Carbon dioxide capture using resin-wafer electrodeionization
The present invention provides a resin-wafer electrodeionization (RW-EDI) apparatus including cathode and anode electrodes separated by a plurality of porous solid ion exchange resin wafers, which when in use are filled with an aqueous fluid. The apparatus includes one or more wafers comprising a basic ion exchange medium, and preferably includes one or more wafers comprising an acidic ion exchange medium. The wafers are separated from one another by ion exchange membranes. The fluid within the acidic and/or basic ion exchange wafers preferably includes, or is in contact with, a carbonic anhydrase (CA) enzyme to facilitate conversion of bicarbonate ion to carbon dioxide within the acidic medium. A pH suitable for exchange of CO 2 is electrochemically maintained within the basic and acidic ion exchange wafers by applying an electric potential across the cathode and anode.
1. A resin-wafer electrodeionization (RW-EDI) apparatus for removing carbon dioxide from a gas stream, the apparatus comprising:
a cathode; and
an anode that is separated from the cathode by a plurality of porous solid basic ion exchange resin wafers, wherein the cathode, anode, and wafers are interleaved with bipolar ion exchange membranes;
the plurality of wafers being arranged in a stack between the cathode and the anode;
each basic wafer comprising a porous basic ion exchange medium;
each basic wafer being adapted to (a) introduce a CO 2 -containing gas into an aqueous transport fluid within the basic ion exchange medium to convert CO 2 from the gas into bicarbonate ion, and (b) vent a CO 2 -depleted gas therefrom;
wherein the basic wafers contain the aqueous transport fluid comprising KHCO 3 or NaH 2 PO 4 ;
wherein in use, the transport fluid flows through each basic wafer and bicarbonate ion is concentrated in the transport fluid, and the basic pH of the basic ion exchange medium is maintained by application of an electric potential across the anode and cathode.
2. The apparatus of claim 1 wherein the basic ion exchange medium of each wafer contains a carbonic anhydrase enzyme to facilitate conversion of gaseous CO 2 in bicarbonate ion.
3. The apparatus of claim 2 wherein the carbonic anhydrase enzyme is chemically bound to the basic ion exchange medium thereof to facilitate conversion of gaseous CO 2 into bicarbonate ion.
4. The apparatus of claim 1 , wherein each wafer has a thickness in the range of about 1 mm to about 20 mm.
5. A method of removing CO 2 from a gas stream comprising introducing a CO 2 -containing gas into the aqueous transport fluid flowing through the basic ion exchange medium of each wafer of the apparatus of claim 1 while applying an electric potential across the cathode and anode of the apparatus to convert CO 2 from the gas into bicarbonate ion and thereby concentrate the bicarbonate in the transport fluid.
6. The method of claim 5 wherein the pH of the aqueous fluid within the basic ion exchange medium of each wafer is maintained in the range of about 7.5 to about 9.5 by application of the electric potential across the cathode and the anode.