Adsorption of carbon dioxide on amine-modified TiO2 nanotubes

TiO₂ nanotubes (TiNT) were prepared by a hydrothermal treatment and modified by three kinds of amines, namely ethylenediamine, polyetherimide and tetraethylenepentamine (TEPA), to study their CO₂ adsorption properties from gas streams. The resultant samples were characterized by X-ray diffraction, transmission electron microscopy, and infrared spectroscopy, as well as low temperature N₂ adsorption. CO₂ capture was investigated in a dynamic packed column at 30°C. TEPA-modified TiO₂ nanotubes showed the highest adsorption capacity of 167.64 mg/g because it had the highest amino-group content among the three amines. CO₂ fixation on TiNT impregnated by TEPA was investigated at 30, 50, and 70°C, and the adsorption capacity increased slightly with temperature. Following the adsorption step, the sorbents were regenerated by temperature programmed desorption, and the TiNT-TEPA sample, as CO₂ sorbent, was found to be readily regenerated and energy-efficient. The cycle test also revealed that the TiNT-TEPA adsorbent is fairly stable, with only a 5% drop in the adsorption capacity after 10 adsorption/desorption cycles. In addition, the CO₂ adsorption behavior was investigated with the deactivation model, and which showed an excellent prediction for the TiNT-TEPA breakthrough curves.