Crystal chemical analysis of natural clay material of different genesis

Crystal chemical analysis of natural clay material that formed under different physicochemical parameters shows that the analyzed samples are represented in series I by almost pure smectite (K,Na,Mg,Ca) _x ·nH₂O·(Fe,Mg)₂(Si,Al,Fe)₄O₁₀(OH)₂, in series II by smectite with a small impurity (~15%) of quartz (SiO₂) and plagioclase (NaAlSi₃O₈/CaAl₂Si₂O₈). The studies are performed by X-ray diffraction, IR spectroscopy, electron microscopy, and microprobe analysis. It is shown that the values of d001 basal reflections of the smectites in question within 11–13 Å are due to the degree of cation occupation and hydration of the interlayer space, and differences in the frequencies of IR spectra are caused by isomorphic substitutions in the structure. Microprobe analysis results, calculated crystal chemical formulas, and values of b parameters are held only for the extreme terms in a series of dioctahedral ferric smectites: nontronites. The results reveal differences both in the composition, structure, properties, morphology and IR spectroscopic characteristics of nontronites of different origin.     

The effect of iron phosphate,alumina and silica coatings on the morphology of carbonyl iron particles

Carbonyl iron powders were coated with iron phosphate using phosphating method and boehmite (γ‐AlOOH) or silicon hydroxide (Si(OH)₄) nanoparticles derived from the hydrolysis of tri‐sec‐butoxide (Al(OC₄H₉)₃) or tetramethylsilane (Si(OCH₃)₄) using sol–gel method. The coated powders were dried and calcined at 400 °C for 3 h in air. Cross‐section morphology of coated carbonyl iron powders were investigated by scanning electron microscopy energy dispersive X‐ray analysis. Coated Fe micro‐particles were spherical in shape with ‘shell/core’ structures. The shells consisted of an amorphous layer with varying thickness (100–800 nm) and the core represented a carbonyl iron. Gelatinous morphology of dried FePO₄ coating composed from nanoparticles of iron oxyhydroxides and hydrated iron phosphate with a shell thickness of ～100 nm around iron particles was observed. In coatings based on alumina or silica xerogels with a thickness of ～100–150 nm or ～200–500 nm, the coatings were composed of iron oxyhydroxides and γ‐AlOOH or Si(OH)₄. The resulting XRD diffractograms revealed the hematite (α‐Fe₂O₃) and magnetite (Fe₃O₄) that were formed in phosphated and sol–gel coated iron powders. The X‐ray diffraction patterns did not verify the presence of phosphates, alumina or silica and indicate the amorphous or nanocrystalline structure of FePO₄, γ‐Al₂O₃ and SiO₂. Copyright © 2009 John Wiley & Sons, Ltd.     

Control over morphology of magnesium-aluminum hydrosilicate nanoscrolls

It is shown that the morphology of nanoparticles based on variable-composition compounds (Mg,Al)₃(Si,Al)₂O₅(OH)₄ can be controlled by varying the content of aluminum, x _Al. Nanoparticles with both tubular (x _Al = 0 mol %) and plate-like (x _Al = 5 mol %) morphologies were obtained by synthesis of nanoparticles under hydrothermal conditions at 350°C and 30 MPa in an aqueous solution of 0.5 M NaOH. A calculation analysis of the existence conditions of the tubular and plate-like forms of (Mg,Al)³(Si,Al)₂O₅(OH)₄ compounds was made. The tubular morphology can be potentially obtained in a wider range of xAl values than that observed in the experiment.     

Hydrothermal synthesis of nanotubular Mg-Fe hydrosilicate

Magnesium iron hydrosilicate nanotubes with a chrysotile ((Mg,Fe)₃Si₂O₅(OH)₄) structure have been synthesized hydrothermally at t = 250–450°C and p = 30–100 MPa. In the hydrothermal synthesis of (Mg,Fe)₃Si₂O₅(OH)₄ chrysotile, part of the Fe²⁺ ions oxidize to Fe³⁺ and are incorporated into the octahedron and tetrahedron layers of the chrysotile structure. The limiting iron content of chrysotile has been determined up to which cylindrically rolled layers can form to yield nanotubes. The hydrothermal treatment of precursors richer in FeO yields platelike hydrosilicates. The iron ions present in the starting components affect the synthesis parameters, morphology, size, optical properties, and thermal stability of the nanotubes.     

