Concentration Of Sodium Hydroxide Solution Research Articles

Considerable humidity response of a well-aligned SOMS micro-wire flexible sensor by moisture-induced releasing of trapped electrons.

Sandia Octahedral Molecular Sieves micro-wires (SOMS MWs) that exhibit ultra-high response to moisture and a short response time can be produced easily in an environmentally friendly mass production process. They are excellent candidate materials for use in humidity sensors. SOMS MWs were synthesized using niobium pentoxide as a precursor in concentrated sodium hydroxide solution. To fabricate humidity-sensing devices, electrophoresis was utilized to align the SOMS MWs on a polyethylene terephthalate (PET) substrate. The degree of alignment of SOMS MWs can be tuned by controlling the electric field during electrophoresis. Both well-aligned SOMS MWs (S-1.00) and randomly distributed SOMS MWs (S-0.00) exhibit maximum sensitivities to humidity (RRH/RDRY) of almost 104 and 107 respectively, and both exhibit short response times (34 and 38 s) and recovery times (7 and 10 s); these MWs outperform metal oxide ceramic-based materials in sensing humidity. Furthermore, the humidity response of S-1.00 exceeds that of S-0.00 by three orders of magnitude, and this result cannot be explained with reference to the Grotthuss mechanism. Therefore, the moisture-induced carriers from trapped electrons contribute significantly to the humidity response of SOMS MWs. In addition, with outstanding humidity sensing-performance under extreme bending conditions and superior durability after being bent hundreds of times, the well-aligned SOMS MW sensor is a favorable candidate for emerging multifunctional electronic-skin.

Pitting Corrosion on Diamond-like Carbon Films to High Concentration Sodium Hydroxide Solution

Pitting Corrosion on Diamond-like Carbon Films to High Concentration Sodium Hydroxide Solution

Utilization of Natural and Waste Pozzolans as an Alternative Resource of Geopolymer Mortar

The objective of this research was to investigate the engineering properties and mix design of geopolymer mortar made using fly ash, natural zeolite and ground granulated blast furnace slag as source material and combination of sodium hydroxide and sodium silicate as alkaline activator. To study the effect of sodium hydroxide concentration on compressive strength, three different sodium hydroxide solutions (8, 10 and 12 M) were used. The ratio of sodium silicate/sodium hydroxide was varied from 1.0, 2.0 to 3.0. The test results demonstrate that the compressive strength of developed geopolymer mortar increases with increase in the concentration of sodium hydroxide solution and sodium silicate content in the activator. The average maximum compressive strength was obtained when the sodium hydroxide concentration was 12 M and sodium silicate content was 3.0. At higher alkali content, the water absorption is less due to lower void spaces. The utilization of industrial waste materials such as fly ash, ground granulated blast furnace slag and natural pozzolans such as zeolite would lead to significant economic and environmental benefits in geopolymer production.

Corundum dissolution in concentrated sodium hydroxide solution

The corundum (α-alumina) core has been considered as a suitable candidate for investment casting of hollow, high pressure turbine engine airfoils due to its excellent properties. However, the efficiency of removing alumina cores in concentrated caustic solution cannot meet the needs of industrial production. In this paper, the effects of temperature and initial solution concentration on dissolution of α-alumina were studied by the classical weight-loss method. The fractal kinetic model was developed in order to describe α-alumina dissolution, assuming that the nonporous particles shrank during reaction process. The results show that the dissolution rate increases with increasing reaction temperature and initial solution concentration. Especially, the initial solution concentration has a significant influence on α-alumina dissolution rate at a higher reaction temperature. The activation energies decrease with increasing initial solution concentration, and the chemical reaction is the rate-controlling step.

Facile and scalable fabrication engineering of fullerenol nanoparticles by improved alkaline-oxidation approach and its antioxidant potential in maize

A feasible in operation, labor-saving and low-cost one-step technology to fabricate fullerenol nanoparticles (FNPs) up to 10 g in laboratory was developed by improved alkaline-oxidation approach using moderately concentrated sodium hydroxide solution as the hydroxylation agent and o-dichlorobenzene as the solvent. This strategy paves the avenue for industrial-scale bulk production of FNPs. The resulted product, [C60(OH)22·8H2O]n, were characterized by various measurements including matrix-assisted laser desorption ionization time-of-flight mass spectrometry, high-resolution 1H nuclear magnetic resonance spectrometry, Fourier transform infrared spectroscopy, UV-Visible spectrophotometer, thermogravimetric analysis, differential scanning calorimetry, dynamic light scattering analysis, scanning electron microscopy, and electron spin resonance spectrometer. Radical scavenging assay in vitro confirmed the high efficiency of water-soluble [C60(OH)22·8H2O]n as a novel radical scavenger. Furthermore, [C60(OH)22·8H2O]n as an excellent candidate has the potential to serve as the plant defense stimulation agent in maize.

