Range Of NaOH Concentrations Research Articles

Structures of sodium vanadate solution under different conditions

Combined with Fourier transform infrared spectroscopy (FTIR) analysis of sodium vanadate solution, the relationship between conductivity and structure was investigated by measuring the electric conductivity of the solution under different alkali concentrations and molar ratios of NaOH to V2O5. Results suggest that the polymerization vanadium acid radical ions gradually transform into monomer with the solution diluting. When the solution is diluted to a certain extent, only the vanadium acid radical ion with V–OH chemical bond exists in the solution. At NaOH concentration of below 105.21 g·L−1, the vanadate anions mainly exist in the form of vanadium acid radical ion with V–OH chemical bond and the ion transference number is approximately from 0.58 to 0.82. In the medium NaOH concentration range of 105.21–117.03 g·L−1, the vanadate anions mostly exist in the form of vanadium acid radical ion with V–OH and V–O–V chemical bonds and the ion transference number is approximately 3.29. At NaOH concentration of above 117.03 g·L−1, vanadate anions exist in the form of vanadium acid radical ion with V–OH and V–O–V chemical bonds.

Phase Diagram for the NaOH–Al2O3–Na2CrO4–H2O System at (120 and 130) °C

The phase diagrams of the NaOH-Al2O3–Na2CrO4–H2O system at (120 and 130) °C and in full NaOH concentration range were determined, and the crystallization zones of each solid were analyzed and discussed. The results show that Na2CrO4, Al2O3·3H2O, Na2O·Al2O3·1.25H2O, Na2O·Al2O3·2.5H2O, and NaOH are present as solid phases in the system at 120 °C, and Na2CrO4, Al2O3·H2O, Na2O·Al2O3·1.25H2O, Na2O·Al2O3·2.5H2O, Na2O·Al2O3, and NaOH are present as solid phases in the system at 130 °C. These results can provide a basis for the separation of Na2CrO4 and Al2O3 from the concentrated alkali solution in the chromate cleaner production process.

Effect of Chemical Treatment on the Mechanical Properties of Pultruded Kenaf Fibre Reinforced Polyester Composites

In this study, Pultruded Kenaf Reinforced Composites (PKRC) has been successfully produced using pultrusion technique. The chemical treatment using sodium hydroxide (NaOH) at different concentration (3%, 6% and 9% M) were carried out to modify the fibre properties. After successfully characterized, it was found that kenaf fibre treated with 6% NaOH recorded the best improvement in term of mechanical properties. In particular, treated pultruded kenaf reinforced composites (TPKRC) shows better tensile and flexural properties compared to those of untreated pultruded kenaf reinforced composites (UTPKRC). It was found that NaOH at 6% concentration give the best composite properties in term of mechanical properties over the range of NaOH concentration studied.

Experimental investigation of egg ovalbumin scaling on heated stainless steel surface and scale-removal compared with that of whey protein

Fouling and cleaning on a heat exchanger surface during milk processing have been studied extensively in the past due to their great importance in energy, product quality, and safety. However, little information is available for egg ovalbumin (OVA) fouling and cleaning behavior. In the present work, fouling and cleaning behaviors of OVA were investigated using a real-time monitoring system for heat transfer coefficient. A comparison was made between the behavior of whey protein concentrate (WPC) and that of OVA. WPC has been well studied which can be used as a benchmark. Ultrasonic cleaning was also applied to investigate the cleaning behavior of OVA fouling. Results have shown that OVA created more thermal resistance than WPC in the 2h fouling process. It was also much more difficult to remove the OVA deposit than the WPC fouling. Different from what were observed from WPC deposit, there was no optimal cleaning rate for OVA deposit in the NaOH concentration range tested (0–2.0wt%), while WPC fouling is known to have the highest cleaning rate around 0.5wt% NaOH concentration at moderate temperatures.

Morphological control of synthetic Ni3Si2O5(OH)4nanotubes in an alkaline hydrothermal environment

Hydrothermal synthesis of nickel silicate nanotubes has been systematically studied in aqueous alkaline environments at 195 °C by varying the Ni/Si molar ratio of the solid materials and the concentration of dissolved NaOH in the precursor suspension. A Ni/Si ratio of 1.5 is ideal for the formation of pure multiwalled nanotubes having a characteristic inner diameter of 10 nm and a typical length of 90–300 nm. The nanotubes have straight walls with a high degree of crystallinity. At lower Ni/Si ratios small nanosheets are formed, with a nickel-deficient layered structure, and nanosheets of β-Ni(OH)2 are formed in addition to nanotubes at Ni/Si > 1.5. Nanotubes are formed over a wide range of NaOH concentration, 2–10 wt%, but the NaOH concentration has a large effect on the aspect ratio, with much longer tubes (almost 300 nm) being formed at 10 wt% NaOH. This result has interesting implications for the design of nickel silicate nanostructures for use in applications such as lithium batteries, mesoporous catalyst supports and reinforced polymer composites.

