Aleksandar M. Mitrašinović

Separation and Recovery of Valuable Metals from Nickel Slags Disposed in Landfills

With the increased requests for more sustainable extraction processes feedstocks with low metal content are becoming more attractive. In this research, an additional refining step is investigated in order to recover valuable metals from slag generated during nickel extraction process, particularly copper, nickel, and cobalt. Slag was settled at the different temperatures for various times in conditions that simulated the industrial environment. The chemical composition and morphology of newly formed matte and slag were determined. Kinetic parameters of matte formation, valuable metal recovery rates and partition coefficients were deduced. Metals separation and settling rate was found to be strongly dependent on temperature. The highest recovery rates were found to occur at 1598 K (1325°C) for two hour settling while the most economical combination of parameters was found when settling at 1573 K (1300°C) for one hour. Silica additions generated higher partition coefficients for copper and nickel than the addition of lime. It is concluded that an additional refining step involving SiO2 and CaO fluxes is an economical way to recover more than 60% of valuable metals from slag that is disposed in landfills.

Modeling of High-Temperature Low-Pressure Silicon-Refining Process

An improved method for the modeling of the impurity reduction factor during high-temperature low-pressure silicon treatment is suggested. The implementation of a modified logistic function in a mathematical model allows it to be utilized for any range of treatment temperatures. The new model defines the maximum reduction factor for each impurity element present in liquid silicon and defines a critical treatment temperature value. Evaporation increase constant, with high adaptability for the implementation of new process parameters, indicated rapid increase in impurity removal at treatment temperatures slightly above melting point of silicon. Various statistical parameters for the logistic regression method were considerably lower for the 16 studied impurity elements than for the linear or logarithmic correlations.

On the assimilation mechanism of additives used in non-ferrous metals extraction processes

The assimilation mechanism of various additives used in non-ferrous metals extraction practices is examined. The most important factor for additive assimilation is the condition at the additive–solution interface. The additives were classified into three major groups based on the predominant transfer of additive from solid to liquid, which can be characterised as melting or dissolution. The thermochemical tests showed that the assimilation mechanism can be subdivided into four major periods: initial temperature drop, exo/endothermic peak, post-reaction temperature convalescing and settling period.

Effect of Reductants on Valuable Metals Separation and Recovery from Copper Cliff Converter Slag

Abstract The aim of the project is to investigate new material as a reductant in nickel extraction and purification processes. The analyzed reductants were coke, pig iron, ferrosilicon and two copper-silicon alloys. The mixture with the slag and reductant was poured into a cylindrical alumina crucible and kept in a furnace for one hour at 1573 K (1300 °C). After settling, the solidified sample consisted of the matte settled at the bottom of the sample separated from the slag at the top. Ferrosilicon was found to be the most effective reductant for cobalt recovery while 70wt%Cu-30wt%Si alloy facilitated 72% copper and 87% nickel recovery. The highest copper recovery is achieved with 90wt%Cu-10wt%Si reductant. Due to low melting point, high exothermicity and suitable density, Cu-Si alloys could be an ideal choice for the pyrometallurgical converting processes.