Damla Izerdem

The flotation of sulfide minerals mostly depends on electrochemical reactions occurring on the mineral surfaces. Understanding the interaction mechanisms in the pulp is crucial for explaining the effects of different flotation chemicals on flotation performance. For this purpose, electrochemical techniques are used in the flotation of sulfide minerals by utilizing the semiconductor properties of these minerals. In this study, three non-destructive electrochemical measurements - open circuit potential (OCP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) - were used to assess the electrochemical reactivity of the locked and liberated sulfide particles. Various combinations of mineral electrodes - Galena/Pyrite (0.52 cm2), Galena/Sphalerite (0.35 cm2), pure Galena (0.20 cm2), pure Sphalerite (0.80 cm2) and pure Pyrite (0.18 cm2) - were tested. A three-electrode electrochemical cell configuration was set up to investigate the electrochemical responses of the prepared electrodes. The changes in the surface chemistry of the mineral electrodes, in the presence (1×10-4 M NaEX) and absence of a collector were compared in detail. During the process, charge transitions occurred between the minerals in the locked particle mineral electrode due to galvanic interactions regardless of the surface area. Thus, the flotation behavior of the minerals changed by reducing and oxidizing each other. The present study suggests that the electrochemical methods may be an alternative technique to the conventional batch scale flotation tests as they can easily monitor the effect of any flotation reagents in the system causing possible reactions that may occur on sulfide mineral surfaces.

The use of gravity concentrators involves several challenges, such as determination of the liberation sizes of the minerals, selection of appropriate particle sizes for the applied concentration method, and the severity of the beneficiation of fines.In this study, the effects of fully liberated (artificial mixtures of magnetite and quartz) and non-liberated particles (chromite ore collected from a chromite processing plant) on various gravity concentration equipment were investigated as a function of particle size considering recoveries, separation efficiencies, and grades of products. A series of tests were conducted on shaking tables, spiral concentrators, and a Falcon concentrator with different design features under various operating conditions. Finally, the separation efficiencies were correlated with the settling rates of the particles.The test results confirmed a certain trend in the separation efficiency as a function of particle size for each condition. The separation efficiency initially increased with increasing particle size, peaked, and eventually decreased with increasing particle size. The maximum separation efficiency attained was 90% for 141 µm particles in the shaking table and 54% for 245 µm particles in the Falcon concentrator, both of which were used to treat the artificial feed. In the spiral concentrator, which treated chromite ore as feed, the maximum separation efficiency attained was 82% for 178 µm particles.This experimental study provides data to identify the concentration behavior of particles by investigating possible separation mechanisms. Consequently, it provides an understanding of the relationships between particle size and separation efficiency in terms of settling rates, especially in spiral concentrators.

In this study, flowsheet development and economic approach studies have been carried outfor a sulphide ore containing gold and clay. For this purpose, previous beneficiation test resultswere used. First, clay separation was performed from the ore. In the following step, directleaching, gravity separation and flotation methods were tested and compared to obtain a goldpre-concentrates at different grinding sizes. According to the test results, 34% of the ore by masswas separated as clay concentrate, which was suitable for the ceramic industry. Different preconcentrateswere obtained from gravity and bulk sulphide flotation tests. The possible flowsheetalternatives were compared and discussed. Product specifications were discussed in terms ofeconomic and environmental aspects. As a result, producing Au containing flotation concentratewithout leaching was decided to be more economical. In this method, 34% of the ore could beobtained as a by-product. 77.77 g/t gold containing sulphide pre-concentrates can be obtainedwith a 70.05 % gold recovery.