sulphuric and nitric acids, to demonstrate the versatility of using brine in polymerization. Effect of other saturated ionic medium such as KCl, Na2SO4 and non-ionic medium like glucose, on the polymerization reaction was also studied.

Effect of Chemically Treated / Untreated Carbon Cloth: Potential Use as Electrode Materials in the Capacitive Deionization Process of Desalination of Aqueous Salt Solution

Capacitive deionization (CDI) process is a novel approach for desalination of an aqueous salt solution. In the present study, an activated carbon cloth (ACC) is proposed as effective electrode material. Initially the carbon cloth was activated in 1 M and 8 M HNO3 for 9 hours at room temperature. The untreated and chemically activated carbon cloth (ACC) electrode materials were subjected to BET surface area measurements in order to get information about their specific surface area, average pore size, total pore volume and micropore area. The above materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) also. The electrochemical studies for the electrodes were done using cyclic voltammetry (CV) in 0.1 M Na2SO4 medium. From the studies, it was found that resistivity of the activated carbon cloth electrodes (treated in 1 M and 8 M HNO3) was decreased significantly by the chemical oxidation in nitric acid at room temperature and its capacitance was found to be 90 F/g (1 M HNO3) and 154 F/g (8 M HNO3) respectively in 0.1 M Na2SO4 solution. The capacitive deionization behavior of a single cell CDI with activated carbon cloth electrodes was also studied and reported in this work. Keywords: Activated carbon cloth, capacitive deionization (CDI), desalination, chemical activation, cyclic voltammetry, chronocoulometry

Photo-electrochemical and physical characterizations of a new single crystal POM- based material. Application to Rhodamine B photodegradation

The physical and photoelectrochemical characterizations of a new inorganic-organic hybrid single crystal material, synthesized by hydrothermal route, based on α-Keggin-type polyoxotungstate and Cu(I)-(trz) coordination complex, namely [Cu6(trz)6][α-PW12O40]2·H2O, [trz=1H-1,2,4-triazole] are investigated for the first time. The crystal structure, determined by single-crystal X-ray diffraction, reveals a 3-D supramolecular host-guest structure with Keggin anion as template. The diffuse reflectance indicates an optical transition at 2.91eV, directly allowed, attributed to the Keggin polyoxoanions. The physical characterization shows a semiconductor behavior and the conductivity follows an exponential type law associated to a small polaron hopping between neighboring ions. The thermo-power measurement indicates n-type conduction with an electron mobility (0.54×10−6cm2V−1s−1), thermally activated. The photoelectrochemical study, performed in Na2SO4 medium, confirms n-type conduction with a flat band potential of −0.65 VSCE and electrons density of 6.59×1018cm−3. The electrochemical impedance spectroscopy reveals the predominance of the bulk contribution with a constant phase element and Warburg diffusion. As application, the photo-degradation of Rhodamine B upon sunlight and UV irradiation is achieved by the radicals O2•- and OH•. The improved activity is attributed to the wide depletion width (460nm) and the potentials of the valence and conduction bands close to the radicals levels.

SYNTHESIS AND CHARACTERIZATION OF POLYCARBAZOL - POLYANILINE COPOLYMER IN DICHLOROMETHANE SOLUTION

Conductive polymers can be synthesized in solution or on the electrode surface by oxidation of aromatic heterocyclic organic molecules. Polypyrrole, polythiophene, polyaniline, polyfuran, polyphenylenevinylene, polytionaphtene, polycarbazole, polyindole and polyazulene are the most well-known conductive polymers. Although less studied among the conductive polymers, carbazole polymers have many advantages such as cheap, environmental and chemically stable because of aromatic structure, optic with nitrogen atom in structure, electrical properties, can give polymers having a lower band gap than p-phenylene polymers because occur from biphenyl group. During the polymerization, poly (2,7-carbazole) derivatives can be obtained by binding from 2- and 7- positions while poly (3,6-carbazole) polymers obtained by binding from 3- and 6- positions. Features and applications area of these polymers are different [1,2]. In previous studies, electrochemical synthesis of Polyaniline was carried out in dichloromethane medium and it was used as modified surface for determination of some phenolic compounds [3,4]. In this study, electropolymerization of polycarbazole- polyaniline (PC - PANI) copolymer was firstly studied using polymerization solution containing dichloromethane / 100 mM tetrabutylammonium perchlorate (TBAP) / 1.0 mM carbazole / 50.0 - 200 mM aniline and optimum polymerization conditions were determined. Aqueous and non-aqueous medium behaviors of prepared PC –PANI modified electrode were investigated. The best electroactive film was determined. Characterization of the synthesized copolymer film was carried out by UV-vis, FT-IR, Raman, SEM and EDS techniques. Electrochemical behavior of hydroquinone was investigated in NaHSO4 / Na2SO4 medium over obtained modified electrode and it was compared with its homopolymers.

