Citation: Can, N.M.; Ba¸ saran, Ç. Effects of Different Grinding Media and Milling Conditions on the Flotation Performance of a Copper-Pyrite Ore. Minerals 2023, 13, 85. https://doi.org/10.3390/ min13010085 Academic Editors: Marinela Ivanova Panayotova and Vladko Panayotov Received: 11 December 2022 Revised: 1 January 2023 Accepted: 3 January 2023 Published: 5 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). minerals Article Effects of Different Grinding Media and Milling Conditions on the Flotation Performance of a Copper-Pyrite Ore N. Metin Can 1, * and Ça ˘ grı Ba¸ saran 2 1 Department of Mining Engineering, Hacettepe University, Beytepe, Ankara 06800, Turkey 2 Konutkent Mah., 2944 Sk., No. 10, Ankara 06810, Turkey * Correspondence: metin.can@hacettepe.edu.tr Abstract: Different milling conditions, such as wet or dry, and use of different grinding media have a great impact on the flotation performance of sulphide minerals. In the present study, the effects of wet and dry grinding and the use of different grinding media, such as mild steel (MS) and stainless steel (SS), were investigated on a Cu-sulphide ore. The samples were ground as dry and wet with both grinding media, to a P 80 value of -75 μm, and then flotation was carried out under the same conditions. The obtained data from flotation were evaluated in terms of solid/water recovery, chalcopyrite/pyrite recovery and separation efficiency. The effects of different milling conditions were discussed with the measured chemical parameters such as redox potential and dissolved oxygen level together with the flotation rate of chalcopyrite. The redox potential of the dry ground ore, irrespective of the type of milling media, was measured considerably higher than the wet grinding conditions. With SS media flotation, the rate of Cu was high for dry grinding, resulting in a higher selective concentrate in terms of grade. However, Cu recovery was lower due to the instability of the froth structure. Separation efficiency pointed out that the best flotation performance could be obtained using a wet grinding condition with MS balls. Keywords: dry/wet grinding; stainless/mild steel ball; flotation; sulphide ore 1. Introduction Dissolution and electrochemical reactions, which have a great impact on flotation recovery, are influenced considerably by the grinding process. As the grinding operation is admitted as the last stage prior to concentration, the grinding environment has a significant effect on the behaviour of solids during subsequent steps, particularly in flotation [1]. The grinding process leads to the formation of highly active surface areas, some changes in the physical behaviour of solids which are attributed to permanent re-arrangement in crystal lattices and the structural alteration of particles [2,3]. Different milling procedures affect liberation, surface properties, particle morphology and surface roughness which can directly determine the hydrophobicity of the minerals and their flotation response [4,5]. The floatability of the ore, separation efficiency of minerals and selectivity are determined by surface properties which are controlled by the grinding process and its conditions [6]. Some defects such as cracks and pores may form on the surface of the particles depending on the grinding method, time and/or grindability of a mineral. These defects may have quite significant effects on the surface adsorption of collectors. Wet grinding generally produces particles of large specific surface and high surface oxidation, while dry grinding accounts for a large amount of surface defects and low surface oxidation. The results of a limited number of comparative studies performed on wet and dry grinding on flotation showed that dry ground materials are generally poorly wettable, while wet ground materials react quickly with water so that active charge centres and radicals are neutralized or disappear as a consequence of dissolving reactions. Gas molecules (especially oxygen) are physically or chemically adsorbed after dry grinding [7]. These films of gas will retard the wetting Minerals 2023, 13, 85. https://doi.org/10.3390/min13010085 https://www.mdpi.com/journal/minerals