Sulfuric Acid Of Various Concentrations Research Articles

Controlled production of spruce cellulose gels using an environmentally “green” system

Stable spruce cellulose suspensions were generated in NaOH/urea aqueous solutions and used to make thermally induced gels with various swelling ratios and compressive strengths. Wood cellulose cannot be easily dissolved in water or any common organic solvent due to its high molecular weight, which largely limits its applications. Spruce cellulose was hydrolyzed by diluted sulfuric acid of various concentrations and hydrolysis times. The dissolution of these partially degraded samples was investigated in a NaOH/urea aqueous solution system considered environmentally “green.” The effects of acid hydrolysis on the structure and properties of subsequent thermally induced gels were examined using scanning electron microscopy, swelling and re-swelling experiments, and mechanical testing. The molecular weight of spruce cellulose was significantly reduced by acid hydrolysis, whereas its crystallinity slightly increased because of the removal of amorphous regions. All samples could be partially dissolved in the NaOH/urea aqueous solution and formed stable suspensions. Hydrolyzed cellulose samples with lower molecular weight exhibited a higher solubility. Rheological experiments showed these cellulose suspensions could form gels easily upon heating. A porous network structure was observed in which dissolved cellulose was physically crosslinked upon heating and then regenerated to form a three-dimensional network, where the dispersed swollen cellulose fibers filled spaces to reinforce the structure. The swelling behavior and mechanical properties of these ‘matrix-filler’ gels could be controlled by varying the mild acid hydrolysis conditions, which adjusts their degree of solubility. This research provides several opportunities for manufacturing wood cellulose based materials.

Study of properties of chemically modified samples of halloysite mineral with X-ray fluorescence and X-ray powder diffraction methods

Elemental and chemical composition of raw and activated samples of halloysite mineral using wavelength dispersive X-ray fluorescence (WDXRF), total reflection X-ray fluorescence (TXRF) and X-ray powder diffraction (XRPD) methods were determined. As the result, it has been shown that application of the complementary X-ray spectrometry techniques allows very precise observation of changes in composition of halloysite mineral samples caused by its chemical modifications. Sample preparation procedure and usability of the research methods applied are described in details. Procedure of activation of raw halloysite mineral samples by etching them in sulfuric acid of various concentrations has been described and discussed. The ability of the samples to adsorb lead from intentionally contaminated water was tested and confirmed.

Adding value to the Brazilian sisal: acid hydrolysis of its pulp seeking production of sugars and materials

The present work is inserted into the broad context of the upgrading of lignocellulosic fibers. Sisal was chosen in the present study because more than 50% of the world’s sisal is cultivated in Brazil, it has a short life cycle and its fiber has a high cellulose content. Specifically, in the present study, the subject addressed was the hydrolysis of the sisal pulp, using sulfuric acid as the catalyst. To assess the influence of parameters such as the concentration of the sulfuric acid and the temperature during this process, the pulp was hydrolyzed with various concentrations of sulfuric acid (30–50%) at 70 °C and with 30% acid (v/v) at various temperatures (60–100 °C). During hydrolysis, aliquots were withdrawn from the reaction media, and the solid (non-hydrolyzed pulp) was separated from the liquid (liquor) by filtering each aliquot. The sugar composition of the liquor was analyzed by HPLC, and the non-hydrolyzed pulps were characterized by viscometry (average molar mass), and X-ray diffraction (crystallinity). The results support the following conclusions: acid hydrolysis using 30% H2SO4 at 100 °C can produce sisal microcrystalline cellulose and the conditions that led to the largest glucose yield and lowest decomposition rate were 50% H2SO4 at 70 °C. In summary, the study of sisal pulp hydrolysis using concentrated acid showed that certain conditions are suitable for high recovery of xylose and good yield of glucose. Moreover, the unreacted cellulose can be targeted for different applications in bio-based materials. A kinetic study based on the glucose yield was performed for all reaction conditions using the kinetic model proposed by Saeman. The results showed that the model adjusted to all 30–35% H2SO4 reactions but not to greater concentrations of sulfuric acid. The present study is part of an ongoing research program, and the results reported here will be used as a comparison against the results obtained when using treated sisal pulp as the starting material.

