Aqueous Ammonium Carbonate Research Articles

Synthesis of nearly monodispersed metal oxide nanoparticles in water

We report a generalized aqueous route for the synthesis of a variety of nearly monodisperse nanostructured metal oxides with controllable sizes and shapes using aqueous metal ammonium carbonate solution as a precursor and decanoic acid under reflux as well as hydrothermal conditions. The procedure is based on direct formation of metal oxide through hydrolysis followed by dehydration of a metal ammonium carbonate complex in basic medium, in situ dissolution and surface modification of an oxide nanoparticle by decanoic acid through the formation of ammonium salt of decanoic acid. All the synthesized metal oxide nanostructures were characterized by transmission electron microscopy, powder X-ray diffraction and IR spectroscopy. The characterization result shows that all the particles are monodispersed in size and shape, and highly crystalline in nature. A probable formation mechanism is proposed to explain the formation of the size and shape selective CeO2.

A carbonate controlled-addition method for size-controlled calcium carbonate spheres by carboxylic acid-terminated poly(amidoamine) dendrimers

Size-controlled calcium carbonate particles were obtained using a ‘carbonate controlled-addition method’ with G0.5 poly(amidoamine) (PAMAM) dendrimer with carboxylate groups at the external surface. An aqueous ammonium carbonate solution was added to an aqueous solution of the dendrimer and CaCl2 at different time periods (3 min, 1 h or 24 h) and was stirred for 1 day. Both crystal phases obtained at incubation times of 1 and 24 h were vaterite. The dendrimer–CaCl2 solution incubated for 3 min produced vaterite particles that coexisted with calcite. The average particle size of the spheres decreased from 2.2±0.2 to 0.61±0.24 μm with an increase in the incubation time of the dendrimer–CaCl2 solution. When the products were kept in the reaction mixtures for 3 days, the CaCO3 phase of the precipitates obtained after incubating the dendrimer–CaCl2 solution for 3 min and 1 h was calcite. However, the product obtained after incubating for 24 h was vaterite. The present results demonstrate that the interaction and the reaction kinetics of the dendrimer–Ca2+ complex have an important role in the mineralization and stabilization of CaCO3 particles. Vaterite particles were obtained by a ‘carbonate controlled-addition method’ by G0.5 poly(amidoamine) (PAMAM) dendrimer with carboxylate groups at the external surface. The average particle sizes of the spheres decreased from 2.2±0.2 to 0.61±0.24 μm and the stability of the spheres increased with an increase in the incubation time of the G0.5–CaCl2 solution from 3 min to 24 h. The interaction and reaction kinetics of the dendrimer–Ca2+ complex have an important role in the mineralization of CaCO3.

A Carbonate Controlled-Addition Method for Amorphous Calcium Carbonate Spheres Stabilized by Poly(acrylic acid)s

Stable amorphous calcium carbonate (ACC) composite particle with a size-controlled monodispersed sphere was obtained by a new simple carbonate controlled-addition method by using poly(acrylic acid) (PAA) (Mw = 5000), in which an aqueous ammonium carbonate solution was added into an aqueous solution of PAA and CaCl2 with a different time period. The obtained ACC composite products consist of about 50 wt % of ACC, 30 wt % of PAA, and H2O. Average particle sizes of the ACC spheres increased from (1.8 +/- 0.4) x 102 to (5.5 +/- 1.2) x 102 nm with an increase of the complexation time of the PAA-CaCl2 solution from 3 min to 24 h, respectively. The ACC formed from the complexation time for 3 min was stable for 10 days with gentle stirring as well as 3 months under a quiescent condition in the aqueous solution. Moreover, the ACC was also stable at 400 degrees C. Stability of the amorphous phase decreased with an increase of the complexation time of the PAA-CaCl2 solution. No ACC was obtained when the lower molar mass PAAs (Mw = 1200 and 2100) were used. In the higher molar mass case (Mw = 25 000), a mixture of the amorphous phase and vaterite and calcite crystalline product was produced. The present results demonstrate that the interaction and the reaction kinetics of the PAA-Ca2+-H2O complex play an important role in the mineralization of CaCO3.

