Sodium Hydroxide System Research Articles

Solubility and thermodynamic properties of sodium theophylline salt in aqueous sodium hydroxide solution at different temperatures

The solubility data of sodium theophylline salt in the water and aqueous sodium hydroxide systems with molarities of 0.00, 0.01, 0.10, 0.20, 0.49, and 0.96 mol kg−1 at temperatures ranging from 283.15 to 368.15 K are determined via the equilibrium method. The experimental results show that the solubility of sodium theophylline increases on increasing the temperature at the same concentration of NaOH solution and decreases with an increase in the NaOH concentration at the same temperature. These results correlate well with the polynomial empirical equation, the modified Apelblat equation, and the λh equation. At the same time, it is found that the modified Apelblat equation gives better correlation results than the polynomial empirical and the λh equations. The results show that the three models correlate well with the solubility data of sodium theophylline. The modified Van’t Hoff equation is used to estimate the thermodynamic properties including the dissolution enthalpy, the dissolution entropy, and the Gibbs free energy change of sodium theophylline when dissolved in aqueous NaOH solution at different concentrations. The solubility data and correlation results obtained from the experiments can provide basic data for the cooling crystallization, separation, and purification of sodium theophylline and are expected to be of great significance for the research and development of sodium theophylline and for caffeine production.

Electrochemical Characteristics of Modified Heterogeneous Bipolar Membrane and Electromembrane Process of Nitric Acid and Sodium Hydroxide Recuperation from Sodium Nitrate and Boric Acid Solution

Characteristics of an аMB-2m bipolar membrane containing ion-polymer with phosphoric-acid groups, catalytically active in the water dissociation reaction, were studied by the electrochemical-impedance spectroscopy. The study is carried out in 0.1 М nitric acid–0.1 М sodium hydroxide system. The аMB-2m membrane bipolar region resistance is shown to be an order of magnitude less than that of the MB-1 and MB‑2 commercial membranes. The process of nitric acid and sodium hydroxide production from 0.5 М sodium nitrate solution, as well as from 0.5 М sodium nitrate solution containing 0.75 М boric acid is studied in an electrodialysis apparatus with three-chamber unit cells comprised of Ralex CMH cation-exchange membrane, аMB-2m bipolar membrane, and Ralex AMH anion-exchange membrane. The electrochemical characteristics (the current efficiency, the specific energy consumption, and the specific productivity) are shown to remain unchanged in the presence of boric acid, its transfer into the acid and alkali chambers of the electrodialyzer does not exceed 7%. A probable mechanism of the boric acid and borate ion transfer through the ion-exchange membranes into the acid and alkali chambers is suggested.

Synthesis and phase behavior of double sensitive linear amphiphilic prepolymers before gelation

A series of amphiphilic linear prepolymers for gelation, poly(poly(ethylene glycol) diglycidyl ether—monoethanolamine—poly(propylene glycol) diglycidyl ether), i.e. polyPEMPPs, were designed and synthesized by using poly(ethylene glycol) diglycidyl ether (PEGDGE), Poly(propylene glycol) diglycidyl ether (PPGDGE), and monoethanolamine (MEA) as main raw materials through nucleophilic addition/ring-opening reaction. The amphiphilic structure in the backbone of the prepolymers polyPEMPPs causes a phase transition in aqueous solution and has multiple stimuli responsiveness. The effects of hydrogen bonding and electrostatic interactions on phase transition behavior were discussed and analyzed structural reasons in detail. This has important guiding significance for further research on control sol–gel transition. The effects of polyPEMPPs concentration, content of PEGDGE and solution pH values on the phase transition temperature were examined. The experimental results show that increasing polyPEMPPs concentration promotes the phase transition, the transition temperature decreasing with increasing PEGDGE content. In the pH experiment, intra- and intermolecular association became difficult and the phase behavior will be inhibited, whether hydrochloric acid system or sodium hydroxide system. Moreover, we also experimented oscillatory phase transition, and the result exhibited a stably reversible phenomenon transition.

