Milan M. Antonijević

Kinetics of chalcopyrite dissolution by hydrogen peroxide in sulphuric acid

Abstract The extraction of copper from a chalcopyrite concentrate by hydrogen peroxide in sulphuric acid solutions was studied. The influence of various parameters was investigated in order to elucidate the kinetics of chalcopyrite dissolution. It was determined that stirring speed had no effect on the rate of chalcopyrite dissolution, which suggested that reaction was not controlled by liquid-phase diffusion. Dissolution curves were found to conform to the surface reaction controlled shrinking core model, i.e., 1−(1−X)1/3=kst. Both the magnitude of the activation energy of 60 kJ/mol and the linear relationship between the rate constant and the inverse particle radius support the fact that dissolution is controlled by the surface reaction. Hydrogen peroxide had great influence on the rate of chalcopyrite dissolution; a reaction order of unity was calculated with respect to the concentration of this oxidant. Sulphuric acid also had influence on chalcopyrite dissolution, with a reaction order of 0.3 with respect to the acid concentration being established.

Leaching of pyrite with hydrogen peroxide in sulphuric acid

Abstract The kinetics of leaching pyrite with hydrogen peroxide in sulphuric acid were investigated. The parameters studied were: stirring speed, temperature, particle size and concentrations of H 2 O 2 and H 2 SO 4 . The effects of SO 4 2− and H + additions were also investigated. The leaching rate decreases with increasing stirring speed and H 2 SO 4 concentration. The kinetics of pyrite dissolution are described by means of the surface reaction control shrinking core model. This is supported by an activation energy of 68 kJ/mol and a linear relationship between the rate constant and the inverse of the particle radius. The consumption of H 2 O 2 is greater than that stoichiometrically required, due to its catalytic decomposition. The leaching rate is first order with respect to H 2 O 2 . Additions of SO 4 2− have a negative influence on the leaching rate, whereas H + additions have a beneficial effect. A reaction mechanism is proposed.

Investigation of the possibility of copper recovery from the flotation tailings by acid leaching

The flotation tailings pond of the Bor Copper Mine poses a great ecological problem not only for the town of Bor but also for the surrounding soils and watercourses. Since the old flotation tailings contain about 0.2% of copper on the average, we investigated their leaching with sulphuric acid in the absence and presence of an oxidant. The aim was to determine the leaching kinetics of copper and iron as affected by various factors such as: the pH value of the leach solution, stirring speed, pulp density, particle size, concentration of ferric ions, temperature and time for leaching. The average copper and iron recovery obtained was from 60% to 70% and from 2% to 3%, respectively. These results indicate that the old flotation tailings pond represents an important source of secondary raw material for the extraction of copper and that it should be valorized rather than land reclamation. At the end of the paper, a mechanism of dissolution of copper and iron minerals from the tailings was described.

Kinetics of pyrite dissolution by hydrogen peroxide in perchloric acid

Abstract The kinetics of pyrite dissolution by hydrogen peroxide in perchloric acid were investigated. The effects of stirring speed, temperature, hydrogen peroxide and perchloric acid concentrations and particle size were examined. The activation energy was calculated to be 57 kJ/mol, indicating that the dissolution of pyrite is chemically controlled. The order of the reaction with respect to hydrogen peroxide was found to be approximately 1. The perchloric acid concentration had practically no effect on the rate of pyrite dissolution. In addition, the effects of H + , ClO 4 − , and SO 4 2− ions were examined.

Concentrations of particulate matter and arsenic in Bor (Serbia).

Measurements of air quality in the territory of Bor (Serbia) were performed at the sampling sites in the urban-industrial, suburban and rural area during the 2003-2008 period. A high level of arsenic (As) concentration in suspended particulate matter (PM) is of a predominantly industrial origin. The major source of pollution is the copper smelter which is situated in the close vicinity of the urban area of Bor. The ambient level of PM and As is influenced by meteorological parameters as well as the remoteness from the copper smelter. Continual exceedances of the annual limit value (LV) for As (6 ng m(-3)) were recorded at the sampling sites in the urban-industrial and suburban area. Maximum annual As concentrations were recorded at Town Park (46.5 ng m(-3)) in 2004, Institute (95.4 ng m(-3)) in 2004 and Jugopetrol (74.5 ng m(-3)) in 2003. In the past 15 years not a single mean annual As concentration recorded at the sampling sites Town Park, Institute and Jugopetrol has been within the LV. When the average annual and maximum monthly As concentrations are compared, it can be concluded that the level of pollution is higher in the urban-industrial and suburban areas than in the rural area.

Investigation of the kinetics of pyrite oxidation by hydrogen peroxide in hydrochloric acid solutions

Abstract The kinetics of pyrite oxidation by hydrogen peroxide in hydrochloric acid solutions were investigated. The effects of stirring, temperature, particle size as well as hydrogen peroxide and hydrochloric acid concentrations were studied. The effects of H+ and Cl− additions were also examined. The oxidation kinetics were found to follow a shrinking core model, with the surface chemical reaction as the rate-controlling step. This is in accord with an activation energy of 65 kJ/mol and a linear relationship between the rate constant and the reciprocal of the particle radius. The reaction order with respect to hydrogen peroxide concentration was found to be 1.32. The rate of pyrite oxidation was found to decrease as the hydrochloric acid concentration increases, most likely owing to the adsorption of chloride ions onto the surface of the pyrite particles. H+ ions had no effect on the rate, whereas Cl− ions had an effect similar to that of the hydrochloric acid.

Investigation of the kinetics of chalcopyrite oxidation by potassium dichromate

Abstract The kinetics of chalcopyrite oxidation by potassium dichromate in sulphuric acid were investigated. The effects of stirring rate, temperature, dichromate concentration, sulphuric acid concentration and particle size on the rate of chalcopyrite oxidation were examined. The activation energy is 48–54 kJ/mol, indicating that the rate of chalcopyrite oxidation is chemically controlled. The dichromate ion concentration had no effect on rate of chalcopyrite dissolution and, relative to sulphuric acid, an order of 0.80–0.92 was established. In addition, the effects of chloride, copper(() and iron(III) concentrations on the rate of chalcopyrite oxidation were investigated.

Assessment of the quality of polluted areas based on the content of heavy metals in different organs of the grapevine (Vitis vinifera) cv Tamjanika.

In this study, the samples of the spatial soil and organs of the grapevine (Vitis vinifera) cultivar Tamjanika were collected from the selected zones near the Mining and Smelting Complex Bor (East Serbia). They were analyzed by ICP-OES to determine the content of Cu, Zn, Pb, As, Cd, and Ni with the aim of ascertaining if these data may help in the assessment and improvement of the quality of environment in polluted areas such as Bor and its surrounding area. The results obtained from the calculated biological and enrichment factors, as well as from the Pearson correlation study and hierarchical cluster analysis confirmed that very useful information is recorded in plant organs: root, stem, leaves, and fruit. Yet, when the atmospheric pollution is the sphere of interest, the most informative data are found in unwashed leaves. The results of this study indicated also that the investigated plant species has some highly effective strategies involved in tolerance to the stress induced by heavy metals, which makes it an excellent candidate for phytostabilization purposes. Planting of this grapevine cultivar can be recommended in all areas that are severely polluted with heavy metals.

Inhibition of copper corrosion in acidic sulphate media by eco-friendly amino acid compound

This investigation aimed to study a “green” non-toxic biodegradable copper corrosion inhibitor in an acidic sodium sulphate solution. The methods used in the investigation of cysteine as a copper corrosion inhibitor in an acidic sodium sulphate solution were: potentiodynamic measurements, open circuit potential measurements, and chronoamperometric measurements. Optical microscopy was used in addition to electrochemical methods. Potentiodynamic measurements show that cysteine has good inhibitory properties in an acidic medium. Polarisation curves indicate that the presence of cysteine in a sulphate solution decreases the current density and that using various cysteine concentrations results in the formation of a protective film on the surface of the electrode due to the formation of the Cu(I)-cys complex. These results are confirmed by chronoamperometric measurements. Furthermore, it is clear from microphotographs that a protective film does form on copper electrode in the presence of cysteine. The Langmuir adsorption isotherm indicates that cysteine is chemisorbed on the surface of the electrode.

Investigation of pyrite oxidation by potassium dichromate

Abstract The results obtained in the investigation of the kinetics of pyrite oxidation by potassium dichromate in sulphuric acid are presented. The effects of temperature, dichromate and sulphuric acid concentrations, particle size and stirring speed were examined. The results obtained showed that the reaction is chemically controlled and that the activation energy is 50 kJ/mol. The concentration of dichromate ions had no effect on the rate of pyrite oxidation (zero order), whereas for sulphuric acid concentration a first order dependence was established. The rate of pyrite oxidation was also found to be independent of stirring speed. On the addition of chloride ions the rate of pyrite oxidation remained unchanged.