Synthesis and characterization of mesoporous ceria/alumina nanocomposite materials via mixing of the corresponding ceria and alumina gel precursors

Mesoporous ceria/alumina, CeO 2/Al 2O 3, composites containing 10, 20 and 30% (w/w) ceria were prepared by a novel gel mixing method. In the method, ceria gel (formed via hydrolysis of ammonium cerium(IV) nitrate by aqueous ammonium carbonate solution) and alumina gel (formed via controlled hydrolysis of aluminum tri-isopropoxide) were mixed together. The mixed gel was subjected to subsequent drying and calcination for 3 h at 400, 600, 800 and 1000 °C. The uncalcined (dried at 110 °C) and the calcined composites were investigated by different techniques including TGA, DSC, FTIR, XRD, SEM and nitrogen adsorption/desorption isotherms. Results indicated that composites calcined for 3 h at ⩽800 °C mainly kept amorphous alumina structure and γ-alumina formed only upon calcinations at 1000 °C. On the other hand, CeO 2 was found to crystallize in the common ceria, cerinite, phase and it kept this structure over the entire calcination range (400–1000 °C). Therefore, high surface areas, stable surface textures, and non-aggregated nano-sized ceria dispersions were obtained. A systematic texture change based on ceria ratio was observed, however in all cases mesoporous composite materials exposing thermally stable texture and structure were obtained. The presented method produces composite ceria/alumina materials that suit different applications in the field of catalysis and membranes technology, and throw some light on physicochemical factors that determine textural morphology and thermal stability of such important composite.

Survey of Inorganic Arsenic in Marine Animals and Marine Certified Reference Materials by Anion Exchange High-Performance Liquid Chromatography−Inductively Coupled Plasma Mass Spectrometry

A method for the determination of inorganic arsenic in seafood samples using high-performance liquid chromatography-inductively coupled plasma mass spectrometry is described. The principle of the method relied on microwave-assisted alkaline dissolution of the sample, which at the same time oxidized arsenite [As(III)] to arsenate [As(V)], whereby inorganic arsenic could be determined as the single species As(V). Anion exchange chromatography using isocratic elution with aqueous ammonium carbonate as the mobile phase was used for the separation of As(V) from other coextracted organoarsenic compounds, including arsenobetaine. The stability of organoarsenic compounds during the sample pretreatment was investigated, and no degradation/conversion to inorganic arsenic was detected. The method was employed for the determination of inorganic arsenic in a variety of seafood samples including fish, crustaceans, bivalves, and marine mammals as well as a range of marine certified reference materials, and the results were compared to values published in the literature. For fish and marine mammals, the results were in most cases below the limit of detection. For other sample types, inorganic arsenic concentrations up to 0.060 mg kg(-)(1) were found. In all samples, the inorganic arsenic content constituted less than 1% of the total arsenic content.

Effects of Transition-Metal Substitution on the Catalytic Properties of Barium Hexaaluminogallate

The effects of the substitution of transition-metal ions and/or reductant gases on the catalytic properties of barium hexaaluminogallate were investigated. Transition-metal-substituted hexaaluminogallates (BaM(Al,Ga) 11 O 19 , M = transition metal, Al/Ga = 9/3) were synthesized from aqueous metal nitrates and ammonium carbonate by the coprecipitation followed by crystallization at 1100°C. The direct NO x reduction was observed over BaM(Al,Ga) 11 O 19 to be around 10%. The NO x removal activity of BaM(Al,Ga) 11 O 19 powders was improved by addition of C 3 H 6 as a reductant gas. Co-, Ni- and Cu-substituted BaM(Al,Ga) 11 O 19 catalysts exhibited about 40% NO x reduction with C 3 H 6 in excess oxygen at a high space velocity of 10000 h -1 . The NO x reduction on Mn- and Fe-substituted BaM(Al,Ga) 11 O 19 catalysts was less than 10% even in the presence of C 3 H 6 . The temperature of the effective NO x reduction on BaM(Al,Ga) 11 O 19 catalysts could be adjusted from 350° to 500°C by the selection of the transition-metal substitution in the catalysts. The catalysts hold high activities for NO x reduction even at 500°C in water vapor produced in the combustion system of reductant gases.

Hydrothermal Synthesis of ZnO–Ga2O3–Al2O3Spinel for NO Reduction by Hydrocarbon Under Oxygen-Rich Conditions

Spinel powders with addition of ZnO into Ga2O3–Al2O3 were synthesized from a mixed solution of nitrate salts in the presence of aqueous ammonium carbonate under hydrothermal conditions at 150 °C for 48 h. The crystallization of the spinel was promoted by an increase in reaction temperature and time. This powder was studied for the selective reduction of NO with hydrocarbons (CH4, C2H4, and C3H6) in the presence of oxygen. High durability was observed for the reduction of NO by C2H4 in the presence of water vapor and sulfur oxides, maintaining a high stability over 100 h.

DeNOx Properties of Barium Hexaaluminogallates.

NO/O2 and NO/C3H6/O2 reactions were investigated over barium hexaaluminogallate (Ba (Al, Ga)12O19 and BaCo (Al, Ga)11O19) with Al/Ga=9/3, 6/6 and 3/9 ratios. BaCo(Al, Ga)11O19 was synthesized by crystallization at 1100°C via the coprecipitation precursor powders prepared by aqueous metal nitrates and ammonium carbonate. The NOx conversion amount in the NO/O2 reaction over all hexaaluminogallates was less than 10%. The addition of C3H6 as a reductant gas significantly improved the NOx conversion over BaCo(Al, Ga)11O19 in excess oxygen compared with that in the case of Ba(Al, Ga)12O19. The Al/Ga ratio influenced the morphologies and catalytic activities of hexaaluminogallate powders. With increasing Al/Ga ratio, the NOx reduction with C3H6 to N2 increased up to 40% and 28% for BaCo(Al, Ga)11O19 powders and Ba(Al, Ga)12O19 powders, respectively. Highly dispersed Co species are effective in accelerating the NO activation step in selective reduction with C3H6.

Analysis of raw materials, intermediates and subsidiary colours in Food Yellow No. 5 (Sunset Yellow FCF) by LC/MS

Raw materials, intermediates and subsidiary colours in Food Yellow No. 5 (Sunset Yellow FCF) were determined using liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization. A gradient consisting of acetonitrile and 0.04% aqueous ammonium carbonate solution was used for the HPL C mobile phase. Quasi-molecular ions of impurities were used as monitor ions. It was necessary to use fragment ions of the sodium salts of 6-hydroxy-5-phenylazo-2-naphthalenesulphonic acid (SS-AN) and 4-(2- hydroxy-1- naphthylazo) benzenesulphonic acid (2N-SA) as monitor ions because the compounds are not resolved by chromatography and have the same molecular weight. Fifteen samples of commercial Sunset Yellow FCF were examined. The results obtained by UV-Vis spectroscopy were in good agreement with the results of LC/MS analyses. The detection limits of the impurities in Sunset Yellow FCF ranged from 0.01 to 0.1%.

XPS Analysis of Carbon Fiber Surfaces—Anodized and Interfacial Effects in Fiber–Epoxy Composites

High strength carbon fibers were electrochemically treated in an aqueous ammonium carbonate solution, with increasing electric current density, using an original continuous treatment process. The electrochemical treatment induced a modification of the surface properties, i.e., surface functional groups as observed by XPS. As a result, the O1s/C1s and the N1s/C1s ratios of the fiber surfaces increased with the increase of current intensity of the electrochemical treatment in the interval of about 30–50 A m−2. However, no significant change in the surface functional activity characters was observed for strong treatments. Hence, a moderate treatment (30 A m−2) was sufficient to obtain optimum (O1s + N1s)/C1s ratios in this system. This treatment is possibly suitable for carbon fibers to be incorporated in a polar organic matrix, resulting in increasing the interlaminar shear strength (ILSS) of the resulting composites.

