Researchers from the University of Pittsburgh, Drexel University in Philadelphia, and Brookhaven National Laboratory are collaborating to solve a complex mystery aimed at making water disinfection procedures more sustainable.
Scalable electrochemical ozone generation (EOP) technologies for dirty water disinfection could one day replace the centralized chlorine treatment used today, whether in modern cities or remote villages. But little is understood about EOP at the molecular level and how the technologies that enable it can be made efficient, cost-effective and sustainable.
Their research was recently published in the journal ACS Catalysis . In addition to lead author, Drexel graduate student Ryan Alaufei, Drexel researchers include Maureen Tang, assistant professor of chemical and biological engineering, Andrew Lindsay, PhD, Tana Sibunruang, PhD, and Ezra Wood, assistant professor of chemistry; co-author John A. Keith, associate professor of chemical and petroleum engineering, and Pitt graduate student Lingyan Zhao; and Qin Wu of Brookhaven.
Advantages of ozone over chlorine
“People have been using chlorine to purify drinking water since the 19th century, but today we better understand that chlorine may not always be the best option. For example, EOP can produce ozone, a molecule that has nearly the same cleaning power as chlorine, directly in water. Unlike chlorine, which is stable in water, “Ozone in water breaks down naturally in about 20 minutes, meaning it is less likely to harm people when drinking tap water, swimming in the pool, or cleaning wounds in the hospital,” they explained. Keith, who is also a research assistant professor in the RK Mellon Department of Energy at the Pitt Swanson School of Engineering.
“EOP for permanent disinfection might make a lot of sense in some markets, but it requires a good enough catalyst, and since no one has yet found a good enough EOP catalyst, EOP is too expensive and energy intensive for broader use. My colleagues and I believe that if a mediocre EOP catalyst works at the atomic level, “We thought if we could figure out what makes it possible, maybe we could make an even better EOP catalyst.”
Examining the effectiveness of NATO catalysts
Unraveling the mystery of how EOP catalysts work is critical to understanding how best to develop one of the most promising and least toxic EOP catalysts known today: nickel-antimony doped tin oxide (Ni/Sb-SnO2 or NATO).
Herein lies the puzzle, Keith said: What is the role of each atom in NATO to help the EOP? Does ozone form catalytically as we would like, or does it form because the catalyst breaks down and is there future work to be done to make NATO catalysts more stable?
Surprisingly, researchers found that it was likely a mixture of both. Using experimental electrochemical analysis, mass spectrometry and computerized quantum chemical simulations, the researchers constructed an “atomic-scale story” to explain how ozone is produced in NATO’s electrocatalysts. They discovered for the first time that some of the nickel in NATO had leached from the electrodes, possibly due to corrosion, and that these nickel atoms, now floating in solution near the catalyst, could contribute to chemical reactions that would eventually form ozone.
“If we want to make a better electrocatalyst, we need to understand which parts work and which don’t. “Factors such as metal ion leaching, corrosion and solution phase reactions may give the impression that the catalyst is working in one direction, when in fact it is working in the other direction.”
Determining the prevalence of corrosion and chemical reactions occurring outside the catalyst are important steps that need to be clarified before other researchers can develop EOP and other electrocatalytic processes, Keith said. In conclusion, they state that “identifying or refuting the existence of such fundamental technological limitations will be critical for future applications of EOP and other advanced electrochemical oxidation processes.”
“We know that electrochemical water purification works on a small scale, but the discovery of better catalysts will take this to a global scale. The next step is to look for new atomic combinations in materials that are more resistant to corrosion, while also contributing to an economical and sustainable EOP,” said Keith.
Source: Port Altele
