Nanomotors should help filter carbon dioxide from water

American scientists have built tiny motors that make it possible to filter carbon dioxide from water by precipitating it as calcium carbonate. Such motors may be able to help combat the greenhouse effect.

The system was designed by researchers at the University of California at San Diego. In a publication in the authoritative scientific journal Angewandte Chemie, they explain that the structures they have built are more or less small tubes, six micrometers long, with a kind of swinging tail attached to them. This allows the motors to propel themselves when released into water at a speed of about 100 micrometers per second.

Attached to the tubes is an enzyme that can convert carbon dioxide in the water to calcium carbonate, which appears in solid form as a precipitate. Incidentally, calcium chloride must be added to the water in order to obtain the necessary calcium for the conversion. Experiments show that the motors in such a solution can quickly remove carbon dioxide. In a period of 5 minutes, approximately 90 percent of the CO2 present was captured. The effectiveness was about the same in seawater, with a percentage of carbon dioxide filtered out of 88 percent.

One of the drawbacks of the current system is that, despite the nanostructure, ‘fuel’ is needed to propel the engines. With the help of hydrogen peroxide added to the water, the structures are stimulated to move; in future versions, the scientists want to ensure that fuel is no longer required, but that the motors can propel themselves in water. If that succeeds, it is possible that such devices will eventually be used to reduce the greenhouse effect; CO2 is a known greenhouse gas and thus causes global warming. The researchers think that special water filter installations equipped with the nanomotors can make a contribution to the environment.