Thermal behavior of mixtures of bentonitic clay and saline solutions L.M. Casás a , M. Pozo b, ⁎, C.P. Gómez c , E. Pozo d , L.D. Bessières e , F. Plantier e , J.L. Legido c a Laboratoire de Thermique, Energétique et Procédés (LaTEP), École Nationale Supérieure en Génie des Technologies Industrielles, Université de Pau et des Pays de l'Adour, rue Jules Ferry, BP 7511, 64075 Pau, France b Departamento de Geología y Geoquímica, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco s/n, 28049 Madrid, Spain c Departamento de Física Aplicada, Facultade de Ciencias Experimentais, Universidade de Vigo, Lagoas Marcosende s/n, 36310 Vigo, Spain d Instituto Geológico y Minero de España (IGME), Tres Cantos 28760, Madrid, Spain e Laboratoire des Fluides Complexes et leurs Réservoirs - UMR 5150, Université de Pau et des Pays de l'Adour, BP 1155, 64013 Pau, France abstract article info Article history: Received 9 March 2012 Received in revised form 23 December 2012 Accepted 29 December 2012 Available online xxxx Keywords: Bentonitic clay Seawater Salinity Thermophysical properties Specific heat capacity Thermotherapy Thermophysical characterization is a useful tool for studying mixtures of clay and saline solutions and evaluating their suitability from a thermotherapic point of view. This work focuses on studying the specific heat capacity, density, thermal conductivity and viscosity of a bentonitic clay (composed mainly of 55% Na + -saturated trioctahedral smectite, 28% sepiolite and 15% illite) mixed with different saline solutions (0, 1, 2, 3 and 3.5%) in the temperature range 293.15 to 317.15 K. The results indicate meaningful differences in the thermal behavior of the studied pastes in relation to thermotherapy and pelotherapy. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Mixtures of clays and solutions with different mineralization rates are some of the most common components of so-called peloids or therapeutic muds used in thermal centers (Thalasso centers and spas) for therapeutic and cosmetic applications (Carretero et al., 2006; Veniale et al., 2007). The thermotherapic effect is especially important in the therapeutic action and is based on the heat released by a paste composed of a fine-grained material (mostly silty clay to clay) blended with mineral medicinal water. The development of thermalism, and consequently, of different ther- mal products is of great importance in thermal medicine, as described in the Balneo-Declaration of the XXIII Congress of Polish Association of Balneology and Physical Medicine (held in Naleczow, Poland, in September 2011). In addition, presentations at the II Ibero-American Congress of Peloids (held in Lanjarón, Spain, in July 2010) highlighted the importance of mixtures of clays and solutions of different composi- tion for pelotherapeutic applications. In recent years, several authors have made significant contribu- tions to the study of pelotherapy. Among the published studies on the characterization and physical-chemical properties of clay-water pastes or peloids composed of common clays and/or special clays (e.g. bentonite, kaolin, sepiolite) are those undertaken by Bettero et al. (1999), Cara et al. (2000a, 2000b), Carretero et al. (2007), Curini et al. (1990), Ferrand and Yvon (1991), Gamíz et al. (2009), Karakaya et al. (2010), Legido et al. (2007), Rambaud et al. (1986), Rebelo et al. (2011a, 2011b), Sánchez et al. (2002), Summa and Tateo (1998), Tateo et al. (2009, 2010), Veniale (1997), Veniale et al. (1999, 2004), Viseras et al. (2007), Yvon and Ferrand (1996). Al- though clayey pastes and peloids are the most commonly studied, sulphide-rich peloids (Baschini et al., 2010) and those composed of organic muds have also been reported (Britschka et al., 2007; Suárez et al., 2011; Tserenpil et al., 2010). The process of mixing clays with water of different ionic composition produces muds with different properties. Thus, the water adsorption capacity differs depending on the ionic concentration, and e.g. increases from 60% by weight of seawater to 80% of distilled water (Casás et al., 2011). This process is marked by the presence of electrolytes, as shown in several studies (Carretero et al., 2007; Gamíz et al., 2009; Veniale et al., 2004). The physical properties of such mixtures are very important as regards their thermotherapeutic properties (Silva et al., 2003). In addition to a high specific heat capacity and thermal conductivity, suit- able rheological properties favor the application and spreading of the mixtures (Rebelo et al., 2011b; Viseras et al., 2007). The therapeutic effects of peloids are probably caused by their thermal properties, which include specific heat capacity, thermal Applied Clay Science 72 (2013) 18–25 ⁎ Corresponding author. Tel.: +34 914974808; fax: +34 914974900. E-mail addresses: lidia.martinezcasas@univ-pau.fr (L.M. Casás), manuel.pozo@uam.es (M. Pozo), carmengomez@uvigo.es (C.P. Gómez), epozo@igme.es (E. Pozo), david.bessieres@univ-pau.fr (L.D. Bessières), frederic.plantier@univ-pau.fr (F. Plantier), xllegido@uvigo.es (J.L. Legido). 0169-1317/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clay.2012.12.009 Contents lists available at SciVerse ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay