Vladimir Bermanec

Microstructure evolution of an equimolar powder mixture of ZrO2-TiO2 during high-energy ball-milling and post-annealing

Abstract High-energy dry ball-mill and post-anneal processing were applied to synthesise ZrTiO 4 oxide powder from an equimolar TiO 2 –ZrO 2 powder mixture. X-ray diffraction was used to identify structural changes in the milled and the subsequently post-annealed samples. Applied milling assemblies, vials and balls made of WC–Co hard-metal and also of agate materials, were successful in such way that a fully amorphous structure appeared in the samples if milling lasted long enough. The milling time required for complete disordering was almost five times longer with the agate assembly (about 50 h) in comparison with the WC–Co one (about 10 h). Also, the hard-metal assembly incorporated in the milled samples some amount of a WC impurity due to contamination, whereas contamination of samples by agate material was not observed by XRD. The preparation of the crystalline ZrTiO 4 powder phase from the amorphous one, was possible if the samples were exposed to a subsequent heat treatment. The structural transformations occurring during heating the samples went in two different ways depending upon the previously used milling assembly. In the first case annealing of samples performed for 1 h at 650°C caused a structural transformation of the WC phase into the WO 3 phase, whereas this temperature was not high enough to allow the crystallisation of the amorphous ZrTiO 4 . Annealing of the samples at 900°C for 1 h caused complete crystallisation of the amorphous powder into the crystalline ZrTiO 4 phase, without any evidence of the presence of the former W-base phases. Apparently this temperature favoured the formation of the solid solution of the WO 3 phase in the ZrTiO 4 crystalline phase. The crystallisation of the amorphous ZrTiO 4 phase in samples milled in an agate assembly was possible even at 650°C, although at this temperature it was a very slow process, and prolonged annealing time was necessary. If the samples, milled in an agate assembly up to 50 h, were heated at 900°C for 1 h, they can fully transform into the crystalline ZrTiO 4 phase.

Metavivianite, Fe2+Fe23+(PO4)2(OH)2·6H2O: new data and formula revision

Abstract The composition, structure, X-ray powder diffraction pattern, optical properties, density, infrared, Raman and Mössbauer spectra, and thermal properties of a homogeneous sample of metavivianite from the Boa Vista pegmatite, near Galiléia, Minas Gerais, Brazil are reported for the first time. Metavivianite is biaxial (+) with α = 1.600(3), β = 1.640(3), γ = 1.685(3) and 2Vmeas = 85(5)°. The measured and calculated densities are D meas = 2.56(2) and D calc = 2.579 g cm-3. The chemical composition, based on electronmicroprobe analyses, Mössbauer spectroscopy (to determine the Fe2+:Fe3+ ratio) and gas chromatography (to determine H2O) is MgO 0.70, MnO 0.92, FeO 17.98, Fe2O3 26.60, P2O5 28.62, H2O 26.5; total 101.32 wt.%. The empirical formula is (Fe3+1.64Fe2+1.23Mg0.085Mn0.06)Σ3.015(PO4)1.98(OH)1.72·6.36H2O. Metavivianite is triclinic, P1, a = 7.989(1), b = 9.321(2), c = 4.629(1) Å, α = 97.34(1), β = 95.96(1), γ = 108.59(2)°, V = 320.18(11) Å3 and Z = 1. The crystal structure was solved using a single-crystal techniques to an agreement index R = 6.0%. The dominant cations in the independent sites are Fe2+ and Fe3+, with multiplicities of 1 and 2, respectively. The simplified crystal-chemical formula for metavivianite is Fe2+ (Fe3+, Fe2+)2(PO4)2(OH,H2O)2·6H2O; the endmember formula is Fe2+Fe3+2(PO4)2(OH)2·6H2O, which is dimorphous with ferrostrunzite.

Monitoring of total metal concentration in sludge samples: case study for the mechanical-biological wastewater treatment plant in Velika Gorica, Croatia.

In this paper, monitoring of total metal concentration in sludge samples from wastewater treatment process is elaborated. The presented results summarize the analyses of sludge samples in a period from 2008 to 2012. Possible sources of pollutions are given. Primarily, waste solid samples were collected from different pretreatment steps: (A) coarse grid, (B) fine grid and (C) aerated sand grease grid. Samples of A and B followed a repeatable pattern in 2008 and 2010. According to the results from 2008, samples of C contained measurable concentration of the following metals (mg/kg dry matter): Zn (21), Ni (1.05) and Ba (14.9). Several types of sludge samples were analyzed: fresh raw sludge (PS; 6-12 hour old), the sludge from the digester for anaerobic sludge treatment (DS; 48-72 hour old), samples from lagoons where the sludge is temporarily deposited (DOS and DOSold; 30-120 days) and sludge samples from agricultural areas (AA; aged over 180 days). Additionally, samples of dehydrated sludge (DEHS and DEHSold; 90-180 days) were collected upon construction of equipment for sludge dehydration in 2011. An analysis of total metal concentrations for Cu, Zn, Cr, Pb, Ni, Hg, Cd, Ba, As, Se, Sb, Co, Mo, Fe and Mn was performed by flame atomic absorption spectrometry (FAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The most recent results (year 2011) indicated a high concentration of heavy metals in PS samples, exceeding the MCLs (mg/kg dry matter): Cu (2122), Zn (5945), Hg (13.67) and Cd (6.29). In 2012 (until July), only a concentration of Cu exceeded MCL (928.75 and 1230.5 in DS and DEHS, respectively). A composition of sludge was variable through time, offering the limited possibility for future prediction. The sludge is being considered as a hazardous waste and a subject of discussion regarding disposal.

