Increasing Sodium Hydroxide Research Articles

Effect of NaOH Solution on Mechanical Properties and Morphology of Fly Ash Based Cold-Pressed Geopolymer

Cold-pressing method is beneficial in reducing the porosity of geopolymer matrix, but the low liquid volume will result in unreacted aluminosilicate materials. This problem can be resolved by increasing sodium hydroxide (NaOH) concentration. This paper thus investigates the effect of NaOH concentration on the properties of cold-pressed geopolymer. The fly ash was activated by sodium silicate (Na2SiO3) and 10, 12, 14 and 16 M of NaOH solution. The dry mix was compacted with a uniaxial hydraulic press and cured for 7 and 28 days. The specimens were measured by porosity and compressive strength measurements. Scanning electron microscopy (SEM) analysis was performed to determine the microstructure of specimens. The geopolymer was optimized at 14 M NaOH with the highest 28-day compressive strength (109.6 MPa) and lowest porosity (8.1%). The SEM micrographs proved that the geopolymer have a dense and compact microstructure.

The Effect of Different Concentration of NaOH on Mechanical Properties of Allium sativum L. Peels Thin Sheet Paper

Allium sativum L. peels were used as raw material to obtain cellulosic pulps for paper making. The peels were treated with sodium hydroxide at different concentrations (5%, 12.5%, and 20%) before the paper production. The sheets were measured for weight and thickness and evaluated for tensile, tear and bursting strength. The chemical compositions of the peels were analysed. The results indicated that the peels are suitable for papermaking due to the appropriate contents of cellulose (37.22%), hemicellulose (35.21%) and lignin (9.96%) values. The colour of the sheets varies from dark to light brown when the amount of sodium hydroxide solution was increased. It was estimated that the weight of peels was in the range of 5.0 - 6.5 % of garlic clove. All the sheet samples have uniform weight and thickness. The results showed that increasing sodium hydroxide concentration from 5% to 20% decreased tensile and bursting strength, except tearing strength. Two kinds of microscopic observations showed that peels treated with the highest sodium hydroxide concentration had a fine and thin layer of binder within the fibres. The sheets appear to be transparent with due to a decrease in the tensile and bursting strength except for the tear strength.

Recycling rice straw ash to produce low thermal conductivity and moisture-resistant geopolymer adobe bricks

Rice straw ash (RSA) geopolymer adobe bricks were produced using the geopolymerization reaction among the RSA, soil, and alkaline activator at the Biosystem Engineering Department, Faculty of Agriculture, Alexandria University, Egypt, to optimize adobe brick advantages. The bulk density, water absorption, compressive strength, and thermal conductivity of the new composite were measured at RSA contents of 0%, 5%, 10%, and 20% and sodium hydroxide contents of 2.5%, 5%, 7.5%, and 10% after curing the composite for 28 days. Results indicated that increasing RSA from 0% to 20% increased the compressive strength and decreased the bulk density, water absorption, and thermal conductivity. Further, increasing sodium hydroxide from 2.5% to 10% increased the bulk density and compressive strength and decreased the water absorption. Significant effects of RSA and sodium hydroxide percentages and their interaction on all the studied characters were reported. The best conditions to minimize bulk density, water absorption, thermal conductivity, and optimize compressive strength of the composite were at 10% sodium hydroxide and 20% RSA. The minimum bulk density, water absorption, and thermal conductivity were 1.463 g/cm3, 8.3%, and 0.46 W/(m·K), respectively, while the maximum CS was 2.1 MPa after 28 days. Using RSA geopolymer adobe bricks on building interior walls is recommended to decrease bricks' thermal conductivity, water absorption, and weight.

