Recent spike in anthropogenic greenhouse gas emissions have resulted in increased atmospheric concentrations of methane, carbon-dioxide, and nitrous oxide. The effects of these gases together with other anthropogenic drivers are the main cause of the global warming experienced since the mid-20th century. The UN Conference on Climate Change (Paris 2015) mandated all member nations to promote mitigation of anthropogenic greenhouse gases. This was in a bid to reaffirm the goal of capping the global temperature increase below 20 C.
Importantly, scientists can provide creative carbon dioxide capture solutions for major CO2 drivers, thus enabling mitigation of atmospheric concentration. For example, in fossil burning plants carbon dioxide could be captured by applying a liquid solvent through an absorption-based method. Once absorbed by the liquid solvent, the carbon-dioxide would be temporarily stored and then released by heating in the form of a high-purity carbon-dioxide stream. The carbon dioxide can be compressed for storage and transport. Unfortunately, liquid sorbents are corrosive, and therefore, solid sorbents gain more attention in recent years.
Researchers lead by professor Cheng-Yu Lai from Delaware State University reported for the first time, the application of stellate macroporous silica nanospheres featuring a hierarchical pore alignment and large surface area, as a carbon dioxide capture platform. Pentaamine was used to functionalize the stellate silica materials. Their work, funded by US DOE National Energy Technology Laboratory, is now published in peer-reviewed journal, Journal of Materials Science.
Stellate macroporous silica nanospheres are a form of silica nanospheres obtained through surfactant template synthesis. In order to convert the stellate macroporous silica nanospheres into a carbon dioxide capture platform, and maximize the accessible sorbent surface, the research team evaluated a wide range of surface functionalization approaches and decided on a relatively simple amine impregnation method which can result in high and stable amine coverage compared to chemical coupling or co-condensation. The authors adopted as model an amine-containing molecule – tetraethylenepentamine, an inexpensive pentaamine molecule.
Tetraethylenepentamine-stellate macroporous silica nanospheres materials were applied in carbon-dioxide capture analysis designed to determine absorptivity of pure carbon-dioxide in these amine functionalized materials. The capture of carbon-dioxide was done using thermogravimetric analysis by tracking weight gain of materials over a predetermined period. The performance of these materials at low and elevated temperatures proved their excellent potential for carbon-dioxide capture.
The highest absorption capacity reached over 100 mg carbon-dioxide per gram of material. This figure achieved in this study exceeds the reported results in silica-amine platforms. Counting on the low amine usage efficiency, improvements in silica scaffold, and subsequent increase in the surface area of untreated silica are feasible paths to further enhance the carbon-dioxide capture capacity of the stellate macroporous silica nanospheres.
Daniela R. Radu, Nicholas A. Pizzi, and Cheng-Yu Lai. Functionalized stellate macroporous silica Nano-spheres for CO2 mitigation. J Mater Sci, volume (2016) 51: pages 10632-10640.Go To Journal of Materials Science