Concentration Of Sodium Hydroxide Solution Research Articles

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.

Investigate coir fibers’ properties produced by coconut fiber extracting machine in Ben Tre and research the treatment for fiber with NaOH solution

Over past few years, the polymer composite materials based on coir fibers have grown rapidly and have even found new markets as well as many research projects due to its cost effect and environmentally-friendly manner. In Vietnam, the coir fibers have a good quality, especially in Ben Tre province. In this research, we investigated the size of coir fibers which was produced from dried nuts stripped via hand-made coir fiber extracting machine. The coir fibers with the largest diameter distribution have evaluated the average tensile strength. In the other hand, the coir fibers have treated via a sodium hydroxide solution process to obtained refine-coir fibers which were following investigated the mechanical testing based on composite materials of polyester resin. The results showed that the treatment of the sodium hydroxide solution process causes a decrease of coir fiber average diameter. Increasing the temperature and concentration of sodium hydroxide solution leads to the decreasing of coir fiber average diameter. Moreover, the optimum condition (5% of NaOH, 50oC) enhanced the tensile strength of fibers reaching to 40% comparing with those untreated fibers.

Effect of Concentration of Sodium Hydroxide and Degree of Heat Curing on Fly Ash-Based Geopolymer Mortar

Geopolymer concrete/mortar is the new development in the field of building constructions in which cement is totally replaced by pozzolanic material like fly ash and activated by alkaline solution. This paper presented the effect of concentration of sodium hydroxide, temperature, and duration of oven heating on compressive strength of fly ash-based geopolymer mortar. Sodium silicate solution containing Na2O of 16.45%, SiO2 of 34.35%, and H2O of 49.20% and sodium hydroxide solution of 2.91, 5.60, 8.10, 11.01, 13.11, and 15.08. Moles concentrations were used as alkaline activators. Geopolymer mortar mixes were prepared by considering solution-to-fly ash ratio of 0.35, 0.40, and 0.45. The temperature of oven curing was maintained at 40, 60, 90, and 120°C each for a heating period of 24 hours and tested for compressive strength at the age of 3 days as test period after specified degree of heating. Test results show that the workability and compressive strength both increase with increase in concentration of sodium hydroxide solution for all solution-to-fly ash ratios. Degree of heating also plays vital role in accelerating the strength; however there is no large change in compressive strength beyond test period of three days after specified period of oven heating.

Direct Electrochemical Reduction of Hematite Pellets in Alkaline Solutions

Our previous studies on the electrowinning of iron from hematite particles suspended in sodium hydroxide solutions demonstrated that iron was produced through a direct solid phase electrochemical reduction of the oxide particles. This suggests that the electro-deoxidation of a hematite powder pellet by the FFC type process should be possible in aqueous solutions at a low temperature. We investigated the electrochemical reduction of a solid hematite pellet cathode manufactured by conventional mechanical pressing followed by sintering process in concentrated sodium hydroxide solutions using a nickel inert anode at 110 °C. The experimental results indicated that hematite was reduced to iron metal. Propagation of the reduction reaction front through the oxide phase occurred at a high speed, and the rate-determining step was the diffusion of the oxygen ion through the shrinking cores of the oxide particle.

Corrosion Inhibition of 6061 Al-15 vol. pct. SiC(p) Composite in Sodium Hydroxide Solution by 4-amino-5-(4-nitrophenyl)-4H-1,2,4-triazole-3-thiol

The inhibition action of 4-amino-5-(4-nitrophenyl)-4H-1,2,4-triazole-3-thiol (ANTT) on the corrosion behavior of 6061 Al-15 vol. pct. SiC(p) composite was studied at different temperatures and in different concentrations of sodium hydroxide solution by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The effect of inhibitor concentration and temperature on the inhibitor action was investigated. The inhibition efficiency increases with the increase in the concentration of the inhibitor and decreases with the increase in temperature. Thermodynamic parameters for dissolution process were determined. The adsorption of ANTT on the composite was found to be through physisorption, obeying Langmuir's adsorption isotherm. The results obtained from both the techniques are in good agreements.

