Cleaning up toxic spills
New technology developed at UNT uses biomass to quickly, cost-effectively clean up toxic spills
While accidents such as the Deepwater Horizon spill that cost BP $65 billion make headlines, billions of dollars also are spent each year to clean up smaller petroleum and industrial spills.
Sheldon Shi, professor of mechanical and energy engineering at UNT, and his graduate student, Changlei Xia, have developed a cost-effective method to rapidly clean up spills and contamination in water and on hard surfaces. By using magnetized activated carbon — or MAC, made from biomass, and a magnetized collection device, the contaminant is quickly adsorbed and then removed with magnets.&
Adsorption is the adhesion of particles to a surface, as opposed to absorption where the particles are soaked into the material itself. Sponges absorb because the water goes into the actual sponge fibers. In activated carbon, the molecules are adsorbed — attached to the surface inside the pores. Adsorption results in greater containment due to the surface area of the pores, and no contaminant remains when the process is complete.
Processing organic materials
Activated carbon can be made from a variety of biomass resources, which could be anything from corn husks to bamboo. Once carbonized and activated, the biomass is extremely porous and highly effective at removing contaminants. Residues from wood processing, such as sawdust, a recycled and renewable resource, is readily available in the North Texas region and is the current vehicle used in the method.
“For the magnetization, you can’t just mix sawdust and iron shavings. When you put it in the water, it will separate,” Shi says. “We have developed a way to process it.”
The technology, developed in Shi’s laboratory and patented by UNT, is a process to magnetize the biomass. The method can be customized to create different levels of porosity (the size of the pores in the carbon) and magnetization so that the process can be used to clean up a range of contaminants.
“The magnetization can be stronger or weaker. The product can be used with large molecules like oil or small molecules such as heavy metals,” explains Shi. “If you know the analysis of what the major contaminants are, you can design the product for that size molecule. The raw materials are the same. We just use different processing parameters.”
After the contaminant is removed with the magnetized collector, it is further remediated by a process similar to squeezing it from a sponge. The MAC can be reactivated to be used again, and the contaminant can either be contained or recycled.
“In an oil spill, it can be recycled,” Shi says, “at least 60 or 70 percent, and the rest of the MAC can be reactivated, which will not generate additional waste.”
Impacting the environment and industry
The technology has the potential to make a tremendous impact on the toxic cleanup industry. It has been licensed to EnviroMAC Solutions, a startup company formed for the commercialization of this new environmental product.
“In developing the technology in our laboratory, we were looking at reliability, recyclability and, of course, optimization of the processing in addition to the functionality,” Shi says. “And we also looked at the cost.”
Michael Loya, CEO and founder of EnviroMAC Solutions, is a long-time advocate for environmental stewardship of water and natural resources, serving as a delegate and presenter at the U.S. Department of Energy’s environmental justice conferences. With more than 35 years’ experience in the construction and renovation industry, Loya has worked as an environmental drilling contractor and has been involved with environmental water and other projects for the U.S. Army Corp of Engineers, U.S. Air Force and other government agencies. He is interested in developing technologies to clean up the environment and learned about the technology when researching advanced methods of environmental remediation.
“It’s technologically advanced. It’s cost effective. It’s easy to implement,” Loya says. “When you have those factors, then you have something that’s a win-win for people in industry, especially the oil industry. Clean up affects the bottom line. The time factor of the implementation and the cost factor of the product are paramount, which are key points in the EnviroMAC Solutions sustainable paradigm.”
The technology has been demonstrated with a variety of substances in Shi’s laboratory. Tests in water show that the magnetized activated carbon picks up virtually all the NAPLs, or non-aqueous phase liquids, contaminants that do not dissolve in or easily mix with water, such as oil and gasoline. NAPLs are common culprits of soil and ground water contamination.
The technology can be used in water, as in the example of oil or chemical spills or in drilling near aquifers, or on dry surfaces such as with vehicle accidents, gas stations or industrial environments. The magnetic collection device will vary based on the application.
Through a capstone project, Shi is supervising a group of UNT mechanical and energy engineering design students to prototype a magnetic collector in the laboratory, targeting a larger demonstration soon in a contaminated pond. For spills on the floor or street, it could be a simple roller on a stick like a broom or vacuum cleaner. Loya and Shi believe that the ease of application and removal will result in faster and safer remediation than current methods.
“Additionally, there is virtually no residual byproduct,” Shi says. “You don’t want another contaminant.”
The product is nontoxic, consisting of carbon and iron. Activated carbon is commonly used in household water filters, and iron is used in cookware. No additional chemicals are involved. In situations such as spills in the open ocean, if the product is not able to be fully recovered, it is not harmful to the environment. Dispersants, chemicals currently used in oil spills, have been criticized for potential harm to wildlife and humans.
“The goal of my research and work is to utilize biomass as much as possible, in order to create sustainable products and increase conservation,” Shi says.