Abstract:
A method of producing iron by: solubilizing iron oxide as a lithiated iron oxide in a molten carbonate having lithium carbonate; and subjecting the lithiated iron oxide to electrolysis to obtain iron and oxygen. The molten alkali metal carbonate salt may further include lithium oxide. Additionally the lithium carbonate may be simultaneously subjected to electrolysis to produce steel instead of iron.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Nos. 61/438,610 filed on Feb. 1, 2011, 61/426,030 filed on Dec. 22, 2010, and 61/331,109 filed on May 4, 2010, all of which are incorporated by reference herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    This technology relates to a method and system of producing iron electrolytically using iron oxide as a starting material. 
         [0003]    Iron is currently produced commercially in blast furnaces where iron ore is reduced by coke to cast iron. This millennia old, greenhouse gas emitting, carbothermal process is responsible for 25% of all carbon dioxide global released by industry. In order to reduce carbon dioxide emissions it is desirable to develop alternate processes to produce iron with a substantial reduction or elimination of carbon dioxide production. 
         [0004]    Previous attempts to produce iron from naturally occurring materials by electrowinning have faced challenges and have not provided a pathway to the commercial, carbon dioxide-free production of iron. Attempts have included room temperature electrowinning, challenged by too high a voltage to be efficient, and molten iron oxides, which faced the material&#39;s challenges of very high temperature (hematite melts at 1565° C.). Non-naturally occurring iron materials have been used as a reactant. Non-naturally occurring starting materials represent additional costs—both environmentally and economically. 
         [0005]    There remains a need in the art for a method of electrowinning iron from naturally occurring materials, at low voltage, at a temperature below that of the melting point of iron oxides, at high rate, and without carbothermal carbon dioxide emission. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Disclosed herein is a method of producing iron comprising: solubilizing iron oxide as lithiated iron oxide in a molten carbonate comprising lithium carbonate; and subjecting the lithiated iron oxide to electrolysis to obtain iron and oxygen. 
         [0007]    Also disclosed herein is a method of producing steel comprising: solubilizing iron oxide as lithiated iron oxide in a molten carbonate comprising lithium carbonate; and subjecting the lithiated iron oxide and the lithium carbonate to electrolysis to obtain steel and oxygen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows the measured electrolysis potentials of iron for dissolved Fe(III) in molten Li 2 CO 3  as described in Example 1. 
           [0009]      FIG. 2  shows the thermogravimetric analysis described in Example 3. 
           [0010]      FIG. 3  shows the solubility of Fe 2 O 3  as described in Example 3. 
           [0011]      FIG. 4  shows the calculated thermodynamic equilibrium constant as a function of temperature as described in Example 4. 
           [0012]      FIG. 5  shows the thermogravimetric analysis of lithium carbonate described in Example 4. 
           [0013]      FIG. 6  shows the calculated electrolysis potential as described in Example 5. 
           [0014]      FIG. 7  is a photograph, cyclic voltammetry and electrolysis potential as described in Example 5. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    As described herein a molten carbonate or a combination of molten carbonates are used as the electrolyte when producing iron or steel from iron oxide. Prior to the work described herein, it was thought that iron oxide had extremely limited solubility in molten alkali metal carbonates, more specifically on the order of 10 −5  to 10 −4  M at 650° C. The limited solubility of iron oxide thus restricted the use of molten carbonates as an electrolyte in electrowinning iron from iron oxide. Surprisingly it has been found that lithiated iron oxide has dramatically increased solubility in molten carbonates compared to non-lithiated iron oxide as well as the sodium and potassium equivalents of the lithiated iron oxide. The solubility of lithiated iron oxide in molten carbonates enables the use of molten carbonates as an electrolyte for the electrodeposition of iron. The increased concentration of iron oxide in the electrolyte decreases the energy voltage required for iron electrowinning. 
         [0016]    Molten carbonates include alkali carbonates such as lithium carbonate, sodium carbonate, potassium carbonate and mixtures of two or more of the foregoing alkali carbonates. Mixtures of alkali carbonates can be advantageous due to lower melting points. For example Li 0.7 Na 0.93 CO 3  has a melting point of 499° C. and Li 0.85 Na 0.61 K 0.54 CO 3  has a melting point of 393° C. and these melting points are compared to the melting points of alkali carbonates (Li 2 CO 3  723° C., Na 2 CO 3  851° C., K 2 CO 3  891° C.). 
