Aqueous Sulfuric Acid Solutions Research Articles

Carrier Assisted Emulsion Liquid Membrane Process for Recovery of Basic Dye from Wastewater using Continuous Extractor

Nowadays, water pollution has become major issue especially dye contaminated wastewaters from the textile industry. Dye causes serious environmental pollution and health problems. The removal of color from dye-contaminated wastewaters in the related industries becomes a major concern all over the world. In this research, several parameters of dye extraction and recovery in the continuous emulsion liquid membrane (ELM) process were investigated. This process consisted of three phases which are external (feed) phase, membrane phase and internal phase. The membrane phase was prepared by dissolving extractant bis(2-ethylhexyl)phosphoric acid (D2EHPA) and hydrophobic surfactant sorbitan monooleate (Span 80) in kerosene as diluents. The internal phase consisted of an aqueous solution of sulfuric acid (H2SO4). The important parameters governing the extraction process of dye such as stirring speed, initial dye concentration, Span 80 concentration and treat ratio (volume ratio of emulsion to external phase) were studied. The results showed that the optimum condition for 25ppm initial concentration of dye extraction are 250 rpm stirring speed, 5% (w/v) Span 80 and treat ratio 1:5. At this condition, the percentage of dye extraction, stripping and recovery were 98%, 82% and 81% respectively. Hence, continuous ELM technique is proven to be a very promising technique in industrial wastewater treatment and recovery of dye.

Electrosynthesis and In Situ Spectroelectrochemistry of Conducting o-aminophenol-p-aminophenol Copolymers in Aqueous Solution

Copolymerization of o-aminophenol (o-AP) and p-aminophenol (p-AP) in aqueous sulfuric acid solution was electrochemically performed using cyclic voltammetry on gold electrode. Copolymerization was carried out at different feed concentrations of homo monomers. The obtained films were characterized with cyclic voltammetry, in situ resistivity measurements, in situ UV-Vis-spectroscopy, FT-IR spectroscopy, and scanning electron microscopy (SEM). Cyclic voltammetry study shows that the onset potentials for o-AP, p-AP and o-AP + p-AP are located at the different values. The results from the electrochemical copolymerization of o-AP with p-AP demonstrate that the CVs of copolymers films growth are different from those of homopolymers, and are strongly affected by the amount of monomers. The in situ resistivity of copolymers measured from −0.20 V to 0.95 V vs. SCE decreased with increasing the [o-AP]/[p-AP] concentration ratio. In situ UV-visible and ex situ FT-IR spectra of homopolymers and copolymers results show intermediate spectroscopic behavior between homopolymers and copolymers. SEM micrographs of the samples show fundamental differences between the morphology of the homo- and copolymers.

球状黒鉛鋳鉄の硫酸水溶液中における腐食挙動に及ぼす黒鉛と基地の境界長の影響

球状黒鉛鋳鉄の硫酸水溶液中における腐食挙動に及ぼす黒鉛と基地の境界長の影響

A flow-injection system coupled to a micro-guard cartridge for monitoring a vinification process.

The present paper describes a flow-injection system coupled to a Micro-Guard cartridge and a miniaturized optical CCD detection system used to monitor the sugars (glucose/fructose) and ethanol content during alcoholic fermentation. The carrier stream (mobile phase) is composed of an aqueous sulfuric acid solution. The flow parameters were studied in order to obtain a good resolution and a wide dynamic concentration range, with a good repeatability. The relative standard deviation (RSD) obtained was inferior to 4%, for n = 3. It was possible to achieve a linear range of up to 12 g L(-1) of sugars and up to 2% (v/v) of ethanol with a detection limit of 2.3 g L(-1) and 0.4% (v/v), for sugars and ethanol concentrations, respectively. The proposed system was successfully applied to monitor a vinification process by the quantification of sugars and ethanol, and also in some finished port wines.