Multi elemental neutron activation analysis of popular medicinal plants used to prevent blood lipid disorders

In this study, five of popularly used medicinal plants as Cichorium intybus, Anethum graveolens seed, Thymus vulgaris, Fumaria officinalis and Hibiscus sabdariffa Syn: Hibiscus gossypifolius were prepared from Herbal Pharmacies in Tehran. The amounts of Al, Br, Ca, Cl, Cr, Fe, K, Mg, Mn, Na, V and Zn in samples were determined using instrumental neutron activation analysis. In this method, Tehran research reactor as a neutron source and relative INAA have been used as the analysis procedure. Highest levels of Cr (5 mg/kg), Ca (28316 mg/kg) and Mg (4134 mg/kg) were detected in Thymus vulgaris and F1umaria officinalis, respectively.     

N-methyl-2-pyrrolidonium-based Brönsted-Lewis acidic ionic liquids as catalysts for the hydrolysis of cellulose

We experimentally studied the catalytic performances of a series of Br?nsted-Lewis acidic N-methyl-2-pyrrolidonium metal chlorides([Hnmp]Cl/MCl_x, where M=Fe, Zn, Al, or Cu) for the hydrolysis of microcrystalline cellulose(MCC) and cotton to produce reducing sugar. A variety of factors, such as temperature, time, ionic liquid(IL) species, IL dosage, and the concentration of the metal chloride were investigated. [Hnmp]Cl/FeCl_3 presented the best hydrolysis performance, affording a 98.8% yield of total reducing sugar from MCC(1 h, 100 °C, 0.1 g MCC, 0.2 g acidic IL, 2.0 g [Bmim]Cl as solvent), which is better than or comparable to results previously obtained with other –SO_3H functionalized acidic ILs. The hydrolysis performances of [Hnmp]Cl/MClx were rationalized using density functional theory calculations, which indicated that interactions between the metal chlorides and the cellulose, including charge-transfer interactions are important in the hydrolysis of cellulose and degradation of glucose. This work shows that Br?nsted-Lewis acidic ILs are potential catalysts for the hydrolysis of cellulose to produce sugar.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

Chemical and Phase Transformations during the Synthesis of Cs[MgR<Subscript>0.5</Subscript>P<Subscript>1.5</Subscript>O<Subscript>6</Subscript>] (R = B,Al, Fe) Complex Oxides from Metal Chlorides

Cesium-containing complex oxides Cs[MgR_0.5P_1.5O₆] (R = B, Al, Fe) are prepared from solutions containing H₃BO₃, metal chlorides, and H₃PO₄/NH₄H₂PO₄. The chemical and phase transformations that occur during the synthesis are elucidated by differential thermal analysis (DTA) and X-ray powder diffraction (XRD). Optimal synthesis parameters are determined. The oxides where R = B or Fe are formed at 800°C, those where R = Al are formed at 1100°C. All compounds crystallize in the pollucite-type structure (cubic system, space group I4₁32).     

Studies on the Synthesis and the Structure of Ferric Aluminum Magnesium Hydrotalcite—like Compounds

Hydrotalcite-like compounds (HTlc) are composed of trivalent and divalent metal ions, the general formula 1 is: [M2+1-xM3+x(OH)2]x+An-x/n·mH2O M3+ is trivalent metal ions, M2+is divalent metal ions, A is negative ions whose valence is n, and m is the amount of water in the crystal, and x is the molar ratio of trivalent metal ions to all metal ions. A lot of studies have been done on the synthesis and property of HTlc, which is made up of two kinds of the metal ions. It has been found …     

Effect of iron sulfides on the physicochemical processes occurring during solidification of synthetic calcium aluminosilicate monolith

Phase formation processes occurring during solidification of two samples of silicate materials obtained by filtration combustion of a mixture of fly ash, limestone, and sand were studied. During the solidification of the material produced in the combustion mode in which impurity pyrite FeS₂ completely decomposed by the interaction with atmospheric CO₂ and water, dicalcium silicate, melilite, and glass phase gradually transformed into a mixture of serpentine-type binder (Ca, Fe, Mg)₃[(Si, Al)₂O₅](OH)₄ · nH₂O and calcium carbonates. The narrowing of the combustion wave front allows one to preserve pyrite particles encapsulated in the glass phase. In this case, the mechanism of solidification of the combustion product changes: the expose to sulfuric acid released by pyrite oxidation of the silicate components of the material results in the formation of gypsum and hydrosilicates filling the pore space. This enables one to reach high strength characteristics of the material without prepressing. The presence of a lower-pH medium in the pore space inhibits ettringite crystallization, thus preventing mechanical destruction.     