The effect of activator ratio on the thermal and hygric properties of aerated geopolymers

Studies on the factors that influence the thermal and hygric performance of aerated geopolymers are limited. One key factor that affects their hygrothermal performance is the activator ratio. In this work, the effect of the activator ratio on the thermal conductivity, porosity, moisture buffer capacity, vapor permeability, and adsorption-desorption isotherms of geopolymers is investigated. The moisture buffer capacity of the samples ranged from 4.32 to 5.20 g/(m2%RH). The moisture inertia of the specimens increased with increasing silicate content but only until a certain critical threshold. This is attributed to an increase in the number of pore networks. The decrease in moisture buffer capacity with a further increase in water glass is because the viscid system prevents the colloidal reaction. This results in unreacted material, desperate geopolymeric agglomerates, and sodium carbonate in the pores. Moreover, a large amount of silicon prevents structural reorganization during the condensation stage of geopolymerization and decreases the formation of capillary pore networks. The vapor permeability of the samples also follows a decreasing trend with increasing sodium hydroxide in the reaction mixture. This is because the resulting matrix becomes less porous as the reaction moisture becomes more alkaline. In addition, the negative impact of efflorescence on the moisture buffer capacity and vapor permeability becomes significant as the hydroxide content increases. The highly hydrophilic crystalline salt that forms because of carbonation inhibits moisture transport. According to the absorption-desorption isotherms the specimens have meso and macro porous microstructure. The isotherms also indicated that alkalinity facilitates the formation of a continuous geopolymer matrix and the decomposition of the foaming agent. This increased the moisture capacity and macro porosity of the samples.

A Mathematical Model for Describing the Rheological Behaviour of Skin Gelatine Extracted from the Caspian Sea Huso huso

ABSTRACTThe effects of different extraction methods (I, II, III, and IV), including two levels of acetic acid (0.2–2.0 N) and sodium hydroxide (0.2–2.0 N), on the skin gelatin extracted from Caspian Sea Huso huso skin was investigated. Furthermore, the gelatin extraction yield, melting point, viscosity, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis pattern of the solutions was studied. Based on preliminary experiments, thawed skins (weight, 50 g) were added to a flask containing four volumes of different sodium hydroxide solutions for 60 min at 7°C. Treated skins were washed thoroughly with excess cold water, rinsed with cold-distilled water, and then, treated with acetic acid. Skins were drained using cheesecloth. Afterward, the extraction of gelatin was performed in four volumes of distilled water in a water bath for 16–18 h. Results showed that the higher melting point belonged to method II, while the uppermost amount of yield and viscosity could be observed in method III. Method III had the highest level of acetic acid (2 N) and the lowest level of sodium hydroxide (0.2 N) among the other samples. High acetic acid concentration caused greater degradation of collagen cross-links, which resulted in the extraction of more protein compounds than sodium hydroxide; therefore, an increase in extraction yield and viscosity was observed. The gelatin viscosity decreased with increasing sodium hydroxide concentration (methods II and IV), while it increased with smaller amounts (methods I and III). Modelling results showed that the power-type model described the influence of soluble solids better than exponential-type model on the viscosity of the mentioned polymer.

Effect of Alkali Treatment on Structure and Properties of High Amylose Corn Starch Film.

Alkali treatment is used for melt extrusion film formation with corn starch, but optimal conditions for this procedure are still unknown. In this study, the changes in properties and structure of high amylose corn starch (70%) films with different concentrations of sodium hydroxide (NaOH), prepared by melting extrusion, were investigated. With increasing sodium hydroxide concentrations, the tensile strength of the high-amylose starch film decreased gradually, while the elongation at break increased. The tensile strength of the high amylose starch (HAS) film with 2% NaOH-treatment was 10.03 MPa and its elongation at break was 40%. A 2% NaOH-treatment promoted the orderly rearrangement of starch molecules and formed an Eh-type crystal structure, which enlarged the spacing of the single helix structure, increased the molecular mobility of the starch, and slowed down the process of recrystallization; a 10% NaOH-treatment oxidized the hydroxyl groups of the high amylose corn starch during extrusion, formed a poly-carbonyl structure, and initiated the degradation and cross-linking of starch molecule chains.

Interplay between silicate and hydroxide ions during geopolymerization

Two sets of activating solutions with increasing sodium hydroxide contents were prepared either with or without silicates. Their buffer capacities, i.e. their ability to resist changes in pH, were determined and compared using the Hammett acidity function, a measure of acidity appropriate for concentrated solutions. This is the first time the Hammett acidity function of sodium silicate solutions has been measured. The effects of the buffer capacity and of the initial Hammett acidity function on the reactivity of metakaolin-based pastes were assessed using isothermal conduction micro-calorimetry. The reactivity of metakaolin in sodium hydroxide solutions is shown to be directly related to the initial Hammett acidity function, whereas for sodium silicate mixtures, the buffer capacity is a more pertinent parameter. The mechanism deduced for the role of hydroxide ions during geopolymerization also highlights the role of silicate species as a hydroxide reservoir that nurtures the dissolution process.

