These Rice University bioengineers may have found a way to efficiently remove bisphenol A from water, with microparticles that attract and then degrade contaminants. A toxic particulate trap for water remediation documented in the journal ACS Environmental Science and Technology.
The micron-sized spheres in question are designed to capture and destroy bisphenol A (BPA), a synthetic chemical used in the manufacture of plastics, used to coat the inside of food cans, the lids of some containers but also the water supply lines. While BPA leaching into food and drink is "considered" safe in low doses, prolonged exposure is suspected of affecting children's health and contributing to hypertension.
The trap is based on reactive oxygen species (ROS), here hydroxyl radicals released by titanium dioxide when exposed to ultraviolet light. Nevertheless, these rapidly disappearing oxidizing molecules had to be in close proximity to the BPA particles to be effective. The Rice researchers therefore designed flexible petals offering a large surface area to anchor the cyclodextrin molecules, two-sided molecules, with a hydrophobic cavity (avoiding water) and a hydrophilic outer surface (attracting water) . BPA is also hydrophobic and naturally attracted to the cavity. Once trapped, the ROS produced by the spheres degrade BPA into harmless chemicals. Here, in the laboratory, researchers show that 200 milligrams of spheres per liter of contaminated water degrade 90% of BPA in one hour,
Not too microparticles: but while most attempts to "capture" BPA or other contaminants in water involve nanoparticles that are very difficult to retrieve from the water, researchers have designed particles that are much larger, recoverable by microfiltration. Once the cyclodextrin is depleted, after approximately 400 hours of continuous ultraviolet exposure, the spheres begin to lose their trapping ability, but once recovered they can be easily recharged.
This new material makes it possible to overcome 2 technological challenges for the photocatalytic treatment of water: it improves the efficiency by minimizing the trapping of ROS by the non-targeted constituents of the water and the ROS are thus mainly used to destroy BPA. Second, it enables low-cost reuse of the catalyst, helping to reduce processing costs.
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