A new study by an American researcher has revealed that bricks made from fly-ash particles captured as waste by coal-fired power plants might be safer than predicted.
Rather than leach minute amounts of mercury as some researchers had predicted, the bricks do the reverse, pulling minute amounts of the toxic metal out of ambient air.
New experiments by Henry Liu, a longtime National Science Foundation (NSF) awardee and the president of Freight Pipeline Company (FPC), which developed the bricks, has revealed that fly ash bricks help lower the concentration of toxic materials in enclosed air.
On average, air contains low amounts of mercury that can range from less than one nanogram per cubic meter (ng/m3) to tens of ng/m3--a small fraction of the Environmental Protection Agency limit for continuous exposure.
Liu found that inside a confined experimental chamber, the bricks did not raise the mercury levels in the surrounding air (originally more than one nanogram).
Instead they appeared to lower the concentration down to roughly half a nanogram.
According to Tom Allnutt, who oversaw Liu's NSF's Small Business Innovation Research (SBIR) program award, fly ash bricks could offset the environmental impact from the manufacture of standard bricks through fire-powered kilns.
"Green manufacturing is a focus for the nation. Liu's innovative use of fly ash to manufacture high quality building materials will potentially decrease some of the negative environmental impact of coal-fired power generation while meeting increasing demands for greener building materials," Allnutt said.
"Manufacturing clay brick requires kilns fired to high temperatures. That wastes energy, pollutes air and generates greenhouse gases that contribute to global warming. In contrast, fly ash bricks are manufactured at room temperature. They conserve energy, cost less to manufacture, and don't contribute to air pollution or global warming," Liu added.
However, further study is required to determine how the mercury adsorption occurs and how tightly the metal is trapped, said Liu.