Aqueous Potassium Carbonate Solution Research Articles

Synthesis of New β,β′-Diketodithioethers via Swern Oxidation and Study of Their Hydrazone Formation Rate

The synthesis of β,β′-diketodithioethers 4b–j from corresponding β,β′-dihydroxydithioethers 3b–j was carried out by a Swern oxidation using DMSO-oxalyl chloride as oxidizing agent. β,β′-Dihydroxydithioethers 3b–j were prepared by the reaction of two molar equivalents of epoxides 1b–j with dimercaptoethane 2 in the presence of a saturated aqueous solution of potassium carbonate. The reactivity behavior of imine formation of the β,β′-diketodithioethers 4b–j by 2,4-dinitrophenylhydrazine was also investigated, and a mechanism was proposed by using molecular orbital (MO) calculations. To confirm the proposed mechanism, the role of the thia function to activate hydrazone formation by measuring HOMO-LUMO energy levels was also demonstrated.

Absorption of carbon dioxide into aqueous potassium carbonate promoted by boric acid

Abstract The absorption of carbon dioxide with alkanolamine or potassium carbonate solvents has gained widespre ad acceptance for the removal of CO2 from natural gas and H 2. However, alkanolamine solutions are prone to oxidative degradation at high temperature. The main advantages of potassium carbonate solution for CO2 removal are the high chemical solubility of CO2 in the carbonate/ bicarbonate system, low solvent costs and the low energy requirement for solvent regeneration. The major challenge concerning absorption of CO2 into aqueous solutions of potassium carbonate is a relatively slow rate of reaction in the liquid phase causing low mass transfer rates. It is often advantageous to add a promoter to increase the absorption rate. While piperazine is often used for this purpose, there are some environmental health concerns with this approach. In this work we consider boric acid as an alternative promoter. Absorption of CO2 in a wetted -wall column by aqueous potassium carbonate solution with and without various concentrations of boric acid as promoter was measured under conditions in which the reaction of CO2 was of pseudo-first order. The equilibrium partial pressure and the rate of absorption of CO2 were measured in 30.0 wt% potassium carbonate and 1.0 to 5.0 wt% of boric acid at 50 to 80 ∘C. The overall pseudo -first-order reaction rate constants were determined fro m the kinetic measurements. The addition of small amounts of boric acid to potassium carbonate resulted in a significant enhancement of CO2 absorption rates.

Desulfation of active paste from lead battery scrap with ammonium carbonate

The results obtained in studying the desulfation of the active paste from lead battery scrap with the use of an aqueous solution of potassium carbonate are discussed.

A Simple Chemical Method Reduces Ochratoxin A in Contaminated Cocoa Shells

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium species, which contaminates cocoa among other food commodities. It has been previously demonstrated that the toxin is concentrated in cocoa shells. The aim of this study was to assay a simple chemical method for ochratoxin A reduction from naturally contaminated cocoa shells. In order to determine the efficiency of the method, a high-performance liquid chromatography method with fluorescence detection was set up beforehand and validated. Ochratoxin A was extracted from cocoa shells with methanol–3% sodium bicarbonate solution and then purified with immunoaffinity columns. The recovery attained was 88.7% (relative standard deviation = 6.36%) and the limits of detection and quantification were 0.06 and 0.2 μg/kg, respectively. For decontamination experiments, the solvent extractor ASE 200 was used. First, aqueous solutions of 2% sodium bicarbonate and potassium carbonate were compared under the same conditions (1,500 lb/in2 at 40°C for 10 min). Higher ochratoxin A reduction was obtained with potassium carbonate (83 versus 27%). Then, this salt was used under different conditions of pressure, temperature, and time. The greatest ochratoxin A reduction was achieved with an aqueous potassium carbonate solution (2%), at 1,000 lb/in2 at 90°C for 10 min. This method could probably be applicable to the cocoa industry because it is fast and relatively economic. From the point of view of human health, the use of potassium carbonate, partially eliminated by rinsing the sample with water, does not likely represent a risk for human health.

