Intrinsic affinity of acid-activated bentonite towards hydrogen and carbon dioxide

The effect of acid activation on bentonite affinity toward carbon dioxide (CO2) and hydrogen (H-2) was investigated at ambient conditions. Characterization through X-ray diffraction and fluorescence, thermal gravimetric analysis, nitrogen adsorption-desorption isotherms, Fourier Transform Infrared spectroscopy and differential scanning calorimetry allowed correlating newly induced textural and structural features with adsorptive properties. Optimum acid treatment improved the specific surface area and porosity. The resulting decrease in dehydration temperature indicates decay in hydrophilic character. The affinity improvement towards hydrogen was due to Bronsted acidity suppression and surface basicity attenuation, which are essential requirements for adsorption on aluminosilicates (AS) via weak Lewis Acid-Base interactions, but excessive acid attack was detrimental. Low Si/Al surfaces should be suitable for CO2 capture, while moderately acid treated clays should be interesting candidates as hydrogen adsorbents. This allows envisaging promising prospects for low-cost AS-based materials intended for selective CO2-free capture and storage of hydrogen without energy and safety constraints. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.