         [0017]    In one embodiment the lithiated iron oxide is formed by the ready dissolution of iron oxides, such as the commonly occurring salts Fe 2 O 3  or Fe 3 O 4 , at temperatures greater than 393° C. in molten lithium carbonate or into a molten mix of carbonates comprising lithium carbonate. In the absence of lithium carbonate, such as in pure sodium or potassium carbonate, or a mix of the two, the solubility of iron oxide is very low, while in the presence of lithium carbonate, the solubility is high and increases with temperature. For example, at 950° C. the solubility in Na 2 CO 3  is less than 0.1 molal (m) of dissolved Fe(III), while it is up to 14 m in Li 2 CO 3 . Iron oxides are also soluble in mixed carbonates which comprise Li 2 CO 3 . For example, in Li 0.87 Na 0.63 K 0.50 CO 3 , Fe(III) solubility increases from 0.7 m at 450° C. up to 4 m at 950° C. It is also contemplated that the lithium ions needed for the formation of the lithiated iron oxide may be provided by another lithium salt, such as lithium chloride, lithium sulphate and the like. 
         [0018]    The initial addition of the iron oxide is accompanied by release of carbon dioxide, which is eliminated when one equivalent of Li 2 O is added for each equivalent of dissolved Fe 2 O 3 . Without being bound by theory Fe 2 O 3  is observed to be dissolved as LiFeO 2 . In either case, further dissolution of Li 2 O is not needed to sustain the electrowinning. For example, electrolysis of LiFeO 2  produces Fe and releases Li 2 O; iron is replenished by the addition of further iron oxide, such as Fe 2 O 3 , which dissolves with the accumulated, released Li 2 O in the carbonate. Hence, additional Li 2 O is not required when the addition of iron oxide occurs at a rate that is similar to the rate at which Li 2 O is released. 
         [0019]    In one embodiment the electrowinning electrolyte stability is enhanced with carbon dioxide gas or with excess Li 2 O added to the molten carbonate. Molten Li 2 CO 3 , open to the air, is highly stable at 750° C., but slowly decomposes at 950° C. into Li 2 O and CO 2 . This decomposition at higher temperature is inhibited, or prevented, when the molten Li 2 CO 3  contains excess dissolved Li 2 O or when heated under carbon dioxide, rather than air. 
         [0020]    In one embodiment steel, rather than iron, is directly formed from iron oxide salts, such as the commonly occurring salts Fe 2 O 3  or Fe 3 O 4 , by electrowinning in molten carbonate and applying higher electrowinning potentials to co-deposit iron and carbon from molten carbonates For example, without being bound by theory, carbon is formed by the electrolysis of lithium carbonate as: Li 2 CO 3 →C+Li 2 O+O 2    
         [0021]    Carbonate is not lost as consumed carbonate is replenished with carbon dioxide, without being bound by theory, in accord with: Li 2 O+CO 2 →Li 2 CO 3 . At higher electrowinning potentials in molten carbonate containing iron oxide, iron containing carbon is formed by coreduction of the dissolved iron oxide and CO 2 , dissolved as carbonate, for example from Fe 2 O 3 , without being bound by theory, as: Fe 2 O 3 +xCO 2 →2FeC x/2 +(3/2+x)O 2 . 
         [0022]    In one embodiment common impurities found in iron oxide salts do not prevent high solubility of iron oxides in molten lithium carbonate. These impurities also do not dissolve beyond a measured solubility limit, and this facilitates electrowinning of low purity iron oxide ores. The predominant iron ores are hematite (Fe 2 O 3 ) and magnetite (Fe 3 O 4 ). These ores also commonly contain various levels of silica, and alumina. SiO 2  and Al 2 O 3  dissolve in molten lithium carbonate as Li 2 SiO 3  and LiAlO 2 . In 750° C. Li 2 CO 3  the respective solubility is 0.06 m Al 2 O 3 , or 0.4 m SiO 2 , and increase with increasing temperature. Dissolution of 0.4 m SiO 2  in 750° C. molten lithium carbonate decreases the solubility of Fe(III) (dissolved as Fe 2 O 3 ) by only a small fraction (less than 10 percent). Furthermore, iron tends to electrowin in carbonate melts without contamination due to the reduction of common impurities found in iron oxide salts. Examples of impurities include in addition to silicon and aluminium salts, alkali salts, magnesium salts, barium salts, manganese salts, titanium salts, chromium salts, beryllium salts and zinc salts. The standard electrode potential for the elements consisting of the Li, Na, K, Al, Mg, Ba, Mn, Zn, Cr, Ti, Si and Be are each more negative than that of iron, and the salts of these metals tend to require a substantially greater electrodeposition potential than those of comparable iron salts 
         [0023]    Iron oxides may be dissolved in carbonates at temperatures as low as 393° C. (eutectic carbonate) or as high over 1000° C. for electrowinning of iron. Higher temperatures provide the advantages of greater iron oxide solubility, and higher current density at electrowinning at lower electrowinning potential. The lower temperature carbonates provide the advantage of enhanced durability of electrowinning cell components (electrodes, cell container and electrolyte) and lower solubility of common iron oxide ore impurities. 
         [0024]    The anode can be made of any inert material which is stable under the operating conditions of the cell. The inert anode can be designed to promote an oxygen evolution reaction at low electrolysis potentials. Effective materials include metals, such as nickel, platinum or iridium, metal oxides such as nickel oxide, metal alloys such as monel and inconel, and carbon based materials such as glassy carbon and graphite. Enhanced anode surface area, such as with screen or spongy materials, by physical roughening, by chemical or electrochemical etching, or as deposited on a conductive support, will decrease electrolysis potential. 