Hydrodynamic, Mass Transfer and RTD Studies of Fluid Flow in a Spiral Microreactor

In this article, the spiral microreactor made of copper tube with U-junction, mixing region, was used to study the reactor performance on sodium hydroxide-n-butyl acetate system. The internal diameter of microreactor is 1.5 mm and length is 2 m. The performance of spiral microreactor was studied considering hydrodynamic flow, mass transfer characteristics, RTD and computational analysis of fluid flow using n-butyl acetate and sodium hydroxide system. Pressure drop was estimated in spiral geometry using dean number and compared with simulation results for laminar flow. The volumetric mass transfer coefficient obtained was in the range of 0.02–0.37 s−1. The dispersion number calculated from the RTD study was equal to 0.0526 indicating the plug flow conditions.

Influence of dolomite on the properties and microstructure of alkali-activated slag with and without pulverized fly ash

In this work, dolomite or a combination of dolomite and pulverized fly ash is to substitute up to 40% of blast-furnace slag in sodium hydroxide and sodium carbonate-activated slag systems. The influence of dolomite incorporation on the strength development, flowability, setting time, pore structure, hydrated phase assemblage, and microstructure of alkali-activated slag (AAS) are studied. The results show that dolomite incorporation up to 20% or up to 40% when fly ash is present, has little detrimental effects on the compressive strength of AAS pastes. Dolomite works mainly as an inert filler in AAS systems, leading to an increased reaction of slag at early stages due to filler effect. Different from its chemical role on ordinary portland cement (OPC) systems with enhanced hydrotalcite formation, the dolomite does not substantially affect the chemistry of reacted products in AAS systems at room temperature.

Prebiotic Syntheses Under Shock in the Water - Formamide - Potassium Bicarbonate - Sodium Hydroxide System.

Syntheses under shock in nitrogen bubbled samples of the water - formamide - bicarbonate - sodium hydroxide system at pH8.63, 9.46 and 10.44 were performed in the stainless steel preservation capsules. The maximum temperature and pressure in the capsules reached 545K and 12.5GPa respectively. Using the LC-MS-MS analysis, the 21 synthesis products have been identified, including amines and polyamines, carboxamide, acetamide and urea derivatives, compounds containing aniline, pyrrolidine, pyrrole, imidazole, as well as alcohol groups. It was found that the Fischer-Tropsch-type syntheses with catalysis on the surface of the stainless steel of the conservation capsule associated with the adsorbed hydrogen cyanide reactions and transamidation processes play the main role in the shock syntheses. Formation reactions of all the above-mentioned compounds have been suggested. It was proposed that hydrogen cyanide, ammonia, isocyanic acid, aminonitrile, aminoacetonitrile, as well as adsorbed species H(a), CH(a), CH2(a), CHOH(a), NH2(a) and H2CNH(a) are especially important for the formation of the products. A reduction reaction of adsorbed bicarbonate with hydrogen to formaldehyde has been first postulated. In the studied system also classical reactions take place - Wöhler's synthesis of urea and Butlerov's synthesis of methenamine. It was suggest that material of meteorites may be an effective catalyst in the Fischer-Tropsch-type syntheses at falling of the iron-nickel meteorites in the water - formamide regions on the early Earth. It was concluded that life could have originated due to the impact of meteorites on alkaline water-formamide lakes located near volcanoes on the early Earth.

Selective leaching of zinc from electric arc furnace dust by a hydrothermal reduction method in a sodium hydroxide system

Electric arc furnace (EAF) dust is a hazardous waste material containing valuable elements, such as zinc (Zn) and iron (Fe), as well as other environmentally harmful elements. In the conventional process, the existence of zinc ferrite (ZnFe2O4) in EAF dust results in a low recovery ratio of zinc and can induce high energy consumption or difficulties utilizing iron resources. In this article, a hydrothermal reduction method in a NaOH system is proposed to recover Zn selectively from EAF dust. First, when pure ZnFe2O4 was used as the input material to test the feasibility of the new method, 70% Zn leaching efficiencies and the isolation of Fe in the residue through the formation of ferroferric oxide (Fe3O4) were achieved at the optimal conditions of 260 °C, 6 M [NaOH], 10 g/L [C6H12O6]n and 50 mL/g of L/S. Second, a leaching process of EAF dust was proposed using the following two procedures: (i) first leaching under normal pressure to dissolve zinc oxide (ZnO); and (ii) second leaching of the first leach residue under hydrothermal reduction conditions to dissolve ZnFe2O4. The leach liquor from the second step was recycled to the first step. Under optimum conditions, the leaching efficiencies of Zn during the first and second leaching were 66.4% and 69.3%, respectively. The total Zn leaching efficiency was calculated to be 89.7%, producing Zn-impregnated leach solution and a leach residue rich in Fe (up to 39.4 wt%) that are suitable as resources for a steel-making plant. However, this process also has its shortcomings owning to larger liquid-solid ratio in the leaching process. Overall, the study technically provides an alternative approach to improve the recycling of zinc and iron and effectively reduce environmental risks from EAF dust.

Understanding the Formation Mechanism of Graphene Frameworks Synthesized by Solvothermal and Rapid Pyrolytic Processes Based on an Alcohol–Sodium Hydroxide System

The determination of ways to facilitate the 2D-oriented assembly of carbons into graphene instead of other carbon structures while restraining the π-π stacking interaction is a challenge for the controllable bulk synthesis of graphene, which is vital both scientifically and technically. In this study, graphene frameworks (GFs) are synthesized by solvothermal and rapid pyrolytic processes based on an alcohol-sodium hydroxide system. The evolution mechanism of GFs is investigated systematically. Under sodium catalysis, the abundant carbon atoms produced by the fast decomposition of solvothermal intermediate self-assembled to graphene. The existence of abundant ether bonds may be favorable for 3D graphene formation. More importantly, GFs were successfully obtained using acetic acid as the carbon source in the synthetic process, suggesting the reasonability of analyzing the formation mechanism. It is quite possible to determine more favorable routes to synthesize graphene under this cognition. The electrochemical energy storage capacity of GFs was also studied, which revealed a high supercapacitor performance with a specific capacitance of 310.7 F/g at the current density of 0.2 A/g.

Phosphorus-specific determination of glyphosate, glufosinate, and their hydrolysis products in biological samples by liquid chromatography–inductively coupled plasma–mass spectrometry

Anion exchange liquid chromatography (LC) with inductively coupled plasma–mass spectrometry (ICP–MS) was used for simultaneous determination of glyphosate and glufosinate (phosphonic and amino acid group-containing herbicides; PAAHs) and their hydrolysis products, aminomethylphosphonic acid (AMPA) and 3-methylphosphinicoacetic acid (MPPA), in biological samples. The target compounds were separated using an anion exchange resin column and gradient elution with sodium carbonate and sodium hydroxide system. The chromatographic eluates were passed through a membrane suppressor system and monitored by phosphorus-specific detection at m/z 31. PAAHs and their hydrolysis products were baseline separated from each other within 40 min of elution time, and phosphoric acid did not interfere with detection. The detection limits in serum samples were 0.1–0.7 µg/ml; those in urine samples, 0.2–1.6 µg/ml for the four compounds. The spiked recoveries for the four compounds were over 91 % in serum and urine samples. The detection of the compounds was not subject to interference from sample matrix components. The present method would be useful for toxicological analysis of PAAHs and their products in actual forensic practice. To our knowledge, this is the first trial to establish an LC–ICP–MS method for analysis of PAAHs and their products in biological samples .