Structural and surface functionality changes in reticulated vitreous carbon produced from poly(furfuryl alcohol) with sodium hydroxide additions

The use of sodium hydroxide to neutralize the acid catalyst increases the storage life of poly(furfuryl alcohol) (PFA) resin avoiding its continuous polymerization. In this work, a concentrated sodium hydroxide solution (NaOH) was added directly to the PFA resin in order to minimize the production of wastes generated when PFA is washed with diluted basic solution. Thus, different amounts of this concentrated basic solution were added to the resin up to reaching pH values of around 3, 5, 7, and 9. From these four types of modified PFA two sample sets of reticulated vitreous carbon (RVC) were processed and heat treated at two different temperatures (1000 and 1700°C). A correlation among cross-link density of PFA and RVC morphology, structural ordering and surface functionalities was systematically studied using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The PFA neutralization (pH 7) led to its higher polymerization degree, promoting a crystallinity decrease on RVC treated at 1000°C as well as its highest percentages of carboxylic groups on surface. A NaOH excess (pH 9) substantially increased the RVC oxygen content, but its crystallinity remained similar to those for samples from pH 3 and 5 treated at 1000°C, probably due to the reduced presence of carboxylic group and the lower polymerization degree of its cured resin. Samples with pH 3 and 5 heat treated at 1000 and 1700°C can be considered the most ordered which indicated that small quantities of NaOH may be advantageous to minimize continuous polymerization of PFA resin increasing its storage life and improving RVC microstructure.

Studies on compressive strength of sand stabilized by alkali-activated ground bottom ash and cured at the ambient conditions

Bottom ash is a by-product generated during the coal combustion of thermal power plant. Bottom ash-based geopolymer has been reported as a promising substitute of cement in concrete. In this study, bottom ash collected from Honam Coal Power Plant was ground to be used as a soil stabilizer. Sodium hydroxide solution (NaOH) with different molarity concentration and sodium silicate solution (Na2SiO3) were added to enhance the polymerization reaction of ground bottom ash. The effects of water/ground bottom ash, Na2SiO3/NaOH ratio and concentration of NaOH solution on the unconfined compressive strength of sand mixture at the ambient curing conditions were investigated. The results indicated that ground bottom ash can be utilized to stabilize sand as a main binder at the ambient curing conditions. In particular, with the 4 M concentration of sodium hydroxide solution, the Na2SiO3/NaOH ratio of 1.5 and the water/binder ratio of 0.35, the highest compressive strength obtained at 28 days was around 9 MPa. The compressive strength of sand mixture increased with an increase of NaOH solution concentration and the ratio of Na2SiO3/NaOH, however, it dramatically decreased with the addition of water to the mixture.

A simple chemical treatment for easy dispersion of carbon nanotubes in epoxy matrix for improving mechanical properties

Carbon nanotubes have considerable potential for use as reinforcements in high-performance polymer composites, but their large-scale application has been hindered by their poor processability. Here, we report an extremely simple and scalable method for the chemical treatment of single-wall carbon nanotubes (SWNTs) to enable easy dispersion in an epoxy matrix. The treatment involves stirring SWNTs in a concentrated solution of sodium hydroxide in ethanol. The chemicals used can be recovered and re-used. The treated SWNTs show greater ease of exfoliation into organic solvents without the need for high-intensity ultrasonic probe treatment. Raman spectroscopy shows that the treatment does not create any noticeable defects or functional groups on the SWNT walls. As a result of the treatment, the SWNTs could be dispersed in epoxy with minimal, low-power ultrasonic treatment. The resulting composites showed increased fracture toughness and tensile strength at SWNT loadings as low as 0.5 weight percent, when compared with neat epoxy. The enhancement in properties of the composites does not decrease with increased SWNT loading, implying that the SWNTs do not re-aggregate.