Synthesis and Characteristic of Precipitated Nano-Silica

The reaction of precipitation of amorphous silicon dioxide from aqueous solution of sodium silicate and sulfuric acid has been studied. The factors affecting the precipitation process of the sodium silicate solution such as sodium silicate concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on particle size, size distribution and degree of agglomeration of the precipitated silica were examined. The precipitation of silica from the produced sodium silicate solution was carried out using sulfuric acid at pH 7. Scaning electron microscope (SEM), transmission electron microscope (TEM) and Dynamic light scattering (DLS) have been used for characterization of the produced nano-silica. The surface area of silica was tested by oil absorption method according to ASTM standard. Results showed that the particle size of the precipitated silica gel was decreased with increasing Na2SiO3 and SDS concentrations and Particle size of about 44nm can be achieved at 20% Na2SiO3 and 200ppm SDS. But with decreasing particle size, degree of agglomeration also increased.

Solubilities of p-Toluenesulfonic Acid Monohydrate and Sodium p-Toluenesulfonate in Aqueous Sulfuric Acid Solutions and Its Application for Preparing Sodium p-Toluenesulfonate

The solubilities of p-toluenesulfonic acid monohydrate (PTSA·H2O) and sodium p-toluenesulfonate (NaPTS) in aqueous sulfuric acid solutions were investigated at a temperature range from 278.45 to 342.95 K. The experimental results showed that the solubilities of PTSA·H2O and NaPTS in aqueous sulfuric acid solutions increased with temperature from 278.45 to 342.95 K and decreased with sulfuric acid concentrations from 0 to 0.7. The experimental data were correlated with the modified Apelblat equation. The calculated results showed good agreement with the experimental data. A new strategy which sodium sulfate was used as a starting material in the preparation of NaPTS was profiled according to the solubility difference between PTSA·H2O and NaPTS. In the continuous preparation of NaPTS, the favorable mole ratio (PTSA·H2O to sodium sulfate) is chosen as 4.0, and the optimum operation conditions of the recycle process were determined, which improved the present process of 4-methylphenol production.

Electrosynthesis and protection role of polyaniline–polvinylalcohol composite on stainless steel

Polyaniline–polyvinyl alcohol (PANI–PVA) composite has been electrodeposited on stainless steel surface from aqueous sulfuric acid solution of aniline monomer in presence of soluble PVA at different concentrations. The PVA increased the rate of electropolymerization where 4g/L PVA formed a composite of 37wt% PANI and 63wt% PVA composition. The composite layer exhibited more adhesion to the steel surface in comparison with PANI layer but with less thermal stability. It has higher protection role for the stainless steel (SS) against general and pitting corrosion. It enhanced the passivation of the SS surface by increasing the thickness of oxide film and improving the composition.

Influence of Oxidation on the Corrosion Resistance of Sintered Titanium

We study the corrosion resistance of sintered titanium specimens obtained by the methods of powder metallurgy in a 40% aqueous solution of sulfuric acid and in a 20% aqueous solution of hydrochloric acid at room temperature. It is shown that the modification of the surface layers of sintered titanium specimens by interstitial elements and, especially oxygen, increases their corrosion resistance. The maximum protection effect against aggressive media is provided by an oxide film obtained by thermodiffusion oxidation under the conditions of saturation in the oxygen-containing controlled atmosphere and by the oxidation in air: the corrosion resistance increases by three orders of magnitude as compared with the corrosion resistance of the unprotected surface.

Dependence of anodic titanium (IV) oxide properties on activator composition

The process of obtaining a secondary carrier of catalytically active substance for its application in catalysis was considered and some results of our research in this field were given. The main objective of the study is to examine the dependence of properties of titanium (IV) oxide, obtained by anodization method, on the activator composition. Porous titanium (IV) oxide layer was obtained by titanium plate anodizing in electrolyte consisting of aqueous solutions of sulfuric acid and activator. By changing the activator composition its effect on the properties of secondary carrier and optimal anodizing time was studied. The presented method allows estimating the dependence of thickness and porosity of the obtained secondary carrier and optimal anodization time on the activator composition. The results of the study can be used in electrochemistry and catalysis for improving the process of obtaining secondary carrier forcatalytically active substances. We propose to improve the process of getting secondary carrier for catalytically active substances on the surface of titanium plate using more efficient activator.

