Modified solution precipitation method was used to prepare pure and doped Mg,
Sr and Na hydroxyapatite type materials (CaP, CaMgP and CaSrNaP).
Modification consisted of partial substitution of ...nitrates by acetate
solution in order to achieve a more soluble and cost effective synthesis.
The obtained samples were calcined at 400?C (CaP400, CaMgP400 and
CaSrNaP400). All powders were characterized by X-ray diffraction (XRD),
Fourier transform infrared (FTIR) spectroscopy and scanning electron
microscopy (SEM). Calcined samples were densified at 1000?C in an air for 3
h (CaP1000, CaMgP1000 and CaSrNaP1000). Sintered samples were characterized
by XRPD, FTIR, SEM, EDS and complex impedance methods. The highest
conductivity was found for the multi-doped phosphate sample (CaSrNaP1000) at
700?C (1.90?10-3?-1cm-1). The corresponding activation energies of
conductivity amounted to 0.31 eV in the temperature range 500-700?C.
Waste material from two active and two abandoned waste rock dumps from the Pb-Zn Rudnik Mine (central Serbia) was studied by optical, scaning microscopy, and X-ray powder diffraction methods. The ...weathering minerals in the active dumps are represented by anglesite, Fe-sulphates and Fe-oxyhydroxides. In the abandoned dumps they appear as a Pb-Cu group (beaverite, brochantite±Fe-sulphoarsenates) and a Zn-Fe group (boyleite, Zn-melanterite, and hydronium jarosite) of minerals. On the basis of textural and compositional evidence a schematic model of oxidative dissolution of primary sulphides and precipitation of byproducts is proposed. The model includes an initial stage dominated by oxidation of pyrrhotite, which is subsequently followed by decomposition of galena, sphalerite, arsenopyrite and chalcopyrite. The environmental impact of the weathering phases is assessed by analyzing the concentration of toxic elements in water that is directly linked to the waste rock dumps. The results show that the arsenic content in the river water increases up to ten times after the inflow of the waste water. One of the reasons is that soluble As-bearing phases (i.e., Fe-sulphoarsenates) were found in the surrounding waste material. By contrast, because of the presence of almost insoluble weathering phases, such as beaverite and anglesite, the concentrations of lead and copper in the studied aquaeous samples are relatively low. We argue that careful studying of oxidative dissolution of sulphides and formation of particular weathering phases can be of large significance in assessing the environmental impact of waste rock dumps associated to mining activities.
Display omitted
•Weathering of material from waste rock dumps of a PbZn mine area•Mechanism of decomposition of sulphides and the formation of sulphate phases•Effects of weathering minerals in waste dumps on environment
This paper describes the physical, chemical and mineral properties of ash and slag, which were taken from thermal power plants Nikola Tesla A, Nikola Tesla B, Kostolac A and Kostolac B. The knowledge ...of the mineralogical material composition is important because the type of minerals directly determines the properties of the fly ash and slag and their possible application. Laboratory tests showed that ash and slag samples consist of the following minerals: amorphous materials, quartz, feldspar, mullite, melilite, cristobalite, haematite and calcite. The fly ash and slag chemical properties are the most important indicators in the evaluation of their suitability as a building material. The ash and slag chemical composition is composed of the following chemical components: SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, S, Na2O and K2O. Results of laboratory tests show that fly ash and slag have variable chemical, mineralogical and physical properties that are dependent on the natural composition, quality of coal from basin, the manner of combustion and place of ash deposition.
