Tiny spheres can trap water pollutant


  • Scientists have created tiny spheres that can catch and destroy bisphenol A (BPA), a synthetic chemical used to make plastics that often contaminates water.

About bisphenol A:

  • BPA is commonly used to coat the insides of food cans, bottle tops and water supply lines, and was once a component of baby bottles.
  • While BPA that seeps into food and drink is considered safe in low doses, prolonged exposure is suspected of affecting the health of children and contributing to high blood pressure.
  • Scientists at Rice University in the U.S. have developed something akin to the Venus’ flytrap of particles for water remediation.
  • The micron-sized spheres resemble tiny flower-like collections of titanium dioxide petals.
  • The supple petals provide plenty of surface area for researchers to anchor cyclodextrin — a benign sugar-based molecule often used in food and drugs. It has a two-faced structure, with a hydrophobic (water-avoiding) cavity and a hydrophilic (water-attracting) outer surface.
  • BPA is hydrophobic and naturally attracted to the cavity. Once trapped, reactive oxygen species (ROS) produced by the spheres degrades BPA into harmless chemicals.
  • In the lab, the researchers determined that 200 mg of the spheres per litre of contaminated water degraded 90% of BPA in an hour, a process that would take more than twice as long with unenhanced titanium dioxide.
  • “The size of the particles is less than 100 nanometers. Because of their very small size, they’re very difficult to recover from suspension in water.
  • While a 100-nanometer particle is 1,000 times smaller than a human hair, the enhanced titanium dioxide is between 3 and 5 microns, only about 20 times smaller than the same hair.


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