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 degrees 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 degrees 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.