Organophilization of a Brazilian Mg-montmorillonite without prior sodium activation M A N O E L L A S I LVA C AVA L C A N T E 1,* , SIMONE PATRÍCIA ARANHA PAZ 2 , RÔMULO SIMÕES ANGÉLICA 1 , EDSON NORYUKI ITO 3 AND ROBERTO FREITAS NEVES 1 1 Programa de Pós-Graduação em Geologia e Geoquímica, Instituto de Geociências, Universidade Federal do Pará, Campus do Guamá, 66075-110, Belém, Pará, Brazil 2 Faculdade de Engenharia de Materiais, Campus de Ananindeua, Universidade Federal do Pará, Ananindeua, Pará, Brazil 3 Departmento de Engenharia de Materiais, Universidade Federal do Rio Grande do Norte, Natal-RN, Brazil (Received 5 September 2015; revised 17 February 2016; Editor: George Christidis) ABSTRACT: The use of Mg-montmorillonite in the production of organoclay without sodium activation was investigated. For this purpose, organophilization experiments were carried out by varying the concentration of two surfactants: hexadecyltrimethylammonium (HDTMA + ) and dodecyltrimethy- lammonium (DTMA + ) ions. These surfactants were used at concentrations 0.7, 1.0 and 1.5 times that of the cation exchange capacity (62.6 meq/100 g) of the clay, with a reaction time of 8 h at temperatures of 25 and 80°C. X-ray diffraction (XRD) results confirmed the intercalation for both in natura and activated samples. The Fourier-transform infrared (FTIR) spectroscopy and XRD results showed that the ratio of gauche/trans conformers decreased with increased basal spacing. The results of thermodifferential and thermogravi- metric analysis (DTA/DTG) confirmed the thermal stability of the organoclay up to 200°C, permitting the use of such material in the synthesis of polymer/clay nanocomposites obtained by the melt blending. Thus, Mg-montmorillonite can be intercalated with alkylammonium ions without prior Na-activation to form organoclays. The possibility of using natural (non-activated) Mg-montmorillonite represents a significant difference in terms of processing cost in comparison with existing Ca-montmorillonite in Brazil or even with imported bentonites that require Na-activation during beneficiation. KEYWORDS: Mg-montmorillonite, organoclay, sodium activation, smectite, bentonite. The process of organophilization of bentonites with alkylammonium ions has been used widely mainly because of the facility to intercalate such ions into the interlayer space of montmorillonite. Once merged, the hydrophilic character on the surface of clay minerals changes to hydrophobic and the organic-inorganic hybrid material formed exhibits chemical and physical properties of both clay minerals and organic compounds (Lagaly et al. 2006; Ruiz-Hitzky & Van Meerbeek, 2006). This type of material, referred to as an organoclay, is potentially indicated for use as an adsorbent for organic pollutants (e.g. oil spills and their derivatives in water bodies), as rheology-control agents, as drilling mud fluids and, more recently, in the synthesis of nanocomposites (Paiva et al., 2008, CMS, 2013). In general, the interlayer space of an in natura montmorillonite is occupied by water molecules and cations (mainly Na + ,K + , Mg 2+ , Ca 2+ ), that are weakly bound to the clay-mineral layers. These cations balance the negative charge generated by isomorphic *E-mail: manoella.cavalcante@hotmail.com DOI: 10.1180/claymin.2016.051.1.04 © 2016 The Mineralogical Society Clay Minerals, (2016) 51, 39–54