Mechanochemical Activation of Aluminum: 3. Kinetics of Interaction between Aluminum and Water

Two regimes of oxidation by water are revealed for nanocrystalline aluminum prepared by the mechanical activation of its mixture with graphite and distributed in the matrix of amorphous carbon. At the temperatures 50°C < T < 90°C, nanosized aluminum particles interact with water under quasi-isothermal conditions. The main products are hydrogen and pseudoboehmite AlOOH; a low content of bayerite Al(OH)₃ is also formed. After the induction period, the kinetics of interaction can be satisfactorily described by the law of a diminishing sphere. The effective activation energy of the reaction is equal to 61 ± 10 kJ/mol and is identical for the samples of submicron aluminum prepared by different procedures. At temperatures above 90–95°C, the oxidation of mechanically activated aluminum by water is transformed into a thermally self-accelerated explosion process. Under these conditions, the oxidation of aluminum to α-Al₂O₃ is accompanied by an exothermal reaction between the metal and the carbon matrix during which aluminum carbide Al₄C₃ is formed.     

Magnetic properties of composite materials based on plant- or mineral-derived amorphous silica

Fe _x (O, OH) _y –SiO₂ composite samples are prepared. The composite matrix is amorphous silica prepared by controlled precipitation from silicate solutions or silica derived from rice husks. The iron is shown to exist in the form of acagenite β-FeO(OH) or hematite α-Fe₂O₃. The magnetic properties of the composites are studied at temperatures in the range 2–300 K and fields in the range ±5 T. The composite samples exhibit superparamagnetic properties.     

Determination of Zn, B, Fe, Mg, Ca, Na and Si in anisette samples by inductively coupled plasma atomic emission spectrometry

A comparative study of several digestion methods of anisette samples has been carried out. Two dry ashing (DA) treatments as well as four wet ashing (WA) procedures using different mixtures of acids were applied for the sample mineralisation before analysis. Once the anisette samples were mineralised, the contents of Zn, B, Fe, Mg, Ca, Na and Si were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each method has been studied statistically and also attending to their feasibility. After performing the optimisation of the different treatments tested, it was concluded that one wet ashing method employing a HNO₃:H₂O₂ (10:1) mixture was the most suitable. This method was applied to the analysis of anisette samples. Na, Ca, Mg and Si were present in concentrations up to 215 mg l⁻¹ for Na, 11.6 for Mg, 6.2 for Ca and 5.1 for Si. Fe and B concentrations were not higher than 0.12 mg l⁻¹ and lower for Zn.     

A Quantum Chemical Study of C<Subscript>60</Subscript>Cl<Subscript>30</Subscript>, C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Molecules and Fe@C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Endocomplex

(U)PBE0/cc-pVDZ method is used to study the structure of C₆₀Cl₃₀, C₆₀(OH)₃₀ molecules and Fe@C₆₀(OH)₃₀ endocomplex. The triplet state of the endocomplex is shown to be the lowest in energy among its four states corresponding to different spin multiplicities and positions of Fe nucleus within the fullerene cavity. This state is characterized by bonding between the iron atom and one of two benzenoid cycles of the carbon cage, six internuclear Fe–C distances (208 pm), and 1s²2s²2p⁶3s²3p⁶3d^7.24s^0.14p^0.3 electron configuration of iron with spin population of 2.36.     

Atomic-absorption spectrometric determination of cobalt,nickel, and copper in geological materials with matrix masking and chelation-extraction

An atomic-absorption spectrometric method is reported for the determination of cobalt, nickel, and copper in a variety of geological materials including iron- and manganese-rich, and calcareous samples. The sample is decomposed with HP-HNO₃ and the residue is dissolved in hydrochloric acid. Ammonium fluoride is added to mask iron and 'aluminum. After adjustment to pH 6, cobalt, nickel, and copper are chelated with sodium diethyl-dithiocarbamate and extracted into methyl isobutyl ketone. The sample is set aside for 24 h before analysis to remove interferences from manganese. For a 0.200-g sample, the limits of determination are 5–1000 ppm for Co, Ni, and Cu. As much as 50% Fe, 25% Mn or Ca, 20% Al and 10% Na, K, or Mg in the sample either individually or in various combinations do not interfere. Results obtained on five U.S. Geological Survey rock standards are in general agreement with values reported in the literature.     

Development of Electroflotation Technology for Extraction of Anionic Surfactants and Nonferrous Metal Ions from Wastewater Produced at Electroplating Industries

Sorption extraction of anionic surfactants NaDDS and NaDBS on freshly formed iron(III) and aluminum(III) hydroxides and on a highly dispersed activated carbon of OU-B brand was experimentally studied. It was shown that NaDDS is the most fully sorbed on Al(OH)₃ and OU-B, whereas on Fe(OH)₃, the maximum sorption is observed for NaDBS. The electroflotation extraction of anionic surfactants and poorly soluble iron(III) and aluminum(III) hydroxides was examined and the influence exerted by the following factors (pH, nature of electrolyte, surfactant concentration) on the degree of extraction of these substances was analyzed. In addition, electroflotation extraction of OU-B in the presence on nonferrous metal hydroxides and surfactants of varied nature from aqueous solutions was performed. The results obtained were used to develop a technological scheme for electroflotation of complex-composition wastewater.     