Non-Boltzmann Population Distributions during Single-Bubble Sonoluminescence

Single-bubble sonoluminescence (SBSL) spectra from aqueous sulfuric acid solutions containing dissolved neon show widely varying emission despite being similar in chemical composition. From a 65 wt % solution, emission from hydroxyl radicals is observed, with the rovibronic progression being well-described by a single temperature of 7600 K. From an 80 wt % solution, however, emission spectra reveal vibrationally hot sulfur monoxide (SO; Tv = 2400 K) that is also rotationally cold (Tr = 280 K). Further, the SO vibrational population distribution is best-described by a non-Boltzmann distribution. Excited neon atom emission observed from the 80 wt % solution gives an estimated temperature of only 3400 K, indicative of emission from a cool outer shell at the interfacial region. The neon atom excited-state population is also best-described by a non-Boltzmann distribution. These observations are consistent with SBSL emission having both a spatial and temporal component, and the implications for these effects are discussed.

Glass Wool Material as Alternative Separator for Higher Rating Electric Double Layer Capacitor

The paper evaluates the electrochemical performance of glass wool as an alternative separator material for electric double layer capacitor (EDLC) construction. Using aqueous solution of sulfuric acid as the electrolyte, two-electrode coin-type capacitors were constructed by sandwiching the electrolyte-containing glass wool with two activated carbon sheets. Electrochemical properties of the capacitors were characterized by cyclic voltammetry, galvanostatic and impedance spectroscopy measurements. The glass wool-based capacitor outperforms the practically used cellulose separator with higher power and energy densities of 566 W/kg and 15 kJ/kg, respectively. The implementation of glass wool separator will enable the utilization of high concentration aqueous electrolytes, which lead to higher rating EDLC at relatively lower cost compared to organic solution-based capacitor.

Energy concentration and positional stability of sonoluminescent bubbles in sulfuric acid for different static pressures

In this study we report several experimental and numerical results on the influence of static pressure (P_{0}) over the main parameters in single bubble sonoluminescence (SBSL), using a sulfuric acid aqueous solution (SA) with low concentrations of argon gas dissolved. Bifrequency driving was used in the experiments to enhance spatial stability of the bubbles. The experimental results were compared with simulations provided by a numerical code that models the radial dynamics of the bubbles. The results showed that an increase on the static pressure of the system shifts the Bjerknes instability threshold, allowing the bubble to access higher acoustic pressures (P_{Ac}^{}). Furthermore, a decrease in the measured ambient radius R_{0} and the calculated relative gas concentration c_{∞}/c_{0} were observed. A notorious increment in the bubble collapse violence and energy focusing for P_{0} above 1 bar was achieved. These were mainly indicated by the growth of the bubble expansion ratio (R_{max}/R_{0}), the bubble mechanical energy density, and the maximum bubble wall velocity dR/dt. In agreement with the previous statement, the maximum temperature during the bubble collapse predicted by the model is augmented as well. The use of different harmonics in the ultrasound pressure field regarding energy focusing is also discussed. Finally, we analyzed the stability regions of the R_{0}-P_{Ac}^{} parameter space via numerical predictions for P_{0} above the measured, identifying the shape instabilities as the main limiting agent to obtain further energy concentration in SA systems at high static pressures.

Effects of intermediate surface treatments on corrosion resistance of cathodic arc PVD hard coatings

Aiming to improve corrosion resistance of CrN coated tool steel parts, intermediate treatments were introduced to remove surface droplets and inclusions of cathodic arc CrN coatings midway of the deposition. Three intermediate treatments were examined: micro-blasting with two types of blasting media and Ar ion plasma etching followed by Ti ion bombardment. CrN coatings with two-layer structures were deposited on refined AISI D2 tool steel substrates. At the interface between the lower and upper layers of the coating, intermediate treatments were applied. Corrosion behavior of the coatings was studied by immersion tests and anodic polarization measurements in 10% sulfuric acid aqueous solutions. Observation of the coatings and their cross-sections was made using field emission scanning electron microscope with refection electron imaging, and focused ion beam scanning electron microscope. The results of the immersion tests showed that applying intermediate treatments enhanced the corrosion resistance of CrN coatings. Particularly, intermediate removal of the droplets and inclusions of a coating surface and smoothing the interface prevented formation of penetrated pathways throughout growth defects, thus preventing the formation of corrosion cells and improving the corrosion resistance of the substrate–coating system. Based on the findings of this study, intermediate treating of cathodic arc coatings showed a promising solution to improve corrosion resistance of coated parts operating at corrosive environments.

