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HOUSTON – (October 5, 2018) – Scientists at Rice University have developed a system similar to the Venus particle fly trap for water depollution.
The one-micron sized spheres created in Pedro Alvarez's laboratory, an environmental engineer at Rice, are designed to capture and destroy bisphenol A (BPA), a synthetic chemical used in the manufacture of plastics.
The search is detailed in the American Chemical Society Science and technology of the environment.
BPA is commonly used to cover the inside of cans, bottle lids and water supply lines. It was once part of baby bottles. While BPA that infiltrates into foods and beverages is considered safe in low doses, prolonged exposure is suspected to affect children's health and contribute to high blood pressure.
The good news is that reactive oxygen species (ROS) – in this case, hydroxyl radicals – are bad news for BPA. Inexpensive titanium dioxide releases ROS when it is triggered by ultraviolet light. But as the oxidizing molecules disappear quickly, the BPA must be close enough to attack.
That's where the trap comes in.
Up close, the spheres turn out to be collections of titanium dioxide petals in the shape of flowers. The soft petals offer Rice researchers a large surface to anchor the cyclodextrin molecules.
Cyclodextrin is a benign sugar-based molecule often used in foods and medications. It has a two-sided structure, with a hydrophobic cavity (avoiding water) and a hydrophilic outer surface (attracting water). BPA is also hydrophobic and naturally attracted to the cavity. Once entrapped, the ROS produced by spheres degrade BPA into harmless chemicals.
In the laboratory, researchers determined that 200 milligrams of spheres per liter of contaminated water degraded 90% of BPA in one hour, a process that would take twice as long with non-enriched titanium dioxide.
The work is part of the technologies developed by the Nanotechnology-based Water Treatment Center funded by the Rice-based Nanotechnology Research Center, as spheres assemble from titanium dioxide nanofilms .
"Most of the processes reported in the literature involve nanoparticles," said Danning Zhang, Rice's graduate student. "The particle size is less than 100 nanometers.Because of their very small size, it is very difficult to recover them in suspension in the water."
The rice particles are much bigger. When a particle of 100 nanometers is 1000 times smaller than a human hair, the titanium dioxide improved is between 3 and 5 microns, about 20 times less than the same hair. "This means that we can use a low-pressure microfiltration with a membrane to recover these particles for reuse," Zhang said. "It saves a lot of energy."
Because ROS also depletes cyclodextrin, the spheres begin to lose their trapping ability after about 400 hours of continuous ultraviolet exposure, Zhang said. But once recovered, they can be easily recharged.
"This new material helps overcome two important technological barriers to photocatalytic water treatment," said Alvarez. "First, it improves treatment efficiency by minimizing ROS trapping by non-target water components, in which case ROS is primarily used to kill BPA."
"Second, it allows low-cost catalyst separation and reuse, helping to reduce treatment costs," he said. "This is an example of how advanced materials can help turn academic currents into achievable processes that improve water safety."
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The co-authors of the article are Hassan Javed, a graduate rice student, and Pingfeng Yu, a postdoctoral researcher. Ms. Rice, former Rice student, Changgu Lee, Assistant Professor at Ajou University, South Korea; and Jae-Hong Kim, professor and president in chemical and environmental engineering at Yale University. Alvarez is George R. Brown Professor of Materials Science and Nanotechnology and Professor of Civil and Environmental Engineering at Rice.
The National Science Foundation supported the research.
Read the summary at https: /
This press release is available online at http: // news.
Follow Rice News and Media Relations via Twitter @RICEUNews.
Linked materials:
Alvarez Lab: http: // alvarez.
Nanosystems Engineering Research Center for Nanotechnology-Based Water Treatment: http: // www.
Department of Rice Civil and Environmental Engineering: http: // www.
George R. Brown School of Engineering: https: /
Images to download:
http: // news.
Researchers at Rice University have improved micron-size titanium dioxide particles to trap and destroy BPA, a water contaminant with health implications. Cyclodextrin molecules at the surface trap BPA, which is then degraded by the reactive oxygen species (ROS) produced by the light – activated particles. (Credit: Danning Zhang / Rice University)
http: // news.
"Petals" of a sphere made of titanium dioxide enhanced with cyclodextrin, seen under a scanning electron microscope. When they are triggered by ultraviolet light, spheres created at Rice University are effective at removing contaminants from bisphenol A from water. (Credit: Alvarez Lab / Rice University)
http: // news.
The cyclodextrin enriched titanium dioxide spheres created at Rice University are effective at removing bisphenol A from water. The micrometer spheres are large enough to be easily extracted from the treated water for reuse. (Credit: Alvarez Lab / Rice University)
http: // news.
The Rice University graduate student, Danning Zhang, who led the development of a particle that attracts and degrades contaminants in the water, controls a sample in a Rice environmental lab. . (Credit: Jeff Fitlow / Rice University)
Located on a 300-acre forest campus in Houston, Rice University consistently ranks among the top 20 universities in the country by US News & World Report magazine. Rice has highly respected schools of architecture, commerce, permanent studies, engineering, social studies, music, natural sciences and social sciences and is home to the Baker Institute for Public Policy. . With 3,970 undergraduate students and 2,934 graduate students, the ratio of undergraduates per Rice teacher is just under 6 to 1. His network of residential colleges builds strong unified communities and lifelong friendships This explains in part why Rice is ranked # 1 for many race / class interactions and # 2 for quality of life by the Princeton Review. Rice is also considered the best value for money among private universities by Kiplinger's personal finances. To read "What they say about rice," go to http://tinyurl.com.
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