This work aimed to investigate the influence of modified titanium(IV) oxide
by different nanosized particles on photocatalytic capacity to decompose the
chosen organic pollutant under simulated ...sunlight. For that purpose,
rutile-phased titanium(IV) oxide (r-TiO2) was decorated with iron vanadate
(FeVO4/r-TiO2) and vanadium-substituted goethite (Fe1-xVxOOH/r-TiO2). The
obtained composites were characterized by field emission scanning electron
microscopy, energy-dispersive X-ray spectroscopy, X ray powder diffraction,
Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy - attenuated
total reflec-tance and ultraviolet-visible diffuse reflectance spectroscopy
techniques. Both synthesized photocatalysts showed higher photoactivity than
the base r-TiO2 for the degradation of the target contaminant -
thiophanate-methyl (2.5 h vs. 5 h). During the tests, parameters like the
irradiation time, catalysts amount, and pesticide concentration were
systematically investigated. Furthermore, photocatalysts were applied in
multicycle degradation tests for examining their effectiveness during
exploitation time. Monitoring of the removal rate was performed both by
UV/visible spectrometry and high-performance liquid chromatography (HPLC).
In order to prove completion of fungicide degradation chemical oxygen demand
was measured in the course of the photocatalytic experiment. The final
concentration of the observed contaminant in treated samples was under the
prescribed legislative level. The fabricated materials displayed great
reliability, durability and photocatalytic activity repre-senting good
potentials for implementing this process in real wastewater treatment
plants.
Acid mine drainage (AMD) is a waste from mining sites, usually acidic, with high concentrations of sulfates and heavy metal ions. This study investigates the AMD neutralization process using fly ash ...(FA) as an alternative material. Samples of FA from coal-fired power plants in Serbia (“Nikola Tesla” (EF) and “Kostolac” (KOST)) were analyzed and used. The results were compared with the treatment efficiency of commercial neutralization agent (NaOH). The alkaline nature of FA was the basis for use in the treatment process of the extremely acid Lake Robule (pH 2.46), located in the mining areas of eastern Serbia. The optimal S/L ratio for the AMD neutralization process determined for EF was 25 wt.%, and for KOST it was 20 wt.%. The mechanism of the neutralization process was analyzed using the ANC test and PHREEQC program. The element concentrations and pH values in solutions indicated that FA samples could neutralize Lake Robule with more than 99% of Al, Fe, Cu, Zn, and more than 89% of Pb precipitated. Formation of insoluble (oxy)hydroxide forms (Fe3+ and Al3+ ions) creates favorable conditions for co-precipitation of other trace metals (Cu, Zn, Ni, Pb, and Cd) from AMD, which is further enhanced by cation adsorption on FA particles. FA proved to be a more effective neutralization agent than NaOH due to its adsorption effect, while among the FA samples, KOST was more effective due to the aging process through the carbonization reaction. Using FA as an alternative material is a promising and sustainable method for treating AMD, with economic and environmental benefits.
A chemometrically based approach was applied to select the most efficient drug adsorbent among the biochars obtained from the novel feedstock, the leaves of the invasive plant (Ailanthus altissima). ...The representative target adsorbates (atenolol, paracetamol, ketorolac and tetracycline) were selected on the basis of their physicochemical properties to cover a wide chemical space, which is the usual analytical challenge. Their adsorption was investigated using design of experiments as a comprehensive approach to optimise the performance of the adsorption system, rationalise the procedure and overcome common drawbacks. Among the response surface designs, the central composite design was selected as it allows the identification of important experimental factors (solid-to-liquid ratio, pH, ionic strength) and their interactions, and allows the selection of optimal experimental conditions to maximise adsorption performance. The biochars were prepared by pyrolysis at 500 °C and 800 °C (BC-500 and BC-800) and the ZnCl2-activated biochars were prepared at 650 °C and 800 °C (AcBC-650 and AcBC-800). The FTIR spectra revealed that increasing the pyrolysis temperature without activator decreases the intensity of all bands, while activation preserves functional groups, as evidenced by the spectra of AcBC-650 and AcBC-800. High temperatures during activation promoted the development of an efficient surface area, with the maximum observed for AcBC-800 reaching 347 m2 g−1. AcBC-800 was found to be the most efficient adsorbent with removal efficiencies of 34.1, 51.3, 55.9 and 38.2 % for atenolol, paracetamol, ketorolac and tetracycline, respectively. The models describing the relationship between the removal efficiency of AcBC-800 and the experimental factors studied, showed satisfactory predictive ability (predicted R2 > 0.8) and no significant lack-of-fit was observed. The results obtained, including the mathematical models, the properties of the adsorbates and the adsorbents, clearly indicate that the adsorption mechanisms of activated biochars are mainly based on hydrophobic interactions, pore filling and hydrogen bonding.
