Patent Abstract:
An apparatus and method for electrocoriolysis, the separation of ionic substances from liquids in the electrodynamic mode. The method maximizes centrifugal forces on a fluid contained in a chamber having oppositely polarized electrodes. A feed fluid is fed into the chamber. Spacing of the electrodes can be minimized for enhancement of the process. A constant voltage can be applied. Centrifugal force and the electric potential across the chamber create enhanced separation. Concentrated solution can be removed from a location in the chamber and depleted solution from another location.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE 
     The present application is a continuation-in-part of U.S. Ser. No. 09/228,432, filed Jan. 11, 1999, now abandoned which is a continuation of U.S. Ser. No. 08/678,892, filed Jul. 12, 1996, now U.S. Pat. No. 5,858,199, issued to Joseph J. Hanak, on Jan. 12, 1999, which is incorporated by reference in its entirety and which was based on U.S. provisional Ser. No. 60/001,485, filed Jul. 17, 1995 and U.S. provisional Ser. No. 60/009,748, filed Jan. 11, 1996. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to an improved device and method for separating and removing ionizable components dissolved in fluids, such as for example, water. Particularly, this invention relates to separating said ionizable substances into fractions by the action of electric current and of Coriolis force. More particularly, the invention relates to a rotary device and a process in which a liquid containing ionizable components is continuously fed in and the purified solvent and the solute in a concentrated solution are continuously removed. Still more particularly, the invention relates to a rotary device and a process in which said ionizable substances are separated in one of three modes, the modes being electrolytic, electrostatic, and electrodynamic. Most particularly, this invention relates to the electrodynamic mode, hereafter referred to as the ELDYN mode. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,858,199, hereafter referred to as the Hanak patent, contains the description of apparatus and method for a water deionization process named Electrocoriolysis, also referred to as the ELCOR™ process. The background of the invention that appears in the Hanak patent, contains a detailed description of the electrolytic and the electrostatic modes, which is also relevant to the instant invention. It should be noted that the term ‘electrostatic’ in this description refers to a deionization process assisted by gravitational or centrifugal forces, while the term ‘capacitive’ refers to a deionization process not involving said forces; otherwise both the electrostatic and capacitive processes involve capacitive charging and discharging of the electrodes. Additional background information, which applies to the ELDYN mode, follows. 
     While conducting tests using a dynamic Electrogravitational (EG) deionization device operating in the electrostatic mode, a new, previously unknown mode, co-existing and competing with the electrostatic mode has been discovered. As stated above, this new mode was named electrodynamic mode, or ELDYN mode. It was observed that unlike in the capacitive method of prior art [References 1, 2, 3], deionization and enhancement in the electrostatic mode were occurring simultaneously and continuously with the newly discovered ELDYN mode, solely by the combined action of an electrostatic field and gravitational force. On account of the fact that this new phenomenon had an implication of potential large gains in the throughput and energy efficiency of the water treatment process, an extensive examination of the results was undertaken to determine the mechanism of the ELDYN mode. 
     Evidence for the Existence of the ELDYN Mode of Deionization 
     The preceding test data indicate that the ELDYN mode occurs simultaneously with the electrostatic mode. The two appear to be competing processes. The occurrence of the ELDYN mode has been inferred from the mechanism previously known to be taking place in the capacitive mode of prior art [References 1, 2, 3], from three observations obtained in the study of EG deionization in the electrostatic mode, and from the first successful deionization using the ELCOR™ process operating in the electrostatic mode. 
     (a) Mechanism of Deionization in the Capacitive Method 
     Oren and Soffer [Ref. 1, 2], in describing their deionization process by ‘electrochemical parametric pumping’ that appears to be the original version of the capacitive method of deionization, observe that “almost all of the electric charge is directed to change NaCl concentration.” Farmer [Ref. 3], in his patent on a capacitive method of deionization, reported that deionization occurs only during charging, and enhancement occurs only during discharging. There was no provision in either case for Earth&#39;s gravity to assist deionization. 
     (b) Evidence from Simultaneous Deionization and Enhancement 
     The first piece of evidence, from FIG. 10 in the Hanak patent, reproduced herein as FIG. 1, is that during a voltage pulse commencing at ˜1350 s and ending at ˜4000 s, as well as during subsequent pulses, a high rate of deionization and enhancement were taking place simultaneously during the charging process, shown by the increasing voltage. Whereas deionization is expected during charging, enhancement is not expected until the polarity reversal, when capacitor discharge and the release of accumulated ions occur, as described in (a) above. We postulate that the simultaneous occurrence of enhancement is the consequence of the presence of the electrical double layer at the electrode surfaces, shown in FIG. 2 [Ref. 4]. The diffuse layer in the double layer contains elevated concentration of solvated ions having polarity opposite that of the electrode, rendering the solution in it more dense. Under the influence of gravitational or centrifugal force, the diffuse layer slides in the direction of this force, like an avalanche, along the surface of the electrode, while being held close to it by electrostatic force, resulting in the observed enhancement at the bottom of a stationary cell or the outer periphery of a rotating cell. The water molecules between the electrode and the diffuse layer act as a lubricant for this sliding motion. At the same time, the partially depleted solution between the electrodes moves in the direction opposite to the gravitational or centrifugal force to cause the observed depletion at the top of a stationary cell or near the hub of a rotating cell. This process constitutes a ‘leaky’ capacitor. Current must be constantly supplied to make up for the ions removed from the electrode surfaces. This current is in addition to the capacitive charging current. 
     This postulated mechanism for the ELDYN mode implies that in the ELCOR™ process, in which centrifugal force is used, which can be made much greater than the gravitational force, the diffuse layer will be removed by the sliding action at a much greater rate, causing the ELDYN mode to predominate over the electrostatic mode. 
     (c) Evidence from the Duration of the Current Pulse 
     The second piece of evidence is the duration of the current pulse at the same, constant level of current, I, for different chemical species. This mode of charging is referred to as the ‘current step’ method, in which the potential, E, across the electrodes increases linearly with time, t, according to the equation: 
     