Liquid–liquid equilibria for the pseudo-ternary system {aqueous sulfuric acid solution + methyl ethyl ketone or methyl isopropyl ketone + phosphonium-based ionic liquids} at 298.15 K and atmospheric pressure

The extractability of molybdenum in an aqueous phase by methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and methyl isopropyl ketone (MIPK) were analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The pseudo-ternary LLE data are reported for the following systems at 298.15K: {aqueous sulfuric acid solution (ASAS)+MEK+tri-hexyl tetradecyl phosphonium chloride ([P666,14][Cl])}, {ASAS+MEK+tri-hexyl tetradecyl phosphonium dicyanamide ([P666,14][DCA])}, {ASAS+MEK+tri-hexyl tetradecyl phosphonium bis(2,2,4-tri-methylpentyl) phosphinate ([P666,14][TMPP])}, {ASAS+MIPK+[P666,14][Cl]}, {ASAS+MIPK+[P666,14][DCA]} and {ASAS+MIPK+[P666,14][TMPP]}. The experimental LLE data have been correlated using the non-random two-liquid (NRTL) activity coefficient model.

Potentiometric determination of pH values of dilute sulfuric acid solutions with glass combination electrode equipped with ionic liquid salt bridge

The pH of dilute aqueous sulfuric acid solutions in the concentration range between 20 and 200μmoldm−3 has been accurately determined by use of glass combination electrodes, in which the reference electrode is equipped with an ionic liquid salt bridge (ILSB) made of gelled tributyl (2-methoxyethyl) phosphonium bis(pentafluoroethanesulfonyl)amide (TBMOEPC2C2N). Experimental pH values determined by calibration of the electrodes with two pH standard buffer solutions are in agreement within 0.03 pH unit with theoretical pH values at all concentrations of H2SO4 studied. The difference at 50μmoldm−3 H2SO4 solution is smaller by 0.03 pH unit than that obtained previously by Metcalf (Analyst 112 (1987) 1573) using conventional glass combination electrodes based on KCl salt bridge (KClSB). The ILSB enables us to accurately determine pH values of low ionic strength aqueous solutions with the same protocol as that used to date in pH measurements based on glass electrode paired with KClSB-equipped reference electrode. The response times of the ILSB-type glass combination electrodes in pH measurements of low ionic strength solutions are shorter than those of KClSB-type glass combination electrodes because the change of ionic strength in a sample during the pH measurement with ILSB-type is small by virtue of the low solubility of the ionic liquid used as a salt bridge into water.

Enhancement of hydrogen evolution reaction on platinum cathode by proton carriers

The catalytic effect of aniline and benzylamine has been investigated for hydrogen evolution reaction on platinum electrode in sulfuric acid aqueous solution using voltammetric methods and electrochemical impedance spectroscopy. Kinetic parameters which characterize the hydrogen evolution reaction (cathodic transfer coefficient, exchange current density) have been determined using Tafel plots. It has been found that the addition of amines leads to an increase of the exchange current density, explained by an increased concentration of protons available at the interface. The catalytic effect of benzylamine and aniline is strongly correlated to their molecular parameters, such as dipole moment and molecular surface coverage. Also, apparent activation energies for hydrogen evolution reaction from solutions with and without addition of aromatic amines have been calculated. Electrochemical impedance spectroscopy results confirm an overall enhancement of hydrogen evolution in the presence of amines, as indicated by the lower values of charge transfer and adsorption resistances and by the decrease of characteristic time constants.

Electronic State of Oxidized Nanographene Edge with Atomically Sharp Zigzag Boundaries

Combined scanning tunneling microscopy (STM) and density functional theory (DFT) characterizations of the electronic state were performed on the zigzag edge of oxidized nanographene samples. The oxidized zigzag edge with atomically sharp boundaries was prepared by electrochemical oxidation of the graphite surface in aqueous sulfuric acid solution. Bias-dependent STM measurements demonstrated the presence of the edge state at the zigzag edges with local density of states (LDOS) split into two peaks around the Fermi level. Our DFT-based analysis showed that the two-peak structure of the edge state was due to the termination of the zigzag edge by carbonyl functional groups. The LDOS arising from the edge states was slowly dampened in the bulk at the carbonyl-terminated zigzag edges (~1.5 nm). This result is in clear contrast to the strongly localized edge states at hydrogenated zigzag edges in previous reports. The oxygen atoms in the carbonyl functional groups act as additional π sites at the edges; thus, the topology of the π electron network changes from "zigzag" to "Klein" type, leading to drastic modification of the edge states at the oxidized edges.

