Ammonium Carbonate Solution Research Articles

Determination of the reactivity of CaSO4 · 2H2O

Abstract Reactivity of energy gypsum was investigated. The method is based on the conversion reaction of aqueous suspension of gypsum with ammonium carbonate solution. Rate of the conversion of all investigated samples, including gypsum originating from flue gas desulphurization (FGD), was high and 80 % conversion was achieved during one hour. It was found that there is a correlation between BET specific surface and the rate of the conversion reaction.

Ca3 − x(Fe, Mn)xWO6 (0 < x ≤ 1) prepared from tungsten-containing materials and its leachability in aqueous ammonium carbonate solution

The conversion of tungsten-containing materials to a readily soluble substance in ammoniacal solution is significant in the development of a cleaning process for manufacturing ammonium paratungstate. In this work, Ca3−x(Fe, Mn)xWO6 (0<x≤1) was prepared by roasting a mixture of tungsten-containing materials and calcium carbonate. The leachability of the roasted products in aqueous ammonium carbonate solution was then tested. Thermodynamic analyses and experimental results showed that Ca2FeWO6 and Ca2MnWO6 can be obtained by roasting the mixture with appropriate ingredients in neutral or weakly reducing atmosphere, and Fe(II) in Ca2FeWO6 can be substituted by Ca to form Ca3−xFexWO6 (0<x<1) with an excess of calcium carbonate. With increased roasting temperature and carbon addition, Fe3W3C and Mn3W3C can be generated. Additionally, leaching results showed that Ca3−x(Fe, Mn)xWO6 had excellent leachability in aqueous ammonium carbonate solution with 99% WO3 recovery. The results presented can be used to exploit a novel technique with recycling solutions for ammonium paratungstate production.

A controlled, template-free, and hydrothermal synthesis route to sphere-like α-Fe2O3nanostructures for textile dye removal

Iron carbonate nanospheres were synthesizedviahydrothermal treatment of aqueous solutions of iron sulfate, ascorbic acid and ammonium carbonate with a molar ratio of 1 : 1 : 3, respectively, at 140 °C for 1.5 h.

Study of the dissolution of chalcopyrite in solutions of different ammonium salts

41BC6=D= The oxidative leaching of chalcopyrite in ammoniacal solutions has been evaluated using electro-analytical techniques and controlled bulk leaching studies. The anodic dissolution process has been established to be a sevenelectron transfer process under nitrogen in ammonia–ammonium sulphate solutions and ammonia–ammonium carbonate solutions, which suggests that the sulphur is oxidized to thiosulphate and the copper and iron released as Cu + and Fe2+ in these systems. The deportment of Fe2+ and S 2O3 2- is affected by choice of the ammonium salt used in the leaching process. In the perchlorate salt, only five electrons are transferred, supporting formation of different sulphur species as proposed for the sulphate and carbonate salts. Scanning electron microscopy and energydispersive spectroscopic analysis of the mineral surface after leaching indicate presence of an iron–sulphur surface layer completely free of copper in the sulphate system, an iron-rich surface layer in the perchlorate solutions, and absence of surface layer build-up in carbonate solutions. XRD analysis of a bulk leach residue from leaching in ammoniaammonium sulphate solutions showed the surface layer to be mostly amorphous (90%). The crystalline content (10%) is composed of 95% polymorphs of anhydrous iron oxide hydroxide FeO(OH). Choice of ammonium salt and the hydrodynamic environment of leaching have been shown to influence the presence or absence of the surface product, as well as its nature. HF1�C@9= chalcopyrite, ammonia, surface deposits, coulometry, iron oxy-hydroxide.

Synthesis of Stable Sols of Layered Titanate Nanoparticles using Dialysis and Applications for Thin Film Preparation

Sols with stable dispersion of layered titanate nanoparticles were prepared at 298 K using dialysis of a mixed solution of ethylene glycol, TiCl3, ammonium carbonate, and H2O2. Raman spectra of the particles in the obtained sols showed Raman scattering peaks which can be assigned to a layered titanate structure. The stability of the obtained sols depended on the molar ratio of [ammonium carbonate] / [Ti ion]. The molar ratios of 3, 4, and 5 produced transparent yellow stable sols. Peptization of titanium hydroxide precipitate with H2O2 formed stable sols with dispersion of layered titanate nanoparticles, which had plate - shaped morphology. The obtained sols formed layered titanate thin films on glass substrates easily by drying the sols. Furthermore, when the layered titanate thin films were heated at 773 K for 1 h, anatase TiO2 thin films were obtained with (101) orientation of crystallites and optical transparency.

