Concentration Of Sodium Hydroxide Solution Research Articles

The effect of fluorine substituents on the polymerization mechanism of 2-methylene-1,3-dioxolane and properties of the polymer products

Perfluoro-2-methylene-1,3-dioxolane ( III) was synthesized and polymerized with an initiator, perfluoro dibenzoyl peroxide, and a white solid product III-P was quantitatively isolated. The polymer was insoluble in organic solvents including fluorinated solvents such as Fluorinert FC 75 and hexafluorobenzene, but dissolved in hexafluorobenzene by heating at around 140 °C in a sealed ampoule. The X-ray measurement showed that III-P was semi-crystalline and melted at 230 °C. The IR spectrum of III-P indicated that the polymer obtained did not show carbonyl peak and it was the vinyl addition product. When the solid product was heated above the melting temperature and pressed under 100–200 kg/cm 2, we obtained an amorphous and flexible film, which is transparent from the UV region to the near IR region. The glass transition temperature was 110 °C and refractive indexes were 1.3443, 1.3434 and 1.3373 at 633, 839 and 1544 nm, respectively. The film did not degrade in concentrated sulfuric acid and aqueous sodium hydroxide solutions even heated at 80–90 °C for 2 days. The film was thermally stable and began to decompose at 300 °C under air atmosphere.

Ionic Association of Hydroperoxide Anion HO2- in the Binding Mean Spherical Approximation. Spectroscopic Study of Hydrogen Peroxide in Concentrated Sodium Hydroxide Solutions

The ultraviolet-visible (UV-vis) spectroscopy of hydrogen peroxide in concentrated sodium hydroxide solutions was studied. The peroxide band in the UV range shifts from approximately 214 nm to approximately 236 nm as the NaOH concentration increases from 0.338 mol dm-3 to 13.1 mol dm-3. The band originates from an intramolecular electronic transition of the hydroperoxide anion HO2-, as indicated by the negligible temperature effect on the band position and confirmed by ab initio quantum mechanical calculations. It is postulated that the bathochromic shift of the peroxide band that accompanies the increase in NaOH concentration originates from the formation of the ion pair (Na+HO2-). The equilibrium constant for the ion association reaction (0.048 mol-1 dm3) and the characteristics of the individual absorption bands of the hydroperoxide anion and its associate with Na+ were determined from the numerical modeling of the absorbance data, using the binding mean spherical approximation (BIMSA).

Preparation and adsorption properties of macroporous tannin resins

In this paper, a new kind of adsorption resin with multi-phenolic hydroxyl was created by immobilizing black wattle bark tannins to chloromethyl polystyrene resin. Its adsorption capacity to cation dye was tested. With an orthogonal test the optimal conditions of synthesis were determined: the concentration of sodium hydroxide solution 1.0 mol·L−1; the reaction time is one hour and the mass concentration of tannins 5%. With single factorial experiment the optimal conditions of adsorption were confirmed: a solidified pH of 5.0; an adsorption temperature of 25°C and a cation dye concentration of 100 mg·L−1. The adsorption for cation dye can be similar to Langmuir isotherms.

Corrosion Resistance of Commercial Si<sub>3</sub>N<sub>4</sub> Bearing Balls

The corrosion rate (Cr) of commercially available ball bearings made of silicon nitride (Si3N4) of high degree (HD) and standard quality (S) was measured at hydrothermal conditions in different aqueous concentrations of sulphuric acid (H2SO4) and sodium hydroxide (NaOH). The Cr magnitude for the materials diminished when increasing the acid concentration. At higher concentrations of H2SO4 (98%) the formation of SiO2 on the surface of the balls inhibited the progress of corrosion. The corrosion rate of the materials was increased when the sodium hydroxide solution concentration was increased. The surface of the materials was analyzed by means of scanning electron microscopy (SEM), while the corrosion rate was determined based on weight losses.

Hg/HgO electrode and hydrogen evolution potentials in aqueous sodium hydroxide

The Hg/HgO electrode is usually utilized as a reference electrode in alkaline solution such as for development of an alkaline hydrogen electrode. The reference electrode provides a suitable reference point but is available from few commercial vendors and suffers from inadequate documentation on potential in varying electrolytes. A new numerical method uses activity, activity coefficients, and a few correlated empirical equations to determine the potential values in both dilute and concentrated sodium hydroxide solutions at temperatures of 0–90 °C and at concentrations of 0.100–12.8 mol k g H 2 O − 1 . The computed potentials of the Hg/HgO electrodes versus a normal hydrogen electrode (NHE) at 25 °C and 1 atm are 0.1634 V for 0.100m, 0.1077 V for 1.00m, and 0.0976 V for 1.45m NaOH solutions. The Hg/HgO reduction potential further changes to −0.0751 V versus NHE and hydrogen evolution potential changes to −0.9916 V versus NHE in a solution of 30.0 wt.% NaOH at 80 °C. The calculated values are compared with the measured data at 25 and 75 °C. The experimental data agree well with the numerical values computed from the theoretical and empirical equations.

