Polymer Filtration^TM —
a universal technology
for worldwide applications

The accomplishments are impressive—a 1995 R&D 100 award, four U.S. patents, a 1995 Distinguished Performance Team Award, and a nomination for a 2000 Los Alamos National Laboratory Distinguished Performance Team Award. The potential is amazing—versatile enough to remove radioactive elements from nuclear waste streams, reclaim silver from electroplating and photofinishing wastewater, and much more. The biggest surprise, however, is that this innovative technology called Polymer Filtration^™ (Tech ID 2041) has not been exploited.

Polymer Filtration uses chemically modified water-soluble polymers to remove valuable or regulated metal ions from aqueous waste streams. The special polymers selectively bind metal ions, creating larger compounds that can then be filtered from the waste stream. While the technology has been successful in several demonstrations, such as capturing nickel and zinc for reuse from electroplating solutions (see Initiatives, June 1996), removing americium and plutonium from wastewaters, and removing mercury from debris for disposal, Polymer Filtration is in only the early stages of commercialization.

Principal investigator and coinventor Barbara Smith is working hard to share the benefits of Polymer Filtration. She believes the technology’s potential is bound only by the periodic table of elements. “There are just so many applications,” Smith said. “You’re almost imagination limited.” Unfortunately, this potential has not been realized, according to Smith, because industries are often inflexible and reluctant to change. “It takes time to penetrate industries,”she said.

Smith identified the international nuclear industry as one potential user of Polymer Filtration. The technology’s effectiveness was recently demonstrated with a small-scale testing unit at the Plutonium Facility (TA-55) at LANL. Polymer Filtration successfully removed radioactive metals, such as plutonium, americium, thorium, and uranium, with the filtered water meeting all regulatory requirements. Experiments demonstrating ultrafiltration on neutralized process solutions have shown that alpha activity can be reduced by 1,000 times or more below current filtration methods. “It remains a work in progress,” said Louis Schulte, from the Nuclear Materials Technology Division. “But I’m very enthused with the planned pilot-scale demonstration.” Smith hopes that, with the help of commercial partner (n,p) Energy, the success demonstrated at LANL’s Plutonium Facility will be replicated on a larger scale. (n,p) Energy is currently communicating with representatives from French nuclear facilities for possible Polymer Filtration use there.

Cleaning up wastewater at nuclear power reactor sites is just one of many applications for Polymer Filtration. The technology, which was developed at LANL in the early ’90s, is still being tested and demonstrated in new areas. In the mining industry, for example, Polymer Filtration could actually recover precious metals, such as copper and zinc, and clean up acid mine drainage as well.



Moreover, Polymer Filtration may be an environmentally sound alternative to mining practices, such as heap leaching with cyanide. Over the years, research has been funded through a number of DOE programs, including OST’s Efficient Separations and Processing Crosscutting Program, the Mixed Waste Focus Area (now known as the Transuranic and Mixed Waste Focus Area), the Laboratory Directed Research and Development Program, and the Office of Industrial Technology.

The chemistry of metal separations is optimized with Polymer Filtration, providing benefits not possible with traditional approaches to metal separation. Precipitation is currently a common method for removing regulated metal ions from aqueous wastewaters. While this process is simple and uses low-cost reagents, it does not completely remove all metal ions, resulting in effluents that may not comply with federal discharge limits. Furthermore, a large volume of waste sludge is produced, since precipitation not only pulls out the targeted metals but also collects other metals. Because of its selectivity, Polymer Filtration produces relatively small amounts of concentrated metals instead of generating large quantities of sludge.

The selectivity of Polymer Filtration is made possible by synthesizing the polymers to target a specific metal and account for unique environments. “We try to tailor the polymer to the particular application,” said Thomas W. Robison, coinventor of the technology. “We have probably developed on the order of 25 to 30 different polymers.” Most, but not all, of the polymers are derivatives of commercially available polymers.

The innovative chemistry in Polymer Filtration is maximized through the use of a commercial ultrafiltration membrane and a closed-loop system. After polymers bind with metal ions, the waste stream is forced through the membrane, which retains the larger polymer-metal ion combination while allowing the smaller water molecules and unbound molecules, or ions, to flow through freely. The metal ions retained by the membrane are then separated from the polymers by adjusting the pH. Most commonly, the polymers and water are reused, while the metal ions are either disposed of or recycled. These metals are typically lost in conventional material-separation processes. Because the polymers are recycled into the system, there is no secondary waste or sludge stream—unlike that produced by precipitation wastewater treatments.

Polymer Filtration will likely become more popular with the national trend toward zero-discharge operations. To reach that goal requires different approaches to wastewater handling than baseline precipitation technologies, which cannot be improved enough to meet more stringent discharge requirements. Polymer Filtration is more efficient and flexible and has been put through a series of U.S. Environmental Protection Agency beta tests as applied to electroplating wastewaters and found to be the technology of choice.

For more information, see http://www.polyfilter.lanl.gov/default_main.htm, or contact Barbara Smith, bfsmith@lanl.gov.