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Rakic V.,University of Belgrade | Rakic V.,CNRS Research on Catalysis and Environment in Lyon | Rajic N.,University of Belgrade | Dakovic A.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Auroux A.,CNRS Research on Catalysis and Environment in Lyon
Microporous and Mesoporous Materials | Year: 2013

In this study, adsorption of salicylic acid, acetylsalicylic acid and atenolol from aqueous solutions onto clinoptilolite modified with sorbed metallic cations (Cu(II), Zn(II), Ni(II) or Mn(II)) have been probed. Natural clays (kaolin and bentonite, pure or ion-exchanged by octadecyl dimethyl benzyl ammonium chloride) have been also probed as adsorbents. The adsorption was studied at 30 °C by titration microcalorimetry, employed to obtain the heats evolved as a result of adsorption. Adsorption experiments were performed under the same conditions, the equilibrium adsorbate concentrations were determined by fluorescence spectrophotometry. The maximal adsorption capacities of investigated solids against target pharmaceuticals lie in the range of 10 -5-10 -6 mol/g. Modified minerals have shown different capacities in comparison with natural ones. The adsorption capacities are dependent on the characteristics of pharmaceutically active compound. The results obtained in this work show that natural materials can be used effectively in the removal of investigated pharmaceuticals by adsorption. © 2012 Elsevier Inc. All rights reserved. Source

Stojanovic J.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Dordevic T.,University of Vienna | Karanovic L.,University of Belgrade
Journal of Alloys and Compounds | Year: 2012

Two new compounds, Cd 1.16Zn 2.34(AsO 4) 1.5(HAsO 4)(H 2AsO 4) 0.5 (1) and Cd 0.74Mg 2.76(AsO 4) 1.5(HAsO 4)(H 2AsO 4) 0.5 (2), have been prepared hydrothermally. Their crystal structures consist of chains of edge-sharing M1O 4(OH 0.5) 2, M1aO 4(OH 0.5) 2, M2O 5(OH 0.5), and M2aO 5(OH 0.5) octahedra (M1, M1a = Zn, Cd; M2, M2a = Zn for 1, and M1, M1a = Mg, Cd; M2, M2a = Mg for 2) that are stacked parallel to (1 0 1) and are connected by the [(AsO 4) 0.5(AsO 3(OH)) 0.5] 2.5- and [(AsO 4) 0.5(AsO 2(OH) 2) 0.5] 2- tetrahedra. These chains produce two types of channels parallel to the c-axis. Cd atoms are located in channels 2, while in channels 1 are situated hydrogen atoms of OH groups. The infrared spectra clearly show the presence of broad OH stretching and bending vibrations centred at 3236, 2392 1575 and 1396 cm -1 in (1), and 3210, 2379 1602 and 1310 cm -1 in (2). The OH stretching frequency is in good agreement with O⋯O distances. Furthermore, structural characteristics of compounds with similar alluaudite-like structures were discussed. © 2011 Elsevier B.V. All rights reserved. Source

Vucinic D.R.,University of Belgrade | Radulovic D.S.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Deusic S.D.,University of Belgrade
Journal of Colloid and Interface Science | Year: 2010