Deacetylation of Chitin and the Properties of Chitosan Films with Various Deacetylation Degrees

The degree of deacetylation is the proportion of glucosamine monomer residues in chitin. It affects many properties of chitosan. The objectives of this research were to study the deacetylation of chitin by alkaline and to investigate chitosan film properties with different degrees of deacetylation. Chitin was deacetylated by boiling (95°C) in concentrated sodium hydroxide (50%) solution for 120-300 minutes. The degree of deacetylation of chitosan was determined by potentiometric titration method. Chitin possessed a degree of deacetylation of 7.74%. The alkaline deacetylation produced chitosan with a degree of deacetyl- ation of 15.24-70.19%. We found a linear relationship between the degree of deacetylation and deacetylation time (degree of deacetylation = 2.476 + 0.230t, R 2 = 0.915). The deacetylation time had no effect on the yield and whiteness of the obtained chitosans. Film was formed from the obtained chitosan at each deacetylation time and their properties investigated. Increasing the deacetylation time increased the tensile strength, elongation and water vapor transmission rate of the films. In contrast, redness (a*) and yellowness (b*) of the films decreased.

Electrochemical behavior of nickel and its oxides in concentrated sodium hydroxide solutions

By using the methods of cyclic voltammetry (the potential scan rates of 20 mV/s and 2–500 V/s) and preparative electrolysis at an ac frequency of 10 to 200 Hz, in 17 M sodium hydroxide, it is found that nickel oxidation proceeds with the formation of oxides of variable composition. It is shown that the dependence of nickel failure rate on the current frequency has a peak. The highest failure rate corresponds to a current frequency of 20 Hz.

Preliminary Study on the Preparation of Bamboo Cellulose Carbamate

In this paper, bamboo fibers were utilized in synthesizing the cellulose carbamate (CC) together with urea for the first time. This paper explored the impact of a serious of factors on Nitrogen content of CC, including the concentration of sodium hydroxide solution used for activating, activation time, aging time, urea socking time, the concentration of urea solution, reaction time and reaction temperatures. Moreover, the analysis and characterizations of CC with different nitrogen contents were conducted by using FTIR, DSC, XRD and SEM. The result indicates that CC was generated as the cellulose reacted with urea, and the crystalline form of cellulose has changed after the esterification reaction. The surface morphology of fibers became wrinkle and rough after the reaction, thereby improving its solubility.

Preparation of Protein-like Silver–Cysteine Hybrid Nanowires and Application in Ultrasensitive Immunoassay of Cancer Biomarker

Novel protein-like silver-cysteine hybrid nanowires (p-SCNWs) have been synthesized by a green, simple, nontemplate, seedless, and one-step aqueous-phase approach. AgNO3 and l-cysteine were dissolved in distilled water, forming Ag-cysteine precipitates and HNO3. Under vigorous stirring, the pH of the solution was rapidly adjusted to 9.0 by addition of concentrated sodium hydroxide solution, leading to quick dissolution of the Ag-cysteine precipitates and sudden appearance of white precipitates of p-SCNWs. The p-SCNWs are monodispersed nanowires with diameter of 100 nm and length of tens of micrometers, and have abundant carboxyl (-COOH) and amine (-NH2) groups at their surfaces, large amounts of peptide-linkages and S-bonding silver ions (Ag(+)) inside, making them look and act like Ag-hybrid protein nanostructures. The abundant -COOH and -NH2 groups at the surfaces of p-SCNWs have been found to facilitate the reactions between the p-SCNWs and proteins including antibodies. Furthermore, the fact that the p-SCNWs contain large amounts of silver ions enables biofunctionalized p-SCNWs to be excellent signal amplifying chemiluminescence labels for ultrasensitive and highly selective detection of important antigens, such as cancer biomarkers. In this work, the immunoassay of carcinoembryonic antigen (CEA) in human serum was taken as an example to demonstrate the immunoassay applications of antibody-functionalized p-SCNWs. By the novel p-SCNW labels, CEA can be detected in the linear range from 5 to 400 fg/mL with a limit of detection (LOD) of 2.2 fg/mL (at signal-to-noise ratio of 3), which is much lower than that obtained by commercially available enzyme-linked immunosorbent assay (ELISA). Therefore, the synthesized p-SCNWs are envisioned to be an excellent carrier for proteins and related immunoassay strategy would have promising applications in ultrasensitive clinical screening of cancer biomarkers for early diagnostics of cancers.