Display omitted
•Carbonaceous materials derived from Ailanthus altissima as potential adsorbents.•Design of Experiments (DoE) in identification of significant factors interactions.•Adsorption mechanisms insight by DoE and careful selection of model substances.•Ailanthus altissima biomass contributes to sustainability of adsorbent production.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•Nano NiFe2O4 powders were prepared under sub- and supercritical conditions of EtOH.•Supercritical synthesis shows higher NiFe2O4 conversion and lower α-Fe2O3 content.•These NiFe2O4 ...powder have mesoporous structure with uniformly sized particles.•Both powders have much better magnetic properties: remanence and coercivity.•Powder obtained under supercritical conditions have higher squareness ratio.
Nano-crystalline nickel ferrite has a broad range of applications due to its favourable magnetic properties. Those characteristics can be significantly influenced by the synthesis pathway including methods conducted in the presence of supercritical alcohols. Nano-crystalline NiFe2O4 powders were obtained in the reaction under subcritical and supercritical conditions of ethanol. Both high pressure synthesis routes resulted in powders with smaller primary particles and higher mesoporosity than co-precipitation method. Upon the annealing treatment the average crystallite size increased while material structure remained uniform, resulting in significantly enhanced magnetic properties, such as coercivity and remanence. It was found that synthesis under supercritical conditions provides higher conversion but also material with larger average crystallite size upon annealing. The time and temperature of annealing stage significantly influenced the morphology and magnetic properties of the obtained powders.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Flotation tailings rich in carbonate minerals from the tailings deposit of the copper mine Majdanpek (Serbia) were applied for neutralization of the water taken from the extremely acidic Lake Robule ...(Bor, Serbia). Tests conducted in Erlenmeyer flasks showed that after neutralization of the lake water to pH 7, over 99% of aluminum (Al), iron (Fe), and copper (Cu) precipitated, as well as 92% of Zn and 98% of Pb. In order to remove residual Mn and Ag, the water was further treated with NaOH. After treatment with NaOH, all concentrations of the metals in the lake water samples were below discharge limits for municipal wastewater according to the national legislation of the Republic of Serbia. The results of this work suggest that mining waste could be used for active neutralization of the acid mine drainage. The use of the mining waste instead of lime could reduce the costs of the active treatment of the acid mine drainage.