       
         E=I(R s +t/C d ),   Eq. 1 
       
     
     where R s  is the resistance in the electrolyte [Ref. 4] and C d  is the double-layer capacitance. With the same set of electrodes, the charging time, t, should be the same to reach the same potential, E. Yet, in FIG. 9 in the Hanak patent, reproduced here as FIG.  3  and in FIG. 1, the average length of the current pulses were 870 s. (0.24 h) and 2390 s. (0.66 h) for CaCl 2  and H 2 SO 4 , respectively, both at a concentration of 0.01 M. Thus, the total charge transported in the case of sulfuric acid was 2.75 times greater. The flow rates of the feed were similar. If the electrostatic mode alone were operative, the total charge transported would have to be similar. 
     With a solution of NaCl at a concentration of 0.001 M and at a low current of 17.5 mA, pulse length of up to 3.62 h was observed, which exceeds by far the time required to charge the electrodes capacitively to the maximum preset voltage. 
     (d) Evidence from Constant Levels of Deionization and Enhancement 
     The third piece of evidence can be seen again in FIG. 1, where nearly constant and similar levels of deionization and enhancement are maintained over the greater part of each pulse. This result is consistent with a constant, high ‘leakage current’ arising from the sliding diffuse layers. Similarly, in the 0.001 M NaCl case above, constant levels of deionization and enhancement of about 50% and 150%, respectively, have been observed for over three hours in each pulse. 
     (e) Evidence from the First Successful Deionization Using the ELCOR™ Process Operating in the Electrostatic Mode 
     A complete discussion of this evidence is presented in the Section entitled “Example.” 
     Process Parameters Affecting the Deionization Process 
     The following parameters have been identified as being likely to affect deionization in the ELDYN mode. 
     Centrifugal Force. This is the prime independent parameter expected to give rise to the ELDYN mode and to have profound, beneficial effects on the process current, rate of deionization, Faradaic and energy efficiency, and the ultimate level of water purity. The rate of sliding and removal of the densified, diffuse layer is expected to be directly proportional to the magnitude of the G force generated by the Coriolis force, which creates ‘outward’ force on said layer, thereby setting it in sliding motion. The resulting continuous removal of the diffuse layer facilitates maintaining the state of charge or polarization of the electrodes at a low level and the voltage across the electrolyte at a high value. This condition, in turn, favors high current and faster ionic transport across the cell width. 
     Electric Field. The rate of ionic transport across the cell is directly proportional to the electric field, which is the second of two key parameters affecting the ELDYN mode. A maximum limiting voltage, just below the decomposition potential for the electrolyte (ca. 1.1 V), can be used for the process. 
     Another parameter for maximizing the electric field is the electrode spacing, as discussed further on. 
     Surface Area of the Electrodes. As in the case of the electrostatic mode, the HSA electrodes are a pre-requisite for maintaining high current density and, thereby, high rate of deionization. In combination with sufficient centrifugal force, HSA electrodes produce a condition of constant, high, dc current at a constant maximum voltage to facilitate a continuous operation without the need of changing polarity. Supercapacitor electrodes such as those described in the Hanak patent, employed in the electrostatic mode, can be used. 
     Flow Rate of the Feed Liquid. The flow rate of the feed liquid affects enhancement and depletion; the ratio of the two quantities is the separation ratio. To date the limit of this ratio for a single stage has not been established. Its magnitude is expected to determine the number of stages in a multi-stage device to achieve a desired degree of deionization and enhancement. 
     Ratio of the Effluent Flow Rates. In order to achieve a cost-effective disposal or recovery of the dissolved solute, it should be concentrated into a minimal practical volume. For this purpose, the ratio of the flow rate of the diluent and the concentrate (Rd/Rc) should be substantially greater than 1, perhaps as large as 10 or more. An additional benefit from the high ratio is a substantial increase in the volume of the purified diluent. 
