Chinese scientists have developed a wood-based steam generator which, with the help of bacterial-produced nanomaterials, harnesses solar energy to purify water.
The steam generation bit isn’t new. Numerous devices have been designed to use solar energy to separate pure water from its contaminants by evaporation.
Their efficiency and effectiveness vary greatly, however, and researchers are always seeking improvements in all four of the key components: light absorption, heat management, water transport and evaporation.
Shu-Hong Yu and colleagues at the University of Science and Technology of China believe they tick all four boxes with a device that makes the most of wood’s sustainability and porous structure – though there is a lot more to it than just wood.
The researchers made their device with the help of bacteria that produced long cellulose nanofibres, which bound the layers of the device together. They added bacteria to the surface of a block of wood, allowed them to ferment, then sprayed an aerosol of glass bubbles onto the surface.
The bubbles, which provide excellent thermal insulation, became embedded in the nanofibres, forming a hydrogel. To this was added carbon nanotubes, which tangled with the nanofibres to form a light-absorbing, water-evaporating top layer.
The device works, Yu and colleagues say, by transporting water upward through the wood to the light-absorbing layer, which is heated by the sun. The water evaporates, and the steam is collected and condensed to produce pure water.
The insulating layer of glass bubbles keeps heat from being transferred downward through the device and lost, and the nanoscale structures lower the energy required for water vaporization.
The research is described in a paper in the journal Nano Letters.
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