Calorimetric study of amino-functionalised SBA-15

Abstract

Amino-functionalised SBA-15 mesoporous silica was prepared with 3-aminopropyltriethoxysilane via post-synthetic reaction from SBA-15. Then, the samples were characterised and used as an adsorbent for heavy metal ions (Co(II)). The structure and physicochemical properties of the materials were characterised by means of nitrogen adsorption–desorption isotherms, FTIR spectroscopy, acid-based titration and immersion calorimetry. In this work, we will focus on the latter technique. Immersion enthalpies were determined using a heat conduction calorimetre Calvet type of local construction. The immersion liquids used for the calorimetric characterisations were benzene, water, ethanol and Co(II) solutions. Calorimetric studies showed that the immersion of the modified solid in each liquid and solution generated values of enthalpy at a range of between 20 and 137 J g–1. Among the results, the highest values were the immersion in ethanol of the SBA-15 sample (137 J g–1) and the SBA-15-NH2 sample (28.32 J g−1). The same tendency was observed for immersion in water (73.58 J g−1 for SBA and 52.67 J g−1 for SBA-15-NH2). Regarding the ion solution, in the calorimetric test, the enthalpies were not significantly different when the immersion was carried out with SBA-15, but when the enthalpy decreased for SBA-15-NH2 up to a 50 %, a blue colouration was evidenced with the Co(II) solution.