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ABSTRACT: The adsorbent, based on the thermal modification of activated carbon impregnated by iron(III) nitrate(V), has been prepared and applied for selenium enrichment from aqueous solution. Various ratios of the impregnating agent to carbon mass were carefully examined with respect to selenium adsorption capacity and selectivity. The basic Se(VI) ions adsorption parameters affecting the adsorption ability onto the prepared activated carbons were studied. The carbon impregnated by 10% Fe(NO(3))(2) and thermally treated at 200°C possessed the highest adsorption capacity and selectivity towards selenium ions. The physico-chemical characterization of the prepared adsorbents before and after selenium uptake were carried out using scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDX) and X-ray photoelectron spectroscopy (XPS). The studies confirmed the surface complexation reactions of iron species and selenium on the Fe-loaded activated carbon. Due to its high adsorption capacity enrichment of selenium on the studied adsorbent has been successfully applied for its determination in the complementary feeds, using the carbon slurry sampling graphite furnace atomic absorption spectrometry technique (GFAAS) and standard calibration method.
Chemosphere 10/2012; · 3.21 Impact Factor
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ABSTRACT: A simple and cost effective preconcentration method on modified activated carbons is described for the determination of traces of gold (Au) in geological samples by carbon slurry sampling graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Au(III) ions on modified activated carbons were studied in detail and the effect of activated carbons modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Au(III) ions onto the modified activated carbons for diluted aqueous solution was also studied in detail in respect to the determination of gold in solid materials after digestion steps in the analytical procedure, which usually involves the application of aqua regia. SEM-EDX and XPS studies confirmed that the surface reduction of Au(III) ions to Au(0) is the main gold adsorption mechanism on the activated carbon. Determination of gold after its preconcentration on the modified activated carbon was validated by applying certified reference materials. The experimental results are in good agreement with the certified values. The proposed method has been successfully applied for the determination of Au in real samples using aqueous standards.
Talanta 09/2012; 99:750-7. · 3.79 Impact Factor
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ABSTRACT: Slurry sampling atomic absorption spectrometry with electrothermal atomization was used for the determination of tin in marine
sediments. A mixture of 4 μg of iridium and 40 μg of tungsten and 12 μg of niobium alone were used as permanent modifiers.
Suspensions were prepared in 7% nitric acid. The influence of amounts of tungsten on iridium removal from graphite tubes modified
by iridium and the mechanism of atomization of tin in slurries were studied in detail. The effect of the amount of added iridium,
tungsten and niobium on the analytical signal, and of the soil matrix on the background signal is described. In order to prevent
interferences by sulfur compounds, barium chloride was added as a matrix modifier. Calibration was performed directly using
aqueous standards. The analysis of certified reference materials confirmed the reliability of the approach. The precision
and accuracy of the determination of tin in sediments by this method is acceptable.
KeywordsTin determination-Slurry sampling-Graphite atomic absorption spectrometry-Permanent modifiers-Marine sediments
Microchimica Acta 04/2012; 168(3):355-362. · 3.03 Impact Factor
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ABSTRACT: Two different types of modification of activated carbon, by treatment with concentrated solution of HNO3 and outgassing treatment at high temperature, were studied in order to obtain the most effective adsorption of chromium(VI)
ions from water solution. The basic parameters affecting the adsorption capacity of Cr(VI) ions on modified activated carbons
were studied in details and the effect of modifications of activated carbons has been determined by studying the initial runs
of adsorption isotherms. The obtained Cr(VI) adsorption isotherms were well fitted in the Freundlich equation. The reduction
of Cr(VI) to Cr(III) and further ion exchange mechanism of adsorption onto oxidizing activated carbon and surface precipitation
to Cr(OH)3 in case of outgassing activated carbon were found as the main adsorption mechanisms of Cr(VI) ions onto modified activated
carbons. Presence of chlorides and nitrates in studied adsorption system strongly decreased the adsorption ability of Cr(VI)
onto outgassing activated carbon and mechanism of this behavior is proposed.
KeywordsChromium adsorption-Modified activated carbons-Enrichment-Atomic absorption spectrometry
Adsorption 04/2012; 16(4):279-286. · 2.00 Impact Factor
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ABSTRACT: Slurry sampling atomic absorption spectrometry with electrothermal atomization was used to the determination of cadmium (Cd) and lead (Pb) in soils and sediments using permanent modifiers. Comparison of action of mixed permanent modifiers niobium (Nb)/iridium (Ir) and tungsten (W)/iridium (Ir) were studied in detail. The effect of amount of Ir, W and Nb on analytical signals of Cd and Pb was examined. The optimal amounts of modifiers for Cd and Pb determination were stated. Niobium carbide formation on graphite surface was studied for different pyrolysis temperatures. Finally for Cd determination in sediments and soils 200 microg of Nb mixed with 5 microg of Ir was used as permanent modifiers and 15 microg of Nb mixed with 200 microg of Ir for Pb determination. Suspensions were prepared in 5% HNO(3). The analytical procedure was optimized carefully basing on data from pyrolysis and atomization curves studies. Ammonium dihydrogen phosphate was used additionally as matrix modifier during Cd determination in samples in order to prevent interferences coming from matrix components. The analysis of CRMs confirmed the reliability of the proposed approach. The precision and accuracy of Cd and Pb determination by the described method for soils and sediments were acceptable.
Talanta 09/2010; 82(4):1325-31. · 3.79 Impact Factor
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ABSTRACT: For comparison of action of mixed permanent modifiers Ir/Nb and Ir/W, the influence of the amounts of modifier components was studied and the atomic absorption pyrolysis and atomization curves were determined with different modifiers. The optimum amounts of modifier components were 30 μg Ir and 40 μg of Nb that were deposited onto the L'vov platform in advance to analytical measurements. The long-term performance of the Ir and Nb permanent modifiers was derived from the investigations by scanning electron microscopy and energy dispersive X-ray spectrometry. The soil and sediment slurries were prepared in 4% hydrofluoric acid and 6% suspension of polytetrafluoroethylene in order to remove the high concentration of silica during the pyrolysis step of 900 °C. The calibration was made by using aqueous standards. The analysis of certified reference materials confirmed the accuracy and reliability of the proposed analytical approach. The precision of Sb determination was characterized with less than 6% RSD.
Spectrochimica Acta Part B Atomic Spectroscopy 66(7):493-499. · 2.88 Impact Factor
