28 research outputs found
Alumina/nano-graphite composite as a new nanosorbent for the selective adsorption, preconcentration, and determination of chromium in water samples by EDXRF
Obtaining new nanocomposites with sorption properties towards chromium is highly important not only from the environmental
point of view but also for developing eco-friendly methods of chromium determination. The potential use of aluminum oxidecoated
nano-graphite (Al2O3/nano-G) as a new nanosorbent in ultrasound-assisted dispersive micro-solid-phase extraction
(DMSPE) for rapid speciation of trace chromium(III) and chromium(VI) ions in natural water was evaluated. In the developed
method, the crucial issue is the new nanocomposite synthesized by coating alumina on a nano-graphite surface with sorption
properties. Structural researches of the nanocomposite were carried out by scanning electron microscopy (SEM), powder X-ray
diffraction (XRD), and Raman spectroscopy. Maximum adsorption capacity of Al2O3/nano-G towards Cr(III) was 32.8 mg g−1.
The influence of the method’s factors like pH, sample volumes, contact time, coexisting ions, and humic acid on the recovery of
chromium was examined. The nanocomposites have been found to be stable and effective as a sorbent in water with high
concentrations of selected cations and anions present in water as well as in water of various pH. Al2O3/nano-G is selective for
Cr(III) in presence of Cr(VI). Cr(III) was determined by the developed method, total Cr after reduction of Cr(VI) to Cr(III), and
Cr(VI) was calculated as the difference between total Cr and Cr(III). After sorption, the nanocomposite with chromium was
collected on 5-mm diameter filters and analyzed by energy-dispersive X-ray fluorescence spectrometry (EDXRF) to determine
the chromium concentration. The method was characterized by correlation coefficient 0.999, limit of detection (LOD)
0.04 ng mL−1, and relative standard deviation (RSD) 3.5%. Al2O3/nano-G combined with proposed DMSPE/EDXRF was
verified by analysis of certificate reference material of natural water (NIST 1640a)
Selective adsorption and determination of hexavalent chromium ions using graphene oxide modified with amino silanes
Novel adsorbents are described for the preconcentration of chromium(VI). Graphene oxide (GO) was modified with various amino silanes containing one, two, or three nitrogen atoms in the molecule. These include 3-aminopropyltriethoxysilane (APTES), N-(3-trimethoxysilylpropyl)ethylenediamine (TMSPEDA), and N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPDETA). The resulting GO derivatives were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray fluorescence spectrometry (EDXRF). Adsorption studies show that these GO based sorbents are highly selective for Cr(VI) in the presence of Cr(III) at pH 3.5. Although the amino silanes applied in modification of GO contain different numbers of nitrogen atoms, the maximum adsorption capacities of GO derivatives are very similar (13.3–15.1 mg·g−1). Such results are in accordance with spectroscopy studies which show that the amount of amino silanes attached to GO decreases in the order of APTES > TMSPEDA > TMSPDETA. The APTES-modified GO was applied to selective and sensitive extraction of Cr(VI) ions prior to quantitation by low-power EDXRF using the Cr Kα line. The Cr(VI) ions need not be eluted from the solid adsorbent. The method has a 0.17 ng·mL−1 detection limit, and the recovery is 99.7 ± 2.2% at a spiking level of 10 ng·mL−1. The method was successfully applied to the determination of Cr(VI) in water samples
Preconcentration of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) with ethylenediamine-modified graphene oxide
We describe a novel solid phase sorbent that was synthesized by coupling graphene oxide (GO) to ethylenediamine (EDA). This nanomaterial (referred to as GO-EDA) is capable of adsorbing the ions of iron, cobalt, nickel, copper, zinc and lead. The ethylenediamine-modified graphene oxide was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. The analytical procedure relies on (a) sorption of metal ions on GO-EDA dispersed in aqueous samples; (b) filtering, and (c) direct submission of the filter paper to energy-dispersive X-ray fluorescence spectrometry. This kind of dispersive micro-solid phase extraction was optimized with respect to pH values, concentration of GO-EDA, contact time, and the effects of interfering ions and humic acid on recovery of determined elements. Under optimized conditions, the recoveries of spiked samples range from 90 to 98 %. The detection limits are 0.07, 0.10, 0.07, 0.08, 0.06 and 0.10 ng mL−1 for Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The method has a relative standard deviation of <6 %, and its accuracy was verified by analysis of two standard reference materials [LGC6016 (estuarine water) and BCR-610 (groundwater)]. It was successfully applied to the determination of trace amounts of these metal ions in water samples
