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At least 757 records · Page 42Linked to original sources
PubMed2005

A study on the chemical and mineralogical characterization of MSWI fly ash using a sequential extraction procedure.

The presence of heavy metals in municipal solid waste incineration (MSWI) fly ash is of environmental concern due to their leaching potential in landfill environments. Sequential chemical extraction was performed on fly ash samples from a large-scale municipal solid waste incineration plant in East China. The transformation of the mineralogical species of fly ash during the sequential extraction was studied using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). The leaching behavior of heavy metals such as zinc, lead, cadmium and copper in MSWI fly ash was considered to have a dependency relationship with the components of calcium, such as aphthitalite, calcite, anhydrite and calcium aluminate or calcium aluminosilicate.

Carbon↗
PubMed2006

Pb speciation versus TCLP release in army firing range soils.

A series of soil parameter and mineralogical investigative techniques were applied to assess the Pb speciation in four US Army firing range soils that presented significantly different Pb leaching regimes and soil characteristics. Soil gradation tests were complemented by total chemical analyses, X-ray powder diffraction (XRPD), Rietveld quantification, optical microscopy and scanning electron microscopy (SEM) analyses. The bulk geotechnical, mineralogical and chemical analyses pointed to two possible Pb retention mechanisms: precipitation as lead carbonate and sorption in the case of fine-grained soils. Lead speciation and mobility was further investigated by the toxicity characteristic leaching procedure (TCLP) and sequential extraction test (SET). As the TCLP Pb concentrations did not necessarily reflect the total Pb analysis of the soils, the Pb leachability ratio (TCLP/total) was found to be controlled by soil mineralogy and its response to changes in system pH. Geochemical modeling, using Visual MINTEQ, was employed to evaluate the mechanisms that controlled the observed TCLP Pb leaching behavior. It was found that lead carbonate precipitation/dissolution reactions controlled Pb TCLP leachability in all soils, while sorptive phenomena did not seem to play a role even in the case of fine-grained soils. More specifically, TCLP Pb leachability was controlled by the pH, the available Pb and the available carbonate in solution. This indicates that geochemical modeling strongly complimented TCLP Pb analyses. Thus, geochemical modeling is an important assessment tool to evaluate the magnitude of site-specific Pb-related environmental problems in firing range soils. Carbonation reactions, involving metallic Pb, that occur during the SET obscure its ability to reliably ascertain Pb speciation. More specifically, SET lumps the extractable Pb into predetermined phase categories that may not be truly representative of the actual soil mineralogy or dominant forms of Pb in the soil. A thorough geotechnical, mineralogical and chemical investigation of firing range soils, complemented by geochemical modeling, was therefore found to be a more reliable approach to evaluate Pb speciation and TCLP release in firing range soils.

Lead↗
PubMed2006

Application of the Rietveld method to assess chromium(VI) speciation in chromite ore processing residue.

The Rietveld method allows the quantification of crystalline phases and amorphous material identified by X-ray powder diffraction (XRPD) and other diffraction methods. The method assists in determining the speciation of contaminants in solid matrices both qualitatively and quantitatively in a statistically defensible approach, as it does not focus on a microscale. Rietveld was applied to chromite ore processing residue (COPR), a cementitious waste containing hexavalent chromium. Calcium aluminum chromium oxide hydrates (CACs) were the crystalline phases identified by XRPD that bind Cr(6+) in COPR according to their chemical formula. Rietveld quantification, combined with mass balances on Cr(6+), showed that CACs may bind Cr(6+) in variable percentages, ranging from 25% to 85%. Analysis of duplicate samples showed that material variability is the predominant factor of uncertainty in evaluating the role of CACs in Cr(6+) speciation, provided that a consistent quantification strategy is pursued. The choice of strategy was performed on the basis of the pertinent literature, preliminary analyses of the equipment and the software settings, and mass balances. The correlation between the average CAC-bound Cr(6+) concentration and the total Cr(6+) for five samples (R(2)=0.94), extracted from different zones and soil borings, suggests that CACs are a primary sink for Cr(6+) in COPR.

Aluminum Oxide↗
PubMed2006

Sorption kinetics and chemical forms of Cd(II) sorbed by thiol-functionalized 2:1 clay minerals.