Evaluation of Na2TiO3 formation for producing crystalline BaTiO3 nanoparticles by liquid–solid–solution process at low temperature

Crystalline barium titanate (BaTiO3) nanoparticles were synthesized by refluxing in an air atmosphere at a low temperature using sodium hydroxide. The reaction mechanism of BaTiO3 nanoparticle formation by this new liquid–solid–solution (LSS) synthesis route with refluxing in an air atmosphere at a low temperature of 80 °C was demonstrated to be a facile fabrication process for BaTiO3 nanoparticles with a high crystalline quality and minimized agglomeration rate. BaTiO3 nanoparticles were formed via sodium titanate (Na2TiO3), and the size of the BaTiO3 nanoparticles decreased with increasing sodium hydroxide concentration. The formation of a Na2TiO3 intermediate phase was confirmed by energy dispersive X-ray spectroscopy and X-ray diffraction analysis. The capping ligands of BaTiO3 suggest that hydroxyl and oleic acid are present. The dielectric constant of the crystalline BaTiO3 nanoparticles was higher than 150.

Effect of water addition, plasticizer and alkaline solution constitution on fly ash based geopolymer concrete performance

Using fly ash based geopolymer concrete (GPC) instead of portland cement concrete, partially or totally, can reduce CO2 emissions released during OPC production, which requires burning large quantities of fuel result in significant CO2 emissions. Development of GPC became a major concern to widen its usage. This paper is a study of the influence of additional water content, plasticizer content, sodium hydroxide solution molarity, alkaline solution to fly ash ratio and sodium hydroxide to sodium silicate ratio on fly ash based GPC. The studied properties of fly ash based GPC was workability, compressive strength, splitting tensile strength, modulus of elasticity, absorption, and porosity. The results showed that, generally, increasing additional water content increased workability, but decreased other fly ash based GPC properties and the optimum additional water content was found to be 30kg/m3 which has slight effect on geopolymer properties. The increase of plasticizer content up to 10.5kg/m3 had acceptable effects on GPC properties due to improved workability. The optimum molarity of sodium hydroxide solution was found to be 16M. GPC properties was significantly affected by alkaline solution to fly ash ratio and 0.40 was expected to be the optimum ratio. Increasing sodium hydroxide solution to sodium silicate solution ratio reduces geopolymer concrete properties; nevertheless, low ratio is not economic due to sodium silicate solution cost.

Base-Catalyzed Transformations of Tetramethyldisiloxane

The behavior of the simplest linear siloxane under base-catalyzed conditions was investigated in the temperature range of 60–110 °C for different concentrations of linear siloxane (0.05–0.5 wt %) in dodecane as the solvent with an aqueous solution of sodium hydroxide added as the alkali agent. Samples were taken regularly and analyzed by GC–MS. The activation energy for the studied conditions was found to be equal to 68 kJ/mol. The reaction rate decreased with increasing sodium hydroxide concentration as a result of the formation of dibasic siloxanolates, which are less reactive than single siloxanolates. The proposed reaction mechanism includes stages of polycondensation and siloxane cyclization. The composition of the final reaction mixture (i.e., the ratio between the solid and liquid products) was found to depend strongly on the reaction parameters. Analysis of the solid products by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), and Fourier transform infrared (FTIR) spect...

Effects of pretreatment on morphology, chemical composition and enzymatic digestibility of eucalyptus bark: a potentially valuable source of fermentable sugars for biofuel production – part 1

