Reality-Based Engineering

Pollutant Cleaning Method Discovered

Researchers Use Iron And Oxygen to Clean Contaminated Water
By BONNIE HO
Contributing Writer
Wednesday, March 2, 2005

The rust coating on an old cooking pan comes from the same process of iron corrosion that can purify drinking water. Scientists have spent years searching for better ways to clean water pollutants and, recently, a group of environmental engineers in Sydney, Australia found a new approach using iron and oxygen that will clean troublesome pollutants from water.
“Over the past twenty or thirty years environmental engineers developed a lot of different ways to clean up this contaminated water,” said UC Berkeley civil and environmental engineering
professor David Sedlak, who is continuing his work from the past year in Sydney as a Fulbright scholar.
Among such water treatment methods, engineers have used bacteria and activated carbon, the same substance found in household water filters.
“New research that we have done on iron provides us with a way with treating a group of chemicals that contaminates water that can’t be cleaned up by other conventional methods,” Sedlak said. In the event of an underground gasoline leakage, the findings could be used to treat water contaminated with the gasoline additive methyl tertiary-butyl ether (MTBE). This process may also be able to clean pesticides from water, and also water contaminated with N-nitrosodimethylamine (NDMA), which is sometimes found in water after it has been treated with chlorine disinfectants.

“There are places in the country where each of these contaminants has shown up in the water supply and when they do it’s quite expensive to treat them. This could lead to the development of less expensive treatment systems,” Sedlak said. In the past, iron was used without oxygen to reduce, or give electrons to, the pollutant compounds in ground water and transform them into less toxic chemicals. Recently, however, Dr. Sung Hee Joo and professor David Waite from the University of New South Wales have determined how iron can transform pollutants into carbon dioxide and water.
In this method, iron first gives electrons to oxygen and the resulting hydroxyl radical will oxidize, or take electrons away, from the pollutant. The traditional method mostly targeted pollutants with many chlorine atoms, but this method can target different kinds of pollutants other than chlorine compounds. Junior environmental engineering major Lindsay Soh is
currently experimenting to find out the time it takes for iron to corrode.

“It would be nice to have a time frame for the experiment so that we know, for example, if iron would take three days or three hours to oxidize the contaminants,” Soh said.
This process of iron corrosion can happen with iron particles of large or small diameters. The smaller sizes can react much more quickly because of their high surface area-to-volume ratio. Sedlak is collaborating with researchers in Sydney to find new ways of making iron nanoparticles.
“In a drinking water process you might want the reaction to occur very quickly,” Sedlak said.
According to Sedlak, these tiny particles can possibly even be put directly into ground water without getting stuck in soil.
Contact Bonnie Ho at science@dailycal.org