The interaction between Cd(II) in aqueous solution and two 2:1 expandable clay minerals (i.e., montmorillonite and vermiculite), showing different layer charge, was addressed via batch sorption experiments on powdered clay minerals both untreated and amino acid (cysteine) treated. Reaction products were characterized via X-ray powder diffraction (XRDP), chemical analysis (elemental analysis and atomic absorption spectrophotometry), thermal analysis combined with evolved gases mass spectrometry (TGA-MSEGA) and synchrotron-based X-ray absorption spectroscopy via extended X-ray absorption fine structure (EXAFS) characterization. Sorption isotherms for Cd(II) in presence of different substrates, shows that Cd(II) uptake depends both on Cd(II) starting concentration and the nature of the substrate. Thermal decomposition of Cd-cysteine treated clay minerals evidences the evolution of H(2)O, H(2)S, NO(2), SO(2), and N(2)O(3). These results are well consistent with XRDP data collected both at room and at increasing temperature and further stress the influence of the substrate, in particular cysteine, on the interlayer. EXAFS studies suggest that Cd(II) coordinates with oxygen atoms, to give monomer complexes or CdO molecules, either on the mineral surface and/or in the interlayer. For Cd-cysteine complexes EXAFS data agree with the existence of Cd-S clusters, thus suggesting a predominant role of the thiol group in the bonding of Cd with the amino acid.

Adsorption↗
PubMed2006

Thermodynamics and kinetics of adsorption of Cu(II) onto waste iron oxide.

This study investigates low-cost sorbents as replacements for current costly methods of removing heavy metals from solution. This investigation explores the waste iron oxide material (F1), which is a by-product of the fluidized-bed reactor (FBR)-Fenton reaction, for use in the treatment of the wastewater in Taiwan. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the F1. In this investigation, F1 are tested as adsorbents for removing copper (Cu(2+)) from aqueous solutions. The highest Cu(2+) adsorption capacity of F1 adsorbent was determined as 0.21 mmolg(-1) for 0.8 mmoldm(-3) initial Cu(2+) concentration at pH 6.0 and 300 K. Adsorption data were well described by the Freundlich model and the thermodynamic constants of the adsorption process, DeltaG degrees , DeltaH degrees and DeltaS degrees were evaluated as -6.12 kJmol(-1) (at 318 K), 9.2 kJmol(-1) and 48.19 Jmol(-1)K(-1) (at 318 K), respectively. Additionally, a pseudo-second-order rate model was adopted to describe the kinetics of adsorption.

Adsorption↗
PubMed2004

Synthesis and structural characterization of silver(I), aluminium(III) and cobalt(II) complexes with 4-isopropyltropolone (hinokitiol) showing noteworthy biological activities. Action of silver(I)-oxygen bonding complexes on the antimicrobial activities.

Through two unequivalent oxygen donor atoms of the hinokitiol (Hhino; C10H12O2; 4-isopropyltropolone) ligand that showed noteworthy biological activities, the dimeric, silver(I)-oxygen bonding complex [Ag(hino)]2 1, the monomeric aluminium(III) complex [Al(hino)3].0.5H2O 4 and the cobalt(II) complex "[Co(hino)2]2.H2O" 6 were synthesized and characterized with elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR and solution (1H and 13C) NMR spectroscopy. The crystal structure of 1 was determined by Rietveld analysis based on X-ray powder diffraction (XPD) data and those of [Al(hino)3].MeOH 4a and [Co(hino)2(EtOH)]2 6a, being obtained as yellow block crystals and red platelet crystals, respectively, by crystallization of 4 and 6, were determined by single-crystal X-ray analysis. The antimicrobial activities of 1, 4 and 6, evaluated with minimum inhibitory concentration (MIC; microg ml(-1)), were compared with those of other metal complexes (M=Na, Li, Cs, Ca, V, Zn) with the hino- ligand. The antimicrobial activities observed in the alkali-metal salts strongly suggested that they were attributed to the effect of the anionic hino- species. The antimicrobial activities of 1 were significantly enhanced, whereas those of other metal complexes were suppressed, compared with those of the neutral Hhino and anionic hino- molecules. The antimicrobial activities observed in 1 were comparable with those of other recently found silver(I)-oxygen bonding complexes, the ligands of which had no activity. Thus, it is proposed that the antimicrobial activities of the silver(I)-oxygen bonding complexes are due to a direct interaction or complexation of the silver(I) ion with biological ligands such as protein, enzyme and membrane, and the coordinating ligands of the silver(I) complexes play the role of a carrier of the silver(I) ion to the biological system.

Aluminum↗
PubMed2004

Analysis of metal-containing granules in the barnacle Tetraclita squamosa.