Preparation and Characterization of Transitional Alumina Obtained through Ammonia Treatment

In this study, different aluminas were obtained by precipitating Al(NO3 )3·9H2O with different concentration of aqueous solution of ammonium carbonate. The obtained aluminas were treated by 50 (vol/vol) % ammonia via low temperature immersing and high temperature hydrothermal treatment, respectively, then, the treated aluminas were calcined again. The crystal types, morphology, textural properties, and pore distribution of the original alumina, ammonia‐treated alumina, and the second calcined alumina were studied by characterizations of X‐ray diffraction, thermogravimetric analyses, nuclear magnetic resonance, Brunauer‐Emmett‐Teller (BET), transmission electron microscopy, and so on. Several modified aluminas with specific morphology, desired pore structure, and pure crystal types were obtained, which can be used in some specific industrial application.

English

The bulking treatment with phenolic resin is well known as a treatment to improve the properties of low density wood but high amount of formaldehyde emission will be released during and after treatment. A study was conducted to determine the performance of phenolic resin treated sesenduk (Endospermum diadenum) wood post treated with ammonium carbonate and urea. Wood strips were treated separately with 30% low molecular weight phenol formaldehyde resin (LmwPF) resin and mixture of LmwPF with urea (30% based on solid PF) using empty-cell process. Two products were produced from the treatment, i.e. impreg and compreg. After conditioning, the surfaces of the samples were applied with ammonium carbonate solution at 10, 20 and 30 g/m2. The samples were then stacked and stored at 60°C for 48 h. Properties such as formaldehyde emission, strength and dimensional stability were evaluated. The results showed that the post treatment with ammonium carbonate has successfully reduced the formaldehyde emission from the sesenduk wood. The degree of reduction was depended on the amount of ammonium carbonate applied on the samples. The results also showed that the sesenduk wood treated with mixture of PF and urea had lower formaldehyde emission. Post treatment with ammonium carbonate did not significantly affect the physical and mechanical properties of the sesenduk wood.

Ca3WO6 prepared by roasting tungsten-containing materials and its leaching performance

Aiming to develop a novel technique to alleviate the environmental stresses caused by waste-water in the prevalent ammonium paratungstate manufacture process, preparation process of tricalcium tungstate (Ca3WO6) from tungsten-containing materials by roasting was studied systematically in this paper. Thermodynamic analyses and experimental results show that Ca3WO6 could be formed by reactions of CaWO4/Fe(Mn)WO4 with CaO, Ca(OH)2 or CaCO3 in air. Increasing roasting temperature not only accelerates the conversion of CaWO4 to Ca3WO6 but also eliminates the dependence of the conversion on calcium compound types. Moreover, additive CaF2 can greatly reduce roasting temperature for complete conversion of tungsten-containing minerals in mixed concentrate of scheelite and wolframite to Ca3WO6. Additionally, Ca3WO6 clinker prepared by mixed concentrate has good leachability in aqueous ammonium carbonate solution with WO3 recovery of 98.4%. The work presented is favorable for developing a promising technique with recycling both auxiliary materials and solutions for cleaner production of ammonium paratungstate.

Surface modification of PVDF membrane by simultaneously using low temperature plasma and ammonium carbonate solution

Polyvinylidene fluoride (PVDF) hollow fiber membrane was surface modified by low temperature O2 and H2O plasma and ammonium carbonate solution treatment, and used in membrane bioreactor (MBR). Effect of the modification on surface characteristics of PVDF membrane was investigated. The FE-SEM and AFM images of membrane showed that low temperature O2 and H2O plasma and ammonium carbonate solution treatment could markedly increase surface roughness of PVDF membrane. Water contact angle decreased obviously with the increase of low temperature plasma treatment time. Hydrophilicity of modified membrane enhanced distinctly. The mass fraction of oxygen of PVDF membrane surface increased markedly after plasma and ammonium carbonate solution treatment. The modification of membrane surface had no significant effect on the removal rates of pollutants when used in a MBR. It could improve antifouling property of membrane and decrease filtration resistance of membrane. The modification using low temperature plasma and ammonium carbonate solution did not reduce membrane flux. And moreover, ammonium carbonate solution treatment could markedly enhance the stability of plasma modification membrane.