알칼리 처리에 따른 아마섬유의 헤미셀룰로스 제거와 결정구조 전이

In this study, delignified flax fiber was treated with a NaOH aqueous solution. XRD diffractometry and FTIR spectroscopy were utilized to examine the structural transition of the alkali-treated flax fibers. Also, the effect of the hemicellulose removal on the structural change of flax fibers was discussed. XRD measurement revealed that the crystallinity of cellulose I increased at low NaOH concentration (3%) due to the elimination of amorphous hemicellulose. The structural transition from cellulose I to cellulose II occurred in a NaOH concentration range of 12~15%. Considering most hemicellulose in flax fiber is removed at 12% NaOH, it can be assumed that the presence of hemicellulose in flax fiber has a role in preventing the structural change of flax cellulose. IR absorbance ratios (<TEX>$A_{1370cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX> and <TEX>$A_{1430cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX>) were utilized as a barometer of cellulose I crystalline exhibiting a similar result with the cellulose I crystallinity from XRD. Another absorbance ratio (<TEX>$A_{895cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX>) reflected the cellulose II crystalline showing almost the same trend as cellulose II crystallinity. On the whole, the total crystallinity of flax fiber was increased at low NaOH concentration (3%) and decreased at 12% due to the reduction of cellulose I content and increased again at 15% attributed to the formation of cellulose II content.

Oxidation of Pu(VI) with ozone and stability of the oxidation products, Pu(VII) and Pu(VIII), in concentrated alkali solutions

Oxidation of Pu(VI) with ozone and stability of the oxidation products, Pu(VII) and Pu(VIII), in 4–15 M NaOH solutions were studied. In a wide range of alkali concentrations, from 1 to 15 M, the Pu(VI) ozonation yields a mixture of Pu(VII) and Pu(VIII). It was proved that Pu(VII) exists in aqueous alkali solutions in the form different from that suggested previously. Pu(VII) is readily reduced with ?2? in aqueous alkali solutions with the NaOH concentration of up to 8 M, whereas at [NaOH] + 8 M it is fairly stable. On the contrary, Pu(VIII) is noticeably reduced with water at room temperature throughout the examined range of NaOH concentrations from 1 to 15 M.

Properties of Desilicated ZSM-5, ZSM-12, MCM-22 and ZSM-12/MCM-41 Derivatives in Isomerization of α-Pinene

Limited information is available on the isomerization of α-pinene proceeding on zeolites and related desilicated materials. We wish therefore to report on the title reaction proceeding over ZSM-5, ZSM-12 and MCM-22 type zeolites, parent and modified by the sodium hydroxide treatment. The NaOH solutions of various concentrations (0.05–1 M) were used as a desilicating agent. Such treatments with basic solutions were applied: (i) under atmospheric pressure, and (ii) under hydrothermal conditions. It was shown that ZSM-12 was more resistant towards the basic solutions treatment, and its structure was retained over a whole range of NaOH concentrations studied. Nitrogen sorption revealed strong influence of the desilication process on the pore structure of modified materials—the mesopores system was formed in the zeolite crystals. Finally, catalytic studies were carried out using ZSM-5, ZSM-12, MCM-22, their desilicated derivatives and a ZSM-12/MCM-41 composite material. Catalytic properties of the samples studied were affected to a large extent by the NaOH treatment.

Investigation of solubility of microcrystalline cellulose in aqueous NaOH

A cost-effective and environmentally friendly method to dissolve microcrystalline cellulose (MCC) has been utilized. A detailed investigation of the effects of cellulose amount and solvent (aqueous NaOH) concentration on MCC solubility has been presented. In the experiments, NaOH solutions with concentrations ranging from 3.7 to 18.6 wt% have been employed to dissolve MCC with various weights. The results show that an optimal NaOH concentration range can always be found to give the best solubility of MCC having a certain weight. The solubility monotonically decreases with either the decreasing or increasing of NaOH concentration away from the optimal concentration range. In addition, the optimal concentration range of NaOH for dissolving cellulose has been shown to shrink as the amount of MCC increases. Copyright © 2005 John Wiley & Sons, Ltd.