Metal-containing granules were isolated from specimens of the barnacle Tetraclita squamosa collected from a metal contaminated site in Hong Kong. The chemical composition, crystallographic and morphological properties of the deposits were analysed by X-ray powder diffraction, electron microscopy, energy dispersive analysis by X-rays and infrared spectroscopy. The most abundant metals were iron, calcium and zinc and the major anion was phosphate. Oxalates, carbonates and sulfur derivates were also found in small amounts. The deposits were amorphous to X-ray and electron diffraction and were approximately spherical in shape with diameters between 100 and 500 nm.

Animals↗
PubMed2005

Quinoline antimalarials decrease the rate of beta-hematin formation.

The strength of inhibition of beta-hematin (synthetic hemozoin or malaria pigment) formation by the quinoline antimalarial drugs chloroquine, amodiaquine, quinidine and quinine has been investigated as a function of incubation time. In the assay used, beta-hematin formation was brought about using 4.5M acetate, pH 4.5 at 60 degrees C. Unreacted hematin was detected by formation of a spectroscopically distinct low spin pyridine complex. Although, these drugs inhibit beta-hematin formation when relatively short incubation times are used, it was found that beta-hematin eventually forms with longer incubation periods (<8h for chloroquine and >8h for quinine). This conclusion was supported by both infrared and X-ray powder diffraction observations. It was further found that the IC(50) for inhibition of beta-hematin formation increases markedly with increasing incubation times in the case of the 4-aminoquinolines chloroquine and amodiaquine. By contrast, in the presence of the quinoline methanols quinine and quinidine the IC(50) values increase much more slowly. This results in a partial reversal of the order of inhibition strengths at longer incubation times. Scanning electron microscopy indicates that beta-hematin crystals formed in the presence of chloroquine are more uniform in both size and shape than those formed in the absence of the drug, with the external morphology of these crystallites being markedly altered. The findings suggest that these drugs act by decreasing the rate of hemozoin formation, rather than irreversibly blocking its formation. This model can also explain the observation of a sigmoidal dependence of beta-hematin inhibition on drug concentration.

Antimalarials↗
PubMed2005

Determination of residual solvents and investigation of their effect on ampicillin trihydrate crystal structure.

In the present work, the relationship between residual solvents concentration and ampicillin trihydrate crystals stability has been investigated. The amounts of residual solvents determined by GC, X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FT-IR) were used for characterization of solid state. The obtained results have shown good relationship between concentration of methylene chloride (as a critical residue solvent) and degree of ampicillin trihydrate crystallinity. As with the increasing methylene chloride concentration in the sample the degree of crystallinity decreased after stability test. From this relationship, critical concentration of methylene chloride into the ampicillin trihydrate is obtained and the results can be used for improving the large-scale production of ampicillin trihydrate.

Ampicillin↗
PubMed2005

IR spectroscopy together with multivariate data analysis as a process analytical tool for in-line monitoring of crystallization process and solid-state analysis of crystalline product.

Crystalline product should exist in optimal polymorphic form. Robust and reliable method for polymorph characterization is of great importance. In this work, infra red (IR) spectroscopy is applied for monitoring of crystallization process in situ. The results show that attenuated total reflection Fourier transform infra red (ATR-FTIR) spectroscopy provides valuable information on process, which can be utilized for more controlled crystallization processes. Diffuse reflectance Fourier transform infra red (DRIFT-IR) is applied for polymorphic characterization of crystalline product using X-ray powder diffraction (XRPD) as a reference technique. In order to fully utilize DRIFT, the application of multivariate techniques are needed, e.g., multivariate statistical process control (MSPC), principal component analysis (PCA) and partial least squares (PLS). The results demonstrate that multivariate techniques provide the powerful tool for rapid evaluation of spectral data and also enable more reliable quantification of polymorphic composition of samples being mixtures of two or more polymorphs. This opens new perspectives for understanding crystallization processes and increases the level of safety within the manufacture of pharmaceutics.

Algorithms↗
PubMed2005

Solid-state study of mepivacaine hydrochloride.

Different crystalline forms of the local anaesthetic mepivacaine hydrochloride (MH) were revealed by Fourier transform infrared spectroscopy (FT-IR), not by conventional differential scanning calorimetry (DSC). The existence of two polymorphic anhydrous modifications was discovered and further characterized by X-ray powder diffraction and thermal analysis: Form II, the commercial one, and the more stable Form I, obtained by re-crystallization from Form II. Two pseudopolymorphs were also obtained: Form III, a solvate crystallized from ethanol and Form IV, a solvate crystallized from methanol. Single crystal X-ray diffraction data for both solvates were collected and their structures were determined. Form II, metastable and monotropically related to Form I, generates through desolvation of Form III, very often present in industrial processing, where crystallization from ethanol solution is a common practice. For the sake of clarity, the presence of polymorphic forms should be reported in the drug master files of MH. However, since MH is readily water soluble, the observed polymorphism has no relevance to its typical clinical use as aqueous solutions.

