Abstract:
An apparatus for electrochemical modification of liquid streams employing an electrolytic cell which includes an anode compartment defined by an anode structure where oxidation is effected, containing a liquid electrolyte anolyte, and a cathode compartment defined by a cathode structure where reduction is effected containing a liquid electrolyte catholyte. In addition, the electrolytic cell includes at least one additional compartment arranged at least partially between the anode compartment and the cathode compartment and separated from the anode compartment and the cathode compartment by a separator structure arranged to supports ionic conduction of current between the anode structure and the cathode structure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims benefits of copending U.S. patent application Ser. No. 13/020,447 entitled “A METHOD FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAMS filed with the U.S. Patent and Trademark Office on Feb. 3, 2011, U.S. patent application Ser. No. 11/623,658 (resulting in the issued U.S. Pat. No. 7,967,967) entitled “APPARATUS AND METHOD FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAMS” filed with the U.S. Patent and Trademark Office on Jan. 16, 2007, copending U.S. patent application Ser. No. 13/117,769 entitled “APPARATUS AND METHOD FOR ELECTROCHEMICAL MODIFICATION OF CONCENTRATIONS OF LIQUID STREAMS” filed with the U.S. Patent and Trademark Office on May 27, 2011, and copending U.S. patent application Ser. No. 13/251,646 entitled “APPARATUS FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAMS” filed with the U.S. Patent and Trademark Office on Oct. 3, 2011; all of which are incorporated herein by reference. 
     
