Painting with Acid Mine Drainage

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Coal has been king throughout large portions of hardscrabble Appalachia for as long as most anyone can remember.

Its legacy is mixed, however, as abandoned mines that dot the region leach brightly colored runoff saturated with heavy metals and other pollutants into the watershed.

Remediation has proved difficult. In Pennsylvania alone, some 5,000 miles of streams are victims of mine drainage and limited federal and state cleanup funds are hotly contested.

Now, an unusual collaboration between an engineering professor and an art professor shows promise in a potential commercial venture to reclaim the metals to make paint pigment.

Guy Riefler is an associate engineering professor at Ohio University in Athens, deep in the state’s southeastern coal country, who became aware of the issue on a tour of the region shortly after taking his post in 2006.

Later, he met someone “mining” iron sludge deposits at mine runoff sites, separating out the metals, and selling it to paint companies.

“If he was collecting deposits from sites, I thought, ‘Why not treat at the source?’” he says.

Simple Seep

Acid mine waste can contain a complex brew of heavy metals, but Riefler started his research with a focus on iron, and found one nearby seep with an almost exclusive iron content. “Other seeps have other metals in high concentration and you have to work to separate them. From the perspective of the chemistry of water, this [seep] was the easiest to tackle,” he says.

Enlisting his students, they drew samples from the stream in jerry jugs and carried them back to the lab where he settled out the metals in a relatively simple process. “You just neutralize the water with the addition of a base to adjust the ph, and then oxidize the water. The ferrous iron converts to ferric iron and precipitates out,” he says.

Turning the iron into a high-quality base for pigment is more difficult. “Iron can form a variety of different solids,” notes Riefler. “It has to be high in iron content and with a uniform crystal structure. We were producing a dry oxide but had a difficult time assessing things [such as color ranges] in my lab. Producing paint is an art and having an artist’s eye really helps.”

Seeking Help

So Riefler crossed campus and found John Sabraw, an associate art professor with experience in making his own paints. “The color can be affected by how high the heat used to treat [the pigment],” Sabraw says. “With this material, you should be able to get a range from yellow to red to black. You have to learn how to tweak it through trial and testing.”

Sabraw had enough success over a two-year period to produce a series of tremendously vivid paintings using pigments from mine drainage, called Chroma. The exercise dovetailed nicely with his vigorous advocacy of sustainability, especially what he calls sustainable art.

For instance, the Chroma paintings are composed on common signage material, two thin sheets of aluminum sandwiched around a plastic core. Frames are of organically grown bamboo that is formaldehyde free.

Producing acrylic paint is relatively straightforward, he says, as the pigment can be mixed directly with acrylic polymers while it is wet. Oil-based paints are more difficult as the pigment must be dried, and “that’s where the engineering could get crazy,” he says.

The pigment must be heated to different temperatures to produce different colors. (“Think of it as toasting bread.”)

Sabraw had an idea the venture could produce vivid colors after his own travels in the region educating himself on Ohio’s role in coal production. “We went to one of the streams, and half was all white and the other half all orange,” he says. “Later, we tested out the pigment using different methodologies.”

But how to make the venture profitable? Sabrow admits the market for such paints is minimal. “Almost nobody makes their own paint,” he says. “The commonly available stuff is very good quality.”

The Next Step

Riefler hopes to bring the concept up to a commercial scale, noting government statistics from 2007 that the U.S. market for iron oxide pigment is about 230,000 tonnes per year.

Some 178,000 tonnes is imported, primarily from China. Just as important, the project would remediate a longstanding local problem, he says.

“I became an engineer because I wanted to achieve something; to use engineering principles to reduce pollution,” he says. “This would meet that lifetime goal. This is a local problem that nobody is really doing anything about. One site can kill several miles of stream so to me this is really satisfying.”

Riefler says the seep he has targeted discharges about one million gallons per day of polluted water with a potential yield of some 2,000 pounds of iron per day. Capturing it calls for construction of a water treatment plant at the source to settle out the pollutants, followed by a sludge-processing system.

Those are common technologies, he notes. The part that still needs to be finessed is dewatering and pulverizing the product to be of market quality.

“I’ve run the numbers as best I can and it seems this should be a profitable enterprise,” he says. “And the focus is still on sustainability.”

Riefler’s work has drawn the attention of the U.S. Forest Service, which must deal with acid mine drainage in nearby Anthony Wayne National Forest. The university and the forest service have funded much of Riefler’s work so far, but he’s looking for more funding to take the project to the next level.

Article republished with permission from ASME, the American Society of Mechanical Engineers