Lipid lather removes metals.

Metal contamination has been linked to birth defects, cancer, skin lesions, retardation, learning disabilities, liver and kidney damage, and a host of other maladies, and the United States alone will spend some $7 trillion over the next five years or so to clean up sites contaminated with metals. Until recently, there have only been a few time-consuming, costly methods for dealing with metal contamination in soils, but research developed at the University of Arizona uses biosurfactants, lipids that form emulsions between liquids of different polarities, to virtually "wash" metals out of contaminated soil. Lab tests show that 80-100% of single metals including cadmium and lead can be removed through the use of environmentally benign biosurfactants.

At low concentrations, biosurfactants are present as single molecules (monomers). At higher concentrations, these monomers spontaneously aggregate into complex structures soil washing, produces a solution containing soil and the complexed metal. After mixing, the soil is allowed to settle and the liquid solution is pumped out of the mixture, leaving clean soil. An advantage of this method, says Maier, is that the biosurfactant can be recycled and reused. One way to do this is to acidify the solution to a pH of approximately 2 to precipitate out the biosurfactant, which then can be reused. Another is to blow air through the solution to cause the biosurfactant-metal complex to begin foaming. The foam can then be skimmed off the solution surface and treated to separate the biosurfactant and metal.
Deeper, subsurface contamination requires a different process, says Maier. "Then you have to do what's called 'pump and treat,' which involves pumping the biosurfactant through the contaminated soil, pumping the contaminant-containing solution back to the surface, and then treating it to remove the metals," she says. This is a promising technology, Maier says, but she also admits it is not an all-purpose solution.

Biosurfactant Boom on the Horizon
Biosurfactant metal remediation may still be several years from commercial use, but Maier says interest has already been expressed by several remediation and manufacturing firms, including Bio-Ohio, based in Scottsdale, Arizona, which has been in discussions involving funding research to use this technology to remove metals from sludge. Says Maier, "Here in Arizona, we have a lot of wastewater sludge that's high in copper because copper mining is a big industry in this state. Wastewater sludge makes a great soil additive, and if you could remove the excess copper and other metals, you could apply it much more freely. We're starting a project to address that possibility this summer." Bio-Ohio representative Logan Fanjoy says his firm is developing a process to combine Maier's biosurfactant technology with another technology in development to create a whole new approach to biosolids treatment, an approach that is commercially very attractive. Says Fanjoy, "I can say we're targeting a flow of 120 million gallons a day, with a treatment cost of less than $10 per gallon. When you compare that to current situations, where it can cost $90 per wet ton just to transport the biosolids, and when you figure we're looking at a treatment process that could [shorten the remediation time from] the current 18-30 days into 2 days, you have a very appealing prospect.
There are still a few hurdles to overcome before biosurfactants become a truly viable commercial alternative in environmental remediation. First would be cost, which will drop as the market builds and as improvements in the fermentation and purification processes take place. A second hurdle will be in convincing companies to use the new biosurfactant technology. Many companies have been using synthetic surfactants for a long time (estimates put the synthetic surfactant industry at sales of better than $8 billion annually) and would need convincing to make a substantial change, especially if it involves an increase in cost.
Robert Procopio, a representative of Jeneil Biosurfactant Company, a Milwaukee, Wisconsin-based firm that makes commercial biosurfactants, says his firm is capable of producing biosurfactants in up to 20,000-gallon batches, but because the market is still developing, operates instead on a "batch to order" basis. "We use a proprietary strain of bacteria similar to the one Dr. Maier is using but which has been optimized for maximum biosurfactant production in a short period of time," he says. "It takes several weeks to make a batch, and at this time, it's more expensive than a synthetic surfactant because of the tremendous quantity in which these synthetics can be produced." However, he says, "One thing that is working in our favor is that biosurfactants are becoming competitive with synthetics on a price-performance basis. We're seeing research indicating that many formulations that might use 8-9% synthetics can perform equally well with less than 1% of a biosurfactant." Jeneil's product is used in crude oil tank cleaning, industrial  what we see as an increased sensitivity to the environmental danger posed by synthetic surfactants," Procopio says. "There are some European governments that are moving toward heavy regulation, if not the outright banning, of synthetic surfactants .. . and as that continues, the market for biosurfactants will continue to grow." While there are still technical problems to overcome, says Soberon-Chavez, "I think this is an invaluable technology because of its effectiveness and its environmentally benign nature. I think the most difficult problem for the application of this technology is that the people involved in making decisions about how to treat specific contamination problems need to be sensitized to the benefits of this technology. I think we'll need an intensive educational campaign before we see widespread biosurfactant use in the field." William Suk, deputy director for program development in the Division of Extramural Research and Training at the NIEHS, which provides grant funding for Maier's work, says that one factor that may speed acceptance of this technology for use along the U.S.-Mexico border, where metal contamination is a significant environmental health threat, is the growth of research collaborations between the two countries. Says Suk, "Over the past several years, we've worked more closely with Mexican academics and government officials, and I think we've succeeded in building a high level of trust. The fact that they're looking closely at the technology we've developed is a product of that growing trust. [Maier's] work is a key component of a new way of doing things that will only benefit both countries." "I think the most important way to look at this technology is as part of a list of natural products we're only beginning to explore in any detail," says Maier. "What we've done is to show that one natural, environmentally benign product has unique metalcomplexing properties. It is likely that if we explore other natural products, some with even superior properties will emerge....

This research should encourage us to look
further to see what other biological products have these same kinds of unique properties and how we can use them to clean up contaminants in the environment."