Fabrication and characterization of hardened bodies from Japanese volcanic ash using geopolymerization

Hardened bodies were fabricated from Japanese volcanic ash after mixing with an alkali solution, molding, and curing. The volcanic ash was composed of approximately 70% crystalline anorthite sodium [(Ca, Na) (Si, Al)4O8] phase and ≤30% amorphous silicate phase. First, a starting mixture was prepared by mixing the ground volcanic ash with a sodium hydroxide solution. The mixture was placed in a plastic mold using a glass rod, and then cured at 50°C and 80% relative humidity for 3 days. The compressive strength of the resulting hardened body increased with increasing concentration of sodium hydroxide solution. When a 13.5mol/L sodium hydroxide solution was used, the average compressive strength of the hardened body reached 80.1MPa. The hardening mechanism for the volcanic ash during curing is discussed.

Preparation and characterization of strongly swellable modified-lignosulfonate hydrogel particles

Lignosulfonate is one of the main byproducts of paper industry. The development and research activities on this important substance have drawn widespread interest in the world. Sodium lignosulfonate was modified by heating in acidic environment and then transferred the modified sodium lignosulfonate into sodium hydroxide solution for further stirring. An insoluble fraction was separated and washed thoroughly with de-ionized water to neutral. Finally, the modified sodium lignosulfonate hydrogel particles were obtained. The obtained hydrogel particles were ultrasonically dispersed in water to form a modified sodium lignosulfonate micro-hydrogel with mean sizes of 300–400 nm. This indicated that the modified sodium lignosulfonate hydrogel particles were generated by the agglomeration of modified sodium lignosulfonate micro-hydrogel. The hydrogel particles were characterized by physical and spectral methods involving infrared radiation, thermogravimetric analysis, dynamic light scattering, and scanning electron microscope. The xerogels formed by drying modification of sodium lignosulfonate hydrogel particles showed a high water-adsorption of 31.2 g/g. In addition, the effect of reaction parameters on water swelling capacity and xerogel yield were also investigated, which include heating temperature, base treatment temperature, and concentration of sodium hydroxide solution. The research results indicated that the yield of modified sodium lignosulfonate hydrogel increases with higher heating temperature and decreases with higher alkali treatment temperature and concentration of sodium hydroxide solution. The water swelling capacity of the modified sodium lignosulfonate hydrogel increased slightly with higher heating temperature, but remained unaffected by the alkali treatment temperature and concentration of sodium hydroxide.

Preparation and Formation of Zeolite 5A from Local Kaolin Clay for Drying and Desuphurization of Liquefied Petroleum Gas

This work deals with preparation of zeolite 5A from Dewekhala kaolin clay in Al-Anbar region for drying and desulphurization of liquefied petroleum gas. The preparation of zeolite 5A includes treating kaolin clay with dilute hydrochloric acid 1N, treating metakaolin with NaOH solution to prepare 4A zeolite, ion exchange, and formation. For preparation of zeolite 4A, metakaolin treated at different temperatures (40, 60, 80, 90, and 100 °C) with different concentrations of sodium hydroxide solution (1, 2, 3, and 4 N) for 2 hours. The zeolite samples give the best relative crystallinity of zeolite prepared at 80 °C with NaOH concentration 3N (199%), and at 90 and 100°C with NaOH concentration solution 2N (184% and 189%, respectively). Zeolite 5A was prepared by ion exchange of zeolite 4A prepared at 90°C and 2N NaOH concentration with 1.5 N calcium chloride solution at 90 °C and 5 hours, the ion exchange percentage was 66.6%. The formation experiments included mixing the prepared powder of 5A zeolite with different percentages of kaolin clay, citric acid and tartaric acid to form an irregular shape of zeolite granules. Tartaric acid binder gives higher bulk crushing strength than that obtained by using citric acid binder with no significant difference in the surface area. 7.5 weight% tartaric acid binder has the higher bulk crushing strength 206 newton with surface area 267.4 m2/g. Kaolin clay binder with 15 weight% gives the highest surface area 356 m2/g with bulk crushing strength 123 newton, it was chose as the best binder for zeolite 5A. The prepared granules of 5A zeolite were used for the adsorption experiments of H2O, and H2S contaminants from LPG. Different flow rates of LPG (3, 4, and 5 liter/minute) were studied. It was found that H2O is the strongly adsorbed component and H2S is the weakly adsorbed component. The best flow rate in this work for H2O, and H2S adsorption is 5 liter/minute of LPG. The adsorption capacity for H2O was 7.547 g/g and for H2S was 1.734 g/g.