This paper presents the experimental investigation results of the polymetallic copper concentrate oxidation process with the oxygen from the air. Concentrate characterization included chemical ...analysis, X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), and light microscopy. Chemical analysis and EDXRF results showed that the investigated copper concentrate consisted mainly of copper, iron and sulphur, with small amounts of zinc, lead, arsenic and other minor elements. XRD analysis showed that metals were bonded to sulphur in sulphide minerals: chalcopyrite, pyrite, luzonite, sphalerite and enargite. Those minerals were mutually bonded into aggregates, confirmed by light microscopy. The results of DTA/TG analysis were used for determining the mechanism of the oxidation process. Comparison between experimental data obtained by XRD, DTA/TG and data obtained from the phase stability diagrams, implied that the oxidation process of the investigated concentrate can be divided in two stages: the first stage consisted of sulphide oxidation reactions with the characteristic exothermal effects below 973 K while forming sulphates and oxysulphates, and the second stage, which consisted of sulphates and oxysulphates decomposition reactions and forming copper and iron oxides, with endothermal effects above 973 K. Kinetic studies were carried out in isothermal conditions in the temperature range (573–873) K. Calculations were done according to Sharp’s method of reduced half-time reaction. Calculated values for the activation energies were 82 kJ mol
−1
for the initial stage of the oxidation process (up to 723 K), and 42 kJ mol
−1
for the stage of the process where desulphurization degree reached 68–86 % for the oxidation temperatures 748 K and higher. Calculated activation energy values indicated that the reaction of oxidation is a chemically controlled reaction.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Titanium alloys have been present for decades as the main components for the production of various orthopedic and dental elements. However, modern times require titanium alloys with a low Young’s ...modulus, and without the presence of cytotoxic alloying elements. Machine learning was used with aim to analyze biocompatible titanium alloys and predict the composition of Ti alloys with a low Young’s modulus. A database was created using experimental data for alloy composition, Young’s modulus, and mechanical and thermal properties of biocompatible titanium alloys. The Extra Tree Regression model was built to predict the Young’s modulus of titanium alloys. By processing data of 246 alloys, the specific heat was discovered to be the most influential parameter that contributes to the lowering of the Young’s modulus of titanium alloys. Further, the Monte Carlo method was used to predict the composition of future alloys with the desired properties. Simulation results of ten million samples, with predefined conditions for obtaining titanium alloys with a Young’s modulus lower than 70 GPa, show that it is possible to obtain several multicomponent alloys, consisting of five main elements: titanium, zirconium, tin, manganese and niobium.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Selective arsenic extraction from enargite based complex concentrate from
Copper Mine in Bor (Serbia), using sodium hypochlorite as a leaching agent,
was investigated in this paper. The aim was to ...assess the optimal conditions
for the most efficient arsenic removal from the investigated concentrate,
based on factorial design applied to experimentally obtained data. Five
important factors with three factor levels were used as the input variables
and experimentally obtained arsenic extraction yield was taken as the output
variable. The first and the second final order model equations were obtained.
It was found that the leaching temperature had the strongest effect on the
arsenic extraction. The strongest positive interaction was between the sodium
hypochlorite molar concentration and the stirring speed during extraction.
This paper presents mineralogical and crystallographic characterization of
the zeolitic tuff from the Novakovic deposit, Republic of Bosnia and
Herzegovina. The zeolitic tuff is of a whitish color ...composed of
Ca-clinoptilolite and an amorphous phase (volcanic glass and amorphous
SiO2). The zeolitic tuff was analyzed by X-ray diffraction of the
polycrystalline sample (XRPD), scanning electron microscopy and energy
dispersive spectroscopy (SEM/EDS), and differential thermal and thermo-
gravimetric (DTA/DTG) methods. According to the results obtained, it can be
concluded that the studied zeolitic tuff is composed of Heu-type minerals.
Based on the chemical analysis, thermal treatment and XRPD analysis it was
determined that this is a mineral Ca-clinoptilolite. Thermal analysis in the
temperature range from 300 up to 700?C showed that the examined zeolite
minerals from the Novakovic deposit are stable up to the temperature of
600?C. The crystal structure of Ca-clinoptilolite has been refined in the
centrosymmetric space group C2/m (S.G. 12) with disordered distribution
of Al and Si in the tetrahedral framework. The unit-cell parameters are
as follows: a = 17.662 ?, b = 17.874 ?, c = 7.402 ?, ? = 116.32?
and V = 2122.73 ?3. The basic structural motif is represented by four
channels. Three channels are composed of eight-membered rings, and one of
ten-membered rings. The ten-membered (channel A) and one eight-membered
channel (B) are parallel to the crystallographic axis c, and the other
eight-membered channel is parallel to the a-axis. Ca-clinoptilolite
comprises approximately 90 % of the studied zeolite tuff while the rest 10 %
is the amorphous phase. The overall cation exchange capacity (CEC) amounts
to 187 mmolM+/100g, and calcium represents the most abundant cation in the
studied sample. The atomic ratios of Si/Al, Na+/(Na++K+), and
Ca2+/(Ca2++Mg2+) are as follows: 4.36, 0.14, and 0.55, respectively. The
zeolite tuff is both thermally and structurally stable and has applications
in various areas of industry and agriculture.
PDF