    
     GOVERNMENT LICENSE RIGHTS 
       [0002]    This invention was made and reduced to practice in parts with US government support under National Institutes of Health (NIH) Small Business Innovation Research (SBIR) grant 1 R43 ES20096-01 AND Department of Energy (DOE) Small Business Innovation Research (SBIR) grant DE-SC0006181. The US government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The invention relates to an apparatus and a method for electrochemical modification of concentrations of constituents of liquid streams which contain organic and/or inorganic components. More precisely, the invention is concerned with an electrolytic cell technology with potentials to modification of concentrations of the components. 
       BACKGROUND OF THE INVENTION 
       [0004]    Contamination of liquid streams with various organic and inorganic constituents may represent an environmental problem affecting environment quality and represents significant threat to human health and safety. For example, heavy metals contaminations of aquatic environments may arise from commercial mining and metal extraction processes, surfaces modification and protection processes, or communal and industrial waste sites resulting from a variety of active or defunct industrial fabrication and manufacturing activities. Similarly, significant organic water pollutants, like aliphatic, aromatic, or halogenated hydrocarbons and phenols may be associated with oil exploration, extraction and refining, chemicals production, or large-scale farming and food processing. 
         [0005]    In addition to potentials for significant environmental damage, affected liquid streams my represent dilute sources of desirable raw materials like heavy metals, metal oxides, inorganic salts, and other compounds. For example, the Berkeley Mine Pit in Butte, Mont. alone represents an estimated 30 billion gallons of acid mine drainage which contains ˜180 ppm of copper along with other metals and thus could yield up to 22,000 tons of pure copper by use of a small treatment facility. 
         [0006]    An economically relevant group of prior art methods of removal of heavy metal ions from liquid solutions is based on chemical precipitation. This process is likely burdened by complexity, high cost, clear preference for extremely large facilities and high-volume operations, and efficiency decrease with decrease in concentration of pollutants. Additional disadvantages may concern resulting byproduct of precipitated sludge which may become a concentrated yet mixed contaminant source of the toxins in the source material. The sludge may mandate further processing and costly long term disposal as a highly toxic waste. Many similar disadvantages may burden alternative heavy ion removal methods that may incorporate: filtration, ion exchange, foam generation and separation, reverse osmosis, or combinations of listed processes. 
         [0007]    In contrast, the extraction technologies enabled by several aspects of the current invention may be adapted to alleviate at least some of the above considerations. Additional features of the current invention, for example, may contribute to the feasibility of modifying prior art electrowinning technology so that it can be used to economically concentrate copper generated in low-grade process streams instead of simply removing it. In general, the disclosed embodiments of the copper extraction technology may prepare a process stream so the customer can produce new copper from currently inaccessible sources with existing in-place processing infrastructure, equipment, and processes. 
         [0008]    The present invention may provide some innovative features for unlocking this vast and vitally needed resource. Typical mines contain significant amounts of their copper in such unviable ores. This invention may allow the use of this “waste” ore and thereby increase average heap leach mine output by 25% and thus globally yield 3 Billion lbs/yr of newly recoverable copper. 
         [0009]    Furthermore, additional features of embodiments of the current invention may allow for practical metal recovery from: Acid Rock Drainage (ARD), heavy metal and radionuclide contaminated sites, and metal contaminated industrial effluents such as electrowinning, plating plant, pickling operations, and circuit board manufacture (etching) discharges. 
         [0010]    In addition, different embodiments of the current invention may be applicable pertinent to commercial and municipal processes where potential contaminants may be reprocessed in parallel or in immediate sequence with processes that may generate such materials to start with. Even further, methods and apparatus of the current invention may achieve the above functions in an essentially integrated manner, frequently using at least one common treatment loop to simultaneously refine the desired products, generate materials and compounds that may be reused in the subsequent performances of the process by the disclosed apparatus, and generate essentially non-polluting byproducts. 
         [0011]    Finally, by application of highly integrated multifunctional devices and processes, the components of the current invention may achieve desirable results utilizing optimized quantities of components, raw materials, ingredients, and required energy; thus approaching optimized economic results. 
       SUMMARY OF THE INVENTION 
       [0012]    A method and an apparatus for electrochemical modification of liquid streams employing an electrolytic cell which utilize an anode compartment defined by an anode structure where oxidation is effected, containing a liquid electrolyte anolyte, and a cathode compartment defined by a cathode structure where reduction is effected containing a liquid electrolyte catholyte. In addition at least one additional compartment has been arranged at least partially between the anode compartment and the cathode compartment and separated from the anode compartment and the cathode compartment by a separator structure arranged to support ionic conduction of current between the anode structure and the cathode structure. Also, a system for conducting unidirectional electric current provides a unidirectional current flow supported by the liquid electrolytes from the anode structure through the separator structure and into the catholyte and to the cathode structure have been provided. 
         [0013]    The separator structure incorporates at least one ion conductive membrane positioned to contactly separate the anode compartment and the at least one additional compartment, and arranged to conduct a plurality of Hydrogen-like Cations while impeding transport of at least one selection of Anions, and at least another selective ion conductive membrane positioned to contactly separate the cathode compartment and the at least one additional compartment, and arranged to conduct at least another selection of Anions while impeding transport of the plurality of Hydrogen-like Cations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above and other embodiments, features, and aspects of the present invention are considered in more detail in relation to the following description of embodiments shown in the accompanying drawings, in which: 
           [0015]      FIG. 1 . is a schematic view of devices and processes of some embodiments in accordance with the current invention. 
           [0016]      FIG. 2 . is a schematic view of devices and processes of different embodiments in accordance with the current invention. 
           [0017]      FIG. 3 . is a schematic view of devices and processes of other different embodiments in accordance with the current invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The invention summarized above may be better understood by referring to the following description, which should be read in conjunction with the accompanying drawings. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the invention, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. Similar to the inventions in the applications incorporated by reference above (first paragraph), embodiments of this instant invention can be of planar, circular, and concentric tubular or other configurations containing two or more separate electrolyte compartments as required to address different application needs. 
