Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Note Analysis of sodium polyacrylate as a rheological modifier for kaolin suspensions in seawater Pedro Robles a, ⁎ , Eder Piceros b , Williams H. Leiva c,d , Julio Valenzuela e , Norman Toro f,g , Ricardo I. Jeldres c a Escuela de Ingeniería Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile b Faculty of Engineering and Architecture, Universidad Arturo Pratt, PO Box 121, Iquique, Chile c Departamento de Ingeniería Química y Procesos de Minerales, Facultad de Ingeniería, Universidad de Antofagasta, Av. Angamos 601, Antofagasta, Chile d CSIRO Chile, International Center of Excellence, Las Condes, Santiago, Chile e Centro de Investigación Tecnológica del Agua en el Desierto, Universidad Católica del Norte, CEITASAZA, Antofagasta, Chile f Department of Metallurgical and Mining Engineering, Universidad Católica del Norte, Chile g Department of Mining, Geological and Cartographic Department, Universidad Politécnica de Cartagena, Spain ARTICLE INFO Keywords: Kaolin Seawater Sodium polyacrylate Steric stabilisation Rheology Viscoelasticity ABSTRACT This research aims to analyse the effect of sodium polyacrylate on the rheological behaviour of kaolin pulps in seawater by means of rheograms and dynamic oscillatory assays. Then, the rheological properties were asso- ciated with zeta potential and particle aggregation/dispersion phenomena. Seawater raised the rheological properties compared to distilled water, generating an evident non-Newtonian behaviour, characterised by the appearance of yield stress, followed by a shear-thinning behaviour. This occurred because the high concentration of electrolytes compresses the ionic cloud that surrounds the particles' surfaces, overcoming the electrostatic repulsions, but besides, the seawater counterions (like Mg and Na) contribute to forming cationic bridges be- tween the anionic particles. The addition of sodium polyacrylate did not induce significant alterations on the zeta potential; however, this formed a steric stabilisation where chord length measurements showed a greater presence of fine particles and fewer kaolin aggregates. The yield stress significantly diminished after polymer addition, while the viscoelastic modules and complex viscosity indicate that sodium polyacrylate reduces the strength of the particle networks that make up the slurry, but in turn, the phase angle indicates increase in its solid-like character. 1. Introduction Technological advancement in the mineral processing has enhanced the recovery of low-grade minerals, but this progression and the con- tinuous depletion of ore grade have led to the production of large vo- lumes of tailings that usually must be transported for long distances, before reaching the tailings deposits. Mine tailings management in- volves two main steps. First, the solid must be separated from the liquid to recover as much water as possible and then recirculated for upstream operations. This is usually carried out in large sedimentation tanks, or thickeners, with an intense application of flocculants to improve the mud settling rate and overflow phase clarity. In the next step, the thickened tailings are pumped from the bottom of thickeners to the tailings storage facilities, where the flocculated solid can continue to settle and consolidate over the time (de Kretser et al., 1997). Once the underflow is discharged out, it still contains high volumes of liquid trapped inside particles aggregates, with little compaction rate. For this reason, there is a growing interest in using disposal methods for paste tailings, where pulps can reach solids percentages over than 70 wt%. This can significantly benefit the activities of pulp deposits in tailings dams (de Kretser et al., 1997; Wang et al., 2014). Given that con- centrated suspensions usually acquire a non-Newtonian flow behaviour, a good knowledge of the rheological properties is important to establish the optimum conditions for the handling and transport of the tailings (Boger, 2013; Nguyen and Boger, 1998). This topic is nearly associated to environmental aspects, that is, the seek of implementing basic principles of rheology to reduce risks, recover more water, and reduce the footprint of the residues produced in the mineral processing (Boger, 2013; Sofrá and Boger, 2002). The rheological parameters are affected by many factors, including ore mineralogy and water conditions such as salinity and pH. The presence of clays is of special interest because they are associated with a wide range of minerals and cause major problems https://doi.org/10.1016/j.clay.2019.105328 Received 24 May 2019; Received in revised form 5 October 2019; Accepted 8 October 2019 ⁎ Corresponding author. E-mail address: pedro.robles@pucv.cl (P. Robles). Applied Clay Science 183 (2019) 105328 0169-1317/ © 2019 Elsevier B.V. All rights reserved. T