Inherently Functionalized Carbon from Algae to Adsorb Precursors of Secondary Organic Aerosols in Noncombustion Sources

Recent findings have opened a new window on a hidden source of volatile and semivolatile organic compounds that are released into the atmosphere in the form of gas or aerosol. Asphalt pavement and bituminous composites in general have been found to be noncombustion sources that emit gas-phase precursors of submicron atmospheric aerosols that have serious impacts on human health as well as the climate. This study highlights the merits of using an inherently functionalized carbon (IFC) derived from an algal feedstock to selectively adsorb some potentially hazardous bitumen emissions, alleviating the side effects of intense sun exposure and high temperatures on air quality. With the use of density functional theory (DFT), six organic compounds emitted from bitumen that are precursors to secondary organic aerosols were modeled, then their adsorption to the active zones of a model surface of the IFC containing N-functional groups of amide, amine, pyrrole, and pyridine was measured. In a laboratory experiment, the adsorption properties of the functionalized carbon were also evaluated by a vapor sorption analyzer, supporting the DFT results that indicate the IFC's potential to retain these volatile compounds in the matrix of bitumen. Of the organic molecules studied, benzofuran showed the least interaction with functional groups of the IFC surface (ΔE = -8.3 kcal/mol) and the most total adsorption uptake (2.443 wt %) by the IFC. Dibenzo-thiophene showed the most surface adsorption (ΔE = -18.1 kcal/mol) and the least total adsorption uptake (0.018 wt %) by the IFC. This could be explained by the extent of mobility and penetration of target volatile organic molecules into the IFC's pores. The strong interactions of the IFC's functional groups with organic molecules limit their penetration into the IFC's pores, leading to a decreased total adsorption and vice versa.