Anesthetics, Local↗
PubMed2005

Characterizing the conversion kinetics of carbamazepine polymorphs to the dihydrate in aqueous suspension using Raman spectroscopy.

In an aqueous environment, polymorphic forms I-III of carbamazepine all convert to the dihydrate. This study investigated the conversion of each polymorphic form individually and of a mixture of forms III and I to the dihydrate. Two batches of form I with different crystal morphology were used. Samples were dispersed independently in water at 23+/-1 degrees C and recovered at various timepoints varying from 10 to 210 min. Scanning electron microscopy, X-ray powder diffraction and Raman spectroscopy were used to characterize the initial polymorphic forms and the recovered samples after 210 min. Raman spectroscopy combined with partial least squares analysis was used to generate quantitative models of binary and ternary mixtures of the different polymorphic forms with the dihydrate. On the basis of these models the conversion kinetics of the polymorphic forms I-III were characterized. First-order kinetics with an unconverted portion were used to model the data (R2> or =0.95). The unconverted portions ranged from 16 to 51% after dispersion for 210 min. The conversion kinetics were similar between polymorphic forms with comparable crystal morphology, but differed significantly between batches of the same polymorph (form I) with different crystal morphology. Furthermore, the conversion of forms III and I in the aqueous suspension was not influenced by the presence of the other polymorph when dispersed together.

Anticonvulsants↗
PubMed2005

Physico-chemical characterisation and intrinsic dissolution studies of a new hydrate form of diclofenac sodium: comparison with anhydrous form.

Diclofenac sodium is a non-steroidal anti-inflammatory drug widely used in painful and inflammatory diseases. In standard conditions, by exposure to relative humidity even below 60% at 25 degrees C, the anhydrous form DS gives rise to a hydrate species DSH, a tetrahydrate form different from that obtained by crystallisation from water and previously described. The method of preparation and the physico-chemical properties of the hydrate form were investigated. Data from FTIR spectroscopy, X-ray powder diffraction and thermal analysis were used for the identification and the characterisation of DSH. DS and DSH were easily differentiated by their IR spectra, X-ray patterns and thermal behaviour. DSH stability was followed at room temperature over a period of 1 year and under different conditions of temperature to verify the tendency to solid-solid transition and to study its existence range. Solubility and intrinsic dissolution studies were performed to compare the physico-chemical properties of DS and DSH. Differences in solubility and intrinsic dissolution rates were pointed out: these studies showed that DS dissolved faster than DSH. Storage under uncontrolled environmental conditions or contact with water vapour during manufacturing process could thus influence the performance of the final dosage form.

Calibration↗
PubMed2005

Anisotropic lattice distortions in the mollusk-made aragonite: a widespread phenomenon.

In this paper, we present experimental results demonstrating systematic structural distinctions between biogenic and non-biogenic calcium carbonate. Specifically we show, by high-resolution X-ray powder diffraction on dedicated synchrotron beam lines, that the orthorhombic unit cell of the mollusk-made aragonite is anisotropically distorted as compared with that one of geological aragonite. In all investigated shells, belonging to different classes (bivalve, gastropod, and cephalopod) and taken from different habitat origins (sea, fresh water, and land), the maximum elongation of about 0.1-0.2% was found along the c-axis. The lattice distortions along the a-axis were also of the positive sign (elongation) but lower than those along the c-axis, whereas lattice distortions along the b-axis were always negative (contraction). Supporting experiments, including structural analysis after a bleach procedure, measurements of temperature-dependent lattice relaxation, measurements of the CO(2) release at elevated temperatures, signify that the observed structural distinctions are most probably caused by the organic molecules intercalating into the aragonite lattice during biomineralization. Our findings show that in some sense organisms control the atomic structure of the crystals. Deeper understanding of this phenomenon will aid in the development of new approaches to grow biomimetic composites and tailor their properties on a molecular level.

Animals↗
PubMed2006

Anisotropic lattice distortions in biogenic calcite induced by intra-crystalline organic molecules.