         [0025]    The cathode can be made of any conductive material stable under the operating temperature of the cell. For convenience however it is generally desirable for the cathode to be made of iron. 
         [0026]    The electrolytic reaction is conducted at a temperature greater than the melting point of the molten carbonate (or combination of carbonates) used as the electrolyte. In some embodiments the temperature of the electrolytic reaction is 0 to 300 degrees greater than the melting point of the carbonate. Exemplary temperatures are 723 to 1000° C. when the molten carbonate is lithium carbonate. 
         [0027]    The electrolytic cell can be operated at a current density of 1 milliAmpere per square centimetre (mA/cm 2 ) to 10 Ampere per square centimeter (A/cm 2 ) Within this range the current density can be greater than or equal to 100 mA/cm 2  to ensure greater rate of iron production. Also within this range the current density can be less than or equal to 5 A/cm 2  to ensure lower electrowinning voltage. Higher temperatures and higher concentrations of lithiated iron oxide provide the advantages of higher current density while electrowinning at lower electrowinning potential. For example electrowinning is performed at current densities ≧1 A/cm 2  in 950° C. lithium carbonate with dissolved, concentrated iron oxide. These current densities can be expected to increase ten-fold to ≧10 A/cm 2  when planar (flat) electrodes are replaced with surface area enhanced electrodes. On the planar electrodes, temperature and concentration are sufficient in the eutectic mix (at T≧550° C., dissolved iron oxide concentrations are ≧1 molal in the eutectic mix) to support ≧100 mA/cm 2 , and at T&gt;750° C. in lithium carbonate, solubilities are ≧7 molal, to access &gt;0.5 A/cm 2 . 
         [0028]    Iron is reduced and deposited on the cathode. Salt may become trapped in the deposited material. The deposited iron may be separated from any trapped salt by grinding the deposited material and washing with deionized water. 
         [0029]    The above discussed methods are further explained in the following non-limiting examples. 
       EXAMPLES 
     Example 1 
       [0030]    Experiments were conducted to demonstrate electrowinning of Fe 2 O 3  in molten carbonates. Addition of a lithium salt to molten carbonate adds lithium cations. The melt is then, in part, lithium carbonate. Lithium carbonate, Li 2 CO 3 , provides a simple salt to demonstrate solubilizing Fe 2 O 3 . 16 grams (g) of Fe 2 O 3  were added to 80 g of Li 2 CO 3 , and heated together to 800° C. in a 75 milliliter (ml) alumina crucible. The Fe 2 O 3  fully dissolved to form a red-brown solution. Alternatively, when heated to 800° C. without Fe 2 O 3 , 80 g of Li 2 CO 3  forms a clear (colorless) liquid, and then forms a red-brown solution upon addition of the 16 g of Fe 2 O 3 . A 3 cm×4 cm piece of Ni foil was suspended in the molten mixture to function as the anode. A coiled 2.8 square cm Pt wire (18 cm long, 0.5 millimeter (mm) diameter) was suspended in the molten mixture to function as the cathode. A current of 0.5 A was applied for 2.3 hours while the temperature was maintained at 800° C. 4.8 g of material was deposited on the cathode. When the coiled platinum wire was replaced by an iron wire, similar results were obtained. The platinum wire experiment serves to illustrate the iron product originates solely from the Fe 2 O 3  which was added to the Li 2 CO 3 . The extracted deposited mass contained pure iron metal and trapped salt. The deposited mass was washed to remove the trapped salt by (1) grinding to a fine powder, (2) sonication in water for 30 minutes, (3) settling for 0.5 minute, then pouring off the colloidal suspension and liquid from the precipitate. Steps 2 and 3 were repeated several times with the precipitate, which was observed to be reflective, grey, metallic, and responsive to a magnet. This was followed by further washing, sonicating and decanting the precipitate respectively in methanol, acetone and n-hexane (n-hexane wash was not necessary, but demonstrated that carbon was not present), followed by 10 minutes of vacuum drying and weighing. The material was ground and washed with deionized water to remove any trapped salts. The amount of iron obtained was 0.8 g. As an alternative to the alumina crucible, a nickel crucible was also used, in which case the crucible also served as a large surface area anode. The electrowinning potential measured for a range of constant current densities, J, is shown below in Table 1. J is determined by the cathode surface area. The subscript SA in E denotes a small (4-fold excess), and LA a large, (60-fold excess), surface area of anode. The measured potentials were similar with smooth platinum or iron cathodes, and with anodes of smooth platinum or Ni (nickel oxide, prepared as McMaster 200 pure Ni sheet). E was stable during continuous electrolysis at this range of J. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Experimental constant current full cell potentials at smooth  
               
               
                 electrodes for the electrolysis of 1:5 Fe 2 O 3  in 800° C. Li 2 CO 3 . 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 J(mA/cm 2 ) 
                 3 
                 20 
                   
                 200 
                 500 
               
               
                 E LA (Fe 2 O 3 ) LA   
                 0.85 V 
                 1.18 V 
                   
                 1.40 V 
                 1.70 V 
               
               
                 J(mA/cm 2 ) 
                 7 
                 18 
                 70 
                 200 
                   
               
               
                 E SA  (Fe 2 O 3 ) SA   
                 1.15 V 
                 1.25 V 
                 1.57 V 
                 1.70 V 
               
               
                   
               
             
          
         
       
     
         [0031]    Each dissolved Fe 2 O 3  results in two Fe(III) in the molten carbonate electrolyte. The measured electrolysis potentials of iron, for dissolved Fe(III) in molten Li 2 CO 3 , are shown in  FIG. 1  as a function of the electrolyte temperature and the concentration of dissolved iron. The measured electrolysis potential presented in  FIG. 1  for dissolved Fe(III) in molten lithium carbonate is low. For example 0.7 Volts (V) sustains a current density of 500 mA/cm 2  in 14 m Fe(III) in Li 2 CO 3  at 950° C. The cell contained excess anode surface area and the full cell electrolysis potentials were measured as a function of constant current, with current density constrained by the cathode surface area. The electrowinning voltage falls with increasing Fe(III) concentration, which without being bound by theory, is consistent with the general trend of the Nernst Equation—decrease of the electrolysis potential with increasing Fe(III) concentration, as 6.6×10 −5 V×T(electrolysis,K)/K (=RT/nF), which is accentuated by high temperature. The electrowinning voltage also falls with increasing temperature, which without being bound by theory, is consistent with both the enhanced conductivity and mass diffusion at higher temperature and the trend of the thermodynamic free energy of formation of the reaction: 
         [0000]      Fe 2 O 3 →2Fe+3/2O 2  
 
       Example 2 
       [0032]    Experiments were conducted to demonstrate electrowinning of Fe 3 O 4 , rather than Fe 2 O 3 , in molten carbonates. 16 g of Fe 3 O 4  was added to 80 g of Li 2 CO 3 , and heated together to 800° C. in a 75 ml alumina crucible. The Fe 3 O 4  fully dissolved to form a black solution. A 3 cm×4 cm piece of Ni foil was suspended in the molten mixture to function as the anode. A coiled, 7 square cm iron wire (1.5 mm diameter, 15 cm length) was suspended in the molten mixture to function as the cathode. In two separate experiments, a current of 1.4 A (200 mA/cm 2 ) or 0.14 A (20 mA/cm 2 ) was applied for 1 hour while the temperature was maintained at 800° C. As with the Fe 2 O 3  case, the extracted cooled electrode, following extended electrolysis and iron formation, contained trapped electrolyte. The deposited material was treated as described in Example 1 without the hexane wash. The deposited product weight was consistent, without being bound by theory, with a complete 8 electron per Fe 3 O 4  coulombic reduction to iron metal, in accord with: 
         [0000]      Fe 3 O 4 →3Fe+2O 2  
 
         [0033]    The electrowinning potential measured for a range of constant current densities, J, in the Fe 3 O 4 Li 2 CO 3  mix was tabulated as described in Example 1 and shown in Table 2. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Experimental constant current full cell potentials at smooth  
               
               
                 electrodes for the electrolysis of 1:5 Fe 3 O 4  in 800° C. Li 2 CO 3 . 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 J(mA/cm 2 ) 
                 18 
                 200 
                 500 
               
