TiO2/titanate composite nanorod obtained from various alkali solutions as CO2 sorbents from exhaust gases

• Amine-modified (with tetraethylenepentamine) TiO2/titanate composite nanorods were successfully prepared.
• KOH or NaOH solutions were used for TiO2/titanate composite nanorods preparation.
• The highest adsorption capacity (3.02 mmol CO2/g) was found for P25-NRsK-TEPA sample.
• P25-NRsK-TEPA shows a fair stability and regenerability in multiple-cycle operation.

A series of TiO2/titanate composite nanorods-based CO2 adsorbents with a high capture efficiency was prepared through hydrothermal method, followed by annealing at 350 °C in air, and subsequent functionalization with tetraethylenepentamine (TEPA). The CO2 adsorption performance of the prepared samples was measured using TGA. Firstly, it was found that the increase of adsorption capacity was related to textural properties of tested nanomaterials (higher for nanorod composites than for starting TiO2 and P25 powders). Secondly, the TiO2/titanate composite nanorods, obtained in the presence of KOH, exhibited higher adsorption capacity for CO2 in comparison with the NaOH-modified samples due to the increase of the SBET, total mesopore volume. Moreover, the nanorod composites obtained in presence of KOH exhibited a high content of titanate. TEPA-modified TiO2/titanate composite nanorods (P25-NRsK-TEPA) showed the highest adsorption capacity of 3.02 mmol CO2/g. This result could be indirectly related to high surface area responsible for maximizing exposure of its NH2 functional groups for interaction with CO2 and the higher pore volume, which may reduce the conglomerates of the impregnated TEPA within the pores, leading to better distribution of amine and consequently increasing the CO2 adsorption capacity. The results also indicates that TEPA-titanate interaction enhances CO2 capacity compared to TEPA-anatase materials. That material not only displayed high CO2 adsorption capacity but also exhibited a relatively stable performance during 6 consecutive adsorption-desorption cycles.

CO2 adsorption capacity of unmodified P25, P25-NRsK, P25-NRsNa and TiO2/titanate composite nanorods modified with TEPA.Figure optionsDownload as PowerPoint slide