Article

Journal of Thermal Analysis and Calorimetry

, Volume 105, Issue 3, pp 921-929

Thermal analyis of hexadecyltrimethylammonium–montmorillonites

Part 1. Thermogravimetry, carbon and hydrogen analysis and thermo-IR spectroscopy analysis
  • Isaak LapidesAffiliated withInstitute of Chemistry, The Hebrew University of Jerusalem
  • , Mikhail BorisoverAffiliated withInstitute of Soil, Water and Environmental Sciences, The Volcani Center, Agricultural Research Organization
  • , Shmuel YarivAffiliated withInstitute of Chemistry, The Hebrew University of Jerusalem Email author 

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Abstract

Na-montmorillonite (Na-MONT) was loaded with hexadecyltrimethylammonium cations (HDTMA) by replacing 41 and 90% of the exchangeable Na with HDTMA, labeled OC-41 and OC-90, respectively. Na-MONT, OC-41, and OC-90 were heated in air up to 900 °C. Unheated and thermally treated organoclays heated at 150, 250, 360, and 420 °C are used in our laboratory as sorbents of different hazardous organic compounds from waste water. In order to get a better knowledge about the composition and nature of the thermally treated organoclays Na-MONT and the two organo-clays were studied by thermogravimetry (TG) in air and under nitrogen. Carbon and hydrogen contents in each of the thermal treated sample were determined and their infrared spectra were recorded. The present results showed that at 150 °C both organoclays lost water but not intercalated HDTMA cations. At 250 °C, many HDTMA cations persisted in OC-41, but in OC-90 significant part of the cations were air-oxidized into H2O and CO2 and the residual carbon formed charcoal. After heating both samples at 360 °C charcoal was present in both organo clays. This charcoal persisted at 420 °C but was gradually oxidized by air with further rise in temperature. TG runs under nitrogen showed stepwise degradation corresponding to interlayer water desorption followed by decomposition of the organic compound, volatilization of small fragments and condensation of non-volatile fragments into quasi-charcoal. After dehydroxylation of the clay the last stages of organic matter pyrolysis and volatilization occurred.

Keywords

Carbon content curves Charcoal Hydrogen content curves Organo-montmorillonite Thermo-infrared spectroscopy Thermogravimetry