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ABSTRACT: In this paper, we demonstrate that combined application of X-ray diffraction (XRD), electron microscope/microprobe analysis (EMPA), and Raman microspectroscopy is an available and powerful approach for identification and characterization of iron arsenate minerals in complex environmental samples. Arsenic-rich material from the medieval mining dump close to the Giftkies mine in the Jáchymov ore district (Czech Republic) has been studied. Scorodite, kankite, amorphous iron arsenate (pitticite), and, to a lesser extent, native sulfur were determined in the studied samples as products of low-temperature arsenopyrite weathering. Scorodite and kankite form mixed nodules and crusts, which are locally coated by hardened gel-like amorphous pitticite. Pitticite also borders fractures in the mineralized rock fragments in the dump. Native sulfur, in microscopic crystals and grainy aggregates, originates directly in places with dissolved arsenopyrite and forms pseudomorphs. The Raman spectra presented in the paper can serve as comparative data for phase identification in other contaminated areas. New Raman data for the hydroxyl stretching region of scorodite (important bands: 3514, 3427, and 3600 cm(-1)) and the whole Raman spectrum for pitticite (important bands: 472, 831, 884, 2935, 3091, 3213, 3400, and 3533 cm(-1)) are a valuable output of this paper.
Applied Spectroscopy 07/2009; 63(6):621-6. · 1.66 Impact Factor
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ABSTRACT: The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe(II), Fe(III), Al(III) and Mn(II) salts were used to remove of As from the model anoxic groundwater with As(III) concentration about 0.5 and 10 mg L(-1). All the pre-treating methods were appropriate for bentonite; the efficiency of As(III) sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe(II)- and Mn(II)-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe(III) and Al(III) pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1).
Journal of hazardous materials 10/2008; 165(1-3):134-40. · 4.14 Impact Factor
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ABSTRACT: Adsorption of arsenic on clay surfaces is important for the natural and simulated removal of arsenic species from aqueous environments. In this investigation, three samples of clay minerals (natural metakaoline, natural clinoptilolite-rich tuff, and synthetic zeolite) in both untreated and Fe-treated forms were used for the sorption of arsenate from model aqueous solution. The treatment of minerals consisted of exposing them to concentrated solution of Fe(II). Within this process the mineral surface has been laden with Fe(III) oxi(hydroxides) whose high affinity for the As(V) adsorption is well known. In all investigated systems the sorption capacity of Fe(II)-treated sorbents increased significantly in comparison to the untreated material (from about 0.5 to >20.0 mg/g, which represented more than 95% of the total As removal). The changes of Fe-bearing particles in the course of treating process and subsequent As sorption were investigated by the diffuse reflectance spectroscopy and the voltammetry of microparticles. IR spectra of treated and As(V)-saturated solids showed characteristic bands caused by Fe(III)SO(4), Fe(III)O, and AsO vibrations. In untreated As(V)-saturated solids no significant AsO vibrations were observed due to the negligible content of sorbed arsenate.
Journal of Colloid and Interface Science 10/2006; 302(2):424-31. · 3.07 Impact Factor
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ABSTRACT: Metallurgical slags from primary lead smelting were submitted to a 30-day batch leaching procedure in 20 and 8 mM citric solutions in order to determine the kinetics of release of Pb, Cu, Zn and As. The experiment was coupled with the PHREEQC-2 speciation-solubility modelling and mineralogical study of newly formed products (SEM/EDS, XRD, TEM/EDS and Raman spectrometry). A strong scavenging of metals and metalloids from the 8 mM citric leachate was observed due to the formation of newly formed products. The secondary precipitate consisted of well-developed calcite (CaCO3) crystals and amorphous organo-mineral matrix composed of hydrous ferric oxides and amorphous SiO2. Metals (Pb, Zn, Cu) and arsenic released into the solution were subsequently bound onto the newly formed product (adsorption on oxides) or trapped within the calcite structure (Zn, Mn). Similar scavenging mechanism can be taken into account in real soil systems with lower concentration of citric acid. Then, the covering of slag dumps with a thick soil layer and subsequent re-vegetation might be a possible scenario for slag management on some metallurgical sites.
Chemosphere 12/2004; 57(7):567-77. · 3.21 Impact Factor