Monazite in Hydrothermal Veins from Alinci, Yugoslavia

SummaryA new occurrence of monazite from Alinci, SE Yugoslavia, is described. Crystal morphology studies showed that crystals possess a platelike habit on T01 which we regard as a hitherto unknown morphological feature of monazite. The material has been analysed for uranium, thorium and rare earth element content using gamma spectrometry and inductively coupled argon-plasma atomic emission spectrometry (ICPAES). The monazite displays a complex chemical composition, essentially given as (REE+Y,Th,U,Fe)1.001P0.988O4. The infrared absorption spectra and X-ray diffraction data are in agreement with those for terrestrial monazite, although they indicate minor structural variations caused by the REE distribution in the Alinci monazite.ZusammenfassungEs wird ein neues Monazitvorkommen von Alinci, Jugoslawien, beschrieben. Kristallmorphologische Studien zeigten, daß die Kristalle einen plattigen Habitus nach (T01) aufweisen, eine nach Wissen der Autoren bisher unbekannte morphologische Erscheinung bei Monazit. Das Material wurde auf die Uran-, Thorium- und Seltenerdgehalte mit Gamma-Spektrometrie und induktiv gekoppelter Argonplasma-Atomabsorptions-Spektrometrie (ICPAES) analysiert. Der Monazit zeigt eine komplexe chemische Zusammensetzung, die im wesentlichen als (REE+Y,Th,U,Fe)1.001P0.988O4 angegeben werden kann. Die Ultrarotspektren und die Röntgenbeugungs-Daten stimmen mit jenen von terrestrischem Monazit überein, obwohl sie kleine strukturelle Variationen anzeigen, die durch die REE-Verteilung im Monazit von Alinci verursacht sind.

Solid Solution Between Epidote and Hancockite from Nezilovo, Macedonia

A solid solution between the epidote formula and hancockite formula (Pb equivalent of epidote) was found in the “mixed series” of the Pre-cambrian complex in the central part of the Pelagonian massif near the village of Nezilovo. The mineral is determined by optical investigation, X-ray diffraction and microprobe analyses. A thermogravimetric analysis was performed and determined 1.68 wt.% of H2O. Two distinct compositions were found: one with 20-25 mol% and one with about 70 mol% of hancockite component, indicating two different parageneses where the Ca in epidote is partly substituted by Pb.

Influence of digested wastewater sludge on early growth of the perennial ryegrass (Lolium perenne L.)

Effects of residual wastewater sludge, amended with zeolites, on the early growth of perennial ryegrass (Lolium perenne L.) were investigated. For that purpose growth parameters, content of photosynthetic pigments, substrate characteristics, levels of macro- and micronutrients, as well as toxic elements in plant tissue, plant inorganic matter and substrates, sewage sludge and soil, were determined. Among the growth indicators, only protein content and inorganic matter in plant tissue were found to be influenced by the type and composition of the substrate. Sewage sludge was found to contain elevated levels of Mo, Ni, Pb, Sb, Se, Sr and Zn, while Cu and Sn were found in an order of magnitude higher levels compared to the control sample. Application of sewage sludge, however, modified only the content of Cu and Zn in the plant tissue, inducing accumulation of these elements by a factor of 2. Despite the fact that all other measured elements (Al, As, Ba, Ca, Cd, Co, Cr, Cs, Fe, K, Li, Mg, Mn, Na, Ti, U and V) were found in plant tissue at similar level regardless of the substrate metal loading, accumulation indices point to overall lower bioavailability of elements from digested sludge in comparison with control substrate. Moreover, metal concentrations in all analyzed plant samples were below legally established limits.