Effect of alkaline pretreatment on the preparation of regenerated lignocellulose fibers from bamboo stem

In this study, the effect of alkaline pretreatment on preparation of regenerated lignocellulose fibers from bamboo stem was studied in detail. Prior to being dissolved in [Emim]OAc, bamboo stems were ground and treated with different concentrations of sodium hydroxide solutions. The obtained spinning dopes were then extruded into water coagulation bath and regenerated to composite fibers. The properties of the raw materials, spinning dopes, and regenerated fibers were investigated. Results showed that alkaline pretreatment could break the rigid structure of lignocelluloses by removing part of hemicelluloses and lignin as well as changing the polymorphous lattice and C r I of cellulose. The increased specific surface area of raw materials enhanced the accessibility of solvent, promoted the swelling process and shortened the dissolution time. The viscosity of the spinning dopes and the strength of the regenerated fiber reached the maximum value when the bamboo powder was treated with 20 wt% sodium hydroxide at 60 °C for 4 h. In addition, the fibers prepared from the alkali-treated raw materials showed round cross-section and wrinkled surface. Therefore, the properties of the regenerated lignocellulose fibers could be improved by employing an appropriate alkali pretreatment of raw materials.

Determination of low-molecular-weight amines and ammonium in saline waters by ion chromatography after their extraction by steam distillation.

A new method was developed for the determination of ammonium ion, monomethylamine and monoethylamine in saline waters by ion chromatography. Steam distillation was used to eliminate matrix interferences. Variables such as distillation time, concentration of sodium hydroxide solution and analyte mass were optimized by using a full two-level factorial (2(3) ) design. The influence of steam distillation on the analytical curves prepared in different matrices was also investigated. Limits of detection of 0.03, 0.05 and 0.05 mg/L were obtained for ammoniumion, monomethylamine and monoethylamine, respectively. Saline water samples from the Brazilian oil industry, containing sodium and potassium concentrations between 2.0-5.2% w/v and 96-928 mg/L, respectively, were analyzed. Satisfactory recoveries (90-105%) of the analytes were obtained for all spiked samples, and the precision was ≤ 7% (n = 3). The proposed method is adequate for analyzing saline waters containing sodium to ammoniumion, monomethylamine and monoethylamine concentration ratios up to 28 000:1 and potassium to ammonium, monomethylamine and monoethylamine concentration ratios up to 12 000:1.

Hydrothermal synthesis and formation mechanism of tetragonal barium titanate in a highly concentrated alkaline solution

Tetragonal cube-shaped barium titanate (BaTiO3) was produced by the hydrothermal treatment of a peroxo-hydroxide precursor, a single-source amorphous barium titanate precursor, in a highly concentrated sodium hydroxide solution. Phase pure barium titanate with cube-shaped morphology and particle-sizes in the 0.2–0.5µm range were formed at temperatures above 80°C. Also, the cube-shaped morphology of the BaTiO3 product was preceded by spherical- and plate-like morphologies with, respectively, a Ti-excess and Ba-excess. Coinciding with these morphological observations, changes in the reaction product were also observed. The formation of crystalline BaTiO3 proceeded alongside secondary BaTi2O5 and Ba2TiO4 phases. These secondary phases disappeared as the reaction time was increased leaving only BaTiO3 as the sole reaction product. Kinetic analysis of the formation of hydrothermal BaTiO3 crystallization by the Johnson-Mehl-Avrami method showed that BaTiO3 crystallization is a homogeneous dissolution-precipitation reaction. The mechanism is governed by nucleation and growth in the beginning of the reaction and dissolution-precipitation dominating throughout the hydrothermal reaction process.

Experimental Investigations on Geo Polymer Concrete based on Class C Fly Ash

Background/Objectives: To address the environmental constraints due to cement production, strength properties of high-calcium fly ash based Geo Polymer Concrete (GPC) has been explored in this paper. Methods/Statistical Analysis: High-calcium (class C) fly ash from Neyveli Thermal Power Plant has been used for the production of GPC. Combination of sodium silicate and sodium hydroxide solution was used as alkaline solution. Alkaline solution to fly ash ratio was varied as 0.35 and 0.45. Concentration of sodium hydroxide solution was maintained as 8M and 12M. Three types of curing such as ambient curing, oven curing and External exposure curing were adopted. Findings: The compressive strength of Geo Polymer Concrete was tested at 7, 14, 28 and 60 days. Flexural strength was determined at 28 days. From the test results it was found that 1) Alkaline solution to fly ash ratio of 0.35 and 12M concentration of NaOH solution produced high strength in Geo Polymer Concrete, 2) Compressive strength of external exposure concrete was more than that of oven and ambient cured concrete. Application/Improvements: Class C fly ash can be used for the production of Geo Polymer Concrete with acceptable strength.