The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta potential without and in the presence of sodium oleate (1 × 10-4 mol L-1) was examined within the pH range from 4 to 12. The interpretation of results was based on the HA surface and oleate solution chemistry, and on some floatability tests. HA, with different positive and negative surface sites formed depending on its solubility and pH, had a negative zeta potential over the whole pH range. This mineral is not naturally floatable (flotation recovery, 5% < R < 18%). The oleate ions (Ol-), present in a very low concentration in an acidic medium (pH from 4.8 to 6), chemisorb individually on HA surface centers {triple bond, long}Ca+, {triple bond, long}HPO4Ca+, and {triple bond, long} OH2 +, increasing the negative zeta potential of the mineral. Within the pH range from 7 to 9, the dominant oleate species Ol- ion and ion-molecule complex, H (Ol)2 -, adsorbed on HA by head groups toward the solid and associated due to chain-chain interaction in hemimicelles, made the HA surface with zeta potential about -22/-23 mV, and more floatable (R = 80-100%) than in 4 < pH < 7 (R = 15-35%) or in pH > 9.3. The HA surface is less negatively charged in calcite supernatant than in water from pH 6.6 to 9.2 due to the adsorption on HA negative surface active centers ({triple bond, long} HPO4 - and {triple bond, long} PO4 2 -) of the Ca2+, CaHCO3 +, and CaOH+ ions (present in the calcite supernatant), producing more surface sites {triple bond, long}HPO4Ca+, {triple bond, long}PO4Ca, {triple bond, long}HPO4CaOH, and {triple bond, long} PO4 - CaOH, and new centers {triple bond, long}HPO4CaHCO3 and {triple bond, long} PO4 - CaHCO3. In the presence of 1 × 10-3 mol L-1 CaCl2, the HA sample has positive zeta potential, the same as calcite from the same deposit, up to IEP at pH 11.25. Carbonate ions (1 × 10-3 mol L-1 Na2CO3) do not affect the HA zeta potential. However, a possible process can be the ion-exchange reaction between bicarbonate (or carbonate) and some anion from the surface sites formed on HA. The obtained values of the HA zeta potential with the collector (1 × 10-4 mol L-1 Na-oleate) added into hydroxyapatite/calcite supernatant suspensions corroborate the weak chemisorption of Ol- and H (Ol)2 -. The likely processes in this system also are the ion-exchange reactions on {triple bond, long}HPO4CaOH and {triple bond, long} PO4 - CaOH, {triple bond, long}HPO4CaHCO3 and {triple bond, long} PO4 - CaHCO3 between oleate ion and surface hydroxyl and bicarbonate ions, surface and bulk precipitations of calcium oleate, Ca(Ol)2, and the surface and bulk precipitations of Ca [H (Ol)2 -]2 over the pH range from 7 to 9. Calcite supernatant does not influence natural floatability of the mineral. However, calcite supernatant depresses the hydroxyapatite flotation in the presence of 1 × 10-4 mol L-1 Na-oleate (pH 9, R ∼ 50%), a likely result of the weak chemisorption due to the steric effect of heterogeneous HA surface formed in calcite supernatant, Ca(Ol)2 and Ca [H (Ol)2 -]2 surface and bulk precipitations. © 2009 Elsevier Inc. All rights reserved. Source

Radosavljevic S.A.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Stojanovic J.N.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Pacevski A.M.,University of Belgrade
Chemie der Erde - Geochemistry | Year: 2012

Rujevac is a low-temperature hydrothermal polymetallic Sb(As)-Pb-Zn vein-type ore deposit, hosted in volcanogenic-sedimentary zone situated in Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. The mineralogical composition of the deposit consists of sulfides (stibnite, sphalerite, pyrite, arsenopyrite, galena, realgar and orpiment), sulfosalts (zinkenite, plagionite, robinsonite, twinnite and gratonite), native arsenic, Sb-oxides (valentinite, senarmontite and kermesite), and gangue minerals (quartz, calcite and dolomite). Minerals containing mercury as a major element have not been detected. According to optical features, sphalerite belongs to the cleophane, low Fe content variety (yellowish to colorless). Electron Probe Micro-Analyses (EPMA) of sphalerite revealed wide compositional variations. The Hg content in sphalerite varies between 0.30 and 6.47wt%. The range of other minor elements (Fe and Cd) is highly variable; Mn, Sn, Ge, In, Tl, and As were analyzed, but not detected. Hg-rich zones occur as narrow lamellae and are related to the crystallographic directions of sphalerite. The average values of the EPMA results gave the crystallochemical formula of this sphalerite (Zn 0.981, Fe 0.007, Cd 0.007, Hg 0.008) ∑1.003S 0.997. Strong negative correlations have been determined between ∑Fe+Cd+Hg vs. Zn, and Hg vs. Zn, while these are absent between all other analyzed elements. © 2012 Elsevier GmbH. Source

Kragovic M.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Dakovic A.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Markovic M.,Serbian Institute for Technology of Nuclear and Other Mineral Raw Materials | Krstic J.,University of Belgrade | And 2 more authors.
Applied Surface Science | Year: 2013

The influence of contact time, temperature and particle size on lead sorption by the natural and Fe(III)-modified zeolites was investigated. Characterization of the natural and Fe(III)-modified zeolite before and after lead sorption was performed by determination of textural properties, by scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM-EDS), transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD) analysis. Lead sorption kinetics at 303-333 K, best represented by the pseudo-second order model and activation energy (13.5 and 8.5 kJ/mol for the natural and Fe(III)-modified zeolite respectively) confirmed an activated chemical sorption. Desorption experiments indicated that lead was irreversibly sorbed on both zeolites. XRPD, TEM and SEM results showed that modification of the natural zeolite with Fe(III) ions did not change its crystal structure and iron is mainly located at the zeolite surface, likely in form of amorphous iron oxy-hydroxides. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions (from 30.2 for the natural to 52.5 m2/g for Fe(III)-modified zeolite). Characterization of both lead saturated sorbents suggested that besides ion exchange, lead is both chemisorbed and precipitated at their surfaces, and presence of amorphous iron in Fe(III)-modified zeolite favors sorption of lead. © 2013 Elsevier B.V. All rights reserved. Source

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