Shallow-water benthic foraminiferal assemblages and their response to the palaeoenvironmental changes — example from the Middle Miocene of Medvednica Mt. (Croatia, Central Paratethys)

Abstract During the Middle Miocene, the northern Croatian Medvednica Mt. was an island within the Pannonian Basin System, situated on the SW margin of the Central Paratethys Sea. Miocene sedimentary rocks (the Late Badenian Bulimina–Bolivina Zone and Ammonia beccarii ecozone), from the SW slopes of Medvednica Mt. clearly reflect a transgressive-regressive cycle with emersion during the Badenian/Sarmatian boundary. After the initial phase of transgression, the pioneer Elphidium–Asterigerinata–Ammonia benthic foraminiferal assemblage is present in bioclastic limestones, such as those at the Borovnjak locality. This marginal marine assemblage from a highly energetic, normally saline environment is characterized by poor preservation of foraminiferal tests, low diversity and strong domination. Advanced transgression is followed by establishment of the Elphidium–Asterigerinata assemblage, which is found in biocalcsiltites from the laterally deeper and more sheltered environment at Gornje Vrapče. This diverse assemblage is typical for inner/middle shelf environment with sufficient oxygen content. A general shallowing upward trend can be recognized at both localities, followed by visible interchange of different sedimentological and biotic features. Successive and oscillatory regression in the marginal marine environment was followed by salinity fluctuations and final brackish conditions with Ammonia–Elphidium assemblage. The laterally deeper environment reacted to regressive trends on finer scale with almost regular changes of benthic foraminiferal assemblages in the laminae (Heterolepa–Bolivina assemblage/Bolivina–Cassidulina assemblage/Elphidium–Asterigerinata assemblage). It might reflect sea-level oscillations with periodically increased siliciclastic and nutrient input from land or influence of seasonality on benthic assemblages, which occurred in the advanced phase of the regression near the Badenian/Sarmatian boundary.

Preservation of samarskite structure in a metamict ABO4 mineral: a key to crystal structure identification

Relics of the original samarskite structure were identified in a metamict ABO4 mineral from Beinmyr pegmatite, Norway, using selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The chemical composition of the sample confirmed the affiliation to the samarskite group giving general formula (REE0.322Ca0.269Fe0.231U0.142Mn0.031Pb0.011Th0.010Zr0.010Al0.00 4Sc0.002Na0.001K0.001)1.034(Nb0.707Ta0.267Ti0.069W0.017Sn0.007) 1.067O4 which corresponds well to the general ABO4 stoichiometry of the samarskite group. The structure identified by transmission electron microscopy (TEM) techniques is well related to the proposed low-temperature samarskite modification (Sugitani et al. 1985) crystallizing in Pbcn space group with the cell parameters a=5.69(2) A, b=4.91(2) A, c=5.21(2) A. The original mineral sample showed to be X-ray amorphous. Gradual recrystallisation in air in the temperature range between 400 and 1000oC yielded a pyrochlore phase being stable at all experimental temperatures. At 800oC a high-temperature samarskite phase (s.g. P2/c) co-crystallised with an increase in crystallinity at 1000oC. Recrystallisation in a reducing atmosphere (Ar/H2) did not yield the high-temperature samarskite phase solely. Unsuccessful recrystallisation of the high-temperature samarskite modification is mainly related to an alteration which shifted the composition of samarskite to pyrochlore as evidenced by occurrence of altered domains in the sample. Raman spectra of thermally untreated samarskite showed generally metamict nature of the mineral, although a few normal Nb-O vibration modes can be resolved indicating BO6 arrangement similar to the one of columbite.

Identification of biogenetic calcite and aragonite using SEM

Karst aquifers are heterogeneous terrains, where it is hard to assess any hydraulic parameter. Therefore, a multidisciplinary approach is necessary for research on karst aquifers. Catchment area of the Gacka river springs is typical Dinaric karst terrain built of karstified carbonates. Groundwater flow is mostly directed by preferential flow paths usually connected with main faults and fracture zones. In the presented case study structural geological and tectonic characteristics were defined. A recession diagram was created, and the water balance was calculated. Tracer-test data were also used for analysis. All these data were compared with the bulk hydrogeochemical and isotopic analyses of spring and surface waters. For this purpose, samples were obtained every month for one hydrological year at 17 sampling locations. Processing of all these data allowed a tenable definition of the Gacka spring catchment area.

Thermal stability and vibrational spectra of the sheet borate tuzlaite, NaCa[B5O8(OH)2]·3H2O

Abstract Tuzlaite, a hydrated pentaborate from the Tuzla evaporite deposit in Bosnia and Herzegovina, was analyzed for water content and loss upon heating using thermal analysis methods and vibrational spectroscopy. The resulting phases were identified by X-ray diffraction. The heating of tuzlaite results in a gradual loss of water over several dehydration steps. Two coordinated H2O molecules escape at 191 ℃. Between 248 and 298 ℃ two hydroxyl groups are eliminated, with an associated structural transformation. A continuous escape of the third water molecule occurs above 300 ℃. A phase relationship model for different hydrated borate minerals implies the possible formation pathway of tuzlaite by sequential polymerization of the borate polyanion.