A Study on the Production Process Control ofZanthoxylum bungeanumMaxim Seed Kernel Oil withoutTrans-Fatty Acids

The process control of the production ofZanthoxylum bungeanumMaxim seed kernel oil (ZSKO) with notrans-fatty acids (TFAs) was investigated. Results revealed that drying temperature and time had a small effect on TFA formation in ZSKO. And high concentrations of sodium hydroxide solution had some effect on TFA formation in ZKSO, but there were no TFAs when the concentration of the sodium hydroxide solution was lower than 20% and even at boiling temperature for one hour. The roasting temperature and duration forZanthoxylum bungeanumMaxim seed (ZS) should be properly controlled at 100°C for six hours or 150°C for two hours. ZS, which has a moisture content of 18%, was pressed four times (two hours) at less than 60°C, and ZSKO was obtained by collection through centrifuge separation. This contained 90.84% unsaturated fatty acids, which mainly include 32.49% α-linolenic acid, 29.88% linoleic acid, and 27.52% oleic acids; and there was no TFA. Its acidic value and peroxide value conformed to China standards for edible oil. Therefore, ZKSO could be used as a healthy food for further development.

Influence of coal ash properties on compressive behaviour of FA- and BA-based GPC

This paper presents the results of an experimental study on the behaviour of fly ash (FA) and bottom ash (BA) based geopolymer concretes (GPCs) cured at ambient temperature. A total of 11 batches of coal-ash-based GPCs were manufactured. Axial compression tests were carried out to determine the compressive behaviour and strength development of hardened GPCs. Test parameters included the type, particle size and chemical composition of coal ash, the alkaline liquid to binder ratio and concentration of sodium hydroxide solution. The results indicate that the chemical composition of BA has a pronounced influence on the compressive behaviour of GPCs, with concretes manufactured with BA with a higher silicon dioxide/aluminium oxide ratio developing higher strengths. The results also indicate that milling of the coal ash and the increased calcium oxide content of the BA both lead to significant improvements in the compressive strength of GPCs. It was also found that strength gain of ambiently cured coal-ash-based GPCs continues beyond a concrete age of 28 d and is significantly influenced by the type, particle size and chemical composition of the coal ash and the concentration of sodium hydroxide solution.

Abrasion resistance of alkali-activated slag concrete designed by Taguchi method

In this study, abrasion resistance of Alkali-Activated Slag (AAS) concrete was investigated according to ASTM C1138. Four affecting factors including curing temperature, alkaline solution to slag weight ratio, concentration of sodium hydroxide solution and sodium hydroxide to sodium silicate weight ratio were considered to achieve the maximum compressive strength and abrasion resistance of AAS concrete using the Taguchi design of experiment method. Based on the results, the mixture with alkaline solution to slag weight ratio of 0.45, sodium hydroxide concentration of 6M and sodium hydroxide to sodium silicate weight ratio of 3, that had been cured at 95°C, and the mixture with alkaline solution to slag weight ratio of 0.4, sodium hydroxide concentration of 6M and sodium hydroxide to sodium silicate weight ratio of 3, that had been cured at 25°C, were obtained as the optimal mixtures for maximum compressive strength and abrasion resistance, respectively. The results also showed that abrasion resistance of AAS concrete was significantly increased by improving the quality of surface and changing the curing regime. Water curing as an appropriate method improved the surface conditions and considerably increased the abrasion resistance of AAS concrete too. In addition, the results showed that the CO2 footprint of AAS concrete was approximately 51% less than that of Ordinary Portland Cement (OPC) concrete and therefore the eco-mechanical performance of AAS concrete was superior.

Extraction and Bleaching of Olive Tree Branch Cellulose

The objective of this work was to extract and bleach cellulose from a low-value agricultural waste, namely, olive tree branches. The extraction procedure began by subjecting finely powdered olive tree branches to alkaline treatment, using different concentrations of sodium hydroxide solution to remove/dissolve the non-cellulosic cementing constituents, such as pectin, hemicelluloses, and natural waxes from the structure of this lignocellulosic network. The second step of the extraction procedure was the oxidation/bleaching treatment, and for this purpose, a powerful oxidizing agent composed of sodium chlorite/triethanolamine salt was used. All factors and conditions affecting the bleaching reaction, including triethanolamine salt concentration, bleaching temperature, and utilization of different triethanolamine salts, were extensively studied. The efficiency of the bleaching/oxidation treatment was evaluated by recording the FTIR spectra of the samples before and after extraction and analyzing the bleached samples to estimate the carboxyl content, loss in weight, and whiteness index.