     Concentration of the Solute. The concentration of the feed affects the efficiency of water-treatment processes. As reported in the Hanak patent, the range of concentration selected for the initial feed has been shown to span over a range of over three orders of magnitude, from 0.0001 to 0.3 M, corresponding to ca. 10 to 30,000 mg/L for selected solutes. 
     Temperature. Elevated temperature, by promoting molecular motion and lowering surface tension and intermolecular cohesion, may favor the ELDYN mode in a manner similar to electrolytic processes. Maintaining a constant temperature would minimize the effect of this variable. 
     Ionic Properties as Process Parameters 
     In addition to the preceding process parameters, the following materials&#39; parameters are expected to affect deionization in this mode. 
     Ionic Mass. Ionic transport is inversely proportional to the ionic mass, slowing down the heavy ions. However, the rate of sliding and removal of the densified, diffuse ionic sheath should be also proportional to the ionic mass. In turn, it should help maintain a low state of polarization and high electric field, enhancing the transport of the heavy ions across the cell. Thus, high ionic mass should be an important factor in the deionization of heavy ions, such as those of the transuranic elements. 
     Ionic Radius. The transference number is inversely proportional to the ionic size, meaning slower transit between electrodes. This condition is in part compensated for by a lower state of electrode polarization resulting from a relatively lower population of the ions on the electrode surfaces because of their large size. Furthermore, large ionic size also results in diminished ionic charge density, which would promote sliding. Thus, on balance, large ionic size is expected to favor the ELDYN mode. 
     Ionic Valence. A major impact on ionic transport is that the transport current required is directly proportional to ionic valence. In addition, increased charge on multivalent ions should result in greater attraction to the electrode and possibly an increase in the ‘braking’ action to sliding. On the other hand, greater charge on the cations leads to higher solvation, making the ion larger, with a resulting positive, offsetting effect discussed above. 
     Dependent Process Parameters 
     The dependent process parameters are the process current and the three conductivities for determining concentrations of the feed and the effluents. All are monitored in real time, along with the process voltage, an independent parameter. It should be noted that in the case of the electrolytic and electrostatic modes, the process current, set to a constant level, was an independent process parameter. In the ELDYN mode it is more advantageous for the current to be a parameter dependent on other variables such as centrifugal force and electric field. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 List of Computed Deionization Performance Parameters 
               
             
          
           
               
                  Acronym 
                 Parameter 
                 Units 
               
               
                   
               
               
                 AVIP 
                 Average process current 
                 MA 
               
               
                 DSO 
                 Observed relative deionization 
                 % 
               
               
                 ONH 
                 Observed relative enhancement 
                 % 
               
               
                 DST 
                 Theoretical relative deionization 
                 % 
               
               
                 TNH 
                 Theoretical relative enhancement 
                 % 
               
               
                 FEFD 
                 Faradaic deionization efficiency 
                 % 
               
               
                 FEFC 
                 Faradaic enhancement efficiency 
                 % 
               
               
                 SEP 
                 Separation ratio (ONH/DSO) 
                 —  
               
               
                 KGKWH 
                 rate of mass removal per unit of energy 
                 kg/kWh 
               
               
                 ENERW 
                 energy per unit volume of water desalinated 
                 kWh/m 3   
               
               
                 COSTW 
                 cost per unit volume of water desalinated 
                 $/m 3   
               
               
                 COSTCP 
                 cost per unit mass of chemical compound recovered 
                 $/kg 
               
               
                 COSTR 
                 cost per unit mass of metal ion or anion recovered 
                 $/kg 
               
               
                   
               
             
          
         
       
     
     Computed Performance Parameters 
     Formulas and software have been developed for computing deionization performance parameters. The software provides for continuous monitoring of the independent and dependent parameters during the process. The performance data are based on the starting concentration of the feed, the observed concentrations of the effluents, and other dependent and independent process parameters. The concentrations can be determined conductometrically from the expression log C=a log K+b, where C is the concentration, K is the conductivity, and a and b are constants characteristic of each material. A temperature correction to a common temperature is accomplished automatically by the conductivity meter. A list of deionization parameters that are computed and tabulated automatically at the end of each waste-water-treatment run appears in Table 1. They serve as the data base for evaluating the technical and economic merits of the process. 
     Predicted High Efficiency of Deionization in the ELDYN Mode 
     When the ELCOR™ process can be made to operate predominantly in the ELDYN mode, by substantially increasing the centrifugal force, the energy efficiency, rate of deionization, and cost-effectiveness will rival those of any other process. Consequently, a system design and operational features anticipated for the ELDYN mode can be incorporated into the ELCOR™ process disclosed in the Hanak patent. The ultimate goal will be to develop the most efficient and cost-effective process for the remediation of water resources which have been adversely affected by environmental pollution—including toxic wastes and radionuclides. The process will be also equally suitable for the treatment of water containing high levels of naturally occurring dissolved solids such as deep-well or brackish water. 
     The basis for the predicted high efficiency of deionization is as follows. First of all, there is a set quantity of energy associated with the removal of a solute from the feed solution, which is equivalent for all demineralization processes. Hence, this energy will not be considered in the comparison of the ELCOR™ process with other processes. For the ELCOR™ process operating in the electrolytic and electrostatic modes, it has been demonstrated that the energy efficiency is equal to or exceeds those of reverse osmosis (RO) and of electrodialysis (ED), not taking into account the energy required to run the centrifuge. (For large systems, centrifugation is estimated to be a small fraction of the total energy.) The energy expended in the electrolytic mode is mainly the sum of the resistive loss in the electrolyte, I 2 R, where I is the electric current and R is the electrical resistance of the process liquid, plus the energy consumed by the electroplating and stripping operations. In the electrostatic mode it is again the I 2 R loss plus the energy consumed by the capacitive charging and discharging. The results also indicate that the electrostatic mode is more energy-efficient than the electrolytic mode. In the ELDYN mode at steady state, when additional charging is no longer occurring, the sole source of expended energy is the I 2 R component (again ignoring centrifugation). The ions arriving at the electrodes are simply balanced by those leaving the electrodes by the sliding action due to the centrifugal force. Thus, in the absence of the electrochemical components of energy loss, the process is more efficient in the ELDYN mode and also more efficient than RO or ED. 
     Operating Procedure for Deionization in the ELDYN Mode 
     The existing operating procedure used in the electrostatic mode employs constant current, which is an independent parameter in the Hanak patent. In that method, switching of polarity occurs when the limiting voltage is reached. A new, improved procedure employs constant voltage as an independent parameter. The process current is now a parameter that is dependent directly on the electric field and indirectly on the centrifugal force. As stated above, it is anticipated that in the ELDYN mode the current will saturate at a constant level proportional to the electric field and the centrifugal force, in addition to the ionic concentration in the feed. The software for process control and for evaluation requires appropriate modifications to accommodate this change. 