Synthesis, characterization, flocculation, and rheological characteristics of hydrolyzed and unhydrolyzed polyacrylamide‐grafted poly(vinyl alcohol)

AbstractGraft copolymers of poly(vinyl alcohol) and polyacrylamide (PVA‐g‐PAM) were synthesized using a ceric ion–induced solution polymerization technique at 28°C. Three grades of graft copolymers were synthesized with varying acrylamide concentrations. Three grades of hydrolyzed products of PVA‐g‐PAM were synthesized with varying concentrations of sodium hydroxide solution. Hydrolyzed and unhydrolyzed PVA‐g‐PAM were characterized by viscometry, X‐ray diffractometry, infrared spectroscopy, and thermal analysis. Rheological investigation was also carried out on the aqueous solutions of various samples. The flocculation characteristics of various materials were investigated by the use of jar and settling tests in 0.25 and 5 wt %, respectively, using kaolin and iron ore suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains showed superior performance. The flocculation characteristics of the best‐performing graft copolymer were compared with those of various commercially available flocculants in the two suspensions under investigation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2109–2122, 2006

Effects of mercerization of bamboo strips on mechanical properties of unidirectional bamboo–novolac composites

AbstractBamboo strip reinforced novolac resin composites were fabricated using bamboo strips that were treated with varying concentrations of sodium hydroxide solution at a constant filler loading (25%). The mechanical properties of various composites (flexural modulus, toughness, tensile strength, and elastic modulus) were determined. The physical characteristics, such as the wetting ability of the alkali treated reinforcements, were increased because of alkali treatment. With increasing concentrations of alkali, a higher percent loss in weight occurred. The mechanical properties were increased with increasing mercerizing strength. Maximum improvement in properties was achieved with 16–20% of caustic treated reinforcements. An FTIR study indicated aryl alkyl ether formation with OH groups of cellulose and methylol groups of novolac resin. Beyond 20% there was degradation in all strength properties because of the failure in the mechanical properties of the reinforcements. A correlation was found to exist between the mechanical properties and the developed morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:238–244, 2006

An effective method to enhance the stability on-stream of butene aromatization: Post-treatment of ZSM-5 by alkali solution of sodium hydroxide

The catalytic stability of ZSM-5 zeolite in butene aromatization was improved by the treatment of ZSM-5 zeolite with sodium hydroxide solution of appropriate concentration. By characterizing pore structures, the acidity of the catalyst and the coke amount, we found that alkali-treatment of ZSM-5 led to a formation of new mesopores resulting from a preferential removal of silicon species, while the intrinsic micropores remained unchanged. As for the acidity, the amount and properties of acid sites exhibited a slight change on the alkali-treated ZSM-5 zeolites. In addition, the alkali-treatment to ZSM-5 zeolite led to only a little reduction in the amount of coke during the butene aromatization. But a portion of coke was deposited in the newly created mesopores because of the alkali-treatment and the formation of coke in the micropores was found to be reduced. These changes can suppress the channel blockage of ZSM-5 zeolite by the coke deposits during butene aromatization. The variation of the coking location was the main reason for the favorable enhancement in the reaction stability during butene aromatization.

A novel high-frequency resistance coating by utilizing nano titania particle

In this paper, a liquid-phase hydrolization method to synthesize nanometer rutile titania directly without transformation from anatase is proposed. By utilizing this method, the particle size of the rutile titania nanoparticles can be controlled by adjusting the reaction conditions, e.g. the concentration of sodium hydroxide solution, reaction temperature, and calcining temperature of the powder. These titania nanoparticles have been used for the preparation of a novel composite insulation coating for magnet wires. First results showed that the lifetime of the modified nanomagnet wire in the inverter-fed motor could be prolonged to eight times compared with the non-modified wire.

Evaluating Efficiency of Alkaline Treatment for Waste Bagasse

Cellulose, lignin, raw bagasse fiber, and extracted bagasse fibers chemically processed with different concentrations of sodium hydroxide solution and treatment time were measured by thermogravimetry analysis (TGA). The thermal characteristics of these fibers were determined by thermogravimetry (TG) and derivative thermogravimetry (DTG) profiles and analyzed based on the onset degradation temperature, peak rate of thermal decomposition, and residual weight. According to the observations from the experimental data from TGA and DTG profiles and literature reports, it was found that higher content of cellulose and lower content of lignin would result in higher onset degradation temperature, higher peak rate of decomposition, and lower residual weight. Statistical analysis of the onset decomposition temperatures, peak rate of weight loss, and residual weights of different extracted bagasse fibers showed that most of their values were significantly different. The three‐dimensional surface plots of onset decomposition temperature and peak rate of weight loss indicated that higher content of cellulose occurred in the bagasse fiber treated under the condition close to the region around 2 N NaOH for 2 hours or 1.5 N NaOH for 1.5 hours.