         [0019]    One embodiment of the instant invention is illustrated in  FIG. 1 . It may be noted by the practitioner of the related arts that this embodiment (as illustrated in  FIG. 1 ) may be compared to embodiments of the inventions cited and incorporated (in its entirety) by reference in the section entitled “CROSS REFERENCE TO RELATED APPLICATIONS”. 
         [0020]    In specific embodiments of the current invention, in addition to the features of the above applications incorporated by reference, at least one additional compartment  121  may be added nominally between (at least partially) the cathode and anode compartments  101  and  131  respectively, and separated by at least one separator structure  111  arranged to prevent bulk mixing of the contents of the separated compartments  101 ,  121 , and  131 . In some embodiments, the separator structure  111  may include a pair of ion conductive elements arranged to allow transport of desired ion species between the compartments  101 ,  121 , and  131 . In one group of embodiments the separator structure  111  my incorporate ion conductive membranes  110  and  120  in direct contact with the contents of the compartments  101  and  121 , and compartments  121  and  131  (i.e. contactly separating compartments  101 ,  121 , and  131 ). The ion conductive membranes may incorporate ion conductive channels such that specific ions may be transported between compartments with fluxes depending on specific embodiment parameters including applied voltage, ion concentrations, temperature, ion mobility, and dimensions and surface properties of channels etc. The parameters may be arranged such that desired Anions are preferably transported from the cathode compartment  101  into the at least one additional compartment  121 , while desired Cations may be preferably transported from the anode compartment  131  into the at least one additional compartment  121 . 
         [0021]    A particular combination of the electrical fields for the cell operation in conjunction with the selective nature of the separating membranes may allow one to separate and transfer into the at least one additional compartment  121  ions of interest so that they may be concentrated in the added compartment in the manner comparable to electrodialysis. One feature of such modified cell may be to gain practical utility for several industrially important applications. 
         [0022]    In the  FIG. 1  schematically illustrated example, at least one electrolytic cell  100  having at least three compartments with at least two separate electrolyte flows separated by at least two ion conductive membranes  110  and  120  respectively. The at least one cathode compartment  101  input  106  may depend on the specific circumstances of the application and may include any number of liquid (aqueous and nonaqueous) streams containing dilute metals of suitable redox activity. As in the above-incorporated applications, a cathode structure  107  may be conventional (stationary) assembly or may, in different embodiments, incorporate a moving bed of conductive particulates for which numerous compositions (as incorporated above) may be appropriate. 
         [0023]    Several metals indicative for some aqueous solutions of interest as the input  106 , may include (but not be limited by): copper, iron, nickel, cobalt, cadmium, zinc, indium, gold, platinum, palladium, silver, mercury, tin, and rhenium. Other metals “M(s)” or metal Cations “M (+n) ” or metal containing ion complexes could be addressed in applications where one of the goals my be to reduce the metal&#39;s oxidation state (e.g. from +n to +(n−1), +(n−2), . . . ), and not necessarily to plate the metal out. The solutions&#39; pH may be in the range from strongly acidic to strongly alkaline. 
         [0024]    In particular embodiments, the input  106  may include Acid Rock Drainage (ARD) containing, for example, high sulfate acidic solutions including mixtures of dilute metals, as a result of natural processes attacking exposed sulfide containing rock (ore). The cathode compartment output  108  then may have the concentrations of the target metal ion lowered (this may allow for transformation of the species from one oxidation state to another without actual removal of the target metal ion from solution) and the sulfate concentration lowered. 
         [0025]    Depending upon different embodiments, at least one anode structure  137  of at least one anode compartment  131  may either utilize a conventional geometrically stabile DSA electrode or may incorporate moving beds of particulates, for example, using particulates transferred to/from the cathode compartment  101 , as disclosed in the incorporated application Ser. No. 13/117,789. 
         [0026]    At least one additional compartment  121  may be arranged at least partially between the at least one anode compartment  131  and the at least one cathode compartment  101 , and separated from the anode compartment and the cathode compartment by the separator structure  111 , incorporating at least two ion conductive membranes  110  and  120 , arranged to support ionic conduction of current between the anode structure  137  and the cathode structure  107 , but to restrict transport of selected Anions AN −m2  from the anode compartment  131  into the at least one additional compartment  121 , and to restrict transport of Cations (nH + ) from the at least one cathode compartment  101  into the at least one additional compartment  131 . 
         [0027]    In some embodiments, the at least one ion conductive membrane  110  may represent a selective ion conductive membrane positioned to contactly separate the at least one cathode compartment  101  and at least one additional compartment  121  (while being in direct contact with the liquids contained in the compartments  101  and  121 ) and arranged to selectively conduct specific Anions AN −m1  or a composition of Anions as appropriate to the specific embodiments, while impeding transport of Hydrogen H +  or Hydrogen-like (e.g. “Haydronium”, “Zundel”, or “Eigen”) Cations. In contrast, the at least one ion conductive membrane  120  may represent a selective ion conductive membrane positioned to contactly separate the at least one anode compartment  131  and at least one additional compartment  121  (while being in direct contact with the liquids contained in the compartments  131  and  121 ) and arranged to conduct Hydrogen H +  or Hydrogen-like Cations while restricting transport of the AN −m2  or a composition of Anions as appropriate to the specific embodiments. As a result, operations of the cell  100  may result, inter alia, in gradual increase of concentrations of AN −m1  and H +  ions (and therefore the H m1 AN acid) in the at least one additional compartment  121 . Therefore, outputs  129  from the compartment  121 , having elevated acidity, may be used for other purposes as the particular groups of embodiments may mandate or desire. 
         [0028]    One embodiment may include processing of zinc—where the particulate bed may be transferred into the anolyte but not in electrical contact with the anode structure  137 . The anode structure may utilize a separate DSA electrode for oxygen evolution (for example) from water splitting (H 2 O+4H + +O 2 +e−) and the zinc being spontaneously stripped from the particulate electrode [using an inert substrate like 316 SS] to generate concentrated ZnSO 4  in the anolyte). The water splitting on the anode includes generation of protons which may subsequently be separated from the background supporting electrolyte (salt) via the proton selective Cation conductive membrane  120 . Membranes selective to other Cations could be used (for the appropriate embodiments). 
         [0029]    It may be noted that the supporting electrolyte  139  may include a number of common salts or mixtures thereof. Different embodiments may include (but not be limited to) all combinations of CA Cations where CA=H + , Na + , K + , Li + , and NH 4   + , and AN Anions where AN=Acetate, bromide, chloride, Chlorate, cyanide, hydroxide, hypochlorite, iodate, iodide, nitrate, oxalate, perchlorate, phosphate, and sulfate plus those shown in the following Table I. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Common Ion Chart 
               
             
          
           
               
                 Positive Ions (Cations) 
                 Negative Ions (Anions) 
               
               
                   
               
             
          
           
               
                 Aluminum 
                 Al +3   
                 Acetate 
                 C 2 H 2 O 2   − /CH 3 COO −   
               
               
                 Ammonium 
                 NH 4   +   
                 Bromide 
                 Br −   
               
               
                 Barium 
                 Ba +2   
                 Carbonate 
                 CO 3   −2   
               
               
                 Cadmium 
                 Cd +2   
                 Hydrogen Carbonate Ion/ 
                 HCO 3   −   
               
               
                   
                   
                 Bicarbonate 
               
               
                 Calcium 
                 Ca +2   
                 Chlorate 
                 ClO 3   −   
               
               
                 Chromium (II) 
                 Cr +2   
                 Chloride 
                 Cl −   
               
               
                 Chromium (III) 
                 Cr +3   
                 Chlorite 
                 ClO 2   −   
               
               
                 Cobalt (II) 
                 Co +2   
                 Chromate 
                 CrO 4   2−   
               
               
                 Copper (I) 
                 Cu +   
                 Cyanide 
                 CN −   
               
               
                 Copper (II) 
                 Cu +2   
                 Dichromate 
                 Cr 2 O 7   −2   
               
               
                 Hydrogen 
                 H +   
                 Fluoride 
                 F −   
               
               
                 Hydronium 
                 H 3 O +   
                 Hydride 
                 H −   
               