Kinetic study of uranium residue dissolution in ammonium carbonate media.

The purpose of this study was to determine the kinetics of the dissolution of a uranium residue in ammonium carbonate media. The residue is generated in the production of medical isotopes. The effects of parameters, such as varying peroxide and carbonate concentrations, dissolution time as well as temperature on the extraction rate have been separately studied. Results indicate complete dissolution of the residue at 60 °C, after 30 min, in ammonium carbonate solution enriched with hydrogen peroxide. The yield and rate of uranium extraction were found to increase as a function of both temperature, in the range of 25–60 °C, and hydrogen peroxide concentration. The extraction process was governed by chemical reaction as the activation energy was found to be 45.5 kJ/mol. The order of reaction with respect to uranium concentration was found to be approximately first order.

Synthesis and electrical conductivity of (La1−xSrx)(Al1−yMgy)O3−δ perovskite solid solution

Perovskite solid solution powders with (La1−xSrx)(Al1−yMgy)O3−δ composition (shorten as LSAM) were prepared by a coprecipitation method using corresponding aqueous solutions and ammonium carbonate solution. The freeze-dried powders were heated in air at 1500 °C for 10 h, and subsequently sintered at 1400 °C for 12 h in air. The X-ray diffraction patterns and the lattice parameters for the compositions of x = 0–0.4 at y = 0.1 and y = 0–0.15 at x = 0.2 suggested the formation of rhombohedral LaAlO3 solid solution. The sinterability of LSAM was controlled by the diffusion rate of A site cations and increased by increasing Sr composition at A site and by decreasing Mg composition at B site. The highest electrical conductivity was measured at the composition of (La0.8Sr0.2)(Al0.9Mg0.1)O2.85 (6.79 × 10−3 S/cm at 600 °C, activation energy 98.8 kJ/mol). Although the sintered (La0.8Sr0.2)(Al0.9Mg0.1)O2.85 electrolyte contained 28% porosity, its conductivity was higher than the conductivity of dense 8 mol% yttria-stabilized zirconia electrolyte. The conductivity and activation energy of LSAM greatly vary according to the concentration of available oxygen vacancy and the association of positively charged oxygen vacancy and negatively charged sites or sites. The LSAM composition of (La0.8Sr0.2)(Al0.9Mg0.1)O2.85 provided the perovskite structure of the smaller strain (tolerance factor 1.007). This is another factor for the highest conductivity.

The Study on the Crystallization Conditions of Zn5(OH)6(CO3)2 and its Effect on Precipitation of ZnO Nanoparticles from Purified Zinc Ammoniacal Solution

The authors studied the crystallization conditions and formation mechanism of zinc carbonate hydroxide [Zn5(OH)6(CO3)2] based on the crystallization theory. An ammoniacal ammonium carbonate zinc aqueous solution was employed for this aim. After achieving the maximum solubility of zinc in ammonium carbonate solution by controlling its pH and temperature (85°C and pH = 9.5), the crystallization conditions were performed by both diluting with water and heating the saturated solution. The results showed that heating of saturated solution is more practical than diluting with water. The conversion of Zn5(OH)6(CO3)2 to ZnO was carried out by calcination at 400°C for 2 h, based on its decomposition temperature obtained from TGA-DTA analysis. TEM images of obtained the ZnO powder showed that discrete nanoparticles (with the size of about 50–60 nm) were formed after calcination process. The techniques of SEM, TEM, STA, XRD, BET, and Raman spectroscopy were applied for the characterization of the produced materials.

An assessment of the stability of MDMA, methamphetamine and THC in oral fluid

The stability of drugs proscribed under the Victorian Road Safety Act 1986 (MDMA, MA and THC) was determined in authentic drug-positive oral fluid following short-term storage at room temperature, 4ºC, fluctuating temperatures and long-term storage at –20 ºC. Following pH adjustment with ammonium carbonate solution, drugs were extracted using chloroform:isopropanol (9:1) and analysed by LC-MS/MS operating in multiple reaction monitoring mode. The results were analysed using Wilcoxon matched-pairs signed ranks and interpreted in the context of AS4760:2006 cut-offs. For MA and MDMA only minor changes occurred following all storage conditions, but THC concentrations were reduced by 70–87% (n=10) following storage at fluctuating temperatures (room temperature to 60°C) for 2 weeks. Of the 10 samples that were positive for THC prior to storage, only one remained positive after 2 weeks. This has significant implications for the interpretation of THC concentrations in cases where the possibility exists that samples were stored at higher temperatures.