CO 2 transfer in an aqueous potassium carbonate liquid membrane module with dense polymeric supporting layers: Influence of concentration, circulation flow rate and temperature

Gas–liquid separation systems have already received considerable attention in a great number of situations of industrial interest. The attention paid to membrane contactors and immobilized liquid membranes have recently increased due to their separation performances. For the sake of simplicity, most experiments are usually performed at room temperature. It is, however, obvious that increasing the temperature would increase the reaction rate and thereby also possibly enhance the system's productivity. This work presents a systematic study of CO 2 and H 2 transport in a novel flowing liquid membrane (FLM) module with dense membranes separating layers and aqueous potassium carbonate (concentration 0.1–3 kmol/m 3) solutions in the temperature range 295–353 K. A model of CO 2 transport with reversible chemical reactions through the FLM was developed and compared to a series of experimental data. It was found that increasing the concentration of potassium carbonate as well as the temperature led to large increases in both the CO 2 productivity and the CO 2/H 2 selectivity. The industrial implications of these observations were discussed. Unsteady state transport of CO 2 was also investigated and a simple model of gas transfer in the FLM with physical absorption in the liquid phase was developed.

Stability of gel-supported facilitated transport membrane for carbon dioxide separation from model flue gas

The stability of a facilitated transport membrane for carbon dioxide (CO 2) separation from CO 2/N 2 (nitrogen) mixed gas was studied. This membrane was composed of an aqueous potassium carbonate (K 2CO 3) solution and a vinylalcohol–acrylate copolymer (PVA–PAA, super absorbent polymer), in which the aqueous solution was immobilized. This facilitated transport membrane named a gel-supported membrane worked properly when the PVA–PAA polymer gel held sufficient amount of water. The amount of water in the gel membrane depended on the water vapor pressure above the membrane. Higher water retention was observed at the K 2CO 3 solution because of its ionic strength. The role of the polymer gel in retaining water was not observed clearly. The aqueous K 2CO 3 solution contributed greatly to keeping the membrane wet, and the polymer gel was suitable as substrate of a thin liquid membrane. The gel-supported membrane immobilizing an aqueous 2 mol/kg K 2CO 3 solution worked well even under the evacuating condition for 6 months by controlling the water vapor pressure. Sulfur dioxide (SO 2) which was included in the flue gas obstructed CO 2 transportation. SO 2 may have the influences of restraining CO 2 from dissolving into the carrier solution and of decreasing the concentration of a carrier at the gas–liquid interface. These undesirable effects of SO 2 were weakened by the addition of potassium sulfite (K 2SO 3), and it appeared at low concentration of 0.1 mol/kg K 2SO 3. Nitrogen monoxide (NO) and nitrogen dioxide (NO 2), which were included in the flue gas as well, had no influence to CO 2 transportation through the membrane. As the results of these studies, it was believed that the gel-supported membrane had a potentiality for practical use to recover CO 2 from the high humid gas mixture such as flue gas.

Synthesis of Nanocrystalline KTiOPO4 Powder by Chemical Method

Nanocrystalline potassium titanyl phosphate (KTiOPO4, KTP) powder with average particle size of 25–50 nm has been synthesized from aqueous solution of titanyl chloride through coprecipitation method, using aqueous solution of potassium dihydrogen phosphate and potassium carbonate in the presence of triethanolamine (TEA) as a capping agent. In the presence of tetrapotassium pyrophosphate as a capping agent it produces the particles having average size around 70–80 nm. The same sample with average particle size ∼250 nm has also been synthesized without any capping agent. Initial amorphous phase after precipitation requires heat treatment at 500–550°C for 2 h to generate nanocrystalline powders of KTP. Formation of the KTP phase in the heat‐treated samples has been confirmed through X‐ray powder diffraction, thermogravimetric and differential thermal analysis, 31P Magic angle spinning‐nuclear magnetic resonance and Fourier transform infrared spectroscopy studies, and surface area measurements.

