Thermochimica Acta 552 (2013) 114–122 Contents lists available at SciVerse ScienceDirect Thermochimica Acta jo u r n al hom ep age: www.elsevier.com/locate/tca Thermal characterization of new fire-insulating materials from industrial inorganic TiO 2 wastes S.M. Pérez-Moreno a , M.J. Gázquez a , A.G. Barneto b , J.P. Bolívar a,∗ a Department of Applied Physics, University of Huelva, Huelva, Spain b Department of Chemical Engineering, University of Huelva, Huelva, Spain a r t i c l e i n f o Article history: Received 23 June 2012 Received in revised form 30 August 2012 Accepted 26 October 2012 Available online xxx Keywords: Norm Industry Titanium dioxide Waste Ilmenite Undissolved muds Red gypsum a b s t r a c t Two wastes, red gypsum (RG) and unattacked ilmenite (known as tionite), from the titanium dioxide production industry have been used to study the possibility of manufacturing new fire-isolating materials, and for that they were characterized for mineralogical composition and thermal behavior. Tests have demonstrated that these wastes could be used for fire insulation. Thermogravimetry analysis (TGA) of the thermal behavior of these wastes and tests on the new isolating materials against temperature indicate that they do not undergo significant chemical and structural changes up to about 1000 ◦ C. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The current trend toward recycling the waste material gen- erated in most industrial production processes makes this an important field for research. In this sense, the development of tech- nologies and new applications to valorize these wastes in order to cut disposal costs and avoid environmental pollution environment is of increasing importance. In addition, the appropriate treatment of industrial wastes could lead to the generation of co-products of economic value and broad application [1,2], especially when the waste properties are manufactured for specific applications with high added value and can successfully compete with products made from traditional raw materials [3]. In our case, we valorize two wastes generated by an indus- trial manufacturer of titanium dioxide pigment for plastics in the province of Huelva (southwestern Spain). The pigment is produced by applying the “sulfate method” that uses ilmenite (Fe 2 TiO 3 ) as raw material, which is a heavy mineral containing approximately 43–65% titanium dioxide [4–7]. The first of these two wastes (unattacked mud or tionite) originates in the digestion stage of the ilmenite with sulfuric acid (98% concentration). The tionite is obtained by filtration of the liquor from digestion, making this mud highly acidic, with large ∗ Corresponding author. Tel.: +34 959219793; fax: +34 959219777. E-mail address: bolivar@uhu.es (J.P. Bolívar). concentrations of heavy metals that could potentially damage health and the environment if not adequately managed [8]. The second waste, red gypsum (RG), emerges in the final stage of the industrial process, where a low acidic liquid stream com- posed primarily of sulfuric acid (H 2 SO 4 ) and iron sulfates (FeSO 4 , Fe 2 (SO 4 ) 3 ) is treated in a neutralization plant. Here calcium hydrox- ide and magnesite are added to the weak acid stream in order to precipitate the dissolved materials in the stream, and the red gyp- sum is finally obtained by filtration [5]. In this process the following reactions occur: H 2 SO 4 + Ca(OH) 2 → CaSO 4 · 2H 2 O (1) Fe 3+ + OH - → Fe(OH) 3 (2) Ca 2+ + CO 3 2- → CaCO 3 (3) Mg 2+ + SO 4 2- → MgSO 4 (4) This factory produces about 7 × 10 4 tons of red gypsum and 3 × 10 4 tons of mud, which contain about 40% humidity; currently these wastes have no commercial value and are disposed of in an authorized and controlled repository area. Furthermore, the man- agement of this waste represents a high cost to the company. The potential commercial applications of these wastes are what motivate this research. Due to this problem and the previous chem- ical and mineralogical characterization of these wastes, this study analyzes the possibility of using these wastes (or their mixes) as insulating material in the construction sector. 0040-6031/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tca.2012.10.021