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This article presents the results of the statistical modeling of copper losses in the silicate slag of the sulfide concentrates smelting process. The aim of this study was to define the correlation dependence of the degree of copper losses in the silicate slag on the following parameters of technological processes: SiO2, FeO, Fe3O4, CaO and Al2O3 content in the slag and copper content in the matte. Multiple linear regression analysis (MLRA), artificial neural networks (ANNs) and adaptive network based fuzzy inference system (ANFIS) were used as tools for mathematical analysis of the indicated problem. The best correlation coefficient (R2 = 0.719) of the final model was obtained using the ANFIS modeling approach.

This paper presents the results of the tropospheric ozone concentration modeling as the dependence on volatile organic compounds - VOCs (Benzene, Toluene, m,p-Xylene, o-Xylene, Ethylbenzene); nonorganic compounds - NOx (NO, NO2, NOx, CO, H2S, SO2 and PM10) in the ambient air in parallel with the meteorological parameters: temperature, solar radiation, relative humidity, wind speed and direction. Modeling is based on measured results obtained during the year 2009. The measurements were performed at the measuring station located within an agricultural area, in vicinity of city of Zrenjanin (Serbian Banat, Serbia). Statistical analysis of obtained data, based on bivariate correlation analysis indicated that accurate modeling cannot be performed using linear statistics approach. Also, considering that almost all input variables have wide range of relative change (ratio of variance compared to range), nonlinear statistic analysis method based on only one rule describing the behavior of input variable, most certainly wouldn’t present accurate enough results. From that reason, modeling approach was based on Adaptive-Network-Based Fuzzy Inference System (ANFIS). Model obtained using ANFIS methodology resulted with high accuracy, with prediction potential of above 80%, considering that obtained determination coefficient for the final model was R2=0.802.

This paper presents the results of statistical modeling of the bauxite leaching process, as part of Bayer technology for an alumina production. Based on the data, collected during the period between 2008 - 2009 (659 days) from the industrial production in the alumina factory Birač, Zvornik (Bosnia and Herzegovina), the statistical modeling of the above mentioned process was performed. The dependant variable, which was the main target of the modeling procedure, was the degree of Al2O3 recovery from boehmite bauxite during the leaching process. The statistical model was developed as an attempt to define the dependence of the Al2O3 degree of recovery as a function of input variables of the leaching process: composition of bauxite, composition of the sodium aluminate solution and the caustic module of the solution before and after the leaching process. As the statistical modeling tools, Multiple Linear Regression Analysis (MLRA) and Artificial Neural Networks (ANNs) were used. The fitting level, obtained by using the MLRA, was R2 = 0.463, while ANN resulted with the value of R2 = 0.723. This way, the model, defined by using the ANN methodology, can be used for the efficient prediction of the Al2O3 degree of recovery as a function of the process inputs, under the industrial conditions of the alumina factory Birač, Zvornik. The proposed model also has got a universal character and, as such, is applicable in other factories practicing the Bayer technology for alumina production.

The results of an investigation of the mechanism and kinetics of the oxidation process of synthetic α-NiS are presented in this paper. The mechanism of α-NiS oxidation was investigated based on the comparative analysis of DTA-TG-DTG and XRD results, as well as the constructed phase stability diagrams (PSD) for the Ni-S-O system. The kinetic investigations of the oxidation process were performed under isothermal conditions (temperature range 823-1073 K). The obtained degrees of desulfurization were used in the calculation process according to the Sharp model and the kinetic parameters, inclu­ding the activation energies and the rate constants of the characteristic reac­tions, for the oxidation of α-NiS were determined. These results enabled the formulation of a kinetic equation for the desulfurization process: -ln (1 − α) = = k1τ = 27.89 exp(-9860/T)τ, with an activation energy of 82±4 kJ mol-1, for the first stage of the process and -ln (1 − α) = k2τ = 1.177 exp(-4810/T)τ, with an activation energy of 40±2 kJ mol-1, for the second stage.

The results of calculations of the thermodynamic properties of liquid Ag-In-Sb alloys are presented in this paper. The Redlich-Kister-Muggianu model was used for the calculations. Based on known thermodynamic data for constitutive binary systems and available experimental data for the investigated ternary system, the ternary interaction parameter for the liquid phase in the temperature range 1000-1200 K was determined. Comparison between experimental and calculated results showed their good mutual agreement.

Binary thermodynamic data, successfully used for phase diagram calculations of the binary systems In-Sb, Bi-Sb and In-Bi, were used fort the prediction of phase equilibria in the ternary system In-Sb-Bi at 300ºC. The predicted equilibria were compared with the results of SEM-EDX analysis.

The results of the calculation of the thermodynamic properties for liquid Ga-Sb-Tl alloys at the temperature 1073 K are presented in this paper. Initially, the most appropriate thermodynamic model for the investigated system was selected. Based on a comparison of the values calculated by different geometric models (Kohler, Muggianu, Toop, Hillert, Chou) with the existing experimental based data, asymmetric models of calculation were determined to give the best results. The asymmetric nature of the investigated ternary system was additionally confirmed by the Chou similarity coefficient concept. For these reasons, further complete thermodynamic calculations were performed according to the Hillert model in five sections of the ternary Ga-Sb-Tl system from each corner with the mole ratio of other two components being 9:1; 7:3; 5:5; 3:7 and 1:9. The obtained results include integral excess Gibbs energy dependences on composition for all the investigated sections. The calculated activity values at 1073 K for all components are given in the form of isoactivity diagrams. Comparison between the calculated and experimentally obtained gallium activities shows good agreement.

The kinetics of realgar (As2S2) oxidation was studied under isothermal and non-isothermal conditions. The obtained values of the activation energy indicate that the process occurs in the kinetic domainwith the realgar particles being converted to As2O3 and As4O6 (g). The very fast reaction rates were limited by the chemical reaction. The kinetic equation was found to be: –ln (1–α) = 4.56 x 103 x e(–8780/T) x t. The proposed reaction mechanism and chemical transformation investigated by ICP–AES, EDXRF and thermal analysis are discussed.

The calculations of thermodynamic properties in some gallium-based systems with a miscibility gap – Ga–Tl, Ga–Hg and Ga–Pb are presented in this paper. The determination of the gallium activities in the mentioned liquid alloys was based on their known phase diagrams using the Zhang-Chou method for calculating activities from phase diagrams involving two liquid or solid coexisting phases. The activities of gallium in Ga–Tl, Ga–Hg and Ga–Pb system were calculated in the 973–1273 K, 573–873 K and 1000–1100 K temperature ranges, respectively. The activities of the other component in all the investigated systems were obtained by the Gibbs-Duhem equation. The results of the calculations are compared with literature data.

The results of the determination of the thermodynamic properties for ternary systems Cr.Co.Me (Me = Mo, Al) using a new general solution model for the predictions are presented in this work. For five sections (with mole ratio Co :Me = 2:8, 4:6, 5:5, 6:4, 8:2) investigated in each ternary system at temperature of 2000 K, integral molar excess Gibbs energies and partial molar thermodynamic properties of chromium were calculated.