Charge barrier flow-through capacitor

Abstract

Flow-through capacitors are provided with one or more charge barrier layers. Ions trapped in the pore volume of flow-through capacitors cause inefficiencies as these ions are expelled during the charge cycle into the purification path. A charge barrier layer holds these pore volume ions to one side of a desired flow stream, thereby increasing the efficiency with which the flow-through capacitor purifies or concentrates ions.

What is claimed is:  
     
         1 . A flow-through capacitor comprising: 
 a) a plurality of electrodes; and    b) a first charge barrier located between two of said plurality of electrodes.    
     
     
         2 . The flow-through capacitor of  claim 1 , wherein the charge barrier is characterized by low resistance-capacitance.  
     
     
         3 . The flow-through capacitor of  claim 1 , wherein at least one of the electrodes is an anode and at least one of the electrodes is a cathode.  
     
     
         4 . The flow-through capacitor of  claim 1 , wherein the charge barrier comprises a first semipermeable membrane.  
     
     
         5 . The flow-through capacitor of  claim 4 , wherein said charge barrier further comprises a second semipermeable membrane, said first membrane being a cation exchange membrane and said second membrane being an anion exchange membrane.  
     
     
         6 . The flow-through capacitor of  claim 5 , wherein the anion exchange membrane is proximal to the anode, and the cation exchange membrane is proximal to the cathode.  
     
     
         7 . The flow-through capacitor of  claim 6 , wherein the position of the anion and cation exchange membranes relative to the electrodes are reversed by reversal of voltage polarity on the electrodes.  
     
     
         8 . The flow-through capacitor of  claim 5 , wherein the electrode is operated in the charge cycles of opposite polarity, separated by discharge cycles.  
     
     
         9 . The flow-through capacitor of  claim 1 , further comprising a flow channel.  
     
     
         10 . The flow-through capacitor of  claim 9 , wherein the flow channel is formed by a spacer.  
     
     
         11 . The flow-through capacitor of  claim 9 , further comprising a flow channel located between one of the electrodes and the first charge barrier.  
     
     
         12 . The flow-through capacitor of  claim 11 , further comprising a second charge barrier and further containing a flow channel located between the first and second charge barriers.  
     
     
         13 . The flow-through capacitor of  claim 2 , wherein the charge barrier is an electrically-conductive membrane with a low resistance-capacitance (RC) time constant material.  
     
     
         14 . The flow-through capacitor of  claim 13 , wherein the capacitance of the charge barrier is less than 20 farads/gram.  
     
     
         15 . The flow-through capacitor of  claim 1 , wherein the charge barrier is electrically connected to a first power supply, and at least one of the plurality of electrodes is electrically connected to a second power supply.  
     
     
         16 . The flow-through capacitor of  claim 1 , wherein the charge barrier has a voltage and the electrode has a voltage, the charge barrier voltage being greater than the electrode voltage.  
     
     
         17 . The flow-through capacitor of  claim 5 , wherein the charge barrier membranes are identically-charged semipermeable membranes, selected from the group consisting of cation exchange membranes and anion exchange membranes.  
     
     
         18 . The flow-through capacitor of  claim 1 , wherein the capacitor comprises a series resistance of less than 50 ohm cm 2 .  
     
     
         19 . The flow-through capacitor of  claim 1 , wherein the capacitor has a series resistance to leakage ratio of greater than 100.  
     
     
         20 . The flow-through capacitor of  claim 1 , wherein the electrodes within a cell of the capacitor are ionically insulated and connected electrically in series.  
     
     
         21 . The flow-through capacitor of  claim 20 , further comprising a flow path adjacent to each of the electrodes.  
     
     
         22 . A system comprising the flow-through capacitor of  claim 1  and a valve.  
     
     
         23 . The system of  claim 22 , wherein said valve is a feedback valve.  
     
     
         24 . The system of  claim 22 , wherein said valve is a three-way valve.  
     
     
         25 . The system of  claim 22 , comprising a means for allowing fluid in said system to bypass a flow-through capacitor in said system.  
     
     
         26 . The system of  claim 22 , comprising a means for directing fluid in said system from said flow-through capacitor to a second flow-through capacitor in said system.  
     
     
         27 . The system of  claim 22 , further comprising a means for monitoring the concentration of ions in a fluid in said system.  
     
     
         28 . The system of  claim 22 , further comprising a means for controlling the concentration of ions in a fluid in said system.