Clean water is essential, yet in certain parts of the world, it's very difficult to obtain. Unfortunately, our limited water resources are being polluted by chemicals from industrial plants, pesticides, pharmaceuticals, and more.

Adsorbant materials composed of carbon are often used to remove many of these organic pollutants. However, they act slowly, typically miss hydrophilic micropollutants, and can be difficult to reuse.

Scientists working on developing inexpensive materials that can purify water quickly have been working with an insoluble polymer called β-cyclodextrin (β-CD)—a big loop of linked sugar molecules. Recently, they've discovered a way to cross-link β-CD using aromatic groups forming a porous, cross-linked complex. The porous, cross-linked β-CD has an increased surface area that significantly speeds the removal of pollutants.

Assessing purification

The team tested how well the new material could sequester organic micro pollutants, using Bisphenol A (BPA) as a model pollutant. (BPA is a component of plastics that has raised significant health concerns over the past decade.) The team assessed a variety of activated carbon adsorbents and a few variations of β-CD. All materials eventually removed the majority of the BPA from a solution.

However, they found that the porous, cross-linked β-CD removed the BPA much faster than all the other materials tested—it reached 95 percent of its final uptake in a mere 10 seconds. In general, the material exhibited purification speeds 15 to 200 times faster than other β-CD based materials and commonly used activated carbons materials.

The team compared β-CD to the activated carbon materials currently used for purification using a mixture of organic micropollutants that modeled real-life environmental conditions. The pollutants in this mix include model aromatic compounds, pesticides, plastic components, and pharmaceuticals. The new material again outperformed the leading activated carbon adsorbent.

Reusable, too

The scientists also explored the ability to reuse the material. They found that BPA could be easily removed from the material by rinsing the polymer in methanol at room temperature. They repeated the process five times and saw negligible decrease in performance compared to freshly synthesized polymer.

A cost analysis of the material indicated that this polymer can be sold at a comparable or cheaper price than the current activated carbon adsorbents. Future studies should test this material in various forms, such as microparticles or membranes, in order to fully maximize its purification potential.

Nature, 2015. DOI: 10.1038/nature16185 (About DOIs).