ORIGINAL PAPER Interaction of H 2 O with (CuS) n , (Cu 2 S) n , and (ZnS) n small clusters (n =1–4, 6): relation to the aggregation characteristics of metal sulfides at aqueous solutions Kerry Wrighton-Araneda 1 & René Ruby-Figueroa 1 & Humberto Estay 2 & Diego Cortés-Arriagada 1 Received: 17 April 2019 /Accepted: 14 August 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The interaction of H 2 O onto small CuS, Cu 2 S, and ZnS clusters was theoretically studied by Density Functional Theory computations to get insights into the aggregation characteristics of metal sulfides at aqueous solutions. The results show the charge-controlled interactions with polarized solvent molecules are favored on the ZnS clusters compared with CuS and Cu 2 S clusters. Moreover, the chemical adsorption of H 2 O molecules is energetically favored onto ZnS clusters with higher interaction energies of up to 35.4 kcal/mol compared with CuS and Cu 2 S clusters (up to 31.3 kcal/mol), where the stability of H 2 O adsorption decreases as the size of the clusters increases. However, thermochemical analysis shows that the adsorption of H 2 O on copper sulfides is not a spontaneous process at room temperature. Additionally, the electrostatic energy of H 2 O onto the Cu 2 S and CuS clusters is lower than that associated with the H 2 O–H 2 O interactions, suggesting that copper precipitates prefer to bind between them at early stages of the precipitation process due to an unfavorable solvent-solute interaction. Dispersion forces play a relative key role in the interaction of water on copper sulfides, while for zinc sulfide clusters, the adsorption energy is slightly influenced by dispersion contributions. Accordingly, the aggregation of zinc sulfides in a water environment is expected to be lower compared with copper sulfides, and where the aggregation characteristics are not determined by the binding energy of the sulfides, but of the ability to interact with the solvent molecules. These statements were confirmed by experimental optical microscopy analysis and settling tests during precipitation processes in water. Therefore, this work allows proposing a simple strategy to study the aggregation characteristics of metal sulfides, which turns useful for use in hydrometallurgical applications. Keywords DFT calculations . Metal sulfide precipitates . Hydrometallurgy . Clusters Introduction In the mining industry, the metal sulfide precipitation pro- cesses are widely used to separate or recover different metals from different industrial solutions, according to the following overall reactions: M 2þ þ HS - ↔MS s ðÞ þ H þ M 2þ þ S 2- ↔MS s ðÞ ð1Þ Some applications have been developed, installed, and operating in some hydrometallurgical plants. In particular, one of the most successful applications is the copper re- covery from cyanide solution in gold mining, a technology known as SART (Sulfidization, Acidification, Recycling, and Thickening) process [1, 2]. Some applications include the sulfide precipitations to purify cobalt solutions by two pH controlled steps; in the first one, Cu and Zn are precip- itated and removed and secondly, Co and Ni are precipitat- ed and recovered as products [3], or the development of copper recovery from acid mine drainage [4], zinc recovery from cyanide solutions in gold mining [2], copper recovery This paper belongs to Topical Collection QUITEL 2018 (44th Congress of Theoretical Chemists of Latin Expression) Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-019-4161-x) contains supplementary material, which is available to authorized users. * Diego Cortés-Arriagada dcortes@utem.cl 1 Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación, Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, P.O. Box 8940577, San Joaquín, Santiago, Chile 2 Advanced Mining Technology Center (AMTC), University of Chile, Av. Tupper 2007 (AMTC Building), Santiago, Chile Journal of Molecular Modeling (2019) 25:291 https://doi.org/10.1007/s00894-019-4161-x