Synthesis and Photo-Catalytic Properties Characterization of Graphene/TiO<sub>2</sub> Nanotube Composites

Selecting graphene oxide (GO) and the Degussa P25 TiO2 (80% anatase and 20% rutile) as raw materials, the composites of graphene/TiO2 nano-tubes were simply and quickly prepared under the conditions of a concentrated solution of sodium hydroxide. The as-obtained composites’ phase structure was analyzed and characterized by powder X-ray diffraction (XRD), their morphologies were also observed and cross-confirmed under the Transmission Electron Microscopy (TEM). The measurements showed that the composites prepared in this work have a remarkable structure, and compared to the seperate TiO2 nano-tubes, the agglomeration of TiO2 nano-tubes covered on the surface of the graphene is apparently not so serious. In view of this, we preliminary tested the composites’ photo-catalytic performance with the visible light irradiation, and also made a comparison with TiO2 nano-tubes.

Studies on Borassus fruit fiber and its composites with Polypropylene

This paper summarizes the structural characterization of borassus fruit fibers by means of various characterization techniques, optimization of alkali treatment of borassus fruit fine fibers (BFF) with a 5% concentration sodium hydroxide solution for different time intervals (1, 4, 8 and 12 h) and the changes occurring in borassus fibers. This paper also discusses the manufacturing of BFF/PP compotes using MAPP as a compatibilizer in addition to alkali treatment. Composites were evaluated for their mechanical and morphological properties. The tensile strength and modulus, flexural strength and modulus and impact strength were increased for alkali treated/MAPP composites by 4.5%, 17%, 17.2 %, 9% and 10% respectively.

Parametric Studies on Compressive Strength of Geopolymer Concrete

The demand of concrete is increasing day by day for satisfying the need of development of infrastructure facilities. It is well established fact that the production of OPC not only consumes significant amount of natural resources and energy but also releases substantial quantity of carbon dioxide to the atmosphere. Therefore, it is essential to find alternatives to make the concrete environment friendly. Geopolymer is an inorganic alumino-silicate compound, synthesized from fly ash. The fly ash, one of the source materials for geopolymer binders, is available abundantly in India, but to date its utilization is limited. Hence it is essential to make the efforts to utilize this by-product in concrete manufacturing in order to make the concrete more environmental friendly. This paper describes the experimental work conducted by casting 20 geopolymer concrete mixes to evaluate the effect of various parameters affecting its the compressive strength in order to enhance its overall performance. Various parameters i.e. ratio of alkaline liquid to fly ash, concentration of sodium hydroxide, ratio of sodium silicate to sodium hydroxide, curing time, curing temperature, dosage of superplasticiser, rest period and additional water content in the mix have been investigated. The test results show that compressive strength increases with increase in the curing time, curing temperature, rest period, concentration of sodium hydroxide solution and decreases with increase in the ratio of water to geopolymer solids by mass & admixture dosage, respectively. The addition of naphthalene based superplasticiser improves the workability of fresh geopolymer concrete. It was further observed that the water content in the geopolymer concrete mix plays significant role in achieving the desired compressive strength.

Optimization of Microwave Assisted Alkaline Extraction of Xylan from Birch Wood Using Response Surface Methodology

