SPECIAL ISSUE ARTICLE A ToF‐SIMS investigation on correlation between grinding environments and sphalerite surface chemistry: Implications for mineral selectivity in flotation Liuyin Xia 1 | Brian Hart 1 | Zhe Chen 1 | Mark Furlotte 2 | Gary Gingras 2 | Patrick Laflamme 3 1 Surface Science Western, Research Park, University of Western Ontario, 999 Collip Circle, LL31, London, Ontario, Canada, N6G0J3 2 Mine Matagami, UNE Compagnie Glencore, 500, boul. Industriel, Matagami, Québec, Canada, J0Y 2A0 3 COREM, 1180, Rue de la Minéralogie, Québec, Québec, Canada, G1N 1X7 Correspondence Brian Hart, Surface Science Western, Research Park, University of Western Ontario, 999 Collip Circle, LL31, London, Ontario, Canada, N6G0J3. Email: bhart@uwo.ca Funding information Natural Sciences and Engineering Research Council of Canada (NSERC) CRD project. Changes in mineral surface properties during grinding play a key role in flotation performance. ToF‐SIMS surface chemical analytical studies have shown that flotation separation of sphalerite from chalcopyrite is significantly affected by the oxidation of metal species on the surface of sphalerite. The intensity of iron oxyhydroxyl species on the surface of sphalerite has a positive correlation with poor recovery of sphalerite. Given the link between the presence of oxide spe- cies on the surface of sphalerite and a lower recovery during Cu flotation, a laboratory study was initiated to evaluate the potential for sphalerite surface oxidation control and improve recov- ery through grinding. For the investigation, a ball mill which allowed for monitoring pulp chemis- try during grinding was utilized to study the impact of grinding conditions on selective flotation of sphalerite. ToF‐SIMS was used to identify and measure the variability in sphalerite surface spe- cies as a result of the different test parameters. Variable mill parameters include 2 types of grind- ing media, aeration conditions, addition of FeSO 4 , and altering the pyrite content in the feed ore. TOF‐SIMS analyses of mill discharge samples identified higher intensities of iron oxyhydroxyl species on sphalerite surface subsequent to grinding with mild steel balls, in condition of aeration, use of FeSO 4 , and by increasing the pyrite content of the feed ore. The higher adsorption of iron oxyhydroxyl species on the surface of sphalerite should be consistent with the lower recovery. To verify this, bench scale flotation tests in the presence and absence of FeSO 4 were performed; results correlated iron oxyhydroxyl species with the poor sphalerite recovery. KEYWORDS flotation, grinding, sphalerite, ToF‐SIMS 1 | INTRODUCTION Copper is typically extracted from oxide and sulfide ores that only con- tain 0.5% to 2.0% copper. The refining technology employed by copper producers depends on the ore type, as well as other economic and environmental factors. Currently, approximately 80% of primary cop- per production comes from sulfide ores, but sulphidic copper ores are too dilute to be suitable for direct smelting and require enrichment. In a poly‐metallic sulfide mineral processing plant, copper ores are milled then concentrated by physical separation, generally flotation, to give concentrates. 1 The enrichment process usually involves 2 or more stages. In the flotation process, the recovery of minerals is accomplished by the attachment of a hydrophobic mineral to bubbles introduced to the flotation chamber. The net result is to produce a concentrate of the particular value added mineral of interest and a tail- ings consisting of all other phases. In order to facilitate the recovery of a desired mineral, various reagents are introduced to induce selective hydrophobic surface development on the mineral of interest. For a Cu/Zn ore, consisting for example of chalcopyrite (CuFeS 2 ) and sphal- erite (ZnS), the first stage involves selective chalcopyrite flotation and sphalerite rejection to produce marketable copper concentrate. In the second stage, the reject sphalerite is recovered by flotation to produce a Zn concentrate. In the case of chalcopyrite flotation, this is simply accomplished by the addition of surfactants (collectors) which attach to the mineral surface promoting hydrophobicity and enhance bubble mineral attachment. The flotation of sphalerite on the other hand is somewhat more challenging as there is a requirement of surface acti- vation in order to promote collector attachment. The activation of Received: 20 March 2017 Revised: 8 August 2017 Accepted: 8 August 2017 DOI: 10.1002/sia.6295 Surf Interface Anal. 2017;1–7. Copyright © 2017 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/sia 1