During the construction of the unbound pavement layers of Corridors X and XI in Serbia, a problem was detected regarding the evaluation of cleanliness of the available materials. The European ...standard for the sand equivalent from 1999 to 2015 had significant changes related to the test procedure. A mass correction has been taken into account. It consists of replacing a part of the fines with rinsed material (0.063/2 mm) when the percentage of fines exceeds 10% in a tested fraction. Thus, the test sample usually yields high values of the sand equivalent, which often exceeds the limits of 50% and 60%. From the standpoint of the technical specifications, aggregates are considered clean, while using other methods like methylene blue or a plasticity index, the presence of clay particles above the limits can be confirmed. This paper presents the results of research on 63 laboratory-prepared test samples of limestone aggregate with small quantities of the smectite group of clay minerals, where the fines content in the unbound aggregate, 0/31.5 mm, gradually increased up to 20%. It was found that the sand equivalent values are continuously decreasing from 84 to 14% in the fraction 0/2 mm and from 87 to 18% in the 0/4 mm fraction, with increasing of the methylene blue value of the all-in aggregate (MB
A
) from 0.4 to 4.5 g/kg. Correlations of different methods and fractions, as well as with the content of fines were found. There are no correlations with SE
10
because of grouping the test data around one point.
Infrared attenuated total reflection spectrophotometry, UV data, microelectrophoresis and a Hallimond tube flotation cell have been used to investigate the effect of Pb(II) on the galena and ...sphalerite surface properties (hydrophobicity and charge of the surface), ethyl xanthate adsorption and ethyl xanthate adsorption kinetics in alkaline medium. It has been found that lead adsorbed on the galena or sphalerite surface as Pb(OH)
+ and less as Pb
2+ reduced the collectorless galena floatability from pH 7 to 9.5, but had a strong activating effect on natural sphalerite floatability (in pH range 7.6–10.5). Collecting of Pb(II)-modified minerals with K-ethyl xanthate both forms of lead ethyl xanthate, monolayer,
Pb
EX (chemically adsorbed (EX)
−), and multilayer, physically adsorbed Pb(EX)
2, were detected on the mineral surfaces. Sphalerite floated 90–100% in pH range from 7 to 9.5, but galena floated better only from pH 8 to 9.5 (85–95%). The main surface reaction in pH range 8–9.5 is probably the ion-exchange reaction M
Pb
OH
+
(EX)
−
=
M
Pb
EX
+
(OH)
− (M—mineral), which contributes to the chemical adsorption of (EX)
− as monolayer
Pb
EX, on the surface of either mineral. The reaction between Pb(II)-treated mineral and (EX)
− ion is a reaction of pseudo-first order with respect to ethyl xanthate (on Pb(II)-modified galena the rate constant is
k
1
=
0.711
min
−1; on Pb(II)-modified sphalerite
k
1
=
0.1014
min
−1).
The new geochemical and mineralogical data of soil and water from the PbZn Rudnik Mine area (central Serbia) reveal that the areas close to the mining sites and those located remotely from them are ...both affected by significant pollution by toxic elements, especially As, Pb, Ni and Cr. We, therefore, propose that two main sources are generally responsible for the current state of pollution in this area. The first is the material from waste rock dumps (WRDs) in which the decomposition of primary sulfides plays the most important role. Our results also demonstrate that both sulfides that serve as main carriers of toxic elements, such as galena (Pb) and arsenopyrite (As), and those that carry toxic elements in microquantities act as pollution factors. This pollution affects soil and water in the immediate surroundings of the WRDs, and it is likely combined with the influence of waste mining waters and from rocks from the geological basement. The second source is medieval slag that is related to the pollution of soil and water located at higher altitudes and far away from WRDs. The results of our study argue that leaching of toxic elements is caused by the slag weathering and that this environmental impact can only partly be suppressed by the formation of hardly soluble secondary phases, such as linarite, brochantite and beaverite. Although the presented pollution models are schematic and cannot account for the entire environmental complexity of the Rudnik Mine site, they do represent a solid basis for further environmental studies in this area.
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•The pollution as the result of two sources in the area of PbZn mine•Pollution caused by sulfide decomposition in material from waste rock dumps•The environmental pollution caused by decomposition of medieval slag
•Phase and morphological analysis of urinary stones was done.•XRPD results show phase composition of all samples.•SEM results shows crystal growth and formation of selected samples.•Importance of ...using analytical techniques to examine materials that may also contribute to medical research.
