In Process Citation

Analyses for the metals Cd, Pd and Cu in the estuary and bay of the Scine have been made. The site was chosen because of the very high tides, which produce considerable water displacement. For the purpose of analysis the metals have been divided into three categories: free metals, metals forming complexes that are unstable at low pH, and metals forming stable complexes that are destroyed in an acidic medium by ultraviolet radiation. The special properties of copper have been used to establish a “complexing capacity” of the different water samples studied. By making the simple hypothesis of the existence of an equilibrium of the type Cu + L CuL, where L represents the ligand, the total ligand concentration, as well as the stability constants of the CuL complexes, has been determined. These results are presented and discussed.     

Determination of copper and nickel in vegetable oils by direct sampling graphite furnace atomic absorption spectrometry

The quality of food products has been receiving great attention due to its influence on human nutrition and health. In this sense, the determination of trace metals in foods has turned an important field on food analysis. Concerning vegetable oils, its metal trace composition is an important criterion for the assessment of their quality once it is known that trace metals affect their rate of oxidation, influencing freshness, keeping properties as well as storage. In the present work an analytical method which enables the direct determination of Cu and Ni in vegetable oils by graphite furnace atomic absorption spectrometry (GFAAS), using a “solid” sample strategy is presented: in nature, samples are directly weighed on the graphite platform boat and inserted in the graphite tube. An adequate temperature program permitted the calibration by external aqueous analytical curves. Good concordance between the proposed procedure and EPA procedures was found in the analysis of real samples. Limits of detection of 0.001 and 0.002 μg g⁻¹ were found for Cu and Ni, respectively, in the original samples, and they were comfortably below the concentrations found.     

Chemical Aspects of Heavy Metal Solubility with Reference to Sewage Sludge Amended Soils

Abstract

The long term benefits of applications of sewage sludges to land as an alternative source for plant nutrients are frequently limited by potentially toxic contents of heavy metals. While upper limits for metal contents in amended soils have been defined in both North America and Europe, there has been little attention paid to the fate of the metals if soil management practices are changed and the solubility and hence the mobility of the metals increased. This study investigated the role of changes in pH and additions of chloride ions to the content of soluble Cd, Co, Cr, Cu, Pb, Ni, V and Zn in soils to which sewage sludge had been applied. The contents of soluble metals ranged from less than 1 μmol L^?1 for V to 500 μmol L^?1 for Zn. For all the metals, contents were greater in the presence of Cl^? ions and increased markedly as the pH decreased below about pH 5. Contents of V, Cr, Cu and Pb increased at pH's above 7. As all metal contents were undersaturated with respect to hydroxide or carbonate precipitates, the changes in their contents were probably related to desorption from variable charge sites on mineral and/or humic surfaces.     

Determination of trace metals in water using x-ray fluorescence spectrometry

A simple, rapid and accurate method for water analysis is proposed. The analytical procedure for the determination of Fe, Mn, Zn, Cu, Cd, As, Pb and Se in water in concentrations as low as a few ppM involves precipitation with a carrier of the metals by diethyldithiocarbamate (DDTC) or 1-(2-pyridylazo)-2-naphthol (PAN) and filitration through a Millipore filter. The precipitates collected on the filter disc are examined by X-ray fluorescence analysis. PAN is excellent for the determination of several metal ions at the ppM level, and DDTC can be used with tartrate as a masking agent if water samples contain large amounts of iron(III).     

Precipitation reactions of thiobenzoylphenylhydroxylamine and its use as a reagent for copper

Thiobenzoylphenylhydroxylamine (TBPHA) quantitatively precipitates copper as Cu(C₁₃H₁₀NSO)₂ which can be used as a weighing form for copper; the gravimetric factor is 0.12217. Iron, aluminium, chromium and commonly accompanying elements do not interfere. Quantitative precipitation and separation of several metals from highly acidic solutions is possible. The precipitation reactions of metals with TBPHA, over a wide range of acidity and in the presence of EDTA, are tabulated. TBPHA is of little value as a colorimetric reagent.     

