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Bruce Logan and his team had already surprised us with a device producing electricity and hydrogen from three types of water: salty, soft and worn. Problem: the MREC device could only be used near the coast. It can now be installed anywhere by replacing seawater with recoverable ammonium bicarbonate salts. The new cell is even more efficient than the old one, including for treating wastewater ...
In September, 2011, Bruce Logan of the University of Pennsylvania, proposed an astonishing concept: to produce hydrogen and electricity from seawater, river water and wastewater. His solution: the "cell electrolysis by microbial reverse electrodialysis", called MREC (for Microbial Reverse Electrodialysis Electrolysis Cell).
A reminder: this system consists of a RED inserted between the electrodes of a MFC. But still ? RED (Reverse Electrodyalisis) designates a device of inverse electrodyalysis, which generates a current thanks to a salinity gradient, for example between sea water and fresh water. It works thanks to ion-permeable membranes. An MFC is a microbial fuel cell (Microbian Fuel Cell). It consists of a compartment containing wastewater and bacteria. There is however a trick: these little animals are exoélectrogéniques, rejecting electrons during their meals.
The MREC therefore combines two devices generating free electricity and used to hydrolyze water molecules at electrodes. However, this chemical reaction causes a release of hydrogen, the desired fuel. Between 0,8 and 1,6 m3 gas can be produced daily for 1 m3 of used water. Either, but what's new?
The MREC has two flaws. First, it can only be used near a coastline. Seawater has to be continually replaced. Secondly, suspended particles foul the device. In an article published in Science Express this March 1er, Bruce Logan explains how he freed himself from these problems, in collaboration with two of his students.
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