Polyaniline and its composites with zeolite ZSM-5 for efficient removal of glyphosate from aqueous solution

Nanostructured and granular polyanilines (PANIs) and their composites with zeolite ZSM-5, synthesized by the oxidative polymerization of aniline in water and aqueous solution of sulfuric acid, are evaluated as adsorbents of the organic herbicide glyphosate [N-(phosphonomethyl)glycine] in aqueous solution. The protonated and deprotonated forms of synthesized materials were characterized by elemental and thermogravimetric analysis, scanning electron microscopy, FTIR, Raman and UV–Vis spectroscopies, X-ray powder diffraction, and nitrogen physisorption measurements. The adsorption isotherms of glyphosate on studied materials were best fitted by Freundlich and Langmuir–Freundlich models. The adsorption characteristics of the investigated PANIs and PANI/ZSM-5 composites were found to be much more influenced by the oxidation state and protonation level of PANI in the adsorbents then by the textural and morphological properties of materials. The highest adsorption of glyphosate among all investigated PANI and PANI/ZSM-5 samples, as well as pure ZSM-5, exhibited the deprotonated granular PANI which was synthesized in sulfuric acid medium (98.5mg/g). High adsorption capacity also showed the deprotonated PANI/ZSM-5 composite with ∼50% of zeolite (61.9mg/g) and the protonated nanostructured PANI (59.9mg/g), both materials prepared in water without added acid.

Comparative effect of chrysotile leaching in nitric, sulfuric and oxalic acids at room temperature

The acid leaching of chrysotile was investigated in different acid media with the aim of quantifying and obtaining insights into the dissolution mechanism. Chrysotile was leached in batch reactors for 1 to 30days at 25°C and pH1 in aqueous solutions of nitric and sulfuric acid and different concentrations of oxalic acid (50, 100 and 200mmolL−1). The combined analysis of solutions and solids by XRD and FTIR shows different effects: nitric acid induces a strong dissolution after 30days, lowering the crystallinity of the sample and initiating the transformation of the chrysotile into an amorphous siliceous material. In the case of sulfuric acid, the dissolution is so intense that it is able to destroy the brucitic sheet of chrysotile, leading to an amorphous silica byproduct. Finally oxalic acid is also able to induce amorphization of chrysotile and the precipitation of glushinskite (MgC2O4·2H2O). As the concentration of oxalic increases from 50 to 200mmolL−1 the amorphization process becomes faster. Finally, the relative effectiveness of acid attack to chrysotile is oxalic acid (9days)>sulfuric acid (30days)>nitric acid.

Hydrogenation of nitrobenzene to p-aminophenol using Pt/C catalyst and carbon-based solid acid

Liquid phase hydrogenation of nitrobenzene to p-aminophenol (PAP) in water was studied over a catalyst system composed of Pt/C and carbon-based solid acid which was prepared by one-step hydrothermal carbonization of various carbon sources including starch, sucrose, glucose and furfural in sulfuric acid aqueous solution at 180°C for 4h. The effects of carbon-based solid acid type, Pt/C catalyst loading, hydrogen pressure and reaction temperature on nitrobenzene conversion and PAP selectivity were investigated. The results showed that PAP selectivity was favored at high acid density of the carbon-based solid acid. The carbon-based solid acid prepared from starch, with the highest SO3H amount, gave the highest PAP selectivity among the catalysts used. An increase in Pt/C catalyst loading led to an increased nitrobenzene conversion but a decreased PAP selectivity. A high reaction temperature was in favor of nitrobenzene conversion and PAP selectivity. Under the optimal reaction conditions, nitrobenzene conversion and PAP selectivity reached 61.0% and 77.8%, respectively.