An electrochemical mechanisms study on steel/IrO2–Sb2O3 electrodes for oxidation of phenol in water

Phenol, a known water pollutant, was electrochemically oxidized on a steel/IrO2–Sb2O3 novel anode. Since the oxidation mechanisms vary based on the anode material, a mechanisms study of electrooxidation of phenol on it was conducted. The phenol oxidation was carried out at 20 mA/cm2 constant current density with a pH 11.00 Na2SO4 medium at room temperature. During 6 h of electrolysis, samples were tested for chemical oxygen demand removal efficiency of the anode. The steel/IrO2–Sb2O3anode showed 76.3% chemical oxygen demand removal efficiency. Both 4-nitroso-N,N-dimethylaniline and the HCO3–/CO32– radical scavenger tests confirmed the formation and presence of the hydroxyl radicals in the system. Therefore, it was concluded that the hydroxyl radicals that are generated on the anode surface are the main cause for the oxidation mechanism. Moreover, ICE, HPLC, and UV-vis absorbance and cyclic voltammetry results confirmed the presence of catechol and benzoquinone as intermediates and the reaction mechanism.

Synthesis and characterization of new Ti–Bi2O3 anode and its use for reactive dye degradation

This paper reports the synthesis, characterization and application of a Ti–Bi2O3 anode for the electrochemical decolorization of the textile dye Reactive Red 2. The anode was synthesized by electrodeposition on a Ti substrate immersed in an acidic bismuth (III) solution at constant potential, followed by calcination in air at 600 °C. Thermogravimetric Analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis revealed that the electrodeposited material was predominantly metallic bismuth, which was oxidized to pure α-Bi2O3 during the calcination in air. SEM micrographs revealed that the Bi2O3 coat at the anode surface was inhomogeneous and porous. Reactive Red 2 was completely electrochemically decolorized at the synthesized anode in the presence of H2O2. The applied current density, H2O2 and Na2SO4 concentration, medium pH and initial dye concentration affected the dye decolorization rate. The optimal process parameters were found to be as follows: an applied current density of 40 mA cm−2 using a mixture of 10 mmol dm−3 H2O2 and 10 mmol dm−3 Na2SO4 at pH 7. The dye decolorization rate was shown to decrease as its initial concentration increased. The decolorization reactions were found to follow pseudo-first order kinetics.

Speciation of bioaccumulated uranium(VI) by Euglena mutabilis cells obtained by laser fluorescence spectroscopy

Abstract The ability of Euglena mutabilis cells – a unicellular protozoan with a flexible pellicle, which is typically found in acid mine drainage (AMD) environments – to bioaccumulate uranium under acid conditions was studied in batch sorption experiments at pH 3 and 4 using Na2SO4 and NaClO4 as background media. It was found that axenic cultures of Euglena mutabilis Schmitz were able to bioaccumulate in 5 days 94.9 to 99.2% of uranium from a 1 · 10 –5 mol/L uranium solution in perchlorate medium and 95.1 to 95.9% in sodium sulfate medium, respectively. The speciation of uranium in solution and uranium bioaccumulated by Euglena mutabilis cells, were studied by laser induced fluorescence spectroscopy (LIFS). The LIFS investigations showed that the uranium speciation in the NaClO4 systems was dominated by free uranyl(VI) species and that the UO2SO4 species was dominating in the Na2SO4 medium. Fluorescence spectra of the bioaccumulated uranium revealed that aqueous uranium binds to carboxylic and/or (organo)phosphate groups located on the euglenid pellicle or inside the Euglena mutabilis cells. Reduced uranium immobilization rates of 0.93 – 1.43 mg uranium per g Euglena mutabilis biomass were observed in similar experiments, using sterile filtrated AMD waters containing, 4.4 · 10 –5 mol/L uranium. These lower rates were attributed to competition with other cations for available sorption sites. Additional LIFS measurements, however, showed that the speciation of the bioaccumulated uranium by the Euglena mutabilis cells was found to be identical with the uranium speciation found in the bioaccumulation experiments carried out in Na2SO4 and NaClO4 media. The results indicate that Euglena mutabilis has the potential to immobilize aqueous uranium under acid condition and thus may be used in future as promising agent for immobilizing uranium in low pH waste water environments.

