Papers by Velizar Stanković
Metals
The study on the biosorption of copper ions using raw eggshells as an adsorbent is presented in t... more The study on the biosorption of copper ions using raw eggshells as an adsorbent is presented in this paper. The influence of different process parameters, such as: initial pH value of the solution, initial Cu2+ ions concentration, initial mass of the adsorbent, and stirring rate, on the biosorption capacity was evaluated. The SEM-EDS analysis was performed before and after the biosorption process. SEM micrographs indicate a change in the morphology of the sample after the biosorption process. The obtained EDS spectra indicated that K, Ca, and Mg were possibly exchanged with Cu2+ ions during the biosorption process. The equilibrium analysis showed that the Langmuir isotherm model best describes the experimental data. Four kinetic models were used to analyze the experimental data, and the results revealed that the pseudo-first order kinetic model is the best fit for the analyzed data. Calculated thermodynamic data indicated that the biosorption process is spontaneous, and that copper ...
![Research paper thumbnail of Solvent extraction of silver from nitric acid solutions by calix[4]arene amide derivatives](https://attachments.academia-assets.com/104519849/thumbnails/1.jpg)
Separation and Purification Technology, 2008
Solvent extraction experiments were carried out to recover silver from nitric acid solutions usin... more Solvent extraction experiments were carried out to recover silver from nitric acid solutions using as the extractants calix[4]arene tetramide (LBC) and its thio-analogue (THIO) dissolved in dichloromethane. The stoichiometry of the formation of the silver-calixarene complex differs depending on the used extractant. It was shown that one silver ion reacts with a single molecule of LBC, while two silver ions are extracted with a single THIO molecule. Very high percent extractions (>90% with LBC and >99% with THIO) were achieved with both extractants by just adding surplus extractant (THIO: 0.6 mol/mol Ag + and LBC: 1.4-1.5 mol/mol Ag +). Based on equilibrium data, the extraction isotherm relationship and the extraction constant K ex for each extractant were derived. The extraction results show that THIO is an efficient extractant extracting silver either from acid or from neutral solutions with the same efficiency. Nitric acid, in the concentration range from 0 to 0.1 mol dm −3 , strongly affects the extraction capability of LBC in less acidic solutions, reducing the percent extraction down to 40%. LBC extracts both silver and sodium collectively and with the same efficiency. The selectivity coefficient has a value close to unity (β ≈ 1). THIO has demonstrated extremely high selectivity for silver over sodium in a mixture. Stripping of silver was performed by two-phase electrowinning from the loaded organic phase, thereby achieving a high stripping degree (50-90%) and reasonably high current efficiency (60-90%). The calixarenes did not change their extraction features during the electrowinning process and can be reused for extraction many times.
Revista de Chimie, 2020
Lead ions removal from aqueous solutions onto bean shells is presented in this paper. The experim... more Lead ions removal from aqueous solutions onto bean shells is presented in this paper. The experiments were conducted in a batch system. The bean shells samples were rinsed with distilled water before the adsorption experiments. The analysis of the rinsed water showed that a significant amount of alkali and alkaline-earth metal ions are transferred from the adsorbent structure into the rinsed solution during the rinsing process. The COD analysis showed that these waters should be treated before being discharged into the surrounding watercourses. The influence of different process parameters (the pH value of the solution, the initial metal ions concentration, and the initial mass of the adsorbent) on the adsorption capacity was investigated. The adsorption capacity was higher at higher pH values of the solution. The adsorption capacity showed a decrease with the increase in the mass of the adsorbent. The increase in the initial metal ions concentration was shown to lead to an increase...
Biosorption of copper ions onto wheat straw
Zbornik radova Tehnološkog fakulteta, Leskovac, 2011
Electrodepostion of Gold Onto a Substrate in a Fluidized Bed of Innert Particles
Ispitivana je elektrodepozicija prevlaka zlata iz citratnih rastvora u fluidizovanom sloju inertn... more Ispitivana je elektrodepozicija prevlaka zlata iz citratnih rastvora u fluidizovanom sloju inertnih cestica i van sloja, pri razlicitim strujnim i hidrodinamickim uslovima. Doprinos sloja fluidizovanih cestica procesu depozicije zlata bio je dvojak. Brzina procesa depozicije povecava se u fluidizovanom sloju za 4 -6 puta, zavisno od stepena fluidizacije. Ovo ima za posledicu odgovarajuce skracenje vremena depozicije da se dobije prevlaka iste debljine kao pri konvencionalnom pozlacivanju. Pored ovoga, kvalitet dobijene prevlake zlata u fluidizovanom sloju bio je veci od onoga dobijenog izvan sloja, pri istim ostalim uslovima. Zahvaljujuci bombardovanju povrsine substrata cesticama, dobijene prevlake su bile sjajnije, adhezivnije, kompaktnije i sa mnogo manje izraženim efektom ivica od onih dobijenih u konvencionalnom kupatilu.