Tracing the sources of stream sediments by Pb isotopes and trace elements

The objective of this research is to trace the sources of stream sediments in a small watershed influenced by anthropogenic and lithogenic origins identified by the spatial distributions and temporal variations of stream sediments using geochemical interpretation of the stable and radiogenic isotopes, major components, and heavy metals data and principal component analysis. To know the effects of both present and past mining, the stream sediments were sampled at the stream tributaries and sediment coring work. The spatial distributions of heavy metals clearly showed the effects of Cu and Pb?CZn mineralization zones at the site. Anthropogenic Pb was elevated at the downstream area by the stream sediments due to an active quarry. The results of principal components analysis also represent the effects of the stream sediments origins, including anthropogenic wastes and the active quarry and lithogenic sediment. Anomalous Cu, indicating the effect of past Guryong mining, was identified at the deep core sediments of 1.80?C5.05?m depth. The influence of active quarry was shown in the recently deposited sediments of <1.50?m depth, which was proved by the profiles of radioactive ²¹⁰Pb and stable Pb and Sr isotopes. This study suggests that the chemical studies using radiogenic and stable isotopes and heavy metals and multivariate statistical method are useful tools to discriminate the sources of stream sediments with different origins.     

Supramolecular edifices and switches based on metals

Our studies allowed to unravel at least partially, the “so-called” spontaneous self-assembly processes of supramolecular edifices based on metals. The formation of a tricuprous double-stranded helix in solution was found to be driven by thermodynamics via highly distorted intermediates. Dinuclear europium(III) triple-stranded helices were built in solution via alternative “braiding” and “keystone” mechanism. The overall process was also dominated by thermodynamics. Moreover, multipodal ligand with the appropriate binding sites can operate as Cu(II)/Cu(I) molecular switches. Recently, we examined ligands with neighboring binding functionalities (N,N) and (N,O) which confer to the corresponding divalent metal complexes new properties. They could operate as proton-driven multistage molecular switching devices based on region-selective metal binding.     

Study of the parameters affecting the binding of metals in solution by Chlorella vulgaris

The ability of Chlorella vulgaris to accumulate heavy metals in solution (Mn, Cr, Ni, Zn and Cu) was investigated. Various parameters (algal biomass, pH and contact time of the algae with the sample) have been studied. Nine mg of algal biomass, pH 8 and 15 min of contact time, with 1 ppm of each metal, were the optimized conditions. At pH 8, the optimum value to rise the maximum binding, a fraction of metals in solution precipitates forming hydroxides. Combining both processes, a chemical–biological system for the removing of metals at ppb levels from the environment is obtained. The simultaneous determination of these five metals was performed by capillary electrophoresis (CE) with a UV/Vis detector.     

Interfacial chemistry in internally oxidized (Cu,Mg)-alloys

(Cu,Mg) alloys are internally oxidized at different oxygen chemical potential at 900°C. Oxidation scale microstructure is studied by SEM and TEM. MgO forms as large magnesia agglomerates without any special orientation relationship and isolated cubo-octahedral topotaxial MgO precipitates, the shape of which varies with decreasing oxygen activity from octahedral to cubic. The interfaces of the cubo-octahedral precipitates are studied in detail by CTEM, HREM and EELS. At the highest oxygen activity, important rigid-body contraction/expansion across the interface is found together with a strong modification in the interfacial electronic structure (compared to the adjacent bulk phases) indicating important hybridization of O 2p and Cu 3d states. Both suggest oxide bonding. At lower oxygen activity, interfaces show increasing structural disorder in the copper phase and microfaceting or terracing of the interfacial plane; the intensity of interfacial ELNES features associated to the O 2p and Cu 3d hybridization diminishes and finally disappears with decreasing oxygen activity. Changes with oxygen chemical potential in precipitate morphology, interface atomic and electronic structure are explained by Gibbs’ adsorption/desorption of excess oxygen to the interface. Adsorption isotherms are modeled for various configurations and compared to the experimental results.     

