Polymers 2023, 15, 530. https://doi.org/10.3390/polym15030530 www.mdpi.com/journal/polymers Article Compressive Yield Stress of Flocculated Kaolin Suspensions in Seawater Steven Nieto 1 , Eder Piceros 1,2 , Pedro G. Toledo 3, *, Pedro Robles 4 and Ricardo Jeldres 1, * 1 Departamento de Ingeniería Química y Procesos de Minerales, Facultad de Ingeniería, Universidad de Antofagasta, Antofagasta 1240000, Chile 2 Faculty of Engineering and Architecture, Universidad Arturo Prat, Almirante Juan José Latorre 2901, Antofagasta 1240000, Chile 3 Department of Chemical Engineering and Laboratory of Surface Analysis (ASIF), Universidad de Concepción, Concepción 4030000, Chile 4 Escuela de Ingeniería Química, Pontificia Universidad de Valparaíso, Valparaíso 2340000, Chile * Correspondence: petoledo@udec.cl (P.G.T.); ricardo.jeldres@uantof.cl (R.J.) Abstract: The mining industry has resorted to using seawater while trying to find a solution to the water shortage, which is severe in some regions. Today, the industry looks to tailings dams to re- cover more water and, thus, increase recirculation. The migration of interstitial water due to the consolidation of particle networks can give rise to large water mirrors in different dam areas. These pools can contain enough water to be recovered and recirculated if the external stress caused by the weight of the pulp exceeds the compressive yield stress. The density and rheological properties of the discarded pulps determine the feasibility of water expulsion during tailings consolidation. As these conditions are largely established in the thickening stage, it is necessary to revisit operations, looking at the dam as a water source. Thus, a thorough understanding of the compressive properties that determine the level of consolidation of typical pulps and their relationships to aggregate prop- erties, such as size and fractal dimension, is crucial. Here, the effect of two types of water, industrial water and synthetic seawater, on kaolin flocculation, sedimentation rate, yield stress, and compres- sive yield stress were studied. In addition, the relationship of these properties with the flocculant dose and the resulting aggregate size and fractal dimension was examined. One promising finding to practitioners was that salt and small doses of high molecular weight flocculant improved the consolidation of kaolin slurries under compression. These conditions generated low compressive yield stress compared to fresh water and water with low salt content, favoring the consolidation of the pulps and the release of water. Keywords: seawater flocculation; kaolin clay; yield stress; compressive yield stress; mineral processing 1. Introduction The recovery of water during mineral processing is a crucial aspect of ensuring the sustainability of the mining industry, primarily when sulfide deposits are located in de- sert areas with little availability of water [1]. The primary operations to recover water are based on extraction from the flotation tailings in large thickeners where the particles set- tle, forming a concentrated sludge at the bottom. At the same time, an overflow of clarified water is generated, which is later reused in upstream operations. Efficiency improves after adding flocculants, which increases the particle settling rate and recovered water flow. Flocculants are high molecular weight, soluble polymers with functional groups that ad- here to dispersed particles through various mechanisms, forming large agglomerates that settle quickly. The thickened pulp is withdrawn through the lower cone of the thickener and then transported to the tailings storage facility (TSF). Depending on the density and rheological Citation: Nieto, S.; Piceros, E.; Toledo, P.G.; Robles, P.; Jeldres, R. Compressive Yield Stress of Flocculated Kaolin Suspensions in Seawater. Polymers 2023, 15, 530. https://doi.org/10.3390/ polym15030530 Academic Editor: Dan Rosu Received: 7 November 2022 Revised: 9 December 2022 Accepted: 22 December 2022 Published: 19 January 2023 Copyright: © 2023 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).