Photoelectrochemical Hydrogen Generation and Concomitant Organic Dye Oxidation under TiO2 Nanotube

Highly ordered TiO2 nanotube has been widely employed as photoanode for degradation of organic compounds oxidation during photoelectrochemical process, but its capacity to form hydrogen is not explored. The present work describes the degradation of reactive black 5 dye used as a model of organic pollutant at TiO2 nanotube electrode and concomitant generation of hydrogen at the cathode. A two compartment cell (25mL each compartment) with 0.1 mol L-1 Na2SO4 medium was used and the TiO2 nanotube was photoactivated with UV light using 150W Xe-Arc lamp (Oriel) under bias potential. All photoelectrochemical measurements were carried out in a potenciostat Autolab PGSTAT 302 using a Pt gauze as cathode and as reference electrode a Ag/AgCl. Dye degradation was monitored by spectrophotometric and TOC measurements and hydrogen generation monitored by volume and gas chromatography analysis. The influence of parameters like concentration, pH of the cathode and anode and applied potential was investigated. Using the best experimental conditions of 5x10-5 M dye in 0.1 M Na2SO4 M pH 6, E= 1.0 V and UV irradiation it was obtained 100% of color removal and 72% of TOC removal. Simultaneously was 44% of hydrogen efficiency after 2 h of photoelectrolysis.

Phenolic acids and total antioxidant activity in Ocimum basilicum L. grown under Na2SO4 medium

The antioxidant activity of two basil cvs (Ocimum basilicum L. cvs. Genovese and Fine),grown for 15 and 30 days in the absence or in the presence of 25 mM sodium sulphate(Na2SO4), was measured. At the same time, phenolic acid contents of the same plant materials were determined to evaluate their probable contribution to the total antioxidant capacity. The results showed that Genovese cultivar was a better source of antioxidant compounds than Fine one, irrespective of the salt and the period of treatment, even ifNa2SO4 salinity was less stressful for Fine cultivar that after 15 days of treatment was able to increase its antioxidant power in comparison to Genovese one. In addition, although major phenolic acids in Genovese and Fine basil remained constant or decreased with salinity, we observed an increase in hydrophilic antioxidant power either after 15 or 30 days of treatment. The lack of correlation between phenolic acids present in basil and antioxidant activity could be explained by the fact that other antioxidant hydrophilic molecules are synthesised under stress conditions. Key words: Ocimum basilicum, phenolic acids, Na2SO4 salinity, hydrophilic antioxidant activity, lipophilic antioxidant activity, ABTS+.

Hydride Ion Transfer from Ruthenium(II) Complexes in Water: Kinetics and Mechanism