Speciation of copper and zinc in size-fractionated atmospheric particulate matter using total reflection mode X-ray absorption near-edge structure spectrometry

The health effects of aerosol depend on the size distribution and the chemical composition of the particles. Heavy metals of anthropogenic origin are bound to the fine aerosol fraction (PM_2.5). The composition and speciation of aerosol particles can be variable in time, due to the time-dependence of anthropogenic sources as well as meteorological conditions. Synchrotron-radiation total reflection X-ray fluorescence (SR-TXRF) provides very high sensitivity for characterization of atmospheric particulate matter. X-ray absorption near-edge structure (XANES) spectrometry in conjunction with TXRF detection can deliver speciation information on heavy metals in aerosol particles collected directly on the reflector surface. The suitability of TXRF-XANES for copper and zinc speciation in size-fractionated atmospheric particulate matter from a short sampling period is presented. For high size resolution analysis, atmospheric aerosol particles were collected at different urban and rural locations using a 7-stage May cascade impactor having adapted for sampling on Si wafers. The thin stripe geometry formed by the particulate matter deposited on the May-impactor plates is ideally suited to SR-TXRF. Capabilities of the combination of the May-impactor sampling and TXRF-XANES measurements at HASYLAB Beamline L to Cu and Zn speciation in size-fractionated atmospheric particulate matter are demonstrated. Information on Cu and Zn speciation could be performed for elemental concentrations as low as 140 pg/m³. The Cu and Zn speciation in the different size fraction was found to be very distinctive for samples of different origin. Zn and Cu chemical state typical for soils was detected only in the largest particles studied (2–4 μm fraction). The fine particles, however, contained the metals of interest in the sulfate and nitrate forms.     

Quantitative analysis of precious metals in automotive shredder residue/combustion residue via EDX fluorescence spectrometry

The recovery of precious metals from automotive shredder residue (ASR) dust/combustion residue is an option that is not usually considered due to the lack of available information. Therefore, before any disposal or recovery application can be considered, it is necessary to determine the significance of the levels and distribution of precious metal in ASR dust/ASR combustion residue. In the present study, quantitative analysis of precious metals (Pt, Pd, Au, Ag and Cu) in the ASR residue samples was performed using energy dispersive X-ray (EDX) fluorescence spectrometer. With the fundamental parameter (FP) method, the X-ray intensity is obtained and the quantitative analysis is performed using theoretical calculation. This method is very effective for quantitative analysis of unknown samples without standard samples. Further, in order to analyse the precious metal distribution within the ASR combustion residues, the microstructural characterisation and elemental mapping were also carried out with the aid of field emission scanning election microscopy combined with electron dispersive spectroscopy (FE-SEM EDS). Significant amount of Pt, Pd, Au, Ag and Cu element concentrations in the ASR residue were identified. Total precious (Pt, Pd, Au, Ag and Cu) metals obtainable values are representing about 12.23 wt% from its initial ASR dust/combustion residues. Considering their relevant concentrations, these metals should be properly recovered for recycling purposes before to dispose or landfill.     

Effect of metals on melt oxidation of polyethylene

Oxidation of polyethylene (PE) melts in contact with metals (Cu, Pb, Au, Al, Zn, Ag) has been studied by infrared spectroscopy and differential thermal analysis (DTA). These metals may be divided into two groups, depending on their activity for oxidizing PE: namely, high-activity metals (Cu, Pb, Ag, Zn) and low-activity metals (Al, Au). During the oxidation of PE in contact with high-activity metals dissolution of the surface layer of metal is observed with accumulation of metal-containing compounds (salts of carboxylic acids) in the bulk of the polymer. With low-activity metals these phenomena are not observed. The rate of oxidation of PE on low-activity metals approaches the oxidation rate of nonmetals (polytetrafluoroethylene and inorganic glass). With certain high-activity metals (Cu, Pb) the process of oxidation is accelerated only in the early stage of oxidation; then the oxidation rate slows down and the oxidation process ceases. PE films separated from metal after being oxidized on it possess chemical memory, i.e., their oxidation rate depends on the nature of the metal with which they had been in contact, and on the duration of the contact oxidation. The effect of salts of carboxylic acids (metal stearates) on the oxidation of PE melts was also studied. Based on the data obtained, it is concluded that the rate of oxidation of PE melts on high-activity metals is controlled by metal-containing compounds which are the products of contact reactions.     