               
                 Iron (II) 
                 Fe +2   
                 Hydroxide 
                 OH −   
               
               
                 Iron (III) 
                 Fe +3   
                 Hypochlorite 
                 ClO −   
               
               
                 Lead (II) 
                 Pb +2   
                 Iodate 
                 IO 3   −   
               
               
                 Lead (IV) 
                 Pb +4   
                 Iodide 
                 I −   
               
               
                 Lithium 
                 Li +   
                 Nitrate 
                 NO 3   −   
               
               
                 Magnesium 
                 Mg +2   
                 Nitride 
                 N −3   
               
               
                 Manganese (II) 
                 Mn +2   
                 Nitrite 
                 NO 2   −   
               
               
                 Mercury (I) 
                 Hg 2   +2   
                 Oxalate 
                 C 2 O 4   −2   
               
               
                 Mercury (II) 
                 Hg +2   
                 Oxide 
                 O −2   
               
               
                 Potassium 
                 K +   
                 Hydrogen Oxalate Ion 
                 HC 2 O 4   −   
               
               
                 Silver 
                 Ag +   
                 Perchlorate 
                 ClO 4   −   
               
               
                 Strontium 
                 Sr +2   
                 Permanganate 
                 MnO 4   −   
               
               
                 Sodium 
                 Na +   
                 Peroxide Ion 
                 O 2   −2   
               
               
                 Tin (II) 
                 Sn +2   
                 Phosphate 
                 PO 4   −3   
               
               
                 Tin (IV) 
                 Sn +4   
                 Monohydrogen Phosphate 
                 HPO 4   −2   
               
               
                 Zinc 
                 Zn +2   
                 Dihydrogen Phosphate 
                 H 2 PO 4   −   
               
               
                   
                   
                 Silicate 
                 SiO 3   −2   
               
               
                   
                   
                 Sulfate 
                 SO 4   −2   
               
               
                   
                   
                 Hydrogen Sulfate Ion/ 
                 HSO 4   −   
               
               
                   
                   
                 Bisulfate 
               
               
                   
                   
                 Thiosulfate 
                 S 2 O 3   −2   
               
               
                   
                   
                 Sulfide 
                 S −2   
               
               
                   
                   
                 Hydrogen Sulfide Ion/ 
                 HS −   
               
               
                   
                   
                 Bisulfide 
               
               
                   
                   
                 Sulfite 
                 SO 3   −2   
               
               
                   
                   
                 Hydrogen Sulfite Ion/ 
                 HSO 3   −   
               
               
                   
                   
                 Bisulfite 
               
               
                   
               
               
                 1—mono 
               
               
                 2—di 
               
               
                 3—tri 
               
               
                 4—tetra 
               
               
                 5—penta 
               
               
                 6—hexa 
               
               
                 7—hepta 
               
               
                 8—octa 
               
               
                 9—nona 
               
               
                 10—deca 
               
             
          
         
       