Preparation of hybrids consisting of expanded graphite and carbon nanotubes as conductive fillers of polybutylene terephthalate

Expanded graphite (EG) was loaded with iron by impregnating with ammonium carbonate and ferric nitrate solution. Carbon nanotubes (CNTs) were grown on the EG by iron-catalyzed chemical vapor deposition, using acetylene as a carbon source to form hybrids that were used as a conductive filler to produce conducting polybutylene terephthalate (PBT) composites by an extrusion method. It is found that the CNTs are not entangled and are easy to disperse. The CNT average diameters are 40, 20 and 40 nm, and their lengths are 2, 3.7 and 2.6 μ m for iron loadings of 1.13, 0.75 and 0.57 mass%, respectively. The thickness of the EG is reduced to 10–30 nm as a result of CNT insertion into the graphene layers of the EG. The content of CNTs in the hybrids increases from 50 to 85 mass% with the increasing iron content. The conductive PBT modified by the hybrids (5 mass%) derived from EG loaded with 0.75 w% iron has a surface resistance of 1.55 × 10 4 Ω / cm 2 , significantly lower than that ( 1.55 × 10 10 Ω / cm 2 ) of the PBT modified by CNTs with the same amount of filler added. [New Carbon Materials 2013, 28(6): 480–483]

A Standard Addition Method Utilizing an Endogenous Substance as an Internal Standard for Quantitating Arabinofuranosylguanosine 5?-Triphosphate in Human Peripheral Blood Mononuclear Cells by Lc-Ms/Ms

A highly sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for quantitation of arabinofuranosylguanosine 5’-triphosphate (ara-GTP) in human peripheral blood mononuclear cells (PBMC). The determination of ara-GTP in PBMC was validated using a standard addition method with the human Tlymphoblastoid cell line as an alternative blank matrix. Ara-GTP was extracted with methanol/250 mmol/L ammonium carbonate solution (7/3, v/v) from the cells at a density of 106 cells per 0.5 mL. Extracts were subjected to LC-MS/ MS using a TurboIon spray interface and selected reaction monitoring with the transitions of m/z 524 to m/z 152 for quantitation. Endogenous guanosine triphosphate in the extract was used as an internal standard. Separation of the analytes was achieved on a porous graphitic carbon column (100 mm length × 2.1 mm i.d., 5 μm particle size) by isocratic elution with 250 mmol/L ammonium carbonate buffer (pH 9.5)/water/acetonitrile (40/51.5/8.5, v/v/v) at a flow rate of 0.2 mL/min. The method was validated in the range of 2–250 pg/mL. The pharmacokinetic profile of ara-GTP in PBMC in a Phase I clinical study of nelarabine in relapsed or refractory T-ALL/T-LBL patients was successfully determined using this method.

Analysis of the Simultaneous Gas–Liquid CO2 Absorption and Liquid–Gas NH3 Desorption in a Hydrometallurgical Waelz Oxides Purification Process

Abstract This work deals with the analysis of the mass transfers taking place in a unit operation of a recently developed hydrometallurgical process. This process is a purification treatment of zinc-rich electric arc furnace dusts to generate high purity zinc oxide. In this operation, gaseous CO2 generated in a furnace is injected in a reactor containing an aqueous solution of ammonia and ammonium carbonate, which is the leaching solution of these dusts, to precipitate zinc carbonates. During the operation, the gas–liquid CO2 absorption is coupled with a simultaneous liquid–gas NH3 desorption and with several reactions in the leaching solution. This paper aims to propose a mathematical model of the coupling between the mass transports and the reactions and to present a simulation tool for the computation of the CO2 absorption, the NH3 desorption rates and their evolutions with the solution composition. The ability of the presented simulation tool to predict the time evolution of the liquid composition during a gas injection is evaluated by comparing simulation results to experimental results. The pH time evolution is used as the comparison criterion and the experiments are carried out at a bench-scale stirred tank reactor. In addition, simulations results showing the influence of the solution composition in conditions representative of the operating conditions on the CO2 absorption and NH3 desorption rates are presented and discussed.

Size-Controlled Vaterite Composite Particles with a POSS-Core Dendrimer for the Fabrication of Calcite Thin Films by Phase Transition

Vaterite composite particles with a size-controlled sphere were obtained by a carbonate controlled-addition method by using a carboxylate-terminated poly(amidoamine) (PAMAM)-type polyhedral oligomeric silsesquioxane (POSS)-core dendrimer. An aqueous ammonium carbonate solution was added to an aqueous solution of the dendrimer and CaCl2 at different times (3 min, 30 min, and 1 h) and stirred for 1 h at 30 °C. When the complexation time of the POSS-core dendrimer-CaCl2 solution was increased from 3 min to 1 h, the average particle sizes of the spheres increased from 0.71 ± 0.08 to 1.86 ± 0.22 μm, respectively. However, the average particle sizes decreased with decreasing temperature. Particles with minimum sizes of 70 ± 6 nm were obtained when COONa to calcium ion molar ratio was 16 and the complexation time was 3 min at 20 °C. Incubation of the vaterite composite particles in distilled water for 3 days led to complete phase transition to calcite. Negative zeta potential values, ranging from -30 to -10 mV, were detected for the vaterite particles, indicating that the POSS-core dendrimers were exposed on the CaCO3 particles. The CaCO3 particle surfaces were successfully coated with poly(diallyldimethylammonium chloride) (PDDA) in aqueous dispersions by adding a controlled concentration of the polymer. Alternate vaterite composite particles and polyelectroyte multilayer films were prepared by a layer-by-layer method. The obtained (PDDA/vaterite)10(PDDA) multilayer films were incubated in distilled water at 30 °C. Incubation for 5 days led to complete phase transition to calcite, as estimated by Fourier transform infrared (FTIR) spectroscopic and XRD analyses. The SEM observation of the sample after 5 days of incubation showed a granular network structure of irregularly shaped calcite particles. Although some patches and pores were present in the films, the SEM image clearly demonstrated that large-area and continuous CaCO3 films were formed.

IMPROVED CORROSION RESISTANCE OF FRICTION STIR ZONE OF RARE EARTH MAGNESIUM ALLOY AE42

Corrosion studies on friction stir welded AE42 magnesium alloy were carried out in 0.1 M ammonium carbonate solution. For better understanding, comparative analysis of corrosion rates was carried out before and after welding. Friction stir weld zone was more corrosion resistant than the parent metal under similar experimental conditions. Grain size was refined at weld zone. Second phase intermetallic particles were refined into tiny pieces of 1-2 micron size and evenly distributed throughout the matrix. Local electrochemical imbalance was eliminated due to the grain refinement and elimination of continuous grain boundary. These phenomena improved the corrosion resistance of weld zone. Scanning electron microscopic images confirmed mild and uniform corrosion of weld zone and rigorous inhomogeneous corrosion of parent metal.

Preparation and Electrical Conductivity of Sr(Zr&lt;sub&gt;1-x&lt;/sub&gt;Al&lt;sub&gt;x&lt;/sub&gt;)O&lt;sub&gt;3-x/2&lt;/sub&gt; Perovskite Solid Solution (x = 0-0.5)

Perovskite solid solution of Sr(Zr1-xAlx)O3-x/2 was prepared by a coprecipitation method using corresponding aqueous solutions and ammonium carbonate solution. The freeze-dried powders at x = 0-0.5, heated at 1000°C for 4 h in air, were identified to be an orthorhombic SrZrO3 solid solution. The highest electrical conductivity of Sr(Zr1-xAlx)O3-x/2 system sintered at 1400°C was measured at x = 0.2 (3.80×10-4 S/cm at 800°C, activation energy 109 kJ/mol ). The activation energy also showed a maximum value at x = 0.25 .

The Influence of Morphology on Photo-catalytic Activity and Optical Properties of Nanocrystalline ZnO Powder

Abstract ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obtained zinc oxide particles depend critically on the type of additive which was used. Additives also affected the crystal orientation of precipitate nano-particles. SEM, XRD, BET and UV-visible were used to characterize morphology, microstructure, specific surface area and optical properties of the products. Photo-catalysis properties of the as-prepared ZnO powders were evaluated by degradation of methyl red (acid red) in aqueous solution exposed to UV-light. Results suggested a close relationship among the morphology, size and surface area on photo-catalysis and optical properties of the particles. The widest Eg value (3.56 eV), highest degradation and decolorization efficiency (99%) were obtained from a sample with the smallest grain size (largest surface area) which were used urea as an additive.