Modified surface chemistry of activated carbons
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In this study, immersion calorimetry was used to characterise different samples of commercial granular activated carbon (GAC) which undergo oxidation with HNO3 (GACOxN) and thermal treatments to modify its superficial group contents, as well as to determine the textural characteristics of the materials through nitrogen adsorption at 77 K and its superficial chemistry by Boehm titration and zero point of charge. Correlations between the immersion enthalpies and the results of the other techniques of characterisation were established. The immersion enthalpies in dichloromethane obtained were greater, which were found to be between −88.36 and −155.6 J g−1, in contrast to those in carbon tetrachloride, which were found to be between −50.21 and −94.29 J g−1. The dependence of the immersion enthalpies in water on the contents of total acidity and basicity surface groups was also established, and a good correlation between the accessible surface area determined by calorimetric technique and the BET area was found.
KeywordsImmersion calorimetry Immersion enthalpy Activated carbon
The authors thank the Master Agreement established between the University of the Andes and the University National of Colombia, and the Memorandum of Understanding established by the Departments of Chemistry from both the universities. The authors express their thanks to Research Vice-Rectory of University National of Colombia for the financial support.
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