Thermal properties of different transition metal forms of montmorillonite intercalated with mono-, di-, and triethanolammonium compounds Ali E. I. Elkhalifah • M. Azmi Bustam • T. Murugesan Received: 29 January 2012 / Accepted: 21 August 2012 / Published online: 18 September 2012 Ó Akade ´miai Kiado ´, Budapest, Hungary 2012 Abstract In the present study, different transition metal forms of montmorillonite have been intercalated with mono-, di-, and triethanolammonium cations via d coordination mechanism to investigate their thermal behavior, structural characteristics, surface properties, and elemental composition using TG, XRD, BET, and CHNS techniques. Thermo- gravimetric analysis showed two thermal transition steps for transition metal-exchanged montmorillonites, which attrib- uted to desorption of the physically adsorbed water and hydrated water, and dehydroxylation of the structural water; whereas for ammonium-montmorillonite complexes, the TG curves showed three thermal transition steps which attributed to desorption of the adsorbed water and dehydration, decomposition of the ammonium cations in the interlayer space of montmorillonite, and the dehydroxylation of the structural water. The thermal analysis of ammonium-mon- tmorillonites affirmed that the molar mass of amine com- pounds used affects both desorption temperature (position) and the amount of the adsorbed water (intensity). XRD results revealed that the molar mass of amine used has linear relation with the basal spacings of the corresponding ammonium-montmorillonites, indicating structural changes. BET results showed that the molar mass of amines has an inverse effect on the surface area of the studied samples. CHNS analysis for the studied samples quantitatively con- firmed the intercalation of ammonium cations into the interlayer space of montmorillonite. Keywords Thermal analysis Á Ammonium- montmorillonite Á Transition metals Á Intercalation process Introduction Montmorillonite is a T-O-T phyllosilicate clay mineral that consists of two tetrahedral silicon oxide sheets linked to a central octahedral aluminum oxide sheet. Montmorillonite clay mineral shows a broad spectrum of essential properties and characteristics, which reflect a variety of final uses and applications [1]. The development and preparation of or- ganoclays was started in 1940s for their use as thixotropic agents to control flow characteristics of oils, greases, paints, suspensions, printing inks, cosmetics, etc. [2]. Recently, organoclays namely montmorillonite clay min- eral treated with amine compounds have extensively been used in various industrial applications such as adsorbents in environmental remediation, polymer nanocomposites, and rheological control additives [1, 3, 4]. Transition metal cations, such as Ni 2? , Cu 2? , Zn 2? , and Cd 2? , initially present in the interlayer space of montmorillonite clay mineral interact with amine compounds via cationic coor- dination d complexes, where amines act as electron donors. Thermal analysis of clays and modified clay minerals records the thermal reactions and transformations occur- ring in the examined samples upon heating. The thermal reactions for untreated clays may include: dehydration of the adsorbed water, dehydroxylation of structural water, and phase transformation [5]. On the other hand, the A. E. I. Elkhalifah (&) Department of Chemical Engineering, Faculty of Engineering, Al-Neelain University, Khartoum 12702, Sudan e-mail: lkhlfh@gmail.com M. Azmi Bustam Á T. Murugesan Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia 123 J Therm Anal Calorim (2013) 112:929–935 DOI 10.1007/s10973-012-2657-z