Pennsylvania State University (Penn State; University Park) researchers continue to develop and improve the microbial reverse-electrodialysis cell (MRC) design.
In December, WE&T reported on the development of the MRC by environmental engineering professor Bruce Logan. The article, “Saltwater may unlock ‘inexhaustible’ source of hydrogen,” describes how the researchers combined microbial fuels and stacks of reverse-electrodialysis (RED) electrolysis cells to create the MRC, which produces hydrogen without adding auxiliary electricity.
The MRC produces enough electricity to hydrolyze water — that is, split it into hydrogen and oxygen. The microbial fuel cells produce electricity using exoelectrogenic bacteria; the RED stacks work by taking advantage of the ionic difference between fresh water and saltwater.
Now, Logan, along with graduate student Roland Cusick and post-doctoral fellow Younggy Kim, have switched salt sources to enable more electricity to be produced at more locations. Instead of saltwater from the sea, the researchers are using an ammonium bicarbonate salt solution, according to a Penn State press release.
Even though the researchers have shown that the MRCs can work with seawater, organic matter in the water fouls membranes without precleaning and treatment. Using seawater also restricts MRC operation to coastal areas, the news release says.
So, the researchers decided to use ammonium bicarbonate solution, which works similarly to seawater in the MRC and does not foul the membranes. The solution also is easily removed from the water at 43°C (110°F), because the ammonia and carbon dioxide that make up the salt in the solution boil out and can be recaptured and recombined with water for reuse, the news release says.
After testing the ammonium bicarbonate MRC, researchers found that the initial production of electricity was greater than that from an MRC using seawater. The tested MRC produced 5.6 W/m2, the news release says.
In addition, the MRCs can be configured to produce electricity from hydrogen without contributing to greenhouse gases, Logan said in the release.
The King Abdullah University of Science and Technology (Thuwal, Saudi Arabia) supported this work.
The submerged membrane electro-bioreactor discussed in the January 2012 article, “Charge it!: A ‘submerged membrane electro-bioreactor’ achieves high removal efficiencies,” is patented under United States Patent No. 8,147,700. The patent was filed Sept. 3, 2009 under application number 12/553,680.
©2012 Water Environment Federation. All rights reserved.