Gas transport in combined membrane system with moving liquid carrier

The study of selective membrane valve (SMV)—the membrane system which consists of two polymeric membranes and a layer of liquid between them (moving or non-moving) is presented in this paper. Permeability of pure gases such as oxygen, carbon dioxide and hydrogen are investigated. Distilled water and aqueous solutions of potassium carbonate were used as liquid carriers. Aqueous potassium carbonate was used as chemical absorbent of carbon dioxide. The dependencies of gas transport parameters of SMV on water flow rate and potassium carbonate concentration have been obtained. Two models of gas transport in membrane system were developed. A first model describes SMV with flowing physical liquid absorbent, the second one—with non-moving chemical liquid absorbent. The first model was found to be in good agreement with experimental results for hydrogen. Carbon dioxide permeability through SMV with potassium carbonate aqueous solution is well described by the second model. The increasing of the time-lag of non-steady state permeability process of carbon dioxide when concentration of chemical absorbent increases was also demonstrated by the second model.

Gas permeability of combined membrane systems with mobile liquid carrier

Gas transfer in a membrane system called a selective membrane valve (SMV) is studied. The SMV is a system consisting of two mobile gas phases, one mobile liquid phase, and two membranes acting as interfaces between gas and liquid. Such a membrane system has supplementary variable parameters and is designated for the separation of multicomponent gas mixtures. System permeability for individual gases (CO2, O2, and H2) and its dependence on a flow rate of a liquid phase are studied. Time dependences of the non-steady state transfer of CO2 through the immobile layer of chemisorbent (aqueous K2CO3 solution) at its different concentrations are studied for the first time. Two theoretical models are developed: the model of gas transfer through a selective membrane valve system with a mobile liquid absorbent (in the absence of chemical interaction) and the model of a non-steady-state transfer of CO2 through the immobile layer of aqueous potassium carbonate solution. The first model makes it possible to determine gas-to-liquid diffusion coefficients; the second model permits us to plot kinetic permeability curves and to calculate system permeability with allowance for the CO2 transfer accompanied by reversible chemical reaction with the carrier. The model dependences agree well with the experimental data.

Optimization of vaterite synthesis for application to coating pigment of ink-jet paper

Calcium carbonate in the crystal form of vaterite can be expected as a coating pigment because of fineness of primary particles and the spherical secondary structure. So far, the interfacial reaction method has been applied to prepare vaterite particles. However, to avoid using volatile organic solvents, an aqueous system with no organic solvent was developed in this study. Consequently, vaterite was successfully synthesized from only two aqueous solutions of potassium carbonate and calcium chloride with no additive. As parameters of the reaction condition, temperature, agitation rate and effects of surfactants were examined. The optimum temperature of the reacting liquids was around 40 °C. Reduced volumes of the reacting liquids to intensify the agitation effect increased the vaterite ratio for a given homogenizer at a constantly rotating speed. Among surfactants used, there was no difference observed in the effect on vaterite generation. At a suitable condition about other parameters, pure vaterite was obtained even under no surfactant condition. In summary, it was speculated that the vaterite form was generated at an early stage of the reaction. At insufficient levels of shear stress, vaterite growth is not promoted and generated vaterite transfers spontaneously to calcite. Surfactants are assumed to adsorb onto surfaces of primary particles and trigger an orderly aggregation.

Thermodynamics of proton dissociation from aqueous bicarbonate: apparent molar volumes and apparent molar heat capacities of potassium carbonate and potassium bicarbonate at T=(278.15 to 393.15) K and at the pressure 0.35 MPa

We have determined the apparent molar volumes V φ and apparent molar heat capacities C p, φ of aqueous potassium carbonate and potassium bicarbonate solutions in the ranges (0.014⩽ m/(mol · kg −1)⩽0.51) and (278.15⩽ T/K⩽393.15) at the pressure p=0.35 MPa. Corrections for speciation due to hydrolysis and disproportionation in solution were applied using Young's rule, and semi-empirical equations representing ( V φ , m, T) and ( C p, φ , m, T) for the species {2K +, CO 3 2−(aq)} and {K +, HCO 3 −(aq)} were fitted to the experimental results. We have used these equations to estimate the change in volume Δ r V m, change in heat capacity Δ r C p,m, enthalpy change Δ r H m, entropy change Δ r S m, and equilibrium molality quotient pQ for the second proton dissociation reaction from aqueous carbonic acid.

