The effect of mechanical activation on metal dissolutions by pressure leaching of massive rich copper ore taken from Küre copper ore deposit (Turkey) was investigated. The dissolution efficiencies of sulfide minerals are significantly improved by ultrafine grinding, also known as mechanical activation. This grinding results in decrease of particle size and an increase in crystal distortion of sulfide minerals. Leaching efficiencies of copper, cobalt, and Zinc increased from 45.2%, 25.9%, and 87.7% to 98%, 85%, and 97%, respectively, after 3-h mechanical activation. At the end of the activation, leaching was carried out at a temperature of 110°C, 10-bar oxygen partial pressure, and 150-g/L solid concentration without addition of acid. This study has also indicated that mechanical activation involving fine milling as a pretreatment is not only effective on copper minerals dissolution but also on the dissolution of other associated minerals, such as cobalt and zinc sulfides.

A combination of semicoking followed by a permanent roll magnetic separator (PERMROLL) has been used for the upgrading of a Turkish low-rank lignitic coal. The lignite samples were subjected to a low temperature carbonization process at 600°C and then upgraded by the PERMROLL. Under optimum conditions, carbonization of lignite particles in −9 + 0.5 mm size range which contained 12.18 wt.% ash and 3.38 wt.% total sulfur produced a product containing 25.90 wt.% ash and 3.19 wt.% total sulfur all reported on a dry basis. Dry magnetic separation employing the PERMROLL upgraded this product to 11.20 wt.% ash and 1.40 wt.% total sulfur with a recovery of 31.52 wt.% based on feed to the carbonization process. The mechanism of desulfurization is discussed on the basis of the presence of iron in the coal that complexes with sulfur to form a magnetic product upon semicoking and its subsequent removal by magnetic separation.

The hydrometallurgical route of zinc hydroxide and synthesis of nanocrystalline ZnO is a particularly attractive method to recover oxidized lead and zinc from lead-zinc flotation tailings. In Turkey, lead-zinc complex/mixed ores along with high iron content are not suitable for conventional mineral processing methods and need hydrometallurgical treatments. Therefore, the control of iron during zinc processes is really important. In this study, hydrometallurgical process route for zinc recovery from Pb-Zn flotation tailings was investigated by considering the effects of H2SO4 concentration, leaching and roasting temperatures on the zinc dissolution considering the Eh-pH variations. The iron and zinc products were also individually examined by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images in order to compare before and after leaching, precipitation and roasting steps. 83.1% Zn and 91.6% Cd leaching efficiencies were obtained from Pb-Zn flotation tailing particles with the size range of 50-110 nm from AFM image cross-sections, while lead and iron were not dissolved. Elemental sulfur started to form and produce a layer around the particles or a partially agglomerated particle in the size of 170 nm during the sulphuric acid leaching. However, majority of the particles was determined to be less than 20 microns, and AFM images showed that the size reduction between the leached and unleached particles was over 50%. Selective precipitations of iron and zinc in the form of hydroxide were performed in high recovery efficiencies of 90.1% and 99%, respectively. After the heat treatment, nanocrystalline zincite clusters of 96.6% purity were produced in the ZnO mineral form and nearly 13 nm in size. Zinc can be successfully recovered and a flotation tailings ore can be a good candidate for the production of high technology needs of nanocrystalline ZnO nanoparticles.