Morphologies and conformation transition of lentinan in aqueous NaOH solution.

Molecular morphologies and conformation transition of lentinan, a beta-(1-->3)-D-glucan from Lentinus edodes, were studied in aqueous NaOH solution by atomic force microscopy (AFM), viscometry, multiangle laser light scattering, and optical rotation measurements. The results revealed that lentinan exists as triple-helical chains and as single random-coil chains at NaOH concentration lower than 0.05M and higher than 0.08M, respectively. Moreover, the dramatic changes in weight-average molecular weight Mw, radius of gyration [s2](1/2), intrinsic viscosity [eta], as well as specific optical rotation at 589 nm [alpha]589 occurred in a narrow range of NaOH concentration between 0.05 and 0.08M NaOH, indicating that the helix-coil conformation transition of lentinan was carried out more easily than that of native schizophyllan and scleroglucan, and was irreversible. For the first time, we confirmed that the denatured lentinan molecule, which was dissolved in 0.15M NaOH to be disrupted into single coil chains, could be renatured as triple helical chain by dialyzing against abundant water in the regenerated cellulose tube at ambient temperature (15 degrees C). In view of the AFM image, lentinan in aqueous solution exhibited the linear, circular, and branched species of triple helix compared with native linear schizophyllan or scleroglucan.

Electrochemical formation and characterization of Ag2O

The process of Ag2O formation has been investigated in 0.1M, 0.3 M, 1.0Mand 2.0 M NaOH solutions on polycrystalline Ag electrodes by cyclic voltammetry potentiostatic pulse and SEM techniques. The SEM micrographs of the chemically polished Ag surface and the surface after oxide formation revealed considerable roughening of the Ag surface after Ag2O formation and reduction. The roughening was more pronounced at higher NaOH concentrations, indicating that only the first cycle or pulse applied on a freshly polished Ag electrode should be considered in mechanistic studies of Ag2O formation. In the given range of NaOH concentrations, it was shown that the process is not controlled simply by the diffusion of the reacting species.Anucleation phenomenon was clearly detected in all the examined solutions. The SEM micrographs confirm that the two anodic peaks, present on the voltammograms of Ag2O formation correspond to two types of oxide film, i.e., non-homogeneously and homogeneously distributed ones. Potentiostatic formation of the oxide at potentials corresponding to the first and second anodic peak yielded simple cubic Ag2O but of very different grain size.

ENZYMATIC HYDROLYSIS OF CORN STOVER PRETREATED BY COMBINED DILUTE ALKALINE TREATMENT AND HOMOGENIZATION

Corn stover, the most abundant agricultural residue in the U.S., is a potential feedstock for production of bioethanolbecause of its high content of carbohydrates, but an efficient pretreatment is required prior to enzymatic hydrolysis. Inthis study, a combination of NaOH treatment and homogenization was used as a pretreatment to enhance the enzymatic hydrolysisof corn stover. The combined pretreatment increased the enzymatic hydrolysis of corn stover five times compared to thecontrol. The effectiveness of such pretreatment was found to be a function of NaOH concentration and particle size. Withinthe NaOH concentration range of 0.1 to 1.0 N, best performance of this combined pretreatment was achieved at 0.3 N NaOH.There is a significant cross effect of homogenization and NaOH treatment. Among the three particle sizes tested (the particlesize was not directly measured; it passed through screens with openings of 2 mm, 0.707 mm, and 0.25 mm respectively), 2 mmwas found to maximize the economic benefit of the pretreatment.

Thermal Behaviour of Phenol-Formaldehyde (PF) Compounds

The self-condensation reactions of 2- and 4-mono-methylol phenols (2-MMP and 4-MMP), in the presence of varying concentrations of NaOH, have been studied by differential scanning calorimetry (DSC). The reaction exotherms were analysed to derive the activation energy, Ea, and the heat of reaction, HT, for the condensation reactions. In the case of 2-MMP an increase in NaOH:2-MMP molar ratio caused an increased in Ea and a decrease in HT up to a molar ratio of 0.6:1. However, for 4-MMP, an increase in NaOH concentration caused an increase in Ea up to a molar ratio of 0.3:1 beyond which there appeared to be no further effect. The presence of NaOH had no effect on HT for this compound. The results suggest that in the range of NaOH concentration used the effect of NaOH was substantially greater on 2-MMP compared to 4-MMP.

