Advanced Trap-and-Zap Techniques Improve PFOA Removal
Outcome/Accomplishment
Researchers with the National Science Foundation (NSF)-funded Nanosystems Engineering Research Center (ERC) for Nanotechnology Enabled Water Treatment (NSF NEWT) have shown that at the environmentally relevant concentration of 100 m grams per liter, advanced electrochemical trap-and-zap techniques remove 99.5 percent of perfluorooctanoic acid (PFOA) with 70 percent defluorination in three hours at a pH of 4.5. Hexagonal boron nitride (h-BN) functionalized with UiO-66—a water-stable zirconium-based metal-organic framework (MOF)—electrocatalytically oxidizes PFOA to shorter chains. This degradation is enhanced by modifying the h-BN surface with an adsorbent, allowing the. h-BN surface to pre-adsorb and concentrate, “trap,” PFOA on the electrocatalytic sites of h-BN anodes, which then “zaps” it away. (See figures 1 and 2.)
Impact/Benefits
The NSF NEWT ERC’s goal is to develop anodic and cathodic electrochemical strategies for the degradation of low-concentration “forever chemicals” or perfluoroalkyl and polyfluoroalkyl substances (PFAS). By comparing various catalytic schemes to develop a flowthrough prototype call that achieves the overall greatest PFAS removal performance, the team is identifying the techniques with the highest energy efficiency and lowest operation costs based on preliminary techno-economic analysis. They are also exploring whether synergistically employing both oxidative and reductive destruction schemes or utilizing one predominant destruction pathway works best. The advanced trap-and-zap technique developed at NSF NEWT ERC avoids corrosion and unwanted side reactions that can lead to the formation of byproducts such as chlorate, perchlorate, and organic halides.
Explanation/Background
Electrocatalytic PFAS destruction has been pursued via both direct electron transfer anodic oxidation and cathodic hydrodefluorination. NSF NEWT ERC researchers led by Pedro Alvarez of Rice University continue to pursue a trap-and-zap approach built on NSF NEWT scientific advances. The team found that h-BN is a cost-effective, widely available, and scalable semiconductor that can catalyze the photooxidation of PFOA. NSF NEWT has previously shown that as a photocatalyst, h-BN is four times more effective for PFOA degradation than the common photocatalyst titanium dioxide (P25-TiO). Using the cost-effective h-BN semiconductor decorated with an MOF adsorbent, stable and efficient anodes for the oxidation of PFOA are built. Three research papers resulted from this work.
The team has studied the reduction of PFOA using electrochemical and computational methods. The defluorination of PFOA has been explored on noble metal surfaces and the mechanism of reduction has been examined. The results are being leveraged towards the fabrication of sensors using functionalized gold nanoparticles.
As part of these studies, NSF NEWT led an international workshop on PFAS Catalytic Degradation Technologies: Research & Innovation Priorities, during the 12th National Conference on Environmental Chemistry in Wuhan, China, in November 2023. The event was co-organized by international academic partner Nankai University.
Location
Houston, Texaswebsite
Start Year
Energy and Sustainability
Energy and Smart Infrastructure
Lead Institution
Core Partners
Fact Sheet
Outcome/Accomplishment
Researchers with the National Science Foundation (NSF)-funded Nanosystems Engineering Research Center (ERC) for Nanotechnology Enabled Water Treatment (NSF NEWT) have shown that at the environmentally relevant concentration of 100 m grams per liter, advanced electrochemical trap-and-zap techniques remove 99.5 percent of perfluorooctanoic acid (PFOA) with 70 percent defluorination in three hours at a pH of 4.5. Hexagonal boron nitride (h-BN) functionalized with UiO-66—a water-stable zirconium-based metal-organic framework (MOF)—electrocatalytically oxidizes PFOA to shorter chains. This degradation is enhanced by modifying the h-BN surface with an adsorbent, allowing the. h-BN surface to pre-adsorb and concentrate, “trap,” PFOA on the electrocatalytic sites of h-BN anodes, which then “zaps” it away. (See figures 1 and 2.)
Location
Houston, Texaswebsite
Start Year
Energy and Sustainability
Energy and Smart Infrastructure
Lead Institution
Core Partners
Fact Sheet
Impact/benefits
The NSF NEWT ERC’s goal is to develop anodic and cathodic electrochemical strategies for the degradation of low-concentration “forever chemicals” or perfluoroalkyl and polyfluoroalkyl substances (PFAS). By comparing various catalytic schemes to develop a flowthrough prototype call that achieves the overall greatest PFAS removal performance, the team is identifying the techniques with the highest energy efficiency and lowest operation costs based on preliminary techno-economic analysis. They are also exploring whether synergistically employing both oxidative and reductive destruction schemes or utilizing one predominant destruction pathway works best. The advanced trap-and-zap technique developed at NSF NEWT ERC avoids corrosion and unwanted side reactions that can lead to the formation of byproducts such as chlorate, perchlorate, and organic halides.
Explanation/Background
Electrocatalytic PFAS destruction has been pursued via both direct electron transfer anodic oxidation and cathodic hydrodefluorination. NSF NEWT ERC researchers led by Pedro Alvarez of Rice University continue to pursue a trap-and-zap approach built on NSF NEWT scientific advances. The team found that h-BN is a cost-effective, widely available, and scalable semiconductor that can catalyze the photooxidation of PFOA. NSF NEWT has previously shown that as a photocatalyst, h-BN is four times more effective for PFOA degradation than the common photocatalyst titanium dioxide (P25-TiO). Using the cost-effective h-BN semiconductor decorated with an MOF adsorbent, stable and efficient anodes for the oxidation of PFOA are built. Three research papers resulted from this work.
The team has studied the reduction of PFOA using electrochemical and computational methods. The defluorination of PFOA has been explored on noble metal surfaces and the mechanism of reduction has been examined. The results are being leveraged towards the fabrication of sensors using functionalized gold nanoparticles.
As part of these studies, NSF NEWT led an international workshop on PFAS Catalytic Degradation Technologies: Research & Innovation Priorities, during the 12th National Conference on Environmental Chemistry in Wuhan, China, in November 2023. The event was co-organized by international academic partner Nankai University.