BackgroundIn recent years, the growing demand for biofuels has encouraged the search for different sources of underutilized lignocellulosic feedstocks that are available in sufficient abundance to be used for sustainable biofuel production. Much attention has been focused on biomass from grass. However, large amounts of timber residues such as eucalyptus bark are available and represent a potential source for conversion to bioethanol. In the present paper, we investigate the effects of a delignification process with increasing sodium hydroxide concentrations, preceded or not by diluted acid, on the bark of two eucalyptus clones: Eucalyptus grandis (EG) and the hybrid, E. grandis x urophylla (HGU). The enzymatic digestibility and total cellulose conversion were measured, along with the effect on the composition of the solid and the liquor fractions. Barks were also assessed using Fourier-transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), X-Ray diffraction, and scanning electron microscopy (SEM).ResultsCompositional analysis revealed an increase in the cellulose content, reaching around 81% and 76% of glucose for HGU and EG, respectively, using a two-step treatment with HCl 1%, followed by 4% NaOH. Lignin removal was 84% (HGU) and 79% (EG), while the hemicellulose removal was 95% and 97% for HGU and EG, respectively. However, when we applied a one-step treatment, with 4% NaOH, higher hydrolysis efficiencies were found after 48 h for both clones, reaching almost 100% for HGU and 80% for EG, in spite of the lower lignin and hemicellulose removal. Total cellulose conversion increased from 5% and 7% to around 65% for HGU and 59% for EG. NMR and FTIR provided important insight into the lignin and hemicellulose removal and SEM studies shed light on the cell-wall unstructuring after pretreatment and lignin migration and precipitation on the fibers surface, which explain the different hydrolysis rates found for the clones.ConclusionOur results show that the single step alkaline pretreatment improves the enzymatic digestibility of Eucalyptus bark. Furthermore, the chemical and physical methods combined in this study provide a better comprehension of the pretreatment effects on cell-wall and the factors that influence enzymatic digestibility of this forest residue.

Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility

BackgroundIn recent years, biorefining of lignocellulosic biomass to produce multi-products such as ethanol and other biomaterials has become a dynamic research area. Pretreatment technologies that fractionate sugarcane bagasse are essential for the successful use of this feedstock in ethanol production. In this paper, we investigate modifications in the morphology and chemical composition of sugarcane bagasse submitted to a two-step treatment, using diluted acid followed by a delignification process with increasing sodium hydroxide concentrations. Detailed chemical and morphological characterization of the samples after each pretreatment condition, studied by high performance liquid chromatography, solid-state nuclear magnetic resonance, diffuse reflectance Fourier transformed infrared spectroscopy and scanning electron microscopy, is reported, together with sample crystallinity and enzymatic digestibility.ResultsChemical composition analysis performed on samples obtained after different pretreatment conditions showed that up to 96% and 85% of hemicellulose and lignin fractions, respectively, were removed by this two-step method when sodium hydroxide concentrations of 1% (m/v) or higher were used. The efficient lignin removal resulted in an enhanced hydrolysis yield reaching values around 100%. Considering the cellulose loss due to the pretreatment (maximum of 30%, depending on the process), the total cellulose conversion increases significantly from 22.0% (value for the untreated bagasse) to 72.4%. The delignification process, with consequent increase in the cellulose to lignin ratio, is also clearly observed by nuclear magnetic resonance and diffuse reflectance Fourier transformed infrared spectroscopy experiments. We also demonstrated that the morphological changes contributing to this remarkable improvement occur as a consequence of lignin removal from the sample. Bagasse unstructuring is favored by the loss of cohesion between neighboring cell walls, as well as by changes in the inner cell wall structure, such as damaging, hole formation and loss of mechanical resistance, facilitating liquid and enzyme access to crystalline cellulose.ConclusionsThe results presented herewith show the efficiency of the proposed method for improving the enzymatic digestibility of sugarcane bagasse and provide understanding of the pretreatment action mechanism. Combining the different techniques applied in this work warranted thorough information about the undergoing morphological and chemical changes and was an efficient approach to understand the morphological effects resulting from sample delignification and its influence on the enhanced hydrolysis results.

Study on Vanadium Recovery from Spent Catalyst Used in the Manufacture of Sulfuric Acid

Spent catalysts for sulfuric acid production have large amount of vanadium and due to environmental authority it is required to reduce the vanadium contain of the spent catalyst. Experimental investigation was conducted to study the vanadium recovery from spent catalyst via leaching process using sodium hydroxide to study the effect of process variables (temperatures, sodium hydroxide molarities, leaching time and particle size) on vanadium recovery. The effect of process variables (temperature, particle size,molarities of sodium hydroxide and leaching time) on the percentages of vanadium recovery were investigated and discussed .It was found that the percentage of vanadium recovery increased with increasing temperature up to 100 , increasing sodium hydroxide molarity from 2 to 4M, increasing leaching time, decreasing particle size from mesh 150, 100 and 65. A complete vanadium recovery was achieved at the following conditions: temperature (100˚c), particle size (150 mesh ) molarity of Na OH(4 molar) and leaching time(5 h).

