Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research paper Characterization and electrochemical treatment of a kaolin Juan Carlos Flores Segura a,b,⁎ , Víctor Esteban Reyes Cruz a , José de Jesús Pérez Bueno b , Elda Marlem Lozada Ascencio a , Felipe Legorreta García a a Universidad Autónoma del Estado de Hidalgo, Área Académica de Ciencias de la Tierra y Materiales, Carretera Pachuca, Tulancingo, Km 4.5 s/n, Mineral de la Reforma, Hgo. C.P. 42184, México b Centro de Investigación y Desarrollo Tecnológico en Electroquímica (CIDETEQ), S.C., Parque Tecnológico de Querétaro s/n, Sanfandila, Pedro Escobedo, Querétaro C. P. 76703, México. ARTICLE INFO Keywords: Kaolin Electrolysis Iron reduction Purification Electrochemical treatment ABSTRACT In this work, studies on characterization and electrochemical treatment of kaolin from the municipality of Agua Blanca, Hidalgo, Mexico were carried out, in order to identify its properties and establish the operating con- ditions for an electrochemical purification treatment. Different characterization techniques were used in order to quantify this clay characteristics, such as X-ray diffraction, scanning electron microscopy, analysis of the whiteness index, particle size, FTIR, Induced Coupled Plasma Spectroscopy, Z potential, cyclic voltammetry, chronopotentiometry and chronoamperometry. This study shows that the tested clay had a high content of kaolinite, but also impurities, such as: quartz, iron oxides, and titanium oxides. These impurities have an in- fluence on the surface charge of the kaolin particles and therefore on their properties. The clay with a heat treatment exhibited a thermal behavior characteristic of this type of clays. The particle size range was between 0.5 and 100 μm with an average particle size about 15 μm. The voltammetry study revealed that a reduction processes occur in a range of 0.07 to -1.2 V (E vs. SCE) and, when a cell potential of 3.3 V for 24 h was imposed, there was a decrease of about 43% in the amount of iron oxides present in the ore. This reduction was of particular significance for the cleaning process. 1. Introduction Nowadays, supplementary cementitious materials (SCMs) such as the metakaolin (amorphous material obtained after kaolinite dihy- droxylation) (Wianglor et al., 2017) are a focus of attention in the al- ternatives to the Portland cement (PC) and this is a dehydroxylated form of kaolin. The main application of kaolin is in the manufacturing of ceramics and cement, but this versatile clay have been used for the manufacturing of many different products, such as paints, pharmaceu- ticals, cosmetics, rubber, plastics, water treatment, substrate for cata- lysis, mortar and concrete, and others (Murray, 2006; Nandi et al., 2009; Peter et al., 2015; Roy et al., 2015; Siddique and Klaus, 2009). Nonetheless, naturally occurring clays are very sandy and have dif- ferent impurities (SGM, 2014), which represent important dis- advantages. Thus, in order to be useful, clays and particularly kaolin and metakaolin requires a low amount of impurities (Murray, 2000). Therefore, a complete characterization study of the clays for specific applications is very important in order to know its properties and the ranges of composition for the different impurities. The characterization, benefit, and purification of kaolin have been widely investigated. Purification techniques has been described in nu- merous works with the main aim of the diminishment of iron oxides (Aghaie et al., 2009; Asala et al., 2016; Cao et al., 2016; González and Ruiz, 2006; Martínez-Luévanos et al., 2011; Murray, 2006; Ondruška et al., 2015; Saikia et al., 2003; Taran and Aghaie, 2015; Xia et al., 2012), where leaching, flotation, flocculation and high-intensity mag- netic separation were the most widely used techniques (Murray, 2006). Only some authors have studied the properties using unconventional techniques, such as: electroremediation, bioremediation and bio- leaching (Aghaie et al., 2012, 2009; He et al., 2011; Hosseini and Ahmadi, 2015; Pazos et al., 2010, 2006; Wang et al., 2006; Zegeye et al., 2013), with important results. However, these techniques have a low efficiency as well as the need for further studies and sometimes require to carry out some post-treatments. Among electrochemical techniques, electrolysis is relevant due to its selectivity used in reduc- tion and deposition of oxidized metal species. There is a deposit of clay in the region of Agua Blanca de Iturbide, located to the East of the State of Hidalgo, Mexico, which extends to the municipality of Huayacocotla, Veracruz, Mexico. This site is the largest deposit of kaolin in the region. This work shows the use of electrolysis http://dx.doi.org/10.1016/j.clay.2017.06.004 Received 24 November 2016; Received in revised form 2 June 2017; Accepted 5 June 2017 ⁎ Corresponding author. E-mail address: jperez@cideteq.mx (J.C. Flores Segura). Applied Clay Science 146 (2017) 264–269 0169-1317/ © 2017 Elsevier B.V. All rights reserved. MARK