Enhanced Oil Recovery of Acidic Crudes by Caustic Cosurfactant-Polymer Flooding

A laboratory study of alkaline flooding behavior of three viscous acidic crude oils has been carried out. Optimum flooding formulations have been selected by constructing 'activity maps' of the phase behavior of the crude oil-NaOH mixtures as a function of oil fraction and NaOH concentration. Crude oil-NaOH mixtures demonstrate Optimum phase behavior within a very narrow range of NaOH concentration. Addition of nonionic surfactant Triton X-100, as cosurfactant, has been found to enlarge the optimum region of the activity map very considerably. The results obtained from a series of one-dimensional core flow experiments using Berea sandstone cores indicate that simple application of dilute NaOH solution does not recover any significant amount of additional oil as compared to waterflooding. Optimum caustic-cosurfactant solutions with adequate mobility control, using polyacrylamide Cyanatrol 960, recovered upto 96% of oil in place. Caustic consumption appeared to be a significant factor and unfavorable mobility ratio precludes high oil recovery even when caustic solution initiates oil mobilization.

Viscosity and colloidal properties of concentrated crude oil-in-water emulsions

A significant fraction of petroleum reserves in the United States, Venezuela, and Canada are heavy crudes. Water continuous emulsions can be used to transport these highly viscous crudes in pipelines. Many crudes form emulsions with alkaline water due to saponification of natural acids. The viscosity of these anionic emulsions varies with continuous phase ionic strength due to electroviscous effects. Experimental studies were undertaken to determine the effect of NaOH and NaCl concentration on the viscosity, particle diameter, and zeta potential of emulsions of a Boscan heavy crude from Venezuela and a Cold Lake heavy crude from Canada. Oil-in-water emulsions could be formed only for a narrow range of NaOH concentrations. This range was approximately 0.010 to 0.080 mmole/g oil for the Boscan crude and 0.010 to 0.050 mmole/g for the Cold Lake crude. The properties of emulsions exhibited extrema at NaOH concentrations approximately equivalent to the total acid number (TAN) of each crude. This occurred because the maximum surfactant concentration obtainable from the natural acids was reached at the TAN equivalence point. High shear rate viscosity, stability, and zeta potential increased with NaOH addition below this concentration, while particle diameter decreased. Addition of excess NaOH or of NaCl above the equivalence point caused decreases in viscosity and increases in particle diameter at equivalent total sodium ion concentrations. For a given crude, variation of emulsion viscosity with electroviscous effects could be explained by zeta potential and particle diameter changes. However, large differences in the magnitude of electroviscous effects for different crudes were observed. These differences could not be explained by relative zeta potentials, particle diameters, or TAN's. Also, electroviscous effects and the stability of emulsions to aging were modified by addition of tall oil. Saponifiable acids present in tall oil differ from those found in crude oils. These two observations indicate the importance of specific surfactant chemistry on emulsion viscosity and electroviscous effects.

Densities, viscosities, and diffusivities in aqueous sodium hydroxide-potassium ferri- and ferro-cyanide solutions

operating under limiting conditions (current independent of cathode potential), so that the cathode reaction becomes diffusion controlled ( 7 , 2 ) . When one correlates and generalizes such mass-transfer information, accurate values of the density and viscosity of the solution as well as the diffusivity of the ferricyanide ion are required. Values recently determined in this laboratory are communicated here and refer to the following conditions: (a) Concentrations of potassium ferriand ferrocyanides were 10 and 20 mol m-3, respectively. (The higher ferrocyanide concentration gives some protection against its anodic oxidation and, together with a larger anode than cathode area, causes the cathodic processes to become rate determining). (b) To suppress mass transfer by ionic migration, 500-3000 mol m-3 of NaOH was added as indifferent electrolyte. (c) Temperature was varied in the range 288-308 K. This variation coupled with the wide range of NaOH concentrations permitted a range of Sc from 873 to 6279 to be obtained.

