Citation: Murga, R.; Rodriguez, C.; Amalraj, J.; Vega-Garcia, D.; Gutierrez, L.; Uribe, L. Use of Polystyrene Nanoparticles as Collectors in the Flotation of Chalcopyrite. Polymers 2022, 14, 5259. https://doi.org/10.3390/ polym14235259 Academic Editors: Kumkum Ahmed and Chanchal Kumar Roy Received: 15 September 2022 Accepted: 27 November 2022 Published: 2 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 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/). polymers Article Use of Polystyrene Nanoparticles as Collectors in the Flotation of Chalcopyrite Romina Murga 1,2 , Camila Rodriguez 1,2 , John Amalraj 3 , Dennis Vega-Garcia 4 , Leopoldo Gutierrez 2,4 and Lina Uribe 1,2, * 1 Escuela de Ingeniería Civil de Minas, Universidad de Talca, Curicó 3340000, Chile 2 Centro de Recursos Hídrico para la Agricultura y la Minería (CRHIAM), Universidad de Concepción, Concepción 4030000, Chile 3 Instituto de Química de Recursos Naturales, Universidad de Talca, Talca 3480094, Chile 4 Departamento de Ingeniería Metalúrgica, Universidad de Concepción, Concepción 4030000, Chile * Correspondence: luribe@utalca.cl; Tel.: +56-75-220-1725 Abstract: This study proposes the use of polymeric nanoparticles (NPs) as collectors for copper sulfide flotation. The experimental phase included the preparation of two types of polystyrene-based NPs: St-CTAB and St-CTAB-VI. These NPs were characterized by Fourier-Transform Infrared (FTIR) spectroscopy and dynamic light scattering (DLS). Then, microflotation tests with chalcopyrite under different pH conditions and nanoparticle dosages were carried out to verify their capabilities as chalcopyrite collectors. In addition, the zeta potential (ZP) measurements of chalcopyrite in the presence and absence of NPs were carried out to study their interaction. Lastly, some Atomic Force Micrographs (AFM) of NPs and Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis of NPs on the chalcopyrite surface were conducted to analyze the size, the morphology and their interaction. The results obtained at pH 6 and pH 8 show that the NPs under study can achieve a chalcopyrite recovery near or higher than that obtained with the conventional collector. In this study, it was possible to observe that the NPs functionalized by the imidazole group (St-CTAB-VI) achieved better performance due to the presence of this group in its composition, allowing to achieve a greater affinity with the surface of the mineral. Keywords: nanoparticles; chalcopyrite microflotation; collector; polystyrene; copper sulfides 1. Introduction The production of copper from sulfide minerals represents more than 70% of the total copper production in Chile, contributing to increased ore processing by flotation plants [1]. It is important to note that, although froth flotation has been developed and commercially applied for more than a century, there are still some shortcomings that need to be overcome to achieve maximum mineral recovery, such as low grades of ores and environmental problems [2]. These shortcomings have become more challenging because the ore grades have consistently decreased, and the environmental awareness has become more relevant in recent years. More specifically, conventional reagents were classified as hazardous materials because they may affect both the environmental and human health as well as flora and fauna if they are improperly managed and disposed of [3,4]. Xanthates, for example, are the most common type of water-soluble collectors used for sulfide minerals, however, these have raised ever-increasing environmental concerns as carbon disulfide is readily emitted from xanthate, thus creating a need to search for a new and more efficient generation of flotation reagents [2,5–7]. Nowadays, one of the most interesting and promising alternatives to the use of con- ventional reagents is the use of nanoparticles (NPs). NPs appear as a potential alternative thanks to a series of extraordinary features, such as a large number of methods of synthesis, increased surface area, the ability to perform physical adsorption and easy detachment, Polymers 2022, 14, 5259. https://doi.org/10.3390/polym14235259 https://www.mdpi.com/journal/polymers