     
         [0030]    As in the discussion of the above embodiments, the at least one additional compartment  121  may be delineated on either side by selective ion conductive membranes  110  and  120  which allow selective ionic conduction. In some embodiments, a simple physical barrier such as a microporous membrane like DARAMIC® available commercially at least from the Daramic, LLC (a business unit of Polypore, Inc. with headquarters in Charlotte, N.C. USA) could also be used but typically achieves lower separation efficiency and resultant concentration differentials than afforded by ion selective membranes. Typically an Anion selective membrane may be employed to separate the cathode compartment  101  and the additional compartment  121 . In such an embodiment, a sulfate selective Anion conductive membrane may be used (several available, for example, from Veolia Water Solutions &amp; Technologies). Many commercial varieties of Anion selective membranes are also available in alternative, and would be suitable for use herein and in different embodiments. For the anode compartment  131 /additional compartment  121  separation, a Cation selective membrane  120  may be used. In some embodiments, a proton selective membrane like DuPont&#39;s Nafion® (or NAFION®) may be used, with Nafion® 325 being a possible choice due to its enhanced suppression of back diffusion of Anions. Again, many other commercial examples of Cation and proton selective Cation selective membranes exist and may be suitable for use herein and in other embodiments. The emerging polymer membrane based fuel cell industry represent a market of choice and a motivator for the future R&amp;D and may be a rich source of new and better membranes for emerging and yet to emerge embodiments of the current invention. 
         [0031]    In the embodiments pertinent to the schematics illustrated in  FIG. 1 , the outputs  129  may be used in an extraction procedure wherein, a strong leachant solution including the output  129  (having e.g. sulfuric acid) may be passed through raw materials  123  (e.g. crushed ore) to leach out target metal or metals from the raw materials  123 . The resultant leachate  124  (pregnant leach solution or PLS) may be subsequently processed in a reactor  115  to remove the dissolved metals. Most of the target metals  116  may be removed, but a residual amount of target metal remains in a weak solution called raffinate  117 . It may be noted that the leaching procedures may consumes the leachant (again as acid contained in the output  129 ) and fresh makeup leachant (here acid) may need to be added to the residual raffinate before it is recycled back to leach more raw materials  123 . 
         [0032]    It may be noted that in some embodiments, the reactor  115  may be based on electrochemical principles and incorporate electrolytic cells as recited above and/or in the above-incorporated applications. 
         [0033]    Regarding embodiments of the current invention pertinent to the schematic illustration in  FIG. 2 , where it may not be desirable to directly input solutions of interest as the input  106  into the cathode compartment  101 , a portion of the raffinate  206  exiting the reactor  115  may be inputted into the at least one cathode compartment  101 . The remaining portion of the raffinate  117  may, as before (e.g.  FIG. 1 ), be directed into the at least one additional compartment  121  for recycling and further concentration of the acid ingredients. It may be noted that the residual metal in the raffinate  117  may not be lost for extraction and is likely to be reacquired (e.g. plated as metal) during the subsequent passages through the reactor  115  and/or the cathode compartment  101 . 
         [0034]    Furthermore, one may note that  FIG. 2-illustrated  embodiments may include addition of further external components  210  intended to improve devices and operations acting, for example, as supporting solvents (aqueous or non-aqueous), detergents, lubricants, emulgators, coagulats, surfactants, buffers, corrosion inhibitors, and/or combinations of the above functions. 
         [0035]    Regarding embodiments of the current invention pertinent to the schematic illustration in  FIG. 3 , where it may not be sufficient amount (or flaw) of the input  106  (e.g. ADR), the input  106  may vary in time (seasonally or in response to meteorological conditions), or/and may be suboptimal to introduce only the input  106  directly into the at least one cathode compartment  101 , the input  106  may be in-mixed with the portion  306  of the raffinate, in-mixed directly into the reactor  115 , and/or co-applied to the raw materials  123 . It may be noted that, as discussed above regarding the  FIG. 2 , the metal content in the input  106  exiting through the portion  117  of the raffinate may not be lost for extraction and is likely to be reacquired (e.g. plated as metal) during the subsequent passages through the reactor  115  and/or the cathode compartment  101 . 
         [0036]    Processes of controlled removal of products of electrochemical reactions can be performed continuously during the operation of the electrolytic cell as customary in the art of electrochemical disinfection or pollution removal, or using batch process as customary in art of conventional electrowinning of metals. Both modes of operation are in accordance with the present invention. 
         [0037]    The present invention has been described with references to the exemplary embodiments arranged for different applications. While specific values, relationships, materials and components have been set forth for purposes of describing concepts of the invention, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the basic concepts and operating principles of the invention as broadly described. It should be recognized that, in the light of the above teachings, those skilled in the art can modify those specifics without departing from the invention taught herein. Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with such underlying concept. It is intended to include all such modifications, alternatives and other embodiments insofar as they come within the scope of the appended claims or equivalents thereof. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein. Consequently, the present embodiments are to be considered in all respects as illustrative and not restrictive.