Selective thorium and uranium extraction from monazite: II. Approaches to enhance the removal of radioactive contaminants

In the first paper of this series, the selective leaching of thorium and uranium from ground monazite with ammonium oxalate was found to depend, inter alia, on their solubility in the lixiviant, which depended on the solution pH, phosphate concentration and temperature. These actinides were released from the monazite matrix during the solution-mediated transformation of the rare earths to oxalates. The latter appeared to eventually passivate the monazite, limiting thorium and uranium leaching. The present article examines the effect of different pretreatments, leach additives, and sonication on the thorium and uranium extraction, and the recovery of the rare earth elements contained in the monazite. Different approaches were explored to suppress the re-precipitation of thorium as phosphate: strongly complexing ligands (citrate and EDTA) and the addition of ferric or aluminum ions that were expected to selectively precipitate phosphate from solution. However, none of these proved successful in experimental testing. Pretreatment with concentrated sodium hydroxide solutions, which removed most of the phosphate, yielded a residue that was amenable to selective leaching of thorium and uranium by oxalate and subsequent extraction of the rare earths with citrate.

Effect of cleaning agents and additives on Protein A ligand degradation and chromatography performance

Protein A chromatography, employing the recombinant Protein A ligand, is widely used as a capture step for antibody and Fc-fusion proteins manufacture. Protein A ligands in these matrices are susceptible to degradation/loss when exposed to cleaning agents such as sodium hydroxide, resulting in loss of capacity on reuse. In this study, MabSelect Protein A ligand and MabSelect SuRe Protein A ligand were chosen to evaluate the impact of alkaline cleaning solutions on the ligands and the packed columns. The Protein A ligands alone and the Protein A columns were incubated or cycled in different concentrations of sodium hydroxide solutions with and without additives, respectively. Ligand integrity (degradation) and ligand function (binding affinity) were studied using SDS–PAGE and customized Biacore technology, surface plasma resonance (SPR) and were successfully correlated with column performance measurement in terms of static binding capacity (SBC), dynamic binding capacity (DBC) and recovery as a function of exposure to cleaning agents with and without additives. The findings and the methodology presented in this study are not only able to determine appropriate cleaning conditions for Protein A chromatography, but also provided tools to enable systematic and rapid study of the cleaning solutions and conditions.

INFLUENCE OF CURING CONDITIONS AND ALKALI HYDROXIDE ON STRENGTH OF FLY ASH GEOPOLYMER CONCRETE

Geopolymer concrete is known as an alternative to Portland cement, with low carbon dioxide emissions compared with the conventional building materials. In this research, the influence of curing conditions and alkali hydroxide were investigated, using curing temperatures between 40 to 100℃, curing times from 4 to 12 hours, and various types of hydroxide and concentrations of sodium hydroxide solution. Geopolymerization needs energy and time to occur, and higher curing temperatures resulted in larger compressive strength, while longer curing times resulted in higher compressive strength. At the same curing temperature, longer curing time resulted in a higher compressive strength because the longer curing time extends the chemical reaction. For geopolymer concrete, sodium hydroxide is a better property than potassium hydroxide, because the atomic size of sodium anion is smaller than potassium. Further, the strength of concrete increased when the concentration of sodium hydroxide increased. In conclusion, geopolymer concrete is suitable for traditional building materials. Finding renewable materials to satisfy the increasing demand for building structures will be the primary challenge in future.

Preparation of Silica by Alkaline-Heating and Precipitation Method from Corn Straw Ash

The preparation of silica by an alkaline-heating and precipitation method from corn straw ash (CSA) obtained from a biomass power plant was the focus of this study. Sodium hydroxide was used as the silica extraction reagent, and H2SO4 was the precipitator. The concentration of sodium hydroxide solution was confirmed to have a significant influence on the production of sodium silicate from CSA. The optimum technological parameters for the preparation of sodium silicate and the suitable parameters for the preparation of silica were obtained by experiments and analysis. Fourier transform infrared spectroscopy (FT-IR) was used for confirming that the as-obtained silica has characteristic IR absorption peaks of typical hydrated silicon dioxide. The microstructures of the as-obtained silica products were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Comparison using HG/T3061 (2009) standards, and the characteristics of silica products were used to estimate whether the as-obtained silica products reached market requirements. The results show that the silica products are superior to the standard requirements and have a large market potential.