Kinetics Studies on a Novel Decomposition Method of Zircon Sand

A novel method was proposed for preparing oxychloride octahydrate by the two – step decomposition of zircon sand concentrate in sodium hydroxide system. The effect of decomposition temperature and NaOH – to – zircon mass ratio of each stage on the decomposition of zircon sand was investigated. The macrokinetics of the two – step decomposition process was also examined. The experimental date showed that the shrinking core model with diffusion through the residual layer is most applicable for the first step decomposition process with the apparent activation energy of 42.9 kJ/mol, but the second step process was controlled by chemical reaction with the apparent activation energy of 30.1 kJ/mol.

Rate of absorption and interfacial area of chlorine into aqueous sodium hydroxide system

Due to excellent mass transfer characteristics with energy efficiency jet ejectors can be used in place of conventional countercurrent systems, namely, packed bed contactors as well as venturi scrubbers, cyclones and airlift pumps. The removal of chlorine from certain gases by absorption in aqueous solutions of sodium hydroxide is industrially important in several chemical processes particularly in pollution control. Although, a number of papers have been published in the past, none of them provided a theoretical basis for the prediction of rate of absorption of chlorine from certain gases by absorption in aqueous solutions of sodium hydroxide in jet ejector. In this work, the rates of absorption of chlorine from different concentration of gas into aqueous sodium hydroxide solutions of various concentrations were measured at 30°C using a liquid jet ejector. The experimental results were analyzed on the basis of the penetration theory for gas absorption. The theoretical model to calculate rate of absorption is developed. The rate of absorption predicted from developed model is compared with experimental results. They were in good agreement. In this work, an attempt also has been made to develop mathematical model to estimate enhancement factor for jet ejector applying Higbie penetration theory. Key words : Higbie penetration theory, jet ejector, chlorine, aqueous solutions, gases.

Developing Optimum ANN Model for Mass Transfer with Chemical Reaction in Packed Column for Air-Carbon Dioxide and Aqueous Sodium Hydroxide System

liquid reactions occupy a large share of the chemical reactions that are carried out industrially. The estimation of reaction rate is the most primary but complex task and is a prerequisite in design & scaling up of reactors. Reaction rate is a function of number of parameters that include flow rates of gas and liquid phases, concentration of reactants and interfacial surface area, among others. Artificial Neural Network (ANN) is viewed as a black box modeling tool and has been applied for modeling of several chemical engineering operations. The present work is aimed at developing artificial neural network model for estimation of interfacial area as a function of gas & liquid flow rates and inlet concentrations of gas & liquid phases. Fifteen ANN models with different topologies have been developed and three models S-20, M-20 and C-50 are shortlisted based on better RMSE values. Further, model C-50 has been observed to be highly acceptable based on comparison of relative error for all the data points.

Liquid–Liquid Equilibria in Ternary and Quaternary Systems Present in Biodiesel Production from Soybean Oil at (298.2 and 333.2) K

Liquid–liquid equilibrium (LLE) data for soybean oil biodiesel (BIO-SO) + ethanol + glycerol and BIO-SO + ethanol + glycerol + sodium hydroxide systems at (298.2 and 333.2) K and atmospheric pressu...

Decomposition Behaviors of Tantalum-Niobium Ore in Sodium Hydroxide System

A new method for the decomposition of low-grade refractory tantalum-niobium ores using sodium hydroxide fusion was proposed. The effects of initial mineral particle size, alkali to ore mass ratio, decomposition temperature and decomposition time on the decomposition rate of the tantalum-niobium ore were investigated. The alkali to ore mass ratio, decomposition temperature and initial mineral particle size showed significant influence on the decomposition of tantalum-niobium ore. The results show that the decomposition rates of cassiterotantalite and pyrochlore in the ore can be above 98% and 99% respectively when the initial mineral particle size is less than 75µm, the mass ratio of alkali to ore is 1:1, the decomposition temperature is 650°C and the decomposition time is 30min.