Relations between synthesis and microstructural properties of copper/zinc hydroxycarbonates

Cu/Zn Hydroxycarbonates obtained by co-precipitation of Cu(2+) and Zn(2+) with Na(2)CO(3) have been investigated regarding phase formation and thermal decomposition in two series with varying Cu/Zn ratios prepared according to the decreasing pH and constant pH method. Hydrozincite, aurichalcite and (zincian)-malachite were found to form at differing Cu/Zn ratios for both series. For the constant pH preparation the Cu/Zn ratio in zincian-malachite was close to the nominal values whereas excess values were found for the decreasing pH samples. The degree of crystallinity as well as the thermal decomposition temperatures were lower for the constant pH series. All samples containing aurichalcite revealed an unexpected decomposition step at high temperatures evolving exclusively CO(2). The differences in composition and microstucture were traced back to the different pathways of solid formation for the two preparation methods. Substantial changes were observed during the post-precipitation processes of ageing and washing. The effects were studied in detail on samples with a cation ratio of Cu/Zn 70:30 mol %. Ageing of the precipitates in their own solutions is accompanied by a spontaneous crystallization of the initially amorphous solids. The decreasing pH sample develops from a hydroxy-rich material comprising basic copper nitrate (gerhardtite) as an intermediate. Only small changes in the chemistry of the samples were detected for the constant pH precipitation. The findings are summarised into a scheme of solid formation processes that explains the phenomenon of a "chemical memory" of the precipitates when they are converted into Cu/ZnO model catalysts.     

Characterization of Precipitates in Ti-Stabilized Steels with Low-Energy Electron-Induced X-Ray Spectrometry and Scanning Electron Microscopy

 Various kinds of precipitates can influence the mechanical properties of Ti-stabilized steels. The qualitative composition of the Ti inclusions can be characterized microscopically, whereas for quantitative information to be obtained time-consuming selective dissolution must be used. The present study aims at chemical speciation of the isolated precipitates as a solid phase with the help of soft-X-ray spectrometry. Whether the method is capable of giving both qualitative and quantitative information on the composition of Ti-mixtures is discussed. The precipitates in Ti-stabilized steels are investigated after chemical dissolution of the steel matrix with a bromine/methanol mixture (1:10). By combination of soft-X-ray spectrometry with X-ray fluorescence (XRF) and scanning electron microscopy (SEM) both qualitative and quantitative characterization of the precipitates can be performed. They were found to consist mainly of TiC and TiN. Received July 1, 1998. Revision December 29, 1998.     

Determination of lanthanum with n-benzoyl-n-phenylhydroxylamine

N-Benzoyl-N-phenylhydroxylamine is proposed for the gravimetric determination of lanthanum, at pH 6.4–7.2. The precipitates can be weighed directly or ignited to the oxide. By suitable pH adjustment, many metals can be separated from lanthanum, which can then be determined in the filtrates. Interferences of Ni, Cu, Zn and Fe(II) are masked with cyanide. About 99.5% of cerium can be separated from lanthanum by precipitating cerium(IV) at pH 4.8–5.2.     

Synthesis of ZrO2-based ceramic pigments

The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO₂-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000°C the pigments presented a good thermal stability. This revised version was published online in August 2006 with corrections to the Cover Date.     

Degradation of RAFT polymers in a cyclic ether studied via high resolution ESI‐MS: Implications for synthesis,storage, and end‐group modification

We report on the detailed mass spectrometric analysis of the degradation products generated during storage of poly(methyl methacrylate) (pMMA) and polystyrene (pSty) carrying cumyldithiobenzoate (CDB) endgroups. Samples were stored in either a cyclic ether (tetrahydrofuran) (THF) or an inert solvent (dichloromethane). The degradation process was followed over a period of 4‐weeks. Degradation rate of the reversible addition fragmentation (RAFT) polymer strongly depends on the hydroperoxide‐content of the solvent. Mass spectrometric evidence supports an unexpected radical degradation mechanism for the pMMA macroRAFT agent. Hydroperoxide functional pMMA was the single product after less than 7 days in high purity THF. No formation of the sulfine/thioester was observed. The identity of the hydroperoxide was unambiguously assigned using accurate mass measurements by Fourier‐Transform ion‐cyclotron‐resonance mass spectrometry together with chemical identification reactions. The hydroperoxide end group formation proceeds efficiently as well as in high yields and thus constitutes a powerful method for end group modification. The degradation pathways of the CDB functional pSty in THF include mainly oxidation towards the sulfine/thioester, with little degradation via thermal elimination of dithiobenzoic acid and subsequent epoxidation. The shelf life of CDB functional polymers is limited even in inert solvent because of this inherent but slow thermal elimination reaction. Because of the short period necessary for the transformation of the functional dithiobenzyl endgroups, substitution of cyclic ethers as solvents for RAFT polymers in synthesis and analysis is strongly suggested. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7447–7461, 2008     