Practical and User-Friendly Procedure for Michael Reactions of α-Nitro­ketones in Water

A variety of α,β-unsaturated carbonyl derivatives gave selective Michael additions with several α-nitrocycloalkanones in water, at room temperature without any added catalyst, or in very dilute, aqueous solutions of potassium carbonate. Both preparative methods constitute new, environmentally benign and more efficient alternatives to previous procedures.

Analysis of CO 2 removal by hollow fiber membrane contactors

A numerical analysis was performed to investigate the removal behavior of carbon dioxide using a hollow fiber membrane contactor in which an aqueous potassium carbonate solution flows as an absorbent. An important feature is the inclusion of the nonlinear reversible reaction terms that result from the reactions between the absorbent solution and carbon dioxide. The coupled nonlinear partial differential equations were derived and solved numerically, which describe either the absorption or desorption of carbon dioxide in a membrane contactor. In a numerical analysis, the absorbent liquid always flows through the inner side of the hollow fiber in both absorption and desorption steps. The analysis includes the effects of the pressure of feed gases and the extent of vacuum, the absorbent flow rates, the concentration of potassium carbonate in an absorbent solution, the diameter and length of the fibers. One important result is the determination of the optimal absorbent flow rate such that it is saturated just at the exit of the contactor.

Separation of isopropanol from aqueous solution by salting‐out extraction

AbstractA novel salting‐out extraction process has been developed to separate isopropanol from aqueous solution. Potassium carbonate was experimentally shown to be effective in modifying the liquid–liquid equilibrium (LLE) of an isopropanol/water/hexane system in favour of the solvent extraction of isopropanol from an aqueous solution with hexane, particularly at suitable salt concentrations. Potassium carbonate enlarged the area of the two‐phase region. This effect essentially increased the distribution coefficient of isopropanol between hexane and water and increased the separation factor for isopropanol vs water, which is an important consideration in designing a solvent extraction process. The effects of potassium carbonate concentration, temperature and pH on the LLE were studied. Finally, a ϕ30 mm × 1200 mm reciprocating plate column (RPC) was tested to separate isopropanol from an aqueous solution. When isopropanol in an aqueous solution with composition of isopropanol/water = 1:0.95 (wt/wt) was extracted by hexane assisted with 30% (wt%) potassium carbonate aqueous solution, the alcohol–water ratio increased to 11:1 in the extract.© 2001 Society of Chemical Industry

Drop size distributions in dispersed liquid–liquid pipe flow

This paper examines drop size distributions in a 0.063 m pipe for a two-phase mixture of kerosene and aqueous potassium carbonate solution. Measurements have been made for both vertical upflow and horizontal geometries, for mixture velocities ranging from 0.8 to 3.1 m/s. Two optical measurement techniques, a backscatter technique using a Par-Tec 300C and a diffraction technique using a Malvern 2600, have been used to obtain the drop size distributions of the dispersions created. Both measurement techniques have been found to be limited to different concentration ranges. Stratification of drop size was observed for low mixture velocities in a horizontal geometry. This did not occur for the vertical geometry. The drop distributions obtained were found to fit an upper limit log-normal distribution (ULLN). The theory of Hinze has been found to agree well with experimentally determined values of maximum drop diameter at low dispersed phase concentrations. At high concentrations, neither Hinze theory, nor a modified version proposed previously, adequately describe the data obtained.

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Degradation of coals and chars from poly(vinyl chloride) (PVC) and mixtures of PVC with other polymers such as polyethylene glycol, poly(vinyl alcohol), polystyrene, and polyethylene using a mixture of copper(II) oxide (CuO) and aqueous potassium carbonate solution at 500 °C to give a mixture of aliphatic and aromatic hydrocarbons, carbon dioxide, potassium hydrogencarbonate, and water soluble and easily decomposable materials with dilute hydrochloric acid. It was revealed that CuO promoted the decomposition of highly aromatized materials such as chars from PVC or coals and the preferential formation of benzene in the decomposition of those materials.