Effect of sodium hydroxide pre-treatment on the optical and structural properties of lyocell

Lyocell is a type of regenerated cellulose. Fibres spun from cellulose solution in N-methylmorpholine- N-oxide hydrate consist of crystalline cellulose II and amorphous cellulose. Lyocell fabrics were treated with aqueous sodium hydroxide solution (NaOH) to study the influence of alkali on optical and structural properties. It was observed that sodium hydroxide treatment causes the density, orientation and crystallinity of lyocell fibre to decrease with increasing sodium hydroxide concentration, a corresponding decrease in tensile strength is also observed. The greatest change in fibre properties occurs between 3.0 and 5.0 mol dm −3 NaOH. This is attributed to the onset of formation of Na–cellulose II at 3.0 mol dm −3 NaOH; a fully formed Na–cellulose II structure is expected above 6.8 mol dm −3 NaOH. Formation of Na–cellulose II causes plasticization of the lyocell fibres as both inter- and intra-molecular hydrogen bonds are broken by these higher sodium hydroxide concentrations.

PARÂMETROS CINÉTICOS DA DEGRADAÇÃO RUMINAL DA CASCA DE CAFÉ (Coffea arabica, L.) TRATADA COM HIDRÓXIDO DE SÓDIO (NAOH)

The objective of this work was to evaluate dry matter ruminal degradation kinetics of coffee hulls treated with increasing sodium hydroxide quantities. Two rumen fistulated cows were used to incubate samples in nylon bags for 12. 24, 36. 48 and 72 hours. Four ruminal incubation periods were used, in a complete randomized block design. Coffee hulls were treated with 0%, 3%, 6% and 9% of sodium hydroxide (dry matter basis), corresponding to treatments T1 to t4 respectively. Experimental results were compared using Tukey test, at 5% probability level, as follows for treatments 1 to 4 respectively: soluble fraction (9.35d; 17.65c; 31.93b; 32.28a), de (34.40d; 40.50c; 43.28b; 50.35a), potential degradability (44.33d; 50.33c; 52.35b; 57.70a) and lag time in hours (4.03a; 3.93a; 4.33a; 2.55a). The results indicate that increasing the levels of NaOH in the coffee hulls treatments increased significantly their ruminal solubility, as well as their effective and potential degradabilities. However that increase had no effect upon coffee hulls lag time in the rumen. KEY WORDS: by-product feedstuffs, rumen degradability, ruminant.

Bagaço de cana-de-açúcar tratado com hidróxido de sódio

O experimento foi conduzido com o objetivo de avaliar a composição química e a digestibilidade in vitro da matéria seca (MS) do bagaço de cana-de-açúcar contendo 60% de MS submetido a doses crescentes de hidróxido de sódio (NaOH) (0; 2,5; 5 e 7,5% de uma solução 2:1 de água:NaOH na MS) em diferentes períodos de tratamento (1, 3, 5 e 7 dias). Foram utilizados baldes plásticos com capacidade de 10 L, mantidos em uma câmara climática à temperatura constante de 25ºC. Não foi verificado efeito dos tratamentos (dose de NaOH e dias de tratamento) sobre os teores de PB, que apresentaram valor médio de 1,6%. A MS aumentou com os dias de tratamento, não sendo observadas alterações para essa variável em relação às doses crescentes de NaOH. Foi observada redução das frações de FDN, FDA, celulose (CEL), hemicelulose (HEM) e lignina (LIG). A digestibilidade in vitro da matéria seca (DIVMS) e o teor de sódio aumentaram quando o bagaço de cana foi submetido a doses crescentes de NaOH, mas não foi observado efeito do período de tratamento sobre essas variáveis. O valor nutritivo do bagaço de cana é melhorado com a adição de NaOH, comprovado pela redução nos constituintes da parede celular e pelo aumento na DIVMS.

