US university discovers catalyst that purifies water of herbicides and produces hydrogen
Oregon State University has developed a dual-use catalyst that cleans water polluted by herbicides such as glyphosate and produces hydrogen gas . The catalyst consists of semiconductor materials such as titanium dioxide. The catalyst is capable of performing photocatalysis, which absorbs light to break down organic contaminants.
Researchers at the Oregon State University College of Science have developed a dual-purpose catalyst that purifies herbicide-tainted water and produces hydrogen.
The project, which involved researchers from OSU College of Engineering and HP Inc., is important because water pollution is a major global challenge and hydrogen is a clean, renewable fuel.
The results of the study, which explored photoactive catalysts, were published in the journal ACS Catalysis.
OSU's Kyriakos Stylianou said, “We can combine oxidation and reduction in one process to get an efficient photocatalytic system. The oxidation occurs through a photodegradation reaction and the reduction through a hydrogen evolution reaction”.
A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent chemical changes.
Photocatalysts are materials that absorb light to reach a higher energy level and can use that energy to break down organic contaminants through oxidation. Among the many applications of photocatalysts are self-cleaning coatings for walls, floors, ceilings and furniture that are resistant to stains and odors.
Stylianou, an assistant professor of chemistry, led the study, which involved titanium dioxide photocatalysts derived from a metal-organic framework, or MOF.
Consisting of positively charged metal ions surrounded by organic linker molecules, MOFs are crystalline, porous materials with tunable structural properties and nanometer-sized pores. They can be designed with a variety of components that determine the properties of the MOF.
By calcining MOFs – high heating without melting – semiconductor materials such as titanium dioxide can be generated. Titanium dioxide is the most commonly used photocatalyst and is found in the minerals anatase, rutile and brookite.
Stylianou and his collaborators, including Líney Árnadóttir of the OSU College of Engineering and William Stickle of HP, have found that nitrogen-sulfur-doped anatase is the best “two birds with one stone” photocatalyst for simultaneously producing hydrogen and degrade glyphosate, a widely used herbicide.
Glyphosate, also known as N-phosphonomethylglycine or PMG, has been widely sprayed on agricultural fields for the past 50 years, ever since it first appeared on the market under the trade name Roundup where it has repeatedly come under fire as a carcinogen.
Stylianou noted: "Only a small percentage of the total amount of PMG applied is taken up by crops, with the rest reaching the environment." “This causes concerns about the leaching of PMG into soil and groundwater, as it should: contaminated water can be detrimental to the health of every living thing on the planet. And herbicides that leach into waterways are a primary cause of water pollution.”
Of the various compounds in which hydrogen is found, water is the most common and producing hydrogen by splitting water through photocatalysis is cleaner and more sustainable than the conventional method of making hydrogen – from natural gas through a carbon dioxide production process known as steam methane reforming.
Hydrogen has many scientific and industrial purposes beyond energy. It is used in fuel cells for automobiles, in the production of many chemicals including ammonia, in the refining of metals and in the production of plastics.
“Water is a rich source of hydrogen, and photocatalysis is one way to harness the Earth's abundant solar energy for hydrogen production and environmental remediation,” Stylianou said. “We are demonstrating that through photocatalysis it is possible to produce a renewable fuel while removing organic pollutants or converting them into useful products.”
It is quite unusual to see a catalyst working in a dual mode, offering two benefits. “Degradation” is offered as a result of PMG, with the formation of glycine, formic acid and phosphoric acid as the main degradation products, which will then need to be separated from water, albeit less toxic than the starting product. The hydrogen production action is not clear with respect to the oxygen of the water. The press release also does not clarify what happens to the oxygen deriving from the splitting of water: obtaining a mix of hydrogen and oxygen would in itself not be particularly useful, as well as being dangerous.
Currently it has only been proven that the process works and the entire engineering and industrialization phase is missing, such as to transform a process that works at an experimental level into one that can be used on a useful scale for human activity. However, it is a progress in the field of catalysts which has the purification of water from herbicides as its main advantage and the production of hydrogen from water as a secondary advantage.
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The article USA University discovers catalyst that purifies water of herbicides and produces hydrogen comes from Economic Scenarios .
This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/universita-usa-scopre-catalizzatore-che-depura-lacqua-dagli-erbicidi-e-produce-idrogeno/ on Fri, 31 Mar 2023 20:00:54 +0000.