Characteristics of Wastewater Streams Within the Bor Copper Mine and Their Influence on Pollution of the Timok River, Serbia
Mine Water and the Environment, 2016
Wastewaters produced by mining and metallurgical treatment of polymetallic sulfide ores have poll... more Wastewaters produced by mining and metallurgical treatment of polymetallic sulfide ores have polluted the Timok River in Serbia for more than 100 years. We have characterized seven different wastewater streams within the RTB Bor facilities, investigating their influence on pollution of the Timok River before its confluence with the Danube River. Their relative contribution was calculated by considering the contaminant load of each wastewater stream and non-conservative transport along their flow paths. Three sampling spots in the Timok River, before and after its confluence with the Borska River, were also monitored.ZusammenfassungAbwässer aus der Gewinnung und Verhüttung polymetallischer Sulfiderze belasten das Timok-Fließsystem in Serbien seit mehr als 100 Jahren. Wir haben sieben verschiedene Abwasserströme innerhalb der RTB Bor-Anlagen charakterisiert und deren Einfluss auf die Kontamination des Flusses Timok vor seiner Mündung in die Donau untersucht. Der relative Anteil der einzelnen Abwässerströme entlang des Fließpfades wurde durch Frachtbetrachtungen jedes Abwasserteilstromes und einer nicht-konservativen Transportberechnung bestimmt. Drei Probeentnahmestellen im Timok-Fluss vor und nach dem Zufluss des Borska Flusses wurden zusätzlich beobachtet.ResumenLas aguas residuales producidas por la explotación minera y el tratamiento metalúrgico de minerales sulfurados polimetálicos, ha contaminado el Río Timok en Serbia por más de 100 años. Hemos caracterizado siete diferentes cursos de aguas residuales dentro de las instalaciones de RTB Bor, investigando sus influencias sobre la contaminación del Río Timok antes de su confluencia con el Río Danubio. Sus contribuciones relativas fueron calculadas considerando la carga de contaminante de cada curso de agua y el transporte no conservativo a lo largo de su curso. También se monitorearon muestras en el Río Timok, antes y después de su confluencia con el Río Borska.摘要多金属硫化物采矿及冶炼废水已经污染塞尔维亚(Serbia)蒂莫克河(Timok River)100多年。描述了RTB Bor铜矿区内七条污水溪的特征,研究了它们汇入丹纽博河(Danube River)前对蒂莫克河(Timok River)潜在污染。通过分析每条污水溪的污染荷载及沿程非保留运移计算了它们对蒂莫克河(Timok River)污染的贡献。同时,在蒂莫克河(Timok River)汇入博斯卡河(Borska River)前后,亦设立了三个取样监测点。
Journal of Engineering, 2013
Ficus benghalensisL., a plant-based material leaf powder, is used as an adsorbent for the removal... more Ficus benghalensisL., a plant-based material leaf powder, is used as an adsorbent for the removal of lead ions from aqueous solution using the biosorption technique. The effects of process parameters such as contact time, adsorbent size and dosage, initial lead ion concentration, and pH of the aqueous solution on bio-sorption of lead byFicus benghalensisL. were studied using batch process. The Langmuir isotherm was more suitable for biosorption followed by Freundlich and Temkin isotherms with a maximum adsorption capacity of 28.63 mg/g of lead ion on the biomass ofFicus benghalensisL. leaves.
Journal of Engineering, 2013
Ficus benghalensisL., a plant-based material leaf powder, is used as an adsorbent for the removal... more Ficus benghalensisL., a plant-based material leaf powder, is used as an adsorbent for the removal of lead ions from aqueous solution using the biosorption technique. The effects of process parameters such as contact time, adsorbent size and dosage, initial lead ion concentration, and pH of the aqueous solution on bio-sorption of lead byFicus benghalensisL. were studied using batch process. The Langmuir isotherm was more suitable for biosorption followed by Freundlich and Temkin isotherms with a maximum adsorption capacity of 28.63 mg/g of lead ion on the biomass ofFicus benghalensisL. leaves.
Transient behavior of electrochemical promotion of gas-phase catalytic reactions
Journal of Electroanalytical Chemistry, 2002
Electrochemical promotion (EP) of gas-phase catalysis with O2−-conducting solid electrolytes is a... more Electrochemical promotion (EP) of gas-phase catalysis with O2−-conducting solid electrolytes is addressed. The behavior of the reference electrode, prepared by deposition of a gold film, was found to be quasi-reversible, 12O2/O2− being the potential determining redox couple. A fairly symmetrical potential distribution in the electrochemical cell was calculated. The IR drop correction was shown to be negligible at low currents
Limiting current density and specific energy consumption in electrochemical cells with inert turbulence promoters
Journal of Applied Electrochemistry, 1994
ABSTRACT
Journal of Applied Electrochemistry, 1995
Pressure drop in a three-dimensional packed bed electrode cell has been investigated during elect... more Pressure drop in a three-dimensional packed bed electrode cell has been investigated during electrowinning of copper with simultaneous hydrogen evolution. The presence of gas bubbles in the packed bed electrode leads to an increase in the pressure drop in the electrolyte flowing through the cell. This pressure drop increase was in the range of 30 to 70% relative to the bubble-free case. Parameters such as current density, electrolyte velocity and particle shape greatly influence the pressure drop behaviour. Experimental results are correlated using the Ergun equation and show satisfactorily good agreement in the investigated range of modified Reynolds number.
A particulate vortex bed cell for electrowinning: operational modes and current efficiency
Journal of Applied Electrochemistry, 1984
The process of electrowinning of copper ions from dilute solutions has been used as a model syste... more The process of electrowinning of copper ions from dilute solutions has been used as a model system to assess the performance of a vortex bed cell with a three-dimensional cathode of conducting particles. Experiments were carried out under three conditions: with ...
Journal of Mining and Metallurgy A: Mining, 2016
This paper deals with the investigation of column leaching of low-grade ores from the copper mine... more This paper deals with the investigation of column leaching of low-grade ores from the copper mine Cerovo, Serbia (the approximate Cu content in the ore ranges from 0.2-0.3 % with >10 % copper in the form of oxide minerals). The leaching experiments were performed using sulphuric acid solutions, whereby the kinetics of copper leaching was investigated with respect to acid concentration and solid to liquid ratio. The copper concentration in the leach solution ranged from 0.80 to 1.75 g dm-3. The total Cu recovery rate ranged from 30 to 56 %, whereas the recovery rate of copper oxide minerals ranged from 67 to 100 %. Furthermore, with increasing the amount of liquid phase, copper recovery increases as well, and copper oxide minerals were completely leached out. Besides copper ions, considerably high ferrous/ferric ion concentrations were achieved in the leach solution. This concentration was sufficiently high for the use of either solvent extraction or ion exchange techniques or both for further treatment of the leach solution.
Chemical Industry and Chemical Engineering Quarterly, 2021
A new process for mine water purification has been proposed, based on biosorption followed by bur... more A new process for mine water purification has been proposed, based on biosorption followed by burning of the loaded biosorbents. Wheat straw and sawdust of trees are both convenient as biosorbents in the proposed process. Biosorption was performed in two stages, in a cross-flow regime between the mine water and the biosorbent. The achieved copper adsorption de-gree was > 95%. Based on the mine water volume and its chemical composition, the estimated amount of the biosorbent was 60.000 t/year. The cogenerative mode of the loaded biosorbent combustion was considered for green energy production. For recovery of metals, which are concentrated in the ash, it must be processed separately. Several possibilities of the ash pro-cessing were proposed and discussed. For an annual volume of mine water and the copper content in it, the balance of mass and energy of the process were both estimated, giving some economic data on the process efficiency. The analysis of the revenues and costs, bas...
Journal of Mining and Metallurgy A: Mining
Through this study special attention was paid to AMDs, originating from copper mines, containing ... more Through this study special attention was paid to AMDs, originating from copper mines, containing different heavy metal ions, and a certain amount of sulphuric acid. The research was conducted on the territory encompassing the RTB Bor mines (now Serbia Zijin Bor Copper). The AMDs occurrences, their water composition, metal potential, and impact on the local surface waters were determined. The major amount of mine waters flow into the Krivelj River damaging extremely its water quality. The research also included monitoring the Timok river water quality along its course from the Krivelj River inflow to the confluence with the Danube. Evaluating the metal losses, it was found that every year around 360 tons of copper, >500 tons of iron, and 30 tons of zinc from mine waters are lost, as being transported via the Krivelj River to the Timok and then to the Danube.