Effect of temperature and concentration on electrochemical corrosion behaviour of Nb–20Ta alloy in sodium hydroxide solutions

The electrochemical behaviour of Nb–20Ta alloy has been investigated in sodium hydroxide solutions at different temperatures, using open circuit potential measurements, potentiodynamic polarisation, and electrochemical impedance spectroscopy (EIS). The open circuit potential and polarisation measurements have shown that the alloy is spontaneously active in 10, 15 and 30 wt-%NaOH at 25, 50, and 75°C. The anodic polarisation curves show in all cases a dissolution/passivation peak followed by a current plateau, corresponding to oxides formation. The active corrosion of the Nb–Ta alloy leads to the formation of sodium niobate–tantalate compounds, as detected by X-ray diffraction analysis of the corrosion products. Corrosion current densities obtained by Tafel extrapolation of polarisation curves indicate that the corrosion rate of Nb–20Ta alloy increases with increasing sodium hydroxide concentration and temperature. The corrosion resistance of the Nb–20Ta alloy is intermediary between those of pure niobium and pure tantalum.

Investigation of kinetics of zinc leaching from electric arc furnace dust by sodium hydroxide

Kinetics of zinc leaching from electric arc furnace dust from a strip mill plant in Thailand was investigated. The studied variables were stirring speeds, sodium hydroxide concentrations, reaction temperatures and percent solid. The experimental results indicate that the rate of zinc leaching from the electric arc furnace dust increases with increasing sodium hydroxide concentration. The order of reaction with respect to sodium hydroxide concentration was determined by initial rate method and found to be 0.76 at 60 °C. At higher temperature, the rate of zinc leaching increases. Plot of 1−(1− F) 1/3 versus reaction time giving linear relationship indicating that a chemical reaction is the rate-determining step. The apparent activation energy was measured to be 10.78 kcal mol −1 (45.28 kJ mol −1). With increasing percent solid in the leaching solution, the rate of zinc leaching decreases. At high percent solid, the maximum zinc extraction obtained depends on the zinc solubility in sodium hydroxide solution, which is lower at lower concentration of sodium hydroxide.

Formation of Ettringite from Monosubstituted Calcium Sulfoaluminate Hydrate and Gypsum

The formation of ettringite (3CaO·Al2O3·3CaSO4·32H2O) from monosulfate (3CaO·Al2O3·CaSO4·12H2O) and gypsum (CaSO4·2H2O) was investigated by isothermal calorimetry and X‐ray diffraction (XRD) analyses. Hydration was carried out at constant temperatures from 30° to 80°C using deionized water and 0.2M, 0.5M, and 1.0M sodium hydroxide (NaOH) solutions. Ettringite was found to be the dominant crystalline phase over the entire temperature range and at all sodium hydroxide concentrations. A sodium‐substituted monosulfate phase was formed as a hydration product in the 1.0M sodium hydroxide solution regardless of temperature. XRD and calorimetry demonstrate that hydration in increasing sodium hydroxide concentrations decreases the amount of ettringite formed and retards the rate of reaction. The apparent activation energy for the conversion of the monosulfate/gypsum mixture to ettringite was observed to vary depending on the sodium hydroxide concentration. Ettringite formation was observed to depend upon the concentration of calcium in solution; thus the formation of calcium hydroxide and sodium‐substituted monosulfate phase competes with ettringite formation.

Effects of substrate particle size and alkaline pretreatment on protein enrichment by Neurospora sitophila

The effects of solid-substrate characteristics (particle size, pretreatment conditions) on microbial biomass protein production and cellulose utilization by Neurospora sitophila (ATCC 36935) were investigated. Corn stover ground to various particle size fractions (< 1 mm, 1–2 mm, 2–3 mm) was the test substrate. The pretreatment utilized sodium hydroxide (0–0.15 kg/kg substrate, at 121°C for 30 min) for delignification and hemicellulose removal. Cellulose utilization by the fungus and the crude protein production increased with decreasing substrate particle size and with increasing sodium hydroxide concentration in the pretreatment step. Under the best conditions, using < 1 mm substrate particles treated with 0.15 kg NaOH/kg substrate, approx. 90% of the initial cellulose was consumed by the fungus and the crude protein concentration in the dry product exceeded 50% by weight.