Strategies for the synthesis and screening of glycoconjugates. 1. A library of glycosylamines.

A simple one-step procedure is found to be highly effective for the "functionalization" of glycodiversity. This study encompasses 50 unprotected mono- and oligosaccharides, which are subjected to Kochetkov aminations in saturated aqueous ammonium carbonate. The reaction allows for the stereo- and regioselective introduction of an amino group into all oligosaccharides tested, as well as into a great variety of monosaccharides including charged species. The resulting unprotected glycosylamines are stable compounds, and the inherent amino group provides a convenient site for chemoselective conjugation and modification as described in the following paper in this issue.

Extraction of plutonium(IV) from oxalic acid-nitric acid solutions by Aliquat-336

The extraction of Pu(IV) from oxalic acid-nitric acid mixtures has been investigated using a liquid anion exchanger, Aliquat-336, in xylene. The presence of oxalic acid is known to have adverse effects on the extraction of Pu(IV) by Aliquat-336. The use of cations, Al(III), Fe(III) or Zr(IV) was explored to overcome the effect of oxalic acid on Pu(IV) extraction. The data obtained reveal that Pu(IV) is quantitatively extracted by Aliquat-336, even in the presence of oxalic acid, when Al(III), Fe(III) or Zr(IV) is added. The extracted Pu(IV) can be back-extracted using aqueous ammonium carbonate.

アルコールによるアンモニア性アルカリ溶液からのコバルトの濃縮および析出

The concentration and deposition of cobalt from ammoniacal alkaline solution was carried out by adding alcohol. Test solutions of cobalt were prepared with the reagent or a leach liquor obtained from cobalt crusts with the mixture of aqueous ammonium carbonate and ammonium sulfite solution. It was found that when propanol was added to an ammoniacal alkaline solution containing cobalt, the solution was separated into two phases of an aqueous phase containing propanol and a cobalt concentrated phase. The concentration rate of the cobalt varied with added amount of propanol. A addition ratio of propanol (PrOH/H20: O/A) of 5 enabled to obtain a cobalt concentration rate of 99% and to increase cobalt concentration to 5 times or more. To deposit the cobalt, methanol or ethanol was effective. A alcohol addition ratio (O/A) of 5, whether it was methanol or ethanol, enabled deposition rate to be 99% or more.

Extraction of technetium(VII) from uranium(VI) in nitric acid system by primary amine — n-heptane solution

Separation of technetium(VII) from uranium(VI) has been studied through experiments on the coprecipitation of technetium(VII) with precipitation of ammonium diuranate, and on the extraction of technetium(VII) from a 3M aqueous nitric acid solution using, as extractant, a primary amine (Primene JMT) dissolved in either chloroform or n-heptane solution. Ammonium diuranate precipitation proved to provide the most satisfactory means of separating technetium(VII) from uranium(VI) in solution. Extraction of technetium(VII) contained in nitric acid solution using Primene JMT dissolved in n-heptane solution proved to be quantitative after several cycles of the procedure and alternatively, upon raising to 5∶1 the volume ratio between the organic phase containing the extractant and the aqueous phase containing technetium(VII). Stripping of technetium(VII) into 2M aqueous ammonium carbonate solution was enhanced to quantitative level by repetition of the stripping procedure, and alternatively, by adding the ammonium carbonate in a volume ratio of 5∶1 with respect to the organic phase containing technetium(VII).

