Sunday, December 11, 2016 by JD Heyes
A team of researchers led by academics at Rutgers University has developed tiny, glowing crystals that are able to detect and then bind heavy-metal toxins in drinking water such as lead and mercury.
The discovery, which was detailed in a paper published by the journal Applied Materials and Interfaces, may wind up being the latest powerful tool that can be used to find and then clean up contaminated water sources like drinking water in Flint, Michigan, and Newark, New Jersey, Nature World News reported.
Known as luminescent metal-organic frameworks (LMOFs), the crystals work like small, reusable sensors and traps for heavy-metal toxins that contaminate drinking water supplies. Researchers also said that there are no other MOFs that have the same dual role of both finding and then capturing toxic heavy metals.
“Others had developed MOFs for either the detection of heavy metals or for their removal, but nobody before had really investigated one that does both,” Jing Li, a Rutgers chemistry professor and lead author of the study, said in a press release.
The team found that one type of LMOF can be selective in identifying and absorbing more than 99 percent of mercury from a test mixture of both heavy and light metals over 30 minutes. Using an X-ray device at Berkeley Lab’s Advanced Light Source (ALS) and software tools, the research team could map a three-dimensional structure of the crystal with an atomic resolution. Simon Teat, a Berkeley Lab scientist, led this particular aspect of the study, the press release said.
The research team also discovered that the crystals contain hydrogen, carbon, nitrogen, oxygen and zinc atoms that line large, open channels. In the case of this study, the openings in the LMOFs’ framework permitted heavy metals to pass into the channels and then bind chemically to the MOFs.
“With MOFs, you’re typically interested in using the holes for something,” Teat said.
The LMOFs were also found to be very selective of their targets. The research team saw that the crystals bound tightly to mercury and lead, while binding very weakly to lighter metals in contaminated water, like magnesium and calcium. The team also noted that the LMOFs can even be recycled, having survived three cycles of collecting, cleaning and reusing before showing any signs of degrading.
“Knowing the crystal structures is one of the most important aspects of our research. You need those in order to perform subsequent characterizations and to understand the properties of these materials,” Li explained.
The researchers said that more study of the LMOFs is still needed, but the results of their study are nonetheless very promising.
The research team noted that heavily industrialized areas, cities with very old water regulations and infrastructure, and farming communities, are particularly susceptible to contamination of groundwater sources, which are often used for drinking water. Contaminated groundwater can also lead to soil contamination if it is not cleaned up. There is also concern that the contamination will spread to plants and animals, which broadens the path of exposure.
One focus of future research, Li said, would be to find a way to lower the cost of the LMOFs and make them even more durable, lasting for many more cycles. In addition, scientists could also look into developing water filters by blending LMOFs with polymers to create a solid film.
“These filters could be used for capture on a larger scale,” she said, adding that the current results are “promising,” but that she and her team would like to continue with their research.
The press release said that researchers from the University of Texas at Dallas and Rider University also participated in this research. The team’s work was supported by the Department of Energy’s Office of Science.