Summary

Combined, Hg and PCB contamination are responsible for the vast majority of fish consumption advisories currently in effect in the US. In addition, public use of Hg- and PCB-contaminated sites is limited due to human health risks associated with these often co-occurring contaminants. The goal of this project is to develop activated carbon (AC) amendment as a multifunctional, in situ sediment remediation technique to reduce the bioavailability of both mercury (Hg) and polychlorinated biphenyls (PCBs) at contaminated sediment sites.

The goal of the project was to impregnate activated carbon particles with nanoscale zero-valent iron (nZVI) to induce Hg reduction and sequestration, and PCB dechlorination. The researchers found PCB dechlorination tests using nZVI AC are very challenging due to the compound’s persistence against any type of the reaction. Polybrominated diphenyl ethers (PBDEs) were added to the target compound group after the project began. Since PBDEs are very similar to PCBs in their structures and physicochemical properties, the alternative use of PBDEs as model compounds provide valuable insight as to the behavior of nZVI AC reactions.

The research team synthesized thiolated-AC (SH-AC). Using a three-step method, the activated carbon was oxidized with ammonium persulfate, chlorinated with thionyl chloride, and finally thiolated with an aminothiol, resulting in thiolfunctionalities tethered to the activated carbon by alkyl chains and anchored by amide bonds. Elemental analysis indicated that 1-5 mmol S g-1 was functionalized on the carbon surface, depending on the synthesis routine.

To screen the synthesized sorbent for mercury sorption performance, several proof-of-concept trials were conducted. The research team believes the research will advance the scientific understanding simultaneous sorption and degradation of PBDEs and will provide fundamental background work for the development of an engineering approach to remediate the contaminated sediment using nZVI-AC amendment.