Modern water purification methods exist that can easily get rid of water contaminants, even salt and bacteria, but some organic toxins and toxic metals, such as arsenic and hexavalent chromium need special processing [read: expensive and carbon-intensive] to be removed.
Water purification by reverse osmosis, filters, and chlorination does not affect these toxic metals or organic toxins, so another approach is needed. Fixed photocatalysts, that is, those are are affixed to a panel or even to a filter medium, can remove these toxins from contaminated water, but because of their orientation, they have limited contact with the contaminants, increasing the time it takes to purify water.
Panasonic has developed a new water purification photocatalyst that does not need to be fixed to a panel or filter, and runs on solar power, specifically the ultraviolet part of the spectrum. Panasonic actually uses the same catalyst that would be used on panels and filters, titanium dioxide, but in nanoparticle form combined with microparticle zeolite.
The titanium dioxide and zeolite particles quickly disperse and bond to one another when mixed with contaminated water. The titanium dioxide is activated by ultraviolet rays from the sun, sequestering toxins in the zeolite matrix. Because the new photocatalyst is heavier than water, it eventually sinks to the bottom, taking the contaminants with it, leaving clean water to be skimmed off the top.
Because the photocatalyst is dispersed throughout the water, it is able to contact much more of the water, reducing the time required to remove contaminants. In one test, the new water purification method removed arsenic from contaminated water about fifty times faster than a typical installation, all using the power of the sun. Panasonic expects to test a prototype plant using the new photocatalyst to purify water in a Jadavpur University project in India, starting in October 2013.
Image © Panasonic