Kinetic Study of Empty Fruit Bunch Using Hot Liquid Water and Dilute Acid

Empty fruit bunch (EFB), a residual product of the palm plantation, is an attractive biomass for biorefinery. As xylan is susceptible to high temperature pretreatment, it is important to setup a proper pretreatment condition to maximize the sugar recovery from EFB. Kinetic parameters of mathematical models were obtained in order to predict the concentration of xylose, glucose, furfural, and acetic acid in the hydrolysate and to find production conditions of xylose. We investigated the kinetics of hot liquid water and dilute sulfuric acid hydrolysis over a 40-min period using a self-designed setup by measuring the concentrations of released sugars (xylose, glucose) and degradation products (acetic acid and furfural). The reaction was performed within the range 160∼180 °C, under reaction conditions of various concentration of sulfuric acid (0.1∼0.2%) and 1:7 solid-liquid ratio in a batch reactor. The kinetic constants can be expressed by the Arrhenius equation with the activation energy for the hydrolysis of sugar and decomposition of sugar. The activation energy of xylose was determined to be 136.2187 kJ mol(-1).

Interaction of two oscillating sonoluminescence bubbles in sulfuric acid

The mutual interaction of two oscillating gas bubbles in different concentrations of sulfuric acid is numerically investigated. A nonlinear oscillation for spherical symmetric bubbles with equilibrium radii smaller than 10 μm at a frequency of 37 kHz in a strong driving acoustical field P(a)=1.8 bar is assumed. The calculations are based on the investigation of the secondary Bjerknes force with regard to adiabatic model for the bubble interior which appears as repulsion or attraction interaction force. In this work the influence of the various concentrations of sulfuric acid in uncoupled and coupled distances between bubbles has been investigated. It is found that the sign and value of the secondary Bjerknes force depend on the sulfuric acid viscosity and its amount would be decreased by liquid viscosity enhancement. The results show that big change in the parameters of produced bubbles occurs in the sulfuric acid with concentrations from 65% to 85%.

SYNTHESIS OF IRON OXIDE-MONTMORILLONITE COMPOSITE AND STUDY OF ITS STRUCTURAL STABILITY AGAINTS SULFURIC ACID

The synthesis and characterization of iron oxide-montmorillonite and its structural stability test with various concentration of sulfuric acid were conducted. Synthesis was performed by treating Na-montmorillonite clay with oligocations of iron, followed by calcinating the intercalation compound of oligocations-montmorillonite at 200oC for 24 hours. Calcined product was then characterized to determine the iron content, basal spacing and its porosities distribution. To test structural stability againts strong acid (i.e. sulfuric acid), the composites were dispersed into solution of sulfuric acid with various concentration, i.e: 1, 2 and 3M for 24 hours. The characterization result, especially from x-ray-diffractometry analysis, demonstrated that modification of montmorillonite using iron (III)oxide produced so called house of card structure as indicated by its broad, low intensity reflection at 2θ = 5-6o. The addition of sulphuric acid into composite resulted in probably the formation of face to face arrangements indicated by the appearance of 001 plane reflection. The acid treatment also caused the decrease in the iron content of the iron oxide-montmorillonite as shown by its neutron activated analysis result. The iron content of iron oxide-montmorillonite before the acid treatment was 32,01% w/w, and after the acid treatment was 14.08% w/w (with sulfuric acid of 1M), 6.05% w/w (sulfuric acid of 2M) and 5,98% w/w (with sulfuric acid of 3M), respectively. In general, the sulphuric acid treatment to the composite did not distore the 001 planes of the montmorillonite. Keywords: pillarization, montmorillonite, structure stability

Corrosion Resistance of Electrodeposited RE-Ni-W-P-SiC-PTFE Composite Coatings

Corrosion rates and anode polarization curves of RE-Ni-W-P-SiC-PTFE composite coatings in various concentrations of sulfuric acid and hydrochloric acid solutions have been studied. Results show that corrosion law of the RE-Ni-W-P-PTFE-SiC composite coatings in various concentrations of sulfuric acid solutions is identical. The corrosion rates of the composite coatings are increased with increasing sulfuric acid concentration while the corrosion rates are decreased with increasing concentration of hydrochloric acid. Anode polarization curves of RE-Ni-W-P-SiC-PTFE composite coatings in various concentrations of sulfuric acid and hydrochloric acid solutions have showed that anode polarization electric current density of the composites at 200°C or 500°C heat treatment was below that at other heat treatment, it is clear that the composite coatings at 200°C or 500°C heat treatment has better corrosion resistance.