The main purpose of this study was to optimize microwave assisted alkaline extraction of the hemicellulose, xylan, from birch wood. The simultaneous effects of process variables such as time (10 - 30 minutes), concentration of sodium hydroxide solution (4 - 8 wt%), solid to liquid ratio (1:8 to 1:20, g:mL), and sample size (5 - 10 g) on the temperature of the wood slurry, wood dissolution, and yield of extraction were evaluated. A central composite design (CCD) and response surface methodology (RSM) were used for the optimization of the extraction process. Based on the CCD, quadratic models were developed to correlate the extraction process variables with the responses such as temperature of wood slurry, wood dissolution, and yield of xylan and the models were analyzed using appropriate statistical methods (ANOVA). Statistical analysis showed that all the models developed were found to be adequate for the prediction of the respective responses. Optimization of the process was performed using a numerical optimization available in the software to maximize the yield of xylan and the optimum process variables for the maximum yield of xylan was found to be: 10 g of wood fibres, 8 wt% of NaOH solution, 1:10 solid to liquid ratio (g:mL) and 25 minutes of irradiation time. About 72.5% of the xylan present in the birch wood was extracted using the optimized extraction parameters.

Kinetics of Leaching Silicon from the Acid Leaching Residue of Pyrolusite

The content of SiO2 was more than 60% in the residue of pyrolusite detached manganese by reduction roasted and acid leached, and it was a better siliceous raw material because of less other impurities. Through leaching silicon process in the residue of pyrolusite with alkali at atmospheric pressure, leaching kinetics of silica in the sodium hydroxide solution was researched. The effects of the leaching temperature and the concentration of sodium hydroxide solution on the leaching behavior of silica from acid-leached pyrolusite slag were examinted. It was found that the extracting rate of silica is significantly influenced by the temperature, and the concentration of NaOH solution. The experimental datas were well interpreted with a shrinking core model under chemical control. On the basis of the Arrhenius expression the apparent activation energy of 77.69 kJ/mol and a reaction order of 0.34 for the extraction of silica was evaluated.

Production of superoxide anion radicals as evidence for carbon nanodots acting as electron donors by the chemiluminescence method

In this communication, a novel chemiluminescence phenomenon was observed for the as-prepared carbon nanodots (CDs) in a concentrated sodium hydroxide (NaOH) solution. The generation of superoxide anion radical (O2˙(-)) directly provides evidence for the excellent electron-donating ability of CDs.

Magnetic properties of multicore magnetite nanoparticles prepared by glass crystallisation

A glass with the composition 13K2O*13Al2O3*16B2O3*43SiO2*15Fe2O3−x was melted and rapidly quenched in water. This leads to the formation of phase-separated droplets with diameters from 100 to 150 nm. Magnetite crystals with a size of 10–20 nm precipitate within these droplets. The magnetite containing phase-separated regions can be separated from the glass by dissolving the SiO2-rich amorphous glass matrix through boiling the pulverized glass in a concentrated aqueous sodium hydroxide solution. The residual, magnetite containing phase-separated droplets match multicore magnetite nanoparticles (McNP). The magnetite nanoparticles show superparamagnetic behaviour and as McNP, lead to a higher effective magnetic radius than single crystals. Magnetisation measurements of the McNP indicate that the particles show a narrow hysteresis, but the ratio of remanent to saturation magnetisation is not high enough for uniaxial anisotropy. The additionally performed temperature-dependent magnetorelaxometry (TMRX) measurements show peaks at 13 and 39 K in the distribution of the magnetic moment relaxation. The obtained inter-particle distance of the magnetite within the McNP is smaller than 5 dC (core diameter), leading to strong magnetic interactions.

A novel green analytical procedure for monitoring of azoxystrobin in water samples by a flow injection chemiluminescence method with off-line ultrasonic treatment

A simple and green flow injection chemiluminescence (FI-CL) method for determination of the fungicide azoxystrobin was described for the first time. CL signal was generated when azoxystrobin was injected into a mixed stream of luminol and KMnO4 . The CL signal of azoxystrobin could be greatly improved when an off-line ultrasonic treatment was adopted. Meanwhile, the signal intensity increases with the analyte concentration proportionally. Several variables, such as the ultrasonic parameters, flow rate of reagents, concentrations of sodium hydroxide solution and CL reagents (potassium permanganate, luminol) were investigated, and the optimal CL conditions were obtained. Under optimal conditions, the linear range of 1-100 ng/mL for azoxystrobin was obtained and the detection limit (3σ) was determined as 0.13 ng/mL. The relative standard deviation was 1.5% for 10 consecutive measurements of 20 ng/mL azoxystrobin. The method has been applied to the determination of azoxystrobin residues in water samples.