Making Fuel While Cleaning Up Arsenic

Arsenic contamination of drinking water is a serious problem in many parts of Asia. The element is also abundant in industrial wastewaters or acidic drainage from mines. Now, researchers have designed a way to increase the cost-effectiveness of removing the toxic element from water by coupling the cleanup with hydrogen fuel generation. To remediate arsenic-laced waters, engineers usually oxidize the more toxic form of the metalloid, As(III), to its easy-to-remove and less toxic form, As(V). Michael R. Hoffmann, an environmental engineer at Caltech, adapted a hydrogen-producing electrochemical cell to oxidize As(III) while reducing water to hydrogen. The cell has a semiconductor anode made of bismuth-doped titanium dioxide and a cathode made of stainless steel. In the presence of 1-mM As(III), the cell’s energy efficiency in producing hydrogen increased by 18% (Environ. Sci. Technol. 2014, DOI: 10.1021/es4046814). The prototype cell can produce up to 9.4 µmol of hydrogen per minute and works best at millimolar As(III) concentrations, which are typical of industrial wastewaters. Hoffmann plans to test the device later this year on drinking water in India.