Effect of Sulfuric Acid Concentration on Acoustic Emission Signals in Uniform-Corrosion

In petroleum industry, corrosion failures of steel structures are common. The severity of corrosion in oil distillery inorganic compounds is higher than in those of organic compounds. Inorganic compounds such as sulfur are the most influential corrosive activators inside oil or chemical storage tanks. They normally have the tanks inspected and repaired along their life time. In addition the concentration of sulfur compound increases due to the accumulation of the residuals inside the tank, and so does the corrosive rate. In this paper, Acoustic Emission (AE) has been chosen to study the characteristic of AE signals received from the uniform corrosion mechanism of mild steel (A36) in various concentrations of Sulfuric acid (H2SO4) solution. AE signals were captured using a wide band sensor (WD) and recorded by AE system model LOCAN 320. The relationship between AE signals and sulfur concentrations as well as pH were exhibited.

Production of xylose from oil palm empty fruit bunch fiber using sulfuric acid

Oil palm empty fruit bunch fiber is a lignocellulosic waste from palm oil mills. It is a potential source of xylose which can be used as a raw material for production of xylitol, a high value product. The increasing interest on use of lignocellulosic waste for bioconversion to fuels and chemicals is justifiable as these materials are low cost, renewable and widespread sources of sugars. Batch hydrolysis of oil palm empty fruit bunch fiber was performed at operating temperature 120 °C using various concentration of sulfuric acid (2–6%) and reaction time (0–90 min). Concentration of xylose, glucose, furfural and acetic acid in the resulting hydrolysate were determined. Kinetic parameters of mathematical models were obtained in order to predict concentration of xylose, glucose, furfural, acetic acid in the hydrolysate and to optimize the process. Optimum H 2SO 4 concentration and reaction time obtained under operating temperature of 120 °C was 6% and 15 min, respectively. Optimum concentration of xylose, glucose, furfural and acetic acid found in the hydrolysate were 29.4, 2.34, 0.87 and 1.25 (g/l), respectively.

Corrosion Resistance of Hastelloy-B in the Ozonized Medium

Corrosion-electrochemical behavior of Hastelloy-B and its components nickel and molybdenum is investigated at various concentrations of sulfuric acid in the presence of ozone. It is found that in ozonized solutions of sulfuric acid the alloy is corrosion-proof, and the effect of molybdenum reduces to ordinarily diminishing the anodic dissolution of nickel.

Kinetics of Reaction of Nickel(II) Hydroxide with Sulfuric Acid

Changes in the concentrations of nickel(II) sulfate and sulfuric acid in the course of the dissolution of nickel(II) hydroxide powder in sulfuric acid of various concentrations at 25, 50, and 75°C were evaluated from variation of the electrolyte resistance. The rate constant and activation energies of the dissolution were calculated.

“In situ”13C NMR study of ethyl alcohol interaction with sulfuric acid

“In situ” NMR study of ethyl alcohol interaction with sulfuric acid of various concentrations confirmed that in accordance with chemical experience the main reaction product in an excess of concentrated acid is the mono-ethyl sulfate. Only traces of diethyl sulfate are formed in a large excess of 95% acid. In addition, ethyloxonium ions and protonated esters, which rapidly exchange protons with solvating water molecules, are detected as the reaction intermediates. The13C chemical shifts of methylene fragments in protonated esters and ethyl oxonium ions are more than 10 ppm higher than in neutral molecules. The study of reaction products at different sulfuric acid concentrations indicated that similarly to dissociation of concentrated sulfuric acid, hydrolysis of mono-ethyl sulfate requires at least two water molecules.

Raman Study of Sulfuric Acid at Low Temperatures

A Raman spectroscopic study has been carried out for aqueous sulfuric acid of various concentrations at room temperature and in the glassy state. Temperature dependence of the Raman spectra was also investigated from 44 to −40 °C. Anomalous Tg (glass transition temperature) behavior of the aqueous sulfuric acid solution at ∼86 wt % H2SO4 is interpreted in terms of ionic species involved in Raman spectral changes. It is shown that ionization of sulfuric acid increases exponentially with decreasing temperature. Complete ionization was attained up to ∼50 wt % H2SO4 concentration in glassy aqueous H2SO4 solution.

High-Pressure Electrical Conductivity and NMR Studies in Variable Equivalent Weight NAFION Membranes

Measurements of the electrical conductivity and proton and fluorine-19 NMR spin−lattice relaxation times (T1) in acid form NAFION 105, 117, and 120 conditioned at various levels of relative humidity have been carried out. Complex impedance studies were made along the plane of the polymer film at frequencies from 10 to 108 Hz at room temperature and pressures up to 0.3 GPa. The NMR measurements were made at room temperature and pressures up to 0.25 GPa. Both types of measurement were also carried out on various concentrations of sulfuric acid in water. The electrical conductivity decreases with increasing pressure for low water content acid solutions and low water content NAFION samples. This behavior (positive activation volumes) is that expected for “normal” liquids and for ions in polymers where the motion of the ions is determined by the host matrix. However, for high water contents, the reverse is true. The electrical conductivity increases with increasing pressure which gives rise to a negative activ...

Solution Properties of Poly(4-vinylpyridine) in Aqueous Solutions of Sulfuric Acid

Abstract The conformation of poly(4-vinylpyridine) (P4VP) in aqueous solutions of sulfuric acid was studied by light scattering and viscosity measurements at 25 °C. Comparing the experimental intramolecular particle scattering factor (P(θ)) and Debye’s theory, it was confirmed that in the Θ-state where the apparent second virial coefficient is zero, the conformation of P4VP is characterized as a Gaussian chain. The intrinsic viscosities of P4VP in aqueous solutions of sulfuric acid of various concentrations were analyzed according to the theoretical equation of Tanaka. The value of the characteristic ratio (C∞) increased with increasing H2SO4 concentration.

Pattern Formation on Aluminum Electrodes

The mechanisms of the cells forming the almost periodic structure on anodized aluminum electrodes in contact with various acid solutions was investigated. Their size was correlated to the product of the electrode wettability variation induced by switching the applied potential from a hydrogen evolution potential to an anodizing potential and the current density during the anodizing process. The mechanism of cell formation is related to solute concentration inhomogeneities at the film‐solution interface generating local variations in the film‐solution interfacial tension. Interfacial tension gradients induce spatial and temporal variations in the electrolyte velocity. Particles dragged by electrolyte motion will also have different velocities, so that interparticle contacts will occur. The internal motion of the fluid film accelerates the aggregation of particles into preferential geometries which were observed on the electrode surface by SEM. The size of cells forming the structure, for various acids and for various concentrations of sulfuric acid, were determined experimentally and a successful matching of these results with the model recently developed was obtained.

Quality of nigerian palm oil after bleaching with local treated clays

AbstractLaboratory investigations into the possibility of using local Nigerian clays in refining the Nigerian crude palm oil revealed that the Okija clay may possess some potential as an adsorptive cleanser in the refining process. Activated bentonite was used as the standard clay of comparison, and the performance of two local natural clays, leached with various concentrations of sulfuric acid, was evaluated for their use as alternative adsorptive cleansers in refining Nigerian crude palm oil. Measurements of peroxide values, para‐anisidine values, carotene content and stabilities of the oils using the active oxygen method were used in assessing the relative performance of the clays.The clays exhibited similar trend of effects on identical batches of alkali‐neutralized palm oil. In one set of experiments poor results were obtained when the degummed and alkali‐neutralized palm oil was treated with clays leached with sulfuric acid at concentrations of 1M and 4M. Better results were obtained at acid concentrations of 2M and 3M. Bentonite proved better than Okija clay when the leaching was performed with 2M H2SO4, but both clays had comparable effectiveness when 3M H2SO4 was used for leaching. The Nsu clay gave the least encouraging results. In another series of experiments the results showed that for various dosages of clay, up to 3% by weight of the oil to be refined, the oxidative stability of the processed oil was reasonably good for an oil which was neither deodorized nor treated with antioxidants.

ChemInform Abstract: Nitration of 4‐Halo‐1‐methylpyrazoles in Sulfuric Acid.

AbstractThe nitration of the 4‐halo‐1‐methylpyrazoles (I) is studied in detail.

Nitration of 4-halo-1-methylpyrazoles in sulfuric acid

The rate of nitration of 4-bromo- and 4-chloro-1-methylpyrazoles with nitric acid in various concentrations of sulfuric acid is higher at position 5 than at position 3.

Simultaneous determination of arsenic(III) and arsenic(V) in metallurgical processing media by ion chromatography

AS(III) and As(V) in simulated zinc processing solutions have been determined simultaneously by ion chromatography with triple-step pulsed-potential electrochemical and conductivity detectors, respectively. The ion chromatograms obtained using single-potential and triple-step pulsed potential are compared for arsenite solutions containing various concentrations of sulfuric acid. As(III) and As(V) in commercial copper processing solutions have been determined simultaneously by ion chromatography with ultraviolet detection. Molar absorptivities at 200 nm are determined, and the effects of acid, chloride, and sulfate on the absorbance are discussed. For both analytical procedures, cations must be preseparated with H +-form ion-exchange resin to avoid partial precipitation of arsenic during dilution.