               
                 E LA (Fe 3 O 4 ) LA   
                   
                 0.60 V 
                 0.90 V 
               
               
                 E SA  (Fe 3 O 4 ) SA   
                 1.27 V 
                 1.70 V 
               
               
                   
               
             
          
         
       
     
       Example 3 
       [0034]    Experiments were conducted to determine the solubility of iron oxides in molten carbonates. In the absence of lithium carbonate, such as in pure sodium or potassium carbonate, or a mix of the two, the solubility of iron oxide is low, while in the presence of lithium carbonate, the solubility is high and increases with temperature. The amount of dissolved iron oxide was measured in molal units, as m, for example as x m Fe(III), where “m Fe(III)” refers to “moles Fe(III) dissolved per kilogram of carbonate”. In lithium carbonate, the lithiated iron oxide was soluble up to 7 m Fe(III) at 750° C., and up to 14 m Fe(III) at 950° C. At 950° C. the solubility in Na 2 CO 3  was less than 0.1 m Fe(III) and in K 2 CO 3  less than 0.2 m Fe(III). In Li 0.87 Na 0.63 K 0.50 CO 3 , the solubility increased from 0.7 m at 450° C. up to 4 m Fe(III) at 950° C. 
         [0035]    In Li 2 CO 3 , without added Li 2 O, 1 equivalent of CO 2  was released for each dissolved Fe 2 O 3  over a wide range of temperatures and concentrations, as seen in  FIG. 2 , and without being bound by theory in accord with: 
         [0000]      Fe 2 O 3 +Li 2 CO 3 →2LiFeO 2  (dissolved)+CO 2  (gas)
 
         [0036]    As indicated in the figure key, the mixture was composed of either 20, 40 or 60 weight percent of Fe 2 O 3  in Li 2 CO 3 . The mass loss over time was measured at the indicated constant temperature of either 650, 750 or 950° C., and corrected for CO 2  evolution measured from the 100% Li 2 CO 3  melt, then converted to moles of CO 2 , and finally normalized by the moles of Fe 2 O 3  in the lithium carbonate ferric oxide mix. 
         [0037]    When 1 equivalent of Li 2 O was added with each equivalent of Fe 2 O 3 , the Fe 2 O 3  also dissolved, but no carbon dioxide was released. Without being bound by theory this is in accord with: 
         [0000]      Fe 2 O 3 +Li 2 O→2LiFeO 2  (dissolved)
 
         [0038]    Dry LiFeO 2  was also formed by ball milling a 1:1 equivalent ratio of dry Fe 2 O 2  with dry Li 2 CO 2 , which displays the same the same solubility as Li 2 O+Fe 2 O 2  directly added to molten Li 2 CO 2 . The solubility of Fe 2 O 3  in a wide range of carbonate conditions was measured and is presented in  FIG. 3 . 
         [0039]    Without being bound by any theory, it is believed that electrowinning of LiFeO 2 (dissolved) forms Fe and dissolved Li 2 O; iron is replenished by the addition of further iron oxide, which is dissolved into the carbonate in combination with the released Li 2 O. Thus electrowinning occurs without the consumption of the electrolyte as: 
         [0000]      Iron Production in carbonate, Li 2 O unchanged (I+II): Fe 2 O 3 →2Fe+3/2O 2  
 
         [0000]      I dissolution in molten carbonate Fe 2 O 3 +Li 2 O→2LiFeO 2  
 
         [0000]      II electrolysis, Li 2 O regeneration: 2LiFeO 2 →2Fe+Li 2 O+3/2O 2  
 
       Example 4 
       [0040]    The electrowinning electrolyte stability was enhanced with carbon dioxide gas or with excess Li 2 O added to the molten carbonate. Molten Li 2 CO 3 , open to the air, is highly stable at 750° C., but slowly decomposes at 950° C. into Li 2 O and CO 2 . This decomposition at higher temperature was inhibited, or prevented, when the molten Li 2 CO 3  contained excess dissolved Li 2 O or when heated under carbon dioxide, rather than air. When decomposition occurs, the CO 2  is released as a gas, and the Li 2 O dissolves or precipitates beyond the solubility limit. 
         [0041]    Using the known thermochemical data provided by the US National Institute of Standards and Technology Chemweb for Li 2 O, CO 2  and Li 2 CO 3  the reaction free-energy of Li 2 O+CO 2 →Li 2 CO 3 , was calculated to determine the thermodynamic equilibrium constant as a function of temperature. From this equilibrium constant, the area above the curve in  FIG. 4  presents the thermodynamic wide domain in which Li 2 CO 3  dominates, that is where excess CO 2  reacts with Li 2 O such that p CO2 ·a Li     2     O &lt;a Li