Desalination without energy possible with organics, claim Chinese

Water desalination can be accomplished without electrical energy input or high water pressure using a source of biodegradable organic matter or bacteria as the fuel.

This is the claim, published in the journal Environmental Science Technology, published by the American Chemical Society, in July by a group of researchers from Tsinghua University, Beijing, and Penn State University, USA.

According to the paper A New Method for Water Desalination Using Microbial Desalination Cells, the researchers modified a microbial fuel cell by placing two membranes between the anode and cathode, creating a middle desalination chamber between the membranes. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber.

The researchers demonstrated this Microbial Desalination Cell (MDC) at salt concentrations of 5, 20 and 35 g/L, with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m² (31 W/m³) while at the same time removing about 90% of the salt in a single cycle.

As the salt was removed from the middle chamber, the ohmic resistance of the MDC increased from 25 Ω to 970 Ω at the end of the cycle. This was reflected by a continuous decrease in the voltage produced over the cycle.

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