Anodic polarization behavior of low-carbon steel in concentrated sodium hydroxide and sodium nitrate solutions

High-level radioactive wastes, primarily consisting of concentrated sodium hydroxide (NaOH) and sodium nitrate (NaNO 3) solutions, are stored in large underground storage tanks made of low-carbon steel. The anodic polarization behavior of low-carbon steel in concentrated solutions of 10 M NaOH and various concentrations of NaNO 3 (0.01–2.0 M) was determined in order to predict the caustic stress corrosion cracking (CSCC) susceptibility of the tanks. The active–passive transition peak exhibited during anodic polarization of low-carbon steel in 10 M NaOH, typically associated with CSCC, at −0.25 and −0.75 V SCE, is still present at the lower and higher concentrations of nitrate. However, there is a mid-range of nitrate concentrations (0.5–1 M) within which the peak is suppressed by the strongly oxidizing nitrate in the presence of oxygen, a cathodic depolarizer. Temperature also affects the magnitude of this mid-range of nitrate concentrations where CSCC is seen to be electrochemically prevented. The data suggest that the oxygen solubility at the relatively low temperatures tested (<95 °C) controls the preference of the cathodic reaction, i.e. oxygen reduction versus nitrate reduction. When oxygen reduction is the preferred cathodic reaction, E corr is driven more noble than the active–passive transition peak.

Study of the possible use of intermediate flax as raw material for production of cellulose

In treating intermediate flax with concentrated solutions (greater than 5 M) of sodium hydroxide, crystalline regions of cellulose totally pass from modification CI to modification CII, despite the presence of contaminants (lignin, hemicellulose, etc.). The presence of hydrogen peroxide in basic solutions shifts the beginning of the CI → CII phase transition toward higher concentrations of sodium hydroxide. A sufficiently high degree of purification of intermediate flax (~93% cellulose content) can be attained in two-step treatment including acid-peroxide cooking in the first stage and alkaline cooking in the second stage and in alkaline-peroxide cooking.

Failure analysis of high-level radioactive waste tank purge ventilation vent pipe

High-level radioactive wastes generated during the processing of nuclear materials are stored in large underground storage tanks made of low-carbon steel. The wastes consist primarily of concentrated solutions of sodium nitrate (NaNO3) and sodium hydroxide (NaOH). Each of the tanks is equipped with a purge ventilation system designed to continuously remove hydrogen gas and vapors from the waste tanks while preventing the release of radionuclides to the atmosphere. Several intergranular cracks were discovered in the vent pipe of the purge ventilation system of a particular high-level waste tank. The vent pipe, fabricated from galvanized steel sheet, was connected to the final exhaust fan downstream of high-efficiency particulate air (HEPA) filters. The failure analysis investigation concluded that nitrate-induced stress-corrosion cracking (SCC) was the cause of the failure.

De-alloying of type 316 stainless steel in hot, concentrated sodium hydroxide solution

The formation of “nickel” layers on austenitic stainless steel in strong caustic solutions was reported in 1979. We now report a detailed study that clarifies the nature of this de-alloying process and establishes firm links with other metal-environment systems that show de-alloying and associated stress corrosion cracking. De-alloying of iron from 316SS in 50% NaOH at 140 °C proceeds only as far as a solid solution with a Ni/Fe atomic ratio of ca. 1.3 (56 at.% Ni if we neglect the other elements present). Chromium is mostly dissolved and/or reprecipitated during this process. X-ray diffraction shows that the residue is a solid solution of intermediate composition, not a mixture of pure Ni and stainless steel. The removal of only half the iron conveniently explains why the de-alloyed layer is a connected porous network. Electrode capacitance measurements and FEG-SEM examination show that the de-alloyed layer has extremely fine nanoporosity.

A selective preparation of phillipsite and sodalite from perlite

The preparation of commercially valuable materials, i.e. phillipsite, sodalite octahydrate and faujasite from perlite via inexpensive direct treatment with sodium hydroxide solution, at low temperatures of 70–100 °C under autogeneous pressure, is reported. The formation of phillipsite and sodalite is shown to be selective, whereas the occurring of faujasite is always found with phillipsite. The influences of sodium hydroxide solution concentration, reaction temperature and time on the type of the solid products, and the amount of Na + and K + incorporated in the zeolitized solids were investigated. The relation between the type of the synthesized zeolites and the uptake of Na + and the leaching of K + is described, and shown to be significant for further investigation as to expand the application as a cation exchanger.

Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites

Natural rubber is reinforced with untreated sisal and oil palm fibers chopped to different fiber lengths. The effects of concentration and modification of fiber surface in sisal/oil palm hybrid fiber reinforced rubber composites have been studied. Increasing the concentration of fibers resulted in reduction of tensile strength and tear strength, but increased modulus of the composites. Composites were prepared using fibers treated with varying concentrations of sodium hydroxide solution and for different time intervals. The vulcanisation parameters, processability characteristics, and stress–strain properties of these composites were analysed. The rubber/fiber interface was improved by the addition of a resorcinol-hexamethylene tetramine bonding system. The reinforcing property of the alkali treated fiber was compared with that of untreated fiber. The extent of fiber alignment and strength of fiber-rubber interface adhesion were analysed from the anisotropic swelling measurements.

Effects of Alkali Treatment to Reinforcement on Tensile Properties of Curaua Fiber Green Composites

Alkali treatment was performed on ‘Curaua' fibers to improve their mechanical properties. Curaua fibers were dipped into 5%, 10%, and 15% concentrated sodium hydroxide solutions for 1h and 2h. The effects of solution concentrations and treatment times on the physical and mechanical properties of curaua fibers were evaluated. Tensile tests of untreated and alkali treated curaua fibers were carried out. Those results showed that the tensile strength of the treated fibers decreased in comparison to untreated fibers, whereas the fracture strain of the treated fibers increased greatly in comparison with that of untreated fibers. In addition, green composites reinforced by untreated and alkali-treated curaua fibers were fabricated by a press forming method. Tensile tests were carried out for both composites. Results showed that both tensile strength and fracture strain of the composite using treated fibers increased in comparison with the composite using untreated fibers.

高温 8kmol m-3 NaOH溶液中における水素発生のための電析Co-FeおよびCo-Fe-C合金

Tailoring of active cobalt alloy cathodes for hydrogen evolution in a hot concentrated sodium hydroxide solution was attempted by electrodeposition. Enhancement of cathodic activity of cobalt for electrolytic hydrogen evolution has been carried out by the formation of Co-Fe and Co-Fe-C alloys containing different content of iron. The carbon addition to Co-Fe alloys was made to enhance the electrolytic hydrogen evolution activity and to prevent open circuit corrosion in 8 kmol m-3 NaOH at 363 K. The best condition for electrodeposition of Co-Fe alloy was pH 4 and the iron sulfate concentration of more than 5 kg m-3. Under this condition the alloy was obtained with nanocrystalline bcc phase as a dominant and with the highest hydrogen evolution activity. The carbon addition slowed down preferential iron dissolution by open circuit corrosion in the hot alkaline solution but was not effective in complete prevention of the open circuit corrosion and in enhancing the hydrogen evolution.

Kinetics of the dissolution of sand into alkaline solutions: application of a modified shrinking core model

The batch dissolution kinetics of sand particles in concentrated alkaline sodium hydroxide solutions was investigated at high temperature and high pressure. The influence of the particle size, the operating temperature (150–220 °C) and the hydroxide ion molality on the kinetic rate were studied. Experimental data fit well into a developed model based on the shrinking core model approach in which a variable activation energy term was introduced. Kinetic analysis of the experimental results reveals that the associated energy and the rate-controlling mechanism are dependent upon both sample temperature as well as the extent of the reaction.

Electrodeposited Co-Fe and Co-Fe-C Alloys for Hydrogen Evolution in a Hot 8 kmol m&lt;SUP&gt;-3&lt;/SUP&gt; NaOH Solution

Tailoring of active cobalt alloy cathodes for hydrogen evolution in a hot concentrated sodium hydroxide solution was attempted by electrodeposition. Enhancement of cathodic activity of cobalt for electrolytic hydrogen evolution has been carried out by the formation of Co-Fe and Co-Fe-C alloys containing different content of iron. The carbon addition to Co-Fe alloys was made to enhance the electrolytic hydrogen evolution activity and to prevent open circuit corrosion in 8 kmol m−3 NaOH at 363 K. The best condition for electrodeposition of Co-Fe alloy was pH 4 and the iron sulfate concentration of more than 5 kg m−3. Under this condition the alloy was obtained with nanocrystalline bcc phase as a dominant and with the highest hydrogen evolution activity. The carbon addition slowed down preferential iron dissolution by open circuit corrosion in the hot alkaline solution but was not effective in complete prevention of the open circuit corrosion and in enhancing the hydrogen evolution.