Conductimetric Titrations: A Predict−Observe−Explain Activity for General Chemistry

A predict−observe−explain framework is used to explore conductimetric titrations of a hydrochloric acid−sodium hydroxide (strong acid−strong base) and an acetic acid−sodium hydroxide (weak acid−strong base) system in which all components are soluble. In the strong acid−strong base system, the conductivity decreases as the titration progresses to the equivalence point and then increases past the equivalence point. In the weak acid−strong base system, the conductivity increases as the titration progressed to the equivalence point and then increases at a greater rate past the equivalence point. In another more sensitive titration of the weak acid−strong base system, the conductivity initially decreases slightly, then increases as the titration progresses to the equivalence point, and then increases at a greater rate past the equivalence point. These characteristic conductimetric titration curves are analyzed and explained.

ChemInform Abstract: Selective Hydrolysis of Nitriles to Amides Using NaOH-PEG under Microwave Irradiation.

Abstract We describe here an efficient, rapid and selective method for the conversion of nitriles in to their corresponding amides in the presence of PEG-400, aqueous sodium hydroxide system under microwave irradiation.

Desiliconization kinetics of nickeliferous laterite ores in molten sodium hydroxide system

A novel process was proposed for treating nickeliferous laterite ores with molten sodium hydroxide. The effect on silicon extraction caused by the factors, such as stirring speed, reaction temperature, particle size and NaOH-to-ore mass ratio, was investigated. The results show that increasing stirring speed, reaction temperature and NaOH-to-ore mass ratio while decreasing particle size increases silicon extraction rate. The desiliconization kinetics of nickeliferous laterite ores in molten sodium hydroxide system was described successfully by chemical reaction control model. The activation energy of the desiliconization process was found to be 44.01 kJ/mol, and the reaction rate based on a chemical reaction-controlled process can be expressed as: 1–(1–α) 1/3= 27.67exp[−44 010/( RT)] t.

Decomposition of acid dissolved titanium slag from Australia by sodium hydroxide

The kinetics of the decomposition of acid dissolved titanium slag with a sodium hydroxide system under atmospheric pressure was studied. The effect of reaction temperature, particle size and NaOH-to-slag mass ratio on titanium extraction was investigated. The results show that temperature and particle size have significant influence on titanium extraction. The experimental data of titanium extraction show that the shrinking core model with chemical reaction controlled process is most applicable for the decomposition of slag, with an apparent activation energy of 62.4 kJ.mol(-1). Approximately 85 wt.%-90 wt.% of the titanium can be extracted from the slag under the optimal conditions. In addition, the purity of titanium dioxide obtained in the product is up to 98.5 wt.%.

Heat Transfer under Buoyancy-Induced Flow at the Chemical Reaction Front Using Thermochromic Liquid Crystal Sheet

Heat transfer and hydrodynamics at the chemical reaction front have been investigated experimentally using a thermochromic liquid crystal sheet. If the chemical reaction occurs, a band region where the temperature, due to the heat of reaction, is higher than the initial temperature appears at the reaction front. Natural convection due to the temperature difference at the reaction front plays an important role in conveying the higher temperature fluid. For the hydrochloric acid (HCl)–sodium hydroxide (NaOH) system, as the frequency of contact between HCl and NaOH due to convection increases with the concentration of ethanol, the temperature beyond the stagnation point becomes higher than that in other areas. On the other hand, for the acetic acid (CH3COOH)–NaOH system, the heat transfer depends mainly on the heat of reaction, because the rate of CH3COOH dissolution is smaller than that of HCl.

Decomposition kinetics of titanium slag in sodium hydroxide system

A novel process was proposed for preparing titanium dioxide by the decomposition of titanium slag in sodium hydroxide system under atmospheric pressure. The kinetics on the decomposition of titanium slag was mainly investigated. The results on effect of reaction temperature, particle size and NaOH-to-slag mass ratio on titanium extraction show that the temperature and particle size have significant influence on the titanium extraction. The experimental data of titanium extraction indicate that the shrinking core model with chemical reaction controlled process is most applicable for the decomposition of titanium slag, with the apparent activation energy of 40.8 kJ mol − 1 . Approximately 95–98% of titanium in the titanium slag could be extracted under the optimal reaction conditions. In addition, the content of TiO 2 obtained in the product is up to 99.3%.