     As detailed in the Section entitled “Example” the data in FIG. 6 indicate that in the first part of each pulse, at lower voltage, charging of the electrodes is predominantly taking place, meaning that the electrostatic mode prevails. In the second part of the pulse, at higher voltage, it is clear that the ELDYN mode predominates, judging from the emergence of extensive concentration. This sequence of occurrence of the electrostatic and the ELDYN modes suggests that the HSA electrodes need to be at least partially populated by ionic species in order for significant rate of sliding of the ionic sheath to take place. The logic of this conclusion follows from the fact that the initially thin ionic sheath is more strongly attracted to the oppositely charged electrode surface than the subsequent thicker sheath. In the latter, additional ionic species can slide with relative ease over ions of the same polarity which are attracted more strongly to the electrode surface. The partial population of the electrode surface occurs automatically upon the application of voltage to discharged electrodes; requiring no additional provision for the ELDYN mode to occur. 
     A need for periodic, infrequent change in polarity of the electrodes is anticipated in order to clean the electrodes possibly soiled by microscopic solid matter, attracted to the surface. The intervals between such polarity reversal might be hours, days or weeks, if at all, most likely dependent on the quality of the feed liquid. 
     It should be pointed out that operation at a constant voltage is used in the capacitive deionization taught by Joseph Farmer in prior art [Ref 3]. However, in that process the current is not constant; it rises to a high value upon initial application of the voltage, and decreases asymptotically to a very low value with time, whereupon the electrodes must be discharged and regenerated. With the decrease of current the rate of deionization also decreases. As already stated, in the ELCOR™ process using the ELDYN mode a high, constant level of current persists, with no need to discharge the electrodes or switch polarity except for optional, occasional cleaning. Thus, the performance characteristics of the instant invention are superior to those of the Farmer patent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a dynamic EG deionization of 0.01 M H 2 SO 4  in the electrostatic mode utilizing reversible high-surface-area electrodes. Other conditions are: process current=35 mA; V max. =1.0 Volt; diluent flow rate=1.85 mL/min; concentrate flow rate=1.85 mL/min. (FIG. 1 is the same as FIG. 10 in the Hanak patent). 
     FIG. 2 is a proposed model of the electrode-solution, double-layer region (from Reference  4 ). IHP and OHP are the ‘inner’ and ‘outer’ Helmholtz planes at distances x 1  and x 2  from the electrode. 
     FIG. 3 is a dynamic EG deionization of 0.01 M CaCl 2  in the electrostatic mode utilizing reversible high-surface-area electrodes. Other conditions are: process current=35 mA; maximum process voltage (V max. )=1.0 Volt; diluent flow rate=1.85 mL/min; concentrate flow rate=1.85 mL/min. (FIG. 3 is the same as FIG. 9 in the Hanak patent). 
     FIG. 4 is a frontal projection of the ELCOR™ deionization device  110  of the Hanak patent, viewed in the direction perpendicular to the end plate of the modules and parallel to its axis. FIG. 4 is analogous to FIG. 2C in the Hanak patent, with an added feature of having an array of dot or rod insulating spacers arranged in a close-packed hexagonal pattern to maintain even spacing of the electrodes. 
     FIG. 5, related to FIG. 4, utilizes a zonal centrifuge design [Ref. 7] for the deionization chamber, which in this case is divided into three equivalent zones. 
     FIG. 6 shows graphical data for the first successful experiment of the ELCOR™ process operating in the electrostatic mode. The data show clearly the existence of both the electrostatic and the ELDYN modes. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The ELCOR™ equipment used for deionization in the ELDYN mode may be identical to that used in the electrostatic mode described in the Hanak patent. For optimum performance the equipment may incorporate one or more of the following enhancements. 
     Reduction of the Electrode Spacing. 
     Spacing between the electrodes is discussed in the Hanak patent. In the electrostatic mode periodic reversal of polarity is required when maximum voltage is reached. Upon polarity reversal the ion sheath, which is attracted to the electrode during charging, is released and starts diffusing away from the electrode and can mix partially with the depleted liquid. In order to prevent substantial mixing of the concentrate and the diluent it is important to provide sufficient electrode spacing and also to employ sufficiently high centrifugal force to sweep the ion sheath and the depleted liquid rapidly into their respective exhaust ports. 
     In the ELDYN mode it is anticipated that the process will operate at a steady state at a constant voltage and essentially at constant current, without polarity switching, except for possible occasional cleaning of the electrodes. In the absence of frequent polarity reversals, the ion sheath remains attracted close to the electrode and will not diffuse away from the electrodes to cause mixing of the concentrated solution and the diluent. Consequently, the spacing between the electrodes may be made smaller than in the electrostatic mode, thereby decreasing the transit time of the ions and increasing the performance parameters. The minimum spacing could be estimated from the thickness of the diffuse layers at the surface of the electrodes and from the ratio of the diluent and the concentrate flow rates. Thus, if the thickness of each diffuse layer is 1 nm and said ratio is 20, then the minimum cathode to anode spacing would be 42 nm. In practice, considerably larger spacing would be used to allow for sufficiently high flow rates. While there is no apparent limit for maximum spacing, in practice it would be dictated by practical levels of deionization, concentration and throughput, which decrease with increasing spacing. A practical, minimum spacing and means of achieving it could be that used in supercapacitors as described below. 
     Use of Insulating Spacers in between the Electrodes 
     Electrode spacers can be used in the form of insulating dots to keep the electrodes apart to help decrease the electrode spacing without risking the electrodes touching each other and to maintain uniform spacing. A method of forming such dots on the surface of supercapacitor electrodes and their use in supercapacitor devices is described by Tong et al. [Ref. 5 and 6]. The dots consist of organic epoxide polymer, about 25 to 31 μm (micrometers) in height and printed over a square grid about 1 mm apart. 
     The preferred configuration of insulating dot or rod electrode spacers is shown in FIG. 4, which is a frontal projection of the ELCOR™ deionization device  110  of the Hanak patent, viewed in the direction perpendicular to the end plate of the modules and parallel to its axis. FIG. 4 is analogous to FIG. 2C in the Hanak patent, with two added features. One of them is that the spacer  192  is inclined away from the direction of rotation with respect to the radial direction. The other feature is that of having an array of dot or rod insulating spacers arranged in a close-packed hexagonal pattern to maintain even spacing between the electrodes. 
     While such narrow electrode spacing in the ELCOR™ module is possible, it appears that spacing of 0.005 cm to 3.0 cm would be more practical, possibly using spacers at the lower end of the range of separation. It is anticipated that use of spacers might interfere with laminar flow of the concentrate and the diluent fluids and thereby give rise to their mixing. Another expected problem with the spacers is possible increased charge leakage caused by partially electrically conducting films formed on the spacers over a period of time. 
     Examples of deionization occurring partially in the ELDYN mode, using the Electrogravitation process were discussed above, and were shown in FIGS. 1 and 3. Another example is described next. 
     Increase in Centrifugal Force. As discussed above, an increase in centrifugal force promotes the ELDYN mode and with it a substantial improvement in the performance parameters of the process. Consequently, the rate of rotation of the ELCOR™ module should be increased to as high a level as is mechanically and economically practical. There appears to be no fundamental limit to the rotational speed or the level of centrifugal force except for the endurance of the mechanical systems, such as the drive system, rotary union, and module components which may be affected by the strength of materials, friction and the like. With substantially enhanced rate of deionization with increasing centrifugal force, it is predicted that the size of the ELCOR™ module may be decreased considerably to achieve equivalent performance, thereby possibly reducing the capital and operational costs of the process. 
     The centrifugal force, generated by the spinning of the rotor and directed away from the axis, is measured in multiples of the Earth&#39;s gravitational force and is known as the “relative centrifugal field (r.c.f.) or ‘G force’. Centrifugation, which is a term used for the separation of a large variety of materials, mostly consisting of more than one phase, has been in use for well over 100 years [7]. Centrifugation has also been applied to the separation of materials in single phase, including gases [8] and liquids. Remarkable progress in the development of advanced centrifuge rotors occurred during World War II, in conjunction with the separation or enrichment of nuclear isotopes, notably of uranium 234 and of plutonium [8]. The advent of zonal centrifuges and the density-gradient method has facilitated the mass separation of subcellular particles including viruses [9]. 
     Centrifuges of special interest in the instant invention are the zonal centrifuges designed for a continuous operation, in which the liquid to be processed is continuously fed in and the separated materials are continuously removed. They are cylindrical rotary devices, having a hollow annular chamber, equipped with two or more radial walls so as to form two or more separate chambers. This construction facilitates maintaining the feed liquid essentially at rest with the rotor, except for the effects due to the Coriolis force and to pumping the liquids into and out of the device. 