Chemical Industry and Chemical Engineering Quarterly
Flotation waste, which was produced through seventy years of copper ore processing in RTB Bor, Se... more Flotation waste, which was produced through seventy years of copper ore processing in RTB Bor, Serbia, is deposited in a flotation tailings pond. In total, almost 26.4 Mt could be considered as available for eventual reprocessing and reuse. Chemical analysis has shown that an average concentration of targeted metals in the tailings is: 0.183% Cu, 0.35 g/t Au and 2.17 g/t Ag. The tailings contain 60 to 70% of SiO2, 10 to 17% of Al2O3 and pyrite 5 to 8%. Flotation tailings reprocessing consisted of acid leaching followed by re-flotation of the leach residue. Leaching of the tailings resulted in leach liquors containing Cu2+ ions from 50 to 580 ppm. The average copper removal degree in the leaching stage was 70%. After re-flotation, the total copper removal degree reached 83 to 85%. Sulphur removal degree reached 77%. Sulphur concentration in the treated tailings was reduced almost 5 times compared to the inlet concentration. An equivalent amount of iron was also reduced through the fl...
Mine waters from Mining and Smelting Basin Bor: A resource for the recovery of copper or polluter of the environment
Long-term exploitation and copper ore processing in Bor has led to degradation wide areas of land... more Long-term exploitation and copper ore processing in Bor has led to degradation wide areas of land by depositing huge amounts of mining waste and the appearance of mine wastewaters in them. Mine waters are the result of spontaneous leaching process of mining waste and take the form of excess water collection and natural resources. Within the active and abandoned copper mines in Bor, great quantity of mine waters has been produced, similar in composition, but different in concentration of heavy metals, with different flow and potential on copper as a possible useful product and now as a pollutant of surface water flows. There are nine sources of mine waters in Mining Basin Bor whose potential on copper varies between 350 and 420 tones per year. So far, only a small amount of copper from mine waters is being recovered (~17% Cu) while the remaining part is lost flowing into the Krivelj River, and further to the Timok and Danube. By collecting the mine wastewaters from the individual sou...
Acta Chimica Slovenica, 1996
Process of electrochemical deposition of gold from citrate solution, with and without thallium, h... more Process of electrochemical deposition of gold from citrate solution, with and without thallium, has been studied using a rotating disc electrode (RDE) and linear sweep voltammetry. RDE was made of monocrystal silicon wafer, layered by a thin film of vaporized gold as a substrate. Obtained results shown that the limiting current density is not achieved in citrate and thallium free electrolyte. The rotation speed had significant influence on the process rate at lower temperatures. At elevated temperatures gold deposition occurred in a kinetic domain. Tafel slopes confirmed that the electrochemical reaction occurs in two steps depending on electrode potential and the presence of thallium ions in the electrolyte. The reaction kinetics is changed in the presence of thallium ions, as well. The mechanism of gold deposition is predominantly dependent on the electrolyte composition. In the citrate solution, free of thallium, the adsorption of Au(CN)- and CN- on the electrode surface is presu...
NICKEL-TiO2 COMPOSITE COATINGS – SURFACE CHARACTERIZATION
Nickel coatings onto brass substrate were produced from conventional suspensions consisted from a... more Nickel coatings onto brass substrate were produced from conventional suspensions consisted from a conventional nickel sulphate bath and fine TiO2 particles (dp < 1µm) kept in suspension by magnetic stirrer. Composite coatings were obtained at different current densities and different concentrations of particles in suspensions for a constant process time and constant temperature. Composite coatings were characterised by means of optical and SEM micrographs, by XRD analysis as well as by determining surface roughness parameters. Metallographic analysis has also been done. Coatings obtained from the pure electrolyte under the same other experimental conditions served as an standard for comparison. It was found that the presence of TiO2 particles in the electrolyte cause an embedment of particles into deposited metal, changing physical characteristics of produced composite. Particles were embedded as smaller or bigger agglomerates at the surface rather than individual ones. Current d...
Journal of Mining and Metallurgy, Section B: Metallurgy
Composite nickel coatings on a brass substrate were produced from suspensions consisted of a conv... more Composite nickel coatings on a brass substrate were produced from suspensions consisted of a conventional nickel sulphate bath and fine TiO2 particles (dp < 0.35 ?m). Characterization of coatings surface was performed by using optical and SEM micrographs, by EDS analysis and by determining the surface roughness parameters. Metallographic analysis has also been done in order to get an insight about particles distribution throughout the thickness of the coating layer. Presence of TiO2 particles in electrodeposited metal affected the surface morphology. Particles were embedded as smaller or bigger agglomerates within the coatings, as well as the individual particles. Metallographic analysis showed uniform distribution of particles and their agglomerates within the coating. Surface roughness parameters of the composites have had up to 35 times higher values than the ones of the pure nickel coatings. Roughness maxima appeared at the concentration of particles between 10 and 20 g dm-3....
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Papers by Velizar Stanković