Top Papers in Environmental Technology, Second Runner-Up: Stars align for PCB cleanup technology
ANTHONY T. ZIMMER, U.S. EPA NRMRL
The technology discussed in the tate the chemical or biochemical “Adsorption and Simultaneous paper uses palladium because degradation of PCBs. The NRMRL Dechlorination of PCBs on GAC/ “we wanted the most efficient researchers’ approach “represents Fe/Pd: Mechanistic Aspects and [metal] for the job,” Al-Abed says. an important first step in a new Reactive Capping Barrier ConOther metals may play the same direction in reactive cap research,” cept” by Hyeok Choi, Shirish role, and the researchers are curDzombak says. Agarwal, and Souhail R. Al-Abed, rently investigating the National Risk Managepotential of less expensive ment Research Laboraalternatives. tory, U.S. EPA, 2009, 43, Al-Abed says “the stars 488-493; DOI 10.1021/ started aligning” when he es8015815. and his colleagues began Developing effective trying to devise a way to technologies for cleaning combine palladium and up the 450 million pounds iron with granular actiof toxic and highly persisvated carbon. He credits tent PCBs released into Choi, who is completing the U.S. environment bepostdoctoral studies at tween 1929 and 1977 is NRMRL, with devising the one of the highest priorinovel process for syntheties of the U.S. EPA Office sizing the material (Chem. of Research and Develop- (Left to right) Hyeok Choi, Souhail R. Al-Abed, and Shirish Mater. 2008, 20, 3649ment (ORD). In one of Agarwal developed their new reactive cap for remediating 3655). Choi says the key ES&T’s best papers of PCBs at NRMRL. They tested the technology with PCB2008, Souhail Al-Abed and laden sediments from Lake Michigan’s Waukegan Harbor in was selecting a form of granular activated carbon Illinois (inset). colleagues at ORD’s Nacontaining mesopores of The reactive cap that Al-Abed tional Risk Management Research 7-40 nanometers (nm) in size. invented with Hyeok Choi and Laboratory (NRMRL) describe “a This pore size limits the growth of Shirish Agarwal consists of granunew environmental risk managethe iron oxides to 7-10 nm. A lar activated carbon impregnated ment option for PCBs-contamisubsequent step in the process with reactive iron and palladium nated sites.” converts the iron to its zerovalent nanoparticles. Their paper shows Most sites contaminated with form, and another deposits the that the cap can adsorb PCBs and PCBs are underwater, notably palladium as 2-3-nm “nanoisdechlorinate them into lower-mosediments at the bottom of the lands” on the iron. The nanoscale lecular-weight formssultimately, Hudson River and the Great configuration renders the material the more biodegradable biphenyl. Lakes. Conventionally, such sites more mechanically stable than it Al-Abed adds that the new are capped with an uncontamicould be with a microsized countechnology was inspired by his nated layer of sand. “Capping ... terpart, Al-Abed says. earlier successes using electrocan be an effective approach for Since publication of the ES&T chemical methods with iron parreducing the release of persistent paper, Al-Abed says that additicles to target chlorinated compounds like PCBs to the overtional development and testing solvents, including trichloroethylying water in a river or lake, but have shown that his team’s matelene and vinyl chloride, in cona criticism of this remediation rial can overcome many of the taminated soils. To enhance technique is that it just delays the concerns raised in the ES&T news dechlorination sufficiently to contaminant release,” explains story published in tandem with tackle PCBs, he and his colleagues David Dzombak, senior professor the paper. He advises interested decided to try a bimetallic system of environmental engineering at readers to stay tuned for subsewith granular activated carbon. Carnegie Mellon University and quent reports about the The group opted for nanoscale an ES&T associate editor. technology. materials because their greater Dzombak says that several U.S. —KELLYN BETTS surface area enhances their reacgroups have been working to detivity and smaller quantities are velop “reactive caps” that combine needed, he says. sand with a material that will facili-
10.1021/es900340n
2009 American Chemical Society
Published on Web 02/18/2009
April 1, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 2201