Colloidochemical Processes in the Biotechnology of Heavy Metal Removal from the Soil

The sorption processes of uranium(VI), copper, cobalt, and strontium by the native soil were studied. It was shown that, by their ability to be accumulated by the podsolized soil, these metals are arranged in the following sequence: U(VI) > Cu > Co > Sr. This selectivity sequence is retained during the sorption of metals from mixed solutions containing their equimolar concentrations. The possibility of the leaching of the studied metals from the contaminated soil by Basillus cereusVKM 4368 metal-resistant culture was demonstrated using glucose and sodium acetate as the sources of carbon and energy. In the first case, 90–99% of heavy metals was extracted from the soil as water-soluble citrate complexes. In the second case (during the metabolism of acetate by bacteria), the removal of heavy metals from the soil as hydroxide–carbonate precipitates and complexes was equal to 80–90%. Sedimentation of particles in the soil suspension is accelerated considerably after the treatment by the metal-resistant culture.     

The use of X-ray fluorescence (XRF) analysis in predicting the alkaline hydrothermal conversion of fly ash precipitates into zeolites

The use and application of synthetic zeolites for ion exchange, adsorption and catalysis has shown enormous potential in industry. In this study, X-ray fluorescence (XRF) analysis was used to determine Si and Al in fly ash (FA) precipitates. The Si and Al contents of the fly ash precipitates were used as indices for the alkaline hydrothermal conversion of the fly ash compounds into zeolites. Precipitates were collected by using a co-disposal reaction wherein fly ash is reacted with acid mine drainage (AMD). These co-disposal precipitates were then analysed by XRF spectrometry for quantitative determination of SiO₂ and Al₂O₃. The [SiO₂]/[Al₂O₃] ratio obtained in the precipitates range from 1.4 to 2.5. The [SiO₂]/[Al₂O₃] ratio was used to predict whether the fly ash precipitates could successfully be converted to faujasite zeolitic material by the synthetic method of [J. Haz. Mat. B 77 (2000) 123]. If the [SiO₂]/[Al₂O₃] ratio is higher than 1.5 in the fly ash precipitates, it favours the formation of faujasite. The zeolite synthesis included an alkaline hydrothermal conversion of the co-disposal precipitates, followed by aging for 8 h and crystallization at 100 °C. Different factors were investigated during the synthesis of zeolite to ascertain their influence on the end product. The factors included the amount of water in the starting material, composition of fly ash related starting material and the FA:NaOH ratio used for fusing the starting material. The mineralogical and physical analysis of the zeolitic material produced was performed by X-ray diffraction (XRD) and nitrogen Brunauer-Emmett-Teller (N₂ BET) surface analysis. Scanning electron microscopy (SEM) was used to determine the morphology of the zeolites, while inductively coupled mass spectrometry (ICP-MS), Fourier transformed infrared spectrometry (FT-IR) and Cation exchange capacity (CEC) [Report to Water Research Commission, RSA (2003) 15] techniques were used for chemical characterisation. The heavy and trace metal concentrations of the zeolite products were compared to that of the post-synthesis filtrate and of the precipitate materials used as Si and Al feed stock for zeolite formation, in order to determine the trends (increase or decrease) and ultimate fate of any toxic metals incorporated in the co-disposed precipitated residues.     

Microsampling and Determination of Metals in Iron Gall Ink

Abstract

Iron gall ink contains transition metals such as Fe, Cu, and Mn which are known to catalyze chemical reactions in support materials such as paper and parchment, which eventually leads to their deterioration over time. Identification of metals in ink can be an important step prior to the conservation treatment of a written document. In this work, syringe needles (16G–23G) were used to sample micro-cores (～0.7 mm in diameter) of ink and paper prior to analysis. Metals were extracted from the micro-core with HNO₃, prior to analysis using graphite furnace atomic absorption spectroscopy (GFAAS).