Reactions of hydride complexes of ruthenium(II) with hydride acceptors have been examined for Ru(terpy)(bpy)H(+), Ru(terpy)(dmb)H(+), and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) in aqueous media at 25 °C (terpy = 2,2';6',2''-terpyridine, bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine). The acceptors include CO(2), CO, CH(2)O, and H(3)O(+). CO reacts with Ru(terpy)(dmb)H(+) with a rate constant of 1.2 (0.2) × 10(1) M(-1) s(-1), but for Ru(η(6)-C(6)Me(6))(bpy)(H)(+), the reaction was very slow, k ≤ 0.1 M(-1) s(-1). Ru(terpy)(bpy)H(+) and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) react with CH(2)O with rate constants of (6 ± 4) × 10(6) and 1.1 × 10(3) M(-1) s(-1), respectively. The reaction of Ru(η(6)-C(6)Me(6))(bpy)(H)(+) with acid exhibits straightforward, second-order kinetics, with the rate proportional to [Ru(η(6)-C(6)Me(6))(bpy)(H)(+)] and [H(3)O(+)] and k = 2.2 × 10(1) M(-1) s(-1) (μ = 0.1 M, Na(2)SO(4) medium). However, for the case of Ru(terpy)(bpy)H(+), the protonation step is very rapid, and only the formation of the product Ru(terpy)(bpy)(H(2)O)(2+) (presumably via a dihydrogen or dihydride complex) is observed with a k(obs) of ca. 4 s(-1). The hydricities of HCO(2)(-), HCO(-), and H(3)CO(-) in water are estimated as +1.48, -0.76, and +1.57 eV/molecule (+34, -17.5, +36 kcal/mol), respectively. Theoretical studies of the reactions with CO(2) reveal a "product-like" transition state with short C-H and long M-H distances. (Reactant) Ru-H stretched 0.68 Å; (product) C-H stretched only 0.04 Å. The role of water solvent was explored by including one, two, or three water molecules in the calculation.

A comparative study of azo dye decolorization by electro‐Fenton in two common electrolytes

AbstractBACKGROUND: This study compared the decolorization behaviors of a model azo dye of methyl red in Na2SO4 and NaCl media by electro‐Fenton process, in which FeSO4 was added into the solution, while H2O2 was efficiently generated on a graphite–polytetrafluoroethylene cathode. Parameters such as pH, cathodic potential, electrolyte concentration, and initial dye concentration as well as the treatment time were investigated to disclose different decolorization behaviour.RESULTS: Decolorization in NaCl medium had an advantage over that in Na2SO4 medium not only in performance but also in its suitability for application, which seemed less sensitive to variations in parameters and thus broadened the optimal performance range. In NaCl medium, indirect oxidation by active chlorine contributed greatly to the decolorization, and the removal of methyl red obeyed pseudo‐first‐order kinetics.CONCLUSION: Electro‐Fenton oxidation in the present system in the presence of NaCl would is a promising procedure for azo dye waste‐water treatment. Copyright © 2009 Society of Chemical Industry

Rapid Synthesis of Multiferroic BiFeO3 Single-Crystalline Nanostructures

A simple and large scale synthesis method was performed to synthesize high-purity BiFeO3 single-crystalline nanostructures in NaCl−Na2SO4 medium. The synthesis of BiFeO3 phase is limited by a very narrow range of sintering conditions, and the BiFeO3 can be obtained after a very short sintering time (20 min).

Anodic Behaviour of Electrodeposited Zn-Sn Alloys

SummaryThe paper discusses the anodic behaviour of the electrodeposited alloys Zn-15%Sn in comparison with pure Zn coatings in 0.5M Na2SO4 and 5% NaCI. A passive state in 0.5M Na2SO4 medium was registered for the alloy while in 5% NaCI the typical passive state was not observed. The selective dissolution of Zn-Sn coatings in media of 0.5 M Na2SO4, and 5% NaCI under the effect of anodic polarisation in the active state was investigated. Strong selective dissolution of some of the alloy components was not established.The elemental and chemical compositions of the surface layers formed on ZnSn coatings after anodic treatment in 0.5 M Na2SO4 were studied by X-ray photoelectron spectroscopy (XPS). A gradual tin-enrichment of the surface layer was established.The changes in the structure and morphology of the studied galvanic alloy in 0.5 M Na2SO4 under the influence of different corrosion-electrochemical treatments were investigated.

Comparative salt responses of callus cultures of Vigna radiata L. Wilczek to various osmotic and ionic stresses

Summary Leaf derived callus cultures of Vigna radiata (L.) Wilczek cv. K-851 were grown on modified PC-L2 medium salinized with various concentrations of NaCl, KCl, Na2SO4 or their mixture and mannitol to study the effect of osmotic and different types of salt stresses on callus growth and ion accumulation. The callus responded differently with stress and salt types. Callus growth was inhibited more severely with Na2SO4, followed by KCl, salt mixture, NaCl and mannitol. A correlation between growth inhibition and the concentration of inorganic solutes in callus tissue was noted. Accumulation of Na+ in callus was accompanied by loss of K+ at all levels of Na2SO4, NaCl and salt mixture. Severe inhibition of cell growth with Na2SO4 was due to more uptake of Na+ by cells under Na2SO4 medium than any other salt and their mixture. SO4−2 ion content in Na2SO4 grown callus was 60–70 times higher than Na+. Similarly, K+ and Cl− contents of KCl callus were greater than Na+ and Cl− of NaCl grown callus. A comparison between salt mixture and its constituent different salts shows that some single salts (Na2SO4 and KCl) were more toxic than a salt mixture. An increase in the osmotic stress (by mannitol) inhibited callus growth less severely than any of the salts. This may be due to higher K+ content of the cells under mannitol stress than iso-osmotic concentration of any of the salts.

Effects of Salt Concentration on the Intracellular Cadmium Content of and the Cadmium Uptake by a Highly Cadmium-tolerant, Moderately HalophilicPseudomonassp.

The intracellular cadmium (Cd) content was measured with early stationary phase cells of a highly Cd-tolerant moderately halophilic bacterium Pseudomonas sp. No. 40 cultivated in 1M and 3M NaCl medium containing 0 to 2500 μg of CdCl2/ml. It was found that the Cd contents were greatly affected by the NaCl concentration of the medium. When the bacterium was cultivated in the 1, 2, 3, and 4M NaCl medium containing 1500 μg of CdCl2/ml, the intracellular Cd content was 25.0, 4.1, 3.1, and 2.0 mg Cd per g of dry cells, respectively. The intracellular Cd content decreased with increases of NaCl concentration of the medium. The fact seems to reflect Cd-tolerance of the bacterium towards the growth in the medium of different NaCl concentration. It is worthwhile to note that the bacterium showed the highest Cd-tolerance (in 3M NaCl) and the lowest Cd content among the bacteria so far known. The bacterial cells grown in the 1M NaNO3 and 1M Na2SO4 medium accumulated 1.8–1.3 times as much Cd2+ as those in the 1M NaCl ...

Stoichiometry of a half-turnover of band 3, the chloride transport protein of human erythrocytes.

The kinetics of human red blood cell Cl transport have been studied under nonequilibrium conditions to determine whether or not an outward Cl gradient can recruit the transport protein from an inward-facing to an outward-facing configuration. Three kinds of evidence are consistent with this outward recruitment. First, the initial net Cl efflux into a Cl-free phosphate medium is independent of the intracellular Cl concentration in the range 20-170 mM. Second, an outward Cl gradient strongly enhances the inhibitory potency of DNDS (4,4'-dinitro-2,2'-stilbene disulfonate), which suggests that DNDS binds primarily to outward-facing states. Finally, we have estimated the number of Cl ions transported during the putative outward recruitment. Resealed red cell ghosts containing only 70 muM 36Cl were resuspended at 0 degrees C in a Cl-free, HCO3-free Na2SO4 medium. In the first 10 s, or approximately 10(6) Cl ions per ghost, followed by a much slower further loss of Cl. The rapid loss of 10(6) Cl ions per ghost, which is abolished by pretreatment with DIDS (4,4'-diisothiocyano-2,2'-stilbene disulfonate), appears to represent the Cl that is transported during the first half-turnover of the transport cycle. These data are strong evidence that the influx and efflux events in the catalytic cycle for anion transport do not take place simultaneously, and that the stoichiometry of the transport cycle is close to one pair of anions exchanged per band 3 monomer.

Oxydation électrochimique de l'acide formique sur électrode d'or en milieu neutre

The electrochemical oxydation of formic acid is studied in 0.5 M Na2SO4 medium on a gold electrode, for pH greater than pK of formic acid. Its characteristics are different from that of an acid medium. The reaction begins at about 200 mV/NHE. The oxidation current shows a maximum at about 800 mV/NHE depending on the rate of potential change. A mechanism is written and one interpretation is given taking into account the aqueous species adsorbed on a gold electrode.