(455b) Development of Double-Functionalized Halloysite Nanotubes with Enhanced Adsorption Capacity for Carbon Capture

The industrial approach to remove CO2 involves the use of solvent-based amines but the amine regeneration step has a high energy requirement due to energy wasted in solvent heating. This has led to the development of solid amine-based adsorbents where most of the energy costs are associated with regeneration of the amines. Solid amine adsorbents capture CO2 molecules through a reversible reaction between the amine functional groups and the CO2 molecules to form carbamates in dry conditions and bicarbonates in humid or wet condition. Common solid amine adsorbents can be prepared by wet impregnation of polymeric amines within the pores of a porous support (class I adsorbents) or covalent grafting of amine functional groups onto the surfaces of a porous support (class II adsorbents). We describe a method of incorporating both class I and class II adsorbents using a novel, sustainable tubular nanoclay, halloysite. Halloysite nanotubes (HNT) are naturally occurring materials with a tubular morphology where the lumen is of the order of 15-30 nm and the length is of the order of a micron. We show that the lumen can be used to encapsulate polymeric amines such as polyethyleneimine which is the class I material and the inner and outer surface of the lumen can be functionalized with aminosilanes which serve as the class II materials. The morphology of this hybrid HNT adsorbent is such that the tubular surfaces are composed of chemically attached amino groups while the HNT lumen is loaded with PEI. The results show that the capture capacity of the hybrid adsorbent is equivalent to or higher than the combined adsorption capacity of the individual class I and class II adsorbents. The capacity can be further enhanced through doubling the surface area of the nanotube by controlled acid etching. In recent work, we also show the integration of such nanotubes into highly porous materials such as MCM-41, where the HNT serves as nanostraws to allow improved access to the interior of MCM-41 and thus enhance capture capacity.

Recent lab publication:

Farinmade, A., et al. (2022). "Tubular Clay Nano-Straws in Ordered Mesoporous Particles Create Hierarchical Porosities Leading to Improved CO2 Uptake." Industrial & Engineering Chemistry Research 61(4): 1694-1703.