     The first zonal centrifuge was built by N. G. Anderson at Oak Ridge National Laboratory, where over 50 different zonal centrifuge rotors have been developed and evaluated [9]. Seven zonal rotor series for different applications have been developed, ranging from low speed of 1000 RPM to ultra high speeds of up to 150,000 RPM. The r.c.f. developed in these rotors ranged from 152 to 994,000 G. These rotors were relatively small devices, ranging in capacity from less than 100 milliliters up to 4000 milliliters. In these devices the capacity varies approximately inversely with the speed of rotation and r.c.f. 
     At very high speeds and r.c.f. balancing of the zonal rotors is extremely important. That is the main reason for dividing the chamber into two or more equivalent zones (usually an even number) to achieve balance. 
     The ELCOR™ device in the Hanak patent also makes use of the zonal centrifuge design, however, having only a single zone. This design is adequate for low r.c.f. and/or with relatively small rotor radius. As the r.c.f. is increased, the multi-zonal centrifuge design becomes increasingly desirable. The multi-zonal design is also preferred as the outer radius is increased. In this case the multi-zonal design facilitates shortening the path that the concentrated and depleted liquids must travel to reach the exhaust ports. 
     An example of a multi-zonal ELCOR™ cell or a series of cells is shown in FIG. 5 in which each cell is divided into 3 equivalent zones, each subtending an angle of 120°. This device contains three sets of insulating spacers  192 , inlet and outlet ports  154 ,  158 , and  160 , each item located 120 degrees from its similar items. In this device the conduits for the feed, the concentrated solution and the depleted liquid are mutually interconnected internally. Thus, the three zones are defined by the insulating spacers  192   a ,  192   b , and  192   c . These spacers are shown inclined away from the direction of rotation with respect to the radial direction, which along with the inner and outer annular insulating spacers  150  and  152  prevent the liquids therein from incursion into the neighboring zones. Each zone is also equipped with three sets of feed liquid inlets  160   a,b,c , concentrated solution outlets  154   a,b,c , and depleted liquid outlets  158   a,b,c . Not shown are internal conduits interconnecting each set of outlets prior to the discharge of the respective outflow liquids. Also shown in FIG. 5 is an array of optional insulating dot or rod electrode spacers  194  as in FIG.  4 . 
     In the multi-zonal ELCOR™ design it is preferable to combine the spacers  192   a,b,c  with the annular insulating inner spacers  150  and the annular insulating outer spacers  152  into a single, integrated spacer, thereby facilitating its fabrication, installation and stability. As in the Hanak patent said integrated spacer can be fabricated of neoprene rubber. For greater rigidity, especially at higher rotational speeds and r.c.f., said spacer may be made of a polymer such as high density polyethylene (HDPE), known for its electrical insulating properties and its resistance to many chemicals and water. The integrated spacers may be held in place either by compression or by thin layers of an adhesive or both. 
     The feed conduits  160   a,b,c  may also be internally connected to a common feed conduit or they may be connected to separate conduits in the rotary union discussed in the Hanak patent. 
     New Potential Applications. The multi-zonal design of the ELCOR™ will facilitate the use of high r.f.c. and/or rotors having large diameters. This design, along with the ELDYN mode will facilitate new applications. Heretofore only the density gradient medium, which provides varying density along a column of varying r.c.f. has been available to assist with the separation of different species in combination with high centrifugal force. In the case of the ELCOR™ process a new, powerful assistance for enhanced separation of a variety of biological and chemical species will be afforded by the use of electric field. 
     EXAMPLE 
     Deionization of 0.01 molar NaNO 3  in the ELCOR™ Device. 
     The ELCOR™ process operating in the ELDYN mode is currently under development. The first successful result is reported next. 
     The ELCOR™ module in this test was of the type depicted in FIGS. 2A,  2 B,  2 C,  2 D 1 B and  2 D 2  appearing in the Hanak patent. It utilized 3 cells, equipped with 4 annular, high-surface-area (HSA) supercapacitor electrodes, connected in electrical series, but with liquid flow in parallel. The ELCOR™ device used external pumps for the concentrate and the diluent; gravity flow was used for the feed. The test conditions were as follows. The rate of rotation was 1350 RPM which corresponds to a r.f.c. of 173 G (i. e., 173 times the force of gravity) at a mean radius of 8.51 cm. The flow rates of the diluent and of the concentrate were 32.7 and 86.8 mL/min, respectively, and the feed rate was 119.5 mL/min. The apparent surface area of one side of each HSA electrode was 321 cm 2 . The spacing between each pair of electrodes was about 0.288 cm. 