PEO−PPO−PEO Block Copolymer Micelles in Aqueous Electrolyte Solutions: Effect of Carbonate Anions and Temperature on the Micellar Structure and Interaction

The structure and interaction of micelles formed by an amphiphilic triblock copolymer P(EO)103−P(PO)39−P(EO)103 (F88) in aqueous electrolyte solutions of potassium carbonate have been investigated using small-angle neutron scattering as functions of temperature and salt concentration. Modeling the SANS data from the copolymer solutions using analytical expressions for the scattering intensity revealed the remarkable effects of carbonate anion concentration and the temperature on the self-assembly of F88 into spherical and cylindrical aggregates and subsequent phase separation. The critical micellization temperature (cmt) of 5 wt % F88 decreases with an increase in the salt concentration, and the cmt approaches ambient temperatures in a solution with 0.1 M K2CO3. An increase in salt concentration also decreases the temperature at which the transition from spherical to cylindrical micelles occurs as well as the phase separation temperature of the copolymer from the solution. These observations clearly indicate that the evolution of the micellar structure and the phase separation are through gradual dehydration of the copolymer chains with an increase in the temperature and/or the salt concentration. The effects of carbonate ions are quite dramatic when compared to those of monovalent ions as the structural transitions occur at a concentration that is lower by an order of magnitude than the published results on monovalent ions.

Comparison of laser-based drop-size measurement techniques and their application to dispersed liquid-liquid pipe flow

Two laser-based, optical techniques for drop-size measurement, which have been employed to obtain drop sizes in liquid-liquid pipe flow, are described. The measurement systems used are a laser diffraction technique (Malvern 2600 instrument) and a laser backscatter technique (Par-Tec 300C). The instruments are checked through measurement of a batch of glass beads suspended in water in a stirred cell. An image analysis technique and a phase doppler anemometer provide independent measurements of the size of the beads. The pipe, which is 0.063 m in diameter is installed on a liquid-liquid flow rig. The liquids used are kerosene (continuous phase) and aqueous potassium carbonate solution (dispersed phase). Special test sections are used to deploy the instruments. There are significant differences between the results from the two instruments.

Facilitated Transport of Carbon Dioxide Through an Immobilized Liquid Membrane of Aqueous Carbonate Solution with Additives

An experimental study has been carried out to investigate the characteristics of facilitated transport of CO2 through hydrophilic polymeric membranes with an immobilized aqueous potassium carbonate solution. The rate of permeation for CO2 increased with increasing K2CO3 concentration, decreasing membrane thickness, and decreasing CO2 partial pressure. The permeation rate for CO2 was predicted by a theoretical model based on mass transfer accompanied by a reversible chemical reaction, such as hydration reaction of CO2, reaction of CO2 with OH−, or dissociation of HCO− 3. The permeation rate for CO2 increased by adding K2SO3, PEG, or DBC to the aqueous K2CO3 solution. By assuming that these additives enhanced the hydration reaction of CO2, the forward-reaction rate constant was estimated by fitting to the experimental R A . The values estimated thus were 1.35, 0.98, and 0.56 s−1, for K2SO4, polyethyleneglycol, and Dibenzo-18-crown-6, respectively. These values amount to 15–36 times as large as those without additives.

Conversion of coals to gaseous products containing benzene as a main organic product by the reaction with copper(II) oxide and aqueous potassium carbonate solution

Coals were converted to gaseous products containing benzene as a main organic product and methane, other aliphatic hydrocarbons and acetone as organic by-products, and carbon dioxide by reaction with a mixture of copper(II) dioxide and aqueous potassium carbonate solution at 400°C. The relation of the yield of benzene and the carbon content of coals was bell-shaped, in which the maximum yield was observed in the intermediate carbon content region.