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Jovanovic I.,Mining and Metallurgy Institute Bor | Miljanovic I.,University of Belgrade
Archives of Mining Sciences | Year: 2015

Flotation process modelling is not a simple task, mostly because of the process complexity, i.e. the presence of a large number of variables that (to a lesser or a greater extent) affect the final outcome of the mineral particles separation based on the differences in their surface properties. The attempts toward the development of the quantitative predictive model that would fully describe the operation of an industrial flotation plant started in the middle of past century and it lasts to this day. This paper gives a review of published research activities directed toward the development of flotation models based on the classical mathematical rules. The description and systematization of classical flotation models were performed according to the available references, with emphasize exclusively given to the flotation process modelling, regardless of the model application in a certain control system. In accordance with the contemporary considerations, models were classified as the empirical, probabilistic, kinetic and population balance types. Each model type is presented through the aspects of flotation modelling at the macro and micro process levels. © 2015 Archives of Mining Sciences.

Dimitrijevic S.,Mining and Metallurgy Institute Bor | Rajcic-Vujasinovic M.,University of Belgrade | Trujic V.,Mining and Metallurgy Institute Bor
International Journal of Electrochemical Science | Year: 2013

Nowadays, the cyanide and ferrous cyanide solutions are used in practice for gold plating. The traditional baths employed for soft gold as well as hard gold plating contain the cyanide complex, [Au(CN)2]-, as the source of gold, which release free cyanide ions during the plating. Those compounds are very toxic, and formation and maintenance of cyanide baths is expensive and risky for technical personnel; also, they attack photoresists used to delineate circuit patterns and bonding pads. Due to this reason, and especially in modern time, there is a trend of using the electrolytes without content of cyanides. These electrolytes are mainly based on some organic compounds. This article is an overview of the non-cyanide electrolytes for gold plating introduced into practice or only tested in the laboratory. The large number of investigated complexes fulfils the coating quality requests, but there are problems related to their stability. Decorative gold plating obtained from classic cyanide electrolyte and an electrolyte based on mercaptotriazole have shown similar characteristics such as microhardness, surface roughness, visual appearance and adhesion. At the same time, this bath remained stable in a period of at least nine months. © 2013 by ESG.

Bogdanovic D.,University of Belgrade | Miletic S.,Mining and Metallurgy Institute Bor
Economic Computation and Economic Cybernetics Studies and Research | Year: 2015

Personnel evaluation is a multicriteria decision making problem that can significantly affect the future caracteristics and the performance of an organization. The aim of this paper is to demonstrate the implementation of an integrated approach that employs AHP and PROMETHEE together for selecting the most suitable personnel from existing organization manpower in process of its reorganization and downsizing. The essence of the problem is how to minimize subjectivism of decision maker(s), that unfortunately, dominates in this process in Serbia. The related problem includes a Serbian company’s department with five employers that has to be reorganized with reduction of employees on three. The AHP is used to analyze the structure of the personnel selection problem and to determine the criteria weights, and PROMETHEE method is used to obtain the final ranking. The results have shown that the proposed integrated method can be successfully used in solving managerial problems. © 2015, Academy of Economic Studies. All rights reserved.

Stankovic V.,University of Belgrade | Gorgievski M.,University of Belgrade | Bozic D.,Mining and Metallurgy Institute Bor
Biomass and Bioenergy | Year: 2016

Cross-flow washing of wheat straw and beech sawdust with water was carried out in order to leach the alkali and alkaline earth metals from them. Incremental concentration change (C = δm/δV) of alkali and alkaline-earth metals in the leachate was plotted against the wash water volume. Maximum increase in δm/δV was achieved after passing 0.04 to 0.06 dm3 of water through the washed biomass. After passing 0.2 dm3 of water through the biomass, leaching of alkali metals was practically completed. Concentration of potassium ion was predominant in the leachate. From the whole amount of alkali and alkaline-earth metal ions, found in the aqueous phase after washing, K+ ions make about 80% in case of wheat straw and 64% in case of beech sawdust. Concentration of other considered metal ions was much less comparing to the potassium ones.Change in the pH and electrical conductivity (EC) were measured after passing of each portion of wash water through the biomass. Change of the EC against the wash water volume follows fairly the change of leachate composition. Based on the experimental results, the process of alkali and alkaline-earth metals leaching was modelled assuming the cross-flow scheme of leaching process. Proposed model follows fairly the experimental data. Discrepancy between the experimental and calculated values for alkaline-earth metals in case of beech sawdust is attributed to a different leaching mechanism. © 2016 Elsevier Ltd.

Stevic Z.,University of Belgrade | Radovanovic I.,University of Belgrade | Rajcic-Vujasinovic M.,University of Belgrade | Bugarinovic S.,Mining and Metallurgy Institute Bor | Grekulovic V.,University of Belgrade
Journal of Renewable and Sustainable Energy | Year: 2013

In this paper a brief overview of research in the field of electrode materials for solar cells and supercapacitors is presented, which the authors dealt with for years. In addition to the standard electrode material (graphite and silicon in supercapacitor with solar cells), different materials were examined, particularly oxides and sulfides of copper. Copper (I) oxide or cuprous oxide is an oxide semiconductor which is used as the anodic material in the form of thin film in lithium batteries and solar cells. The cathodic process of synthesis of cuprous oxide thin film is carried out in a potentiostatic mode from the organic electrolyte. The electrochemical characterization was carried out by cyclic voltammetry. The electro deposition techniques are particularly well suited for the deposition of single elements, but it is also possible to carry out simultaneous depositions of several elements and syntheses of well-defined alternating layers of metals and oxides with thicknesses down to a few nanometers. Electrochemical characteristics of covellite (CuS) are of importance from flotation and metallurgical point of view, due to its potential application in solid state solar cells and in photocatalytic reactions. Also, the compound CuS appears as an intermediary product or a final product in electrochemical oxidation reactions of chalcocite (Cu2S) which exhibits supercapacitor characteristics. Natural copper mineral covellite has been investigated in inorganic sulfate acid electrolytes, as well as in strong alkaline electrolyte. Different electrochemical methods (galvanostatic, potentiostatic, cyclic voltammetry, and electrochemical impedance spectroscopy) have been used in these investigations. © 2013 AIP Publishing LLC.

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