Thermal, spectral, and diffraction properties of Co-exchanged montmorillonite with 2-, 3-, and 4-hydroxyphenol R. Janı ´k • E. Jo ´na • M. Pajta ´s ˇova ´ • D. Ondrus ˇova ´ • P. Liza ´k • V. Pavlı ´k • R. Durny ´ • S. C. Mojumdar CTAS2011 Conference Special Chapter Ó Akade ´miai Kiado ´, Budapest, Hungary 2012 Abstract The influence of the 2-, 3-, and 4-OH phenols on the type of interaction with Co-exchanged montmoril- lonite and thermal properties of these materials were studied. The results of XRD, IR, and thermal (TG, DTG) analysis show that organic species are intercalated into the interlayer space of montmorillonite. Thermal decomposi- tion in the temperature interval 20–700 °C of studied samples with 2- and 3-hydroxyphenol proceeds in three steps (the release of adsorbed H 2 O molecules, combustion/ desorption of protonated hydroxy phenols and dehydr- oxylation), while the sample with 4-hydroxyphenol decom- pose in four steps (the new peak at *222 °C corresponds to directly coordinated organic species). The effect of different position of the hydroxyl groups on the phenol ring on the thermal decomposition is evident. Keywords Co-exchanged montmorillonite Á 2-, 3-, and 4-hydroxyphenols Á TG Á DTG Á IR-spectroscopy Á X-ray diffraction Introduction During the last 60 years much study of the interactions between clays and organic pollutants (especially phenol derivatives) was carried out with the purpose of determining the structures and thermal stability of the organo-clay com- plexes [1–4]. The clay surface and its interlayer space are populated by Bro ¨nsted and Lewis acidic and basic sites. The main interactions between the clay and the adsorbed organic species are of the acid–base type [1, 5]. In the interlayer space of montmorillonite adsorbed water molecules which are coordinated to exchangeable metallic cations serve as proton donors (Bro ¨nsted acid). The organic base may be protonated by accepting a proton from a water molecule, thus gaining a positive charge. The exchangeable cations may also serve as Lewis acids and adsorbed organic species become coordi- nated directly to the cations (organic base may as well form a hydrogen bond with a polar water molecule). Phenol and substituted phenols are important chemicals in the manufacture of synthetic resins, pharmaceutical, dyes, and agrochemicals. Their toxicity is high and they may accumulate in the environment [6]. This study is part of a global research on the adsorption of different organic substances by clay minerals [7–9]. The purpose of the present investigation was to study the adsorption of 2-, 3-, and 4-hydroxyphenols by Co-exchanged montmorillonite. One of the characteristic features of montmorillonite is its layered structure. The layers are formed by two tetrahedral sheets linked with an octahedral sheet. Isomorphous substi- tution in the octahedron (or tetrahedron) generates a negative R. Janı ´k Á E. Jo ´na Á M. Pajta ´s ˇova ´ Á D. Ondrus ˇova ´ Á S. C. Mojumdar Department of Chemical Technologies and Environment, University of Trenc ˇı ´n, 020 32 Pu ´chov, Slovakia P. Liza ´k Department of Industrial Design, Faculty of Industrial Technologies, Trenc ˇı ´n University of A. Dubc ˇek, Trenc ˇı ´n, Slovakia V. Pavlı ´k Á S. C. Mojumdar (&) Department of Chemistry, University of Guelph, Guelph, ON, Canada e-mail: scmojumdar@yahoo.com R. Durny ´ Slovak Institute of Metrology, Karloveska ´ 63, Bratislava, Slovakia 123 J Therm Anal Calorim (2012) 108:915–919 DOI 10.1007/s10973-012-2364-9