Formation Pathway of Oxalic Acid in the Oxidation of Yallourn Coal by Oxygen -Oxidation of Coals in Liquid Phases. VI.-

Yalloun 炭の水酸化ナトリウム溶液中における酸素酸化においてシュウ酸の生成機構を解明する第一段階として, Yallourn 炭とその中間生成物 (残留炭, 水不溶酸, 水可溶芳香族酸, 酢酸) の転化率の経時変化を調べるとともに, その酸化を行ないシュウ酸の生成過程について検討した。また, 質量スペクトルから中間生成物とシュウ酸生成との関連性を考察した。Yallourn 炭にはヒドロキシル基酸素 (10.3% d.a.f.) やカルボキシル基酸素 (5.7% d.a.f) が比も較的多く, 反応性の高さが示唆された。残留物および水不溶酸転化率は反応時間とともに急激に低下した。また, 水可溶芳香族酸および酢酸は反応時間15分でそれぞれ極大転化率 28% および 23% に達した。さらに, シュウ酸および CO2 転化率は反応時間とともに増加し2時間で 42% および 44% に達した。酸化初期の反応速度は大きく, 15分における CO2 転化率は2時間における値の 1/2 であった。残留炭, 水不溶酸, 水可溶芳香族酸いずれの酸化においてもシュウ酸転化率は高く, 水不溶酸において 46% ともっとも高かった。CO2 転化率との比もいずれもほぼ1であった。また, シュウ酸は 275℃以上では酸化されるが, 水酸化ナトリウみ濃度 1mol・kg-1 においてはほとんど酸化されなかった。質量スペクトルは中間生成物とそれから生成するものとでは後者のスペクトルの方が単純になり, 酸化生成物の変化とシュウ酸生成との関連性が推察された。二, 三のモデル化合物の酸化においてもシュウ酸転化率は高く, とくに酢酸からは転化率 75% であった。本法は塩基触媒自動酸化であり, これらの結果から, Yallourn 炭の酸化におけるシュウ酸の生成過程を示す経路を提案する。

Electron spin resonance study of liquid during photolysis. XXIII. The 1-hydro-3,5-pyridinedicarboxylate anion radical in basic aqueous solutions

An electron spin resonance study of the 1-hydro-3,5-pyridinedicarboxylate anion radical is reported for a broad range of NaOH concentrations in aqueous solutions. Observed effects are attributed to a reversible, base-catalyzed dissociation of the NH-hydrogen. At high concentrations of NaOH the radical interchanges rapidly between its undissociated and dissociated forms, resulting in a single sharp-lined spectrum whose couplings depend upon the degree of dissociation. This made it possible to determine the thermodynamic equilibrium constant for the base-catalyzed equilibrium, from which the constant for the ionization in aqueous solution was calculated. The latter for an aqueous solution containing 20 ml of isopropyl alcohol per liter of solution at 25°C, expressed in p K units, is 16.82 ± 0.05. At lower concentrations of NaOH the radical is essentially completely undissociated, but the NH-hydrogen is reoriented by the equilibrium reactions producing lineshape effects which depend upon the second-order rate constant for the reaction between OH − and the undissociated form of the radical. This constant was determined for a range of dilute NaOH concentrations with the help of spectral simulations. The value of the rate constant extrapolated to infinite ionic dilution was found to be (5.0 ± 0.5) × 10 7 M −1 sec −1 at 30°C. The g values and couplings of both forms of the radical are reported.

Electron-cation complex in pulse radiolysis of concentrated alkaline solutions

Shape of the absorption spectrum of e - s in NaOH/H 2O solutions in the range of NAOH concentration from 0,3 t0 16 mol dm -3 at 333 K was investigated by the pulse radiolysis method. Together with the well known absorption band of e - aq a new one was observed at the high-energy tail of the former spectrum. Its intensity was found to be dependent on alkali concentration. An approach is suggested to analysis of electron-cation interactions within formal-thermodynamic theory of electrolyte solutions. The ratio of extinction coefficients of the absorption band of unknown species and that of e - aq was determined ( ϵ +- 700 ϵ - 700 = 1,9). The equilibrium constant K eq = 1,2 at 333 K.

Resistance of Valonia cellulose to mercerization

AbstractThe mercerization behavior at 20°C. of Valonia macrophysa cellulose of Japanese origin was investigated by x‐ray, moisture regain, and infrared spectrographic methods. The NaOH concentration range necessary for mercerization was 16–20%, which is higher than those required for wood pulp (8–11%), ramie or cotton (11–14%), and even the animal cellulose, Tunicin (14–16%). Treatment with the alkaline solution of the ordinary concentration (17.5%) for 4 days could not mercerize it, and even mercerization with a 19% solution brought about the presence of the reflection from (101)II along with those from (101)I and (101)I after regeneration. Such a high resistance to mercerization of the Valonia cellulose may be due to its larger crystallite size rather than the crystalline content.