     The procedure used for the application of electric power was the one used in the electrostatic mode, namely, one of constant current and switching of polarity when limiting voltage is reached, the same as in the electrogravitational (EG) experiments of FIGS. 1 and 3. In this experiment the voltage limit and the average process current were set at 1.0 Volt and 130 mA, respectively. The data for this experiment are shown in FIG.  6 . Comparison of FIG. 6 with FIGS. 1 and 3 reveal significant differences. Whereas in FIGS. 1 and 3 the DSO and ONH were essentially symmetrical with respect to the 100% feed line, an entirely different behavior occured in FIG.  6 . In the first part of each new pulse, in the range of low voltage, the DSO increases from about 100% to a maximum (i.e., it reaches the minimum concentration) while the ONH decreases to a minimum, (i.e., it also goes through a minimum concentration. As the DSO passes the maximum value, the ONH starts increasing with increasing voltage at a fast rate, reaching a maximum (i.e., it reaches maximum concentration) at the point of the switching of polarity. The DSO reaches its minimum value (i.e., also its maximum concentration at the same point. Thus, in the ELCOR™ operation, the DSO and the ONH curves are asymmetrical as opposed to the EG operation. 
     FIG. 6 has additional set of two curves shown. One curve is DIL FEF and the other is CONC FEF, which are the Faradaic efficiencies for the diluent and the concentrate, respectively. The data indicate that the maxima in the diluent coincide with the minima in the concentrate and vice versa. Significantly, the first maximum in the CONC FEF reached a value of 64%, exceeding by 20% the highest value of 44% shown in FIG. 8 of the Hanak patent for the deionization of copper sulfate by the ELCOR™ process in the electrolytic mode. The 64% value also exceeds any CONC FEF values observed in the electrostatic mode in the EG process. Thus, the predicted higher performance has been substantiated. 
     Other features in FIG. 6, following the first pulse, are nearly equivalent DSO and DIL FEF for pulses  2 ,  3 ,  4 , and  6 , while pulse  5  is substantially different, apparently having undergone an anomalous event. By comparison, the values of ONH and CONC FEF for the same pulses show variation. The most likely reason is that a leak had occurred in the rotary union, admixing varying amounts of the feed liquid into the concentrate. 
     A proposed explanation to the data in FIG. 6 is that in the first part of each pulse, at lower voltage, charging of the electrodes is predominantly taking place, meaning that the electrostatic mode prevails. In the second part of the pulse, at higher voltage, it is clear that the ELDYN mode predominates. This sequence of the occurrence of the electrostatic and the ELDYN modes suggests that the HSA electrodes should be at least partially populated by the ionic species in order for a significant rate of the sliding of the diffuse layer to occur. This partial population occurs automatically upon the application of voltage to discharged electrodes. 
     The reason that a “pure” ELDYN mode is not observed is that the current used was higher than that allowed by the magnitude of the centrifugal force. 
     The average values of DSO and ONH calculated for the final pulse, number  6 , were 87.1% and 106.8%, respectively, compared with the relative concentration for the feed of 100%. Thus, enhancement and deionization are approximately inversely proportional to the flow rates. 
     The average Faradaic efficiencies for the diluent and the concentrate were 17.5 and 24.5%, for an average FEF of 21.0%. The two values should be the same as the average; in fact the difference is relatively small. 
     Although the process in this example has not been optimized, the current density was about 74% higher than that in an EG cell operating in partially electrostatic and partially ELDYN mode, thereby providing another proof of concept. 
     REFERENCES 
     1. Oren, Y., and Soffer, A., “Electrochemical Parametric Pumping,”  J. Electrochem. Soc . 125, 869-875 (1978). 
     2. Oren, Y., and Soffer, A., “Water Desalting by Means of Electrochemical Parametric Pumping. I. The Equilibrium Properties of a Batch Unit Cell,”  J. Applied Electrochem . 13, 473-487 (1983). 
     3. Joseph Farmer, “Method and Apparatus for Capacitive Deionization, Electrochemical Purification, and Regeneration of Electrodes,” U.S. Pat. No.5,425,858, Jun. 20, 1995. 
     4. Bard, A. J. and Faulkner, L. R.,  Electrochemical Methods, Fundamentals and Applications , John Wiley &amp; Sons, New York (1980). 
     5. Tong, Robert, et al. U.S. Pat. No. 5,384,685, Jan. 24, 1995. 
     6. Tong, Robert R., et al. U.S. Pat. No. 5,464,453, Nov. 7, 1995. 
     7. Hsien-Wen Hsu, Separations by Centrifugal Phenomena, in Techniques of Chemistry, Volume XVI, Edmond S Perry, editor, A John Wiley &amp; Sons, New York, Chichester, Brisbane, Toronto, 1981. 
     8. H. D. Smyth,  Atomic Energy for Military Purposes , Princeton University Press, Princeton, N.J., (1945). 
     9. N. G. Anderson,  Quarterly Review of Biophysics , 1, [3], 217 (1968).

Technology Classification (CPC): 2