In this paper we present the phase and morphological characteristics of urinary stones from Serbian patients. The study included for the first time the determination of the phase composition and a statistical analysis of the presence of different types of urinary stones in both men and women in Serbia. The main goal of study was representation of collected data for the first time. For past three years, more than 600 samples were collected from Serbian patients. The phase composition of all samples of urinary stones was investigated using XRD analysis. Morphology and chemical composition of phases in some characteristic samples was determinate by the SEM-EDS analysis. Results indicate that there are several different types of urinary stones that vary in mineral composition, chemistry and morphology. It was found that 312 (52%) of the 600 stones were composed of calcium oxalate minerals (CaOx): 17.3% of which were pure calcium oxalate monohydrate COM, 4% were pure calcium oxalate dihydrate COD; 200 (33.3%) were a mixture of CaOx and Hydroxyapatite HA, 19 (3.1%) were uric acid (uricite) UA and uric acid dihydrate UAD, 17 (2.8%) were a combination of UA and CaOx minerals, 41 (6.8%) were combination of CaP minerals and CaOx, 11 (1.9%) were cystine (Cy) stones. The obtained data shows the diversity of types of urinary stones. Morphological, chemical and XRPD analysis give us statistical data which shows that the most common urinary stones from Serbian patients are from CaOx group and in most of cases are associated with CaP.
Toluene Degradation in Water Using AlFe-Pillared Clay Catalysts Predrag BANKOVIC~ Aleksandra MILUTINOVIC-NIKOLIC Zorica MOJOVIC Aleksandra ROSIC Zeljko CUPIC Davor LONCAREVIC Dusan JOVANOVIC
Chinese journal of catalysis,
2009, 2009-1-00, Letnik:
30, Številka:
1
Journal Article
Recenzirano
The catalytic wet peroxide oxidation （CWPO） of toluene on two bentonite-based AlFe-pillared clays （PILCs） with different iron contents was investigated. The PILCs were obtained using bentonite clay ...from Bogovina, Serbia. The change in chemical and phase composition and textural properties of the starting clay and synthesized catalysts was monitored using X-ray diffraction, inductively coupled plasma optical emission spectrometry, UV-Vis diffuse reflectance spectrometry, and physisorption of nitrogen. The catalytic performance was examined using gas chromatography. The Na-exchange process lowered the （001） smectite basal plane spacing, but the clay retained its swelling properties, while the pillaring process increased it. The surface areas of both synthesized pillared clays increased to similar values although their Fe content was different. At 37℃ , both catalysts show significant toluene degradation, with the one richer in Fe having higher efficiency. The leaching of the active cations during reaction was negligible, and the catalysts were stable. AlFe-pillared clay catalysts can be used in CWPO for the elimination of BTEX compounds from plant effluent streams.
Statistically designed experiments were done to study the recovery of Mg content from natural smectite clays from Serbia by hydrochloric acid leaching. The effects of relevant factors, such as ...temperature, leaching time, acid normality, solid-to-liquid ratio and stirring rate on leaching yield of MgO have been investigated. Experiments have been planned by the factorial design method. To test the significance of the effects, an analysis of variance has been conducted at 95% confidence intervals.
The structural and adsorption properties of the starting smectite clay and the sample activated at chosen conditions were investigated by means of a model. Scanning electron microscopy (SEM) and nitrogen adsorption–desorption were used to analyze the morphological characteristic of the starting and the activated sample. The results from the nitrogen adsorption–desorption isotherms show that the activated smectite clay possess a narrow pore size distribution of about 2
nm, and a large specific surface area of 238
m
2/g. The results of X-ray diffraction (XRD) and infrared analysis (IR) of starting and activated samples confirmed that smectite was the dominant mineral phase. Besides, chemical treatment of smectite clay with HCl produces an adsorbent with optimal porosity and other adsorption properties suitable for many industrial processes.
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