The absorption- and luminescence spectra of Mn3+ in beryl and vesuvianite
This research project was supported by the Polish National Science Centre (Grant DEC-2011/03/B/ ST10/06320) and by statutory funding from the Faculty of Earth Sciences at the University of Silesia. Dr. Padhraig S. Kennan (University College Dublin, Ireland) is thanked for help with language.The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5–158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite.Narodowe Centrum Nauk
Ceria nanoparticles deposited on graphene nanosheets for adsorption of copper(II) and lead(II) ions and of anionic species of arsenic and selenium
A nanocomposite prepared from graphene nanosheets and cerium nanoparticles (G/CeO2) was applied to the extraction of
Se(IV), As(V), As(III), Cu(II) and Pb(II). The structure of G/CeO2 was investigated by scanning electron microscopy, X-ray
diffraction and Raman spectroscopy. The optimal pH values for extraction are 4.0 for As(V), 3.0 for Se(IV), and 6.0 for both
Cu(II) and Pb(II). The maximum adsorption capacity of G/CeO2 (expressed as mg·g−1) were calculated by the Langmuir model
and are found to be 8.4 for As(V), 14.1 for Se(IV), 50.0 for Cu(II) and 75.6 for Pb(II). The sorbent was applied to dispersive solid
phase microextraction prior to direct quantitation by energy-dispersive X-ray fluorescence spectrometry without the need for
prior elution. The limits of detection (in ng·mL−1 units) are 0.10 for As(V), 0.11 for Se(IV), 0.19 for Cu(II) and 0.21 for Pb(II).
The precisions (RSDs) are <4.5%. The accuracy of the method (1 - 4%) was verified by analysis of the certified reference material
(CRM 1640a - natural water). The method was successfully applied in ultratrace element determination and to the speciation of
selenium in environmental waters
The Mossbauer and x-ray studies of the spinel ferrites Cu0.5Fe0.8Cr2Se4 prepared by the ceramic method
Seleno-spinels with nominal chemical composition Cu0:5Fe0:5Cr2Se4 and Cu0:2Fe0:8Cr2Se4 were prepared as polycrystalline samples using ceramic method. The assumed composition was verified by wavelength-dispersive X-ray °uorescence spectrometry. The X-ray analysis was carried out in order to make phase analysis and to compare its results with those obtained with the Mossbauer spectroscopy
The Mossbauer spectra of prasiolite and amethyst crystals from Poland
Mössbauer spectroscopy of green (prasiolite) and violet (amethyst) quartz crystals from the Sudety Mountains (Poland) has shown that neither Fe2+ nor Fe4+ ions are present in them. Only Fe3+ ions have been identified and only in interstitial positions in channels parallel or perpendicular to the c-axis. The valence of Fe3+ ions did not change as a result of irradiation or annealing. Instead, we believe that the Fe3+ ions move within channels or between them
Electrolytic copper as cheap and effective catalyst for one-pot triazole synthesis
Electrolytic copper is a well-known form of pure, oxygen free copper that is used for industrial
applications. In this work, the catalytic potential of this relatively cheap material was studied. The
addition of less than 0.015 mol equivalent of copper powder effectively catalysed the one-pot synthesis
of triazoles from a diverse range of organic halides and alkynes. Quantitative conversions in aqueous
solvents can be achieved within minutes. The heterogenous nature of the catalyst afforded a low level
of copper contamination in the products, thus meeting the rigorous criteria of the pharmaceutical
industry
Natural Rubber Latex - Origin, Specification and Application
The chapter contains information about the origin of natural rubber latex (NRL) (Hevea brasiliensis) and the processing of field latex, considering quality changes occurring during the preparation of raw materials for distribution. The main types of concentrated natural rubber latex are described. A specification of natural rubber latex (NRL) in terms of key parameters tested by manufacturers and customers is presented. Test methods for verifying if the material meets the requirements of ISO 2004 and internal specifications are described based on standards and commonly used techniques. The next subject touched in the chapter is prevulcanization as the processing of concentrated latex with a change of its properties. One of the main industrial applications of NRL as prevulcanized latex (PV) is the production of dipped goods like gloves or balloons. Currently, some trends and challenges relate to sustainability issues are presented (carbon footprint, FSC)