Direct multielement determination of trace elements in boron carbide powders by direct current arc atomic emission spectrometry using a CCD spectrometer

The use of direct current arc atomic emission spectrometry (DC-arc-AES) with a CCD spectrometer for the direct determination of the trace impurities Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr in three well characterized boron carbide powders is described. The detection limits obtained by the procedure were found to be between 0.2 (Mg) and 25 (Na) ??g?g^?1 for the above elements. Three boron carbide powder samples with trace element concentrations between 0.9 (Cu) and 934 (Si) ??g?g^?1 for Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr ?? including the standard reference material ERM?-ED102 ?? were analyzed by DC-arc-AES. The relative standard deviations for 9 measurements when using 5.0?±?0.3?mg of the respective samples were found to vary from 6.2 to 27% for Al and Cu, respectively. The trace elements Al, Ca, Cr, Cu, Fe, Mn, Ni, Si, Ti and Zr could be determined in the standard reference material and their concentrations determined by DC-arc AES were found to be between 89 and 116% of the accepted values. Fe and Ti were determined by DC-arc AES in the three boron carbide samples as well as in Al₂O₃, BN, SiC, coal fly ash, graphite and obsidian rock. The correlation coefficients of the plots of the net intensities versus the accepted values over the concentration ranges from 18 to 1750 and from 6 to 8000???g?g^?1 are 0.999 and 0.990 for Fe and Ti, respectively.

Preparation of unsupported alumina membrane by sol-gel techniques

Unsupported alumina membranes were prepared by sol-gel technique using aluminum isoproxide. The influence of the hydrolysis conditions, the type and concentration of peptizant acid on the boehmite sols has been studied. The suitable hydrolysis temperature for the aluminum isoproxide was above 50°C. Crack-free unsupported alumina membranes were obtained by rapid gelation processing of sols. The boehmite gel membrane and γ-Al₂O₃ membrane formed exhibited (020) and (440) preferred orientation.     

On the matrix effect in the determination of main components of dolomite by atomic flame emission and absorption spectrometry

Summary The matrix effects in the determination of the main components of dolomite by flame emission (Na, K) and atomic absorption spectrometry (Ca, Mg, Fe, Mn) have been examined according to the methodology based on the theory of design of experiments. The influence of some auxiliary compounds added to a sample solution has been investigated. The determination of Fe and Mn proved to be specific. The matrix effect has been eliminated in the determination of K by adding a mixture of NaCl and H₃PO₄, in the determination of Na by KCl spectral buffer, in the determination of Mg by NaCl buffer and in the case of Ca by SrCl₂ as a spectral buffer.

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Untersuchung über den Matrixeffekt bei der Bestimmung der Hauptbestandteile von Dolomit durch Atomemissions- und -absorptionsspektrometrie

Zusammenfassung Mit Hilfe methodisch geplanter Versuche wurde der Einfluß der Matrix auf die Bestimmung von Na und K (Emission) sowie Ca, Mg, Fe und Mn (Absorption) untersucht. Ebenso wurde der Einfluß verschiedener Zusätze geprüft. Die Bestimmung von Fe und Mn erwies sich als spezifisch. In den anderen Fällen konnte die Matrixstörung durch folgende Zusätze behoben werden: Gemisch von NaCl und H₃PO₄ für K, KCl für Na, NaCl für Mg, SrCl₂ für Ca.

     

Effect of Solution Chemistry on Preparation of Boehmite by Hydrothermal Assisted Sol-Gel Processing of Aluminum Alkoxides

Various aluminum alkoxide precursors have been used for the preparation of boehmite by hydrothermal assisted sol-gel processing. The coordination status of aluminum in solution for all precursors employed for the preparation of boehmite phase was determined by ²⁷Al NMR and correlation between coordination status of aluminum atoms of precursors and development of boehmite phase has been investigated. Hydrothermal assisted hydrolysis of aluminum alkoxides where the aluminum atoms are four or five coordinated in solution resulted in the formation of boehmite. In contrast, hydrothermal hydrolysis of aluminum alkoxides where the aluminum atoms are six coordinated resulted in the formation of amorphous gel. Development of boehmite phase by hydrothermal hydrolysis of aluminum alkoxides at various temperatures was pursued by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy.