News | Aug 29, 2019

New activated carbon cap helps clean contaminated waterways

In 1984, about 200 miles of the Hudson River between Hudson Falls and New York City were designated an EPA Superfund site. The river was polluted with toxic PCB chemicals for over 30 years.

Julian Colton/Wikimedia

A team of research scientists at the U.S. Army Corps of Engineers has developed a new technique for containing and cleaning underwater sediments contaminated with heavy metals like lead or toxic chemicals like polychlorinated biphenyl.

A U.S. patent application published on Thursday details the results of Steven Larson, Deborah Felt, Mandy Michalsen’s work, a sediment cap made of sand coated in powdered activated carbon, also known as PAC.

That means the activated carbon, which could otherwise float away, is delivered on target because any air pockets within it have been eliminated during the powdering process and the heavy sand makes it quickly sink.

The invention can help clean contaminated waterways like the Hudson River, of which 200 miles are an EPA-designated Superfund site. For decades, factories dumped millions of pounds of toxic PCBs into the Hudson River.

When layered on top of the contaminated soils, the activated carbon begins attaching itself to the contaminants and stopping further environmental damage.

According to the patent application, manufacturing the sand-adhered PAC requires mixing 570 grams of water, 3,720 grams of #30 mesh sand, 200 grams of PAC, and 30 grams of polyvinyl alcohol (PVA), then curing the mixture.  The mixture can be stirred at 5-minute intervals over the first hour of the curing period to make the coated sand grains.

Or, “the mixture stands undisturbed during the curing process and may form a ‘cake’ or aggregate of the material. This material consists of sand grains that are attached to other sand grains as well as the PAC by the cured polymer. Once cured, this cake can be broken into a range of particle sizes or even down to individual sand grains coated with PAC,” the application states.

Like most of the inventions from the Corps’ Engineer Research and Development Center, it has been prototyped and tested, said Quinton King, senior technology manager at TechLink, a non-profit technology transfer organization that helps private companies evaluate and license government-owned intellectual property.

“In the past, sediment caps have largely been layered constructions, and adding sorbent materials was impractical, but this cake just has one layer, so it’s much more practical for large-scale remediations,” King said.

Companies interested in evaluating the technology, discussing the business opportunity, and Army patent licensing can contact Quinton King and or 406-994-7795.