We have performed precise structural measurements on five different calcitic seashells by high-resolution X-ray powder diffraction on a synchrotron beam line and by laboratory single crystal X-ray diffraction. The unit cell parameters a and c of biogenic calcite were found to be systematically larger than those measured in the non-biogenic calcite. The maximum lattice distortion (about 2.10(-3)) was detected along the c-axis. Under heat treatment above 200 degrees C, a pronounced lattice relaxation was observed, which allowed us to conclude that anisotropic lattice swelling in biogenic calcite is induced by organic macromolecules incorporated within the single crystal calcitic prisms during biomineralization. This conclusion is supported by the results of crystallization experiments in the presence of specific protein extracted from one of the shells.

Animals↗
PubMed2006

Accumulation of copper by Acremonium pinkertoniae, a fungus isolated from industrial wastes.

Acremonium pinkertoniae isolated from zinc wastes was studied to understand the mechanisms that allow living organisms to thrive in polluted environments and the possible role of the fungus in the redistribution and cycling of copper. The fungus was cultured on solid media supplemented with copper sulfate at increasing concentrations. At high doses it was observed that the mycelia acquired a characteristic blue color. This was accompanied by morphological changes and the formation of crystalloid structures within thickened cell walls. The material was further analysed with EDX, X-ray powder diffraction and IR spectroscopy. It was demonstrated that A. pinkertoniae is able to accumulate over 20% dry weight of copper by what probably is a chitin-glucan complex.

Acremonium↗
PubMed2004

Structure investigation, spectral, thermal, X-ray and mass characterization of piroxicam and its metal complexes.

[M(H2L)2](A)2.yH2O (where H2L: neutral piroxicam (Pir), A: Cl- in case of Ni(II) or acetate anion in case of Cu(II) and Zn(II) ions and y=0-2.5) and [M(H2L)3](A)z.yH2O (A: SO4(2-) in case of Fe(II) ion (z=1) or Cl(-) in case of Fe(III) (z=3) and Co(II) ions (z=2) and y=1-4) chelates are prepared and characterized using elemental analyses, IR, magnetic and electronic reflectance measurements, mass spectra and thermal analyses. IR spectra reveal that Pir behaves a neutral bidentate ligand coordinated to the metal ions through the pyridyl-N and carbonyl-O of the amide moiety. The reflectance and magnetic moment measurements reveal that these chelates have tetrahedral, square planar and octahedral geometrical structures. Mass spectra and thermal analyses are also used to confirm the proposed formulae and the possible fragments resulted from fragmentation of Pir and its chelates. The thermal behaviour of the chelates (TGA and DTA) are discussed in detail and the thermal stability of the anhydrous chelates follow the order Ni(II) congruent with Cu(II) Fe(II)<Zn(II)<Fe(III)<Co(II) chelates. The water molecules are removed in the first step while the Pir molecule is removed in the second and subsequent steps. X-ray powder diffraction was also used as a confirmatory tool to elucidate the crystallinity of the chelates.

Chelating Agents↗
PubMed2004

Spectroscopic study on sorption of hydrogen sulfide by means of red soil.

This paper reports the results of the characterization of red soils in relation to the sorption of H2S from coal gas at 500 degrees C by spectroscopic techniques in order to provide more information on red soils' structural change both before and after reaction. In addition, by-products analysis has also been studied using Fourier transform infrared (FTIR) spectroscopy. Before and after the experiments the red soils were characterized with X-ray powder diffraction (XRPD), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy. XRPD results indicate that iron oxide species disappear from the original to reacted red soil. EDS analysis shows that a significant amount of sulfur is present in the reacted red soil, which is in agreement with the results of the elemental analysis and the calculated value based on breakthrough curve. XPS regression fitting results further indicate that sulfur retention may be associated with the iron oxides. S 2p XPS fittings point out that the major sulfur species present in the reacted red soil are composed of S(-2), elemental sulfur, polysulfide, sulfite and sulfate. Additionally, the binding energy of iron shifts to a lower position for the reacted red soil, which indicates that iron oxides in the original red soil have been converted into iron sulfide. Appreciable amounts of the by-products CO2, SO2 and COS are detected by on-line FTIR spectroscopy during the initial and later stages of the sorption process. The formation of CO2 is related to the water-shift reaction, and SO2 is probably attributable to the reaction of organic matters and H2S. The concentration of COS is quantified by GC/FPD and found it to be about 350 ppm, which is close to the equilibrium concentration of the reaction of inlet CO and H2S at a temperature of 500 degrees C.

Color↗