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Chemistry In Pictures

Chemistry in Pictures: A sponge for scrubbing the environment

by Manny I. Fox Morone
December 24, 2020

A scanning electron micrograph of a sphere with about 50 pores covering its surface.
Credit: Veronika Kozlovskaya

In the past decade or two, we’ve seen the rise of a whole stable of environmentally friendly sponges—plant-based cellulose ones, recyclable silicone ones, natural loofahs—but here’s a different, and much smaller, kind of eco-friendly sponge. Eugenia Kharlampieva’s lab at the University of Alabama at Birmingham developed these microsponges to clean wastewater using just ultraviolet light and oxygen. After these porous particles have served their purpose, they degrade into natural products. The sponges are made of polylactic acid (PLA) doped with titanium dioxide nanoparticles. When wastewater contaminants such as fertilizers, dyes, and pharmaceuticals come into contact with the sponges, carbonyl groups in the PLA’s polymer chains snag these organic compounds. Then when UV light hits the sponge, the photosensitive titanium dioxide particles catalyze the reaction of those bound contaminants with oxygen and water that breaks apart the contaminant molecules. After even more UV exposure, the titanium dioxide starts to break down the PLA into environmentally benign lactic acid, so sponges don’t need to be retrieved after water treatment.

Credit: Veronika Kozlovskaya. Read the ACS Applied Polymer Materials paper here (2020, DOI: 10.1021/acsapm.0c00937).

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