Researchers from Rice University have developed filters that can remove toxic heavy metals from water. Carbon nanotubes immobilized in a tuft of quartz fiber absorbed 99 percent of cadmium, cobalt, copper, mercury, nickel, and lead from water samples.
The filter is so effective that only one gram of the material could treat 83,000 liters of contaminated water to meet World Health Organization standards, according to calculations made by the researchers. This amount of water could meet the daily needs of 11,000 people.
Lead author Perry Alagappan was still a high school student when he teamed up with Rice University chemist Andrew Barron for the project. Alagappan learned about the contamination of groundwater by electronic waste in India and set out to find a solution.
Barron points out that the raw materials for the filters are inexpensive. The filters can be washed with a mild chemical like vinegar and reused, which simplifies the process of recycling them even in remote locations.
The powerful filters consist of carbon nanotubes grown in place on quartz fibers that are then chemically epoxidized. The quartz provides the framework and the carbon nanotube covering makes the filter tough, but the researchers determined the epoxidation appears to be most responsible for adsorbing the metal.
Scaled-up versions of the “supported-epoxidized carbon nanotube” (SENT) filters were able to treat 5 liters of water in less than one minute. The filters were restored in 90 seconds, and retained almost 100 percent of their capacity to purify water for up to 70 liters per 100 grams of SENT. The metals absorbed in the materials can either be extracted for reuse or turned into a solid for safe disposal.
“This would make the biggest social impact on village-scale units that could treat water in remote, developing regions,” Barron said. “However, there is also the potential to scale up metal extraction, in particular from mine wastewater.”
An analysis of these lab results will be published in this month in the journal Scientific Reports.