ChemInform Abstract: Amination of Pyridinium Betaines. Synthesis of Substituted 2H‐Pyrido‐(1,2‐a)pyrimido(5,4‐e)pyrimidine and Its Dihydro Analogs.

AbstractReaction of the pyridinium betaines (Ia) ‐ (Ic) with aqueous ammonium carbonate solution gives the cyclization products (II).

Uranium In Situ Leaching Sulfur Chemistry

In situ leaching of uranium by aqueous ammonium carbonate containing oxygen or hydrogen peroxide as oxidant results in the partial dissolution of sulfides. While some of the sulfide sulfur is oxidized to sulfate, a considerable portion is oxidized only to thiosulfate and polythionates. Polythionates poison the ion exchange resin used to extract uranium. At the Palangana operation in south Texas, the trithionate ion (S3O62−) was found by infrared spectrometry to be the major resin poison. Treatment of ion exchange feed solutions with hydrogen peroxide only resulted in partial conversion of reduced sulfur species to sulfate. Trithionate conversion was particularly slow. Poisoning of the resin also occurred from the ammonium chloride eluant, which built up trithionate because of recycling. This was essentially eliminated by chlorinating the eluant before yellow cake precipitation.

Anodic Dissolution of Iron in Ammoniacal Ammonium Carbonate Solution

The electrochemical behavior of iron has been characterized in aqueous ammoniacal ammonium carbonate solution. Pure iron anodically polarized in He‐ or solutions exhibits both stable active (, SHE) and passive regions. A cathodic loop was observed in the potential range of −380 to 100 mV. It is suggested, on the basis of cathodic polarization curves of a graphite electrode in various concentrations of ammoniacal solution, that the cathodic loop is due to oxygen discharge. The addition of to the ammoniacal solution has the same effect as oxygen in that it increases the cathodic current and potential range of the cathodic loop and, as such, functions as a strong oxidant.

Pore structures and bulk properties of titania gels prepared from titanous chloride

A series of titanium dioxide gels has been prepared by the oxidation of precipitated hydrous Ti(III) oxide, obtained by the addition of aqueous ammonia or ammonium carbonate to aqueous solutions of titanous chloride. The gels were dried in air at 110°C and their structures and surface properties studied with the aid of DTA, X-ray diffraction, nitrogen adsorption, and spectrophotometry. Analysis of the nitrogen isotherms has revealed that the gels exhibited a wide range of different pore structures, extending from narrow micropores to wide mesopores. The development of the gel porosity appears to have been largely controlled by the mode of removal of water ligands from the hydration sphere of the cations, enlargement of the micropore volume being obtained by the replacement of water by carbonato ligands and pore widening by increase in the pH of precipitation (over the pH range 2.3–7.1). All the gels were X-ray amorphous in their original state: some were converted directly to rutile at 500°C while others underwent the more usual transformation into the intermediate anatase form. It is postulated that the rapid removal of the water ligands can result in the formation of a defect structure which controls the development of the pore structure and also the behavior of the gels on heat treatment.

Absorption of NO<SUB>x</SUB> Gas into Aqueous Ammonium Carbonate Solutions in Packed Column with Cocurrent Downward Flow

Absorption of NO<SUB>x</SUB> Gas into Aqueous Ammonium Carbonate Solutions in Packed Column with Cocurrent Downward Flow

High-performance liquid chromatography of eburnane alkaloids : III. Application of different phase systems

Methods developed for the separation of eburnane alkaloids have been applied for solving different analytical problems; plant extracts, mother liquors and pharmaceutical formulations have been analysed on both reversed-phase and silica packings. For the determination of apovincaminic acid ethyl ester (vinpocetine) in human blood plasma octylsilica was used as the stationary phase and acetonitrile–0.01 M aqueous ammonium carbonate as the eluent. For quantitation apovincamine can be used as an internal standard. The detection limit was found to be 2 ng/ml. To determine the corresponding acids of ester derivatives of eburnane alkaloids a reversed-phase ion-pair chromatographic method was developed.