Research Profiles

Pei Chiu, an environmental engineer at the University of Delaware, is working to understand how tiny particles of black carbon interact with environmental pollutants.

Black carbon comprises a collection of carbon-rich nanoparticles (particles on the order of one billionth of a meter in size) that play a pivotal role in determining the fate and transport of organic pollutants in aquatic and terrestrial environments. The central hypothesis of our project is that black carbon can act as both a sorbent (a substance to which other substances adhere) and a mediator of redox reactions (reactions involving the transfer of electrons from one substance to another). This is in contrast to current dogma, which says that geosorbents such as black carbon can act as sorption sites, but not reaction sites. Recent experimental work has shown that molecules adsorbed to graphite have dramatically increased redox reaction rates, presumably because graphitic structures can conduct electrons from a reducing agent to adsorbed organic molecules. Black carbon contains similar graphitic structures, and a similar enhancement in reactivity is expected.

Our project involves a combination of laboratory experiments and computational studies intended to test the hypothesis that black carbon enhances redox reaction rates and to explore the mechanism of reactivity. Experiments will use graphite and two reference black carbons as models. Initial studies will concern the transformation of black carbon-sorbed nitroaromatic compounds in the presence of an environmentally relevant reductant such as iron [Fe(II)], cysteine, and hydrogen sulfide (H₂S). Computational studies will provide a mechanistic explanation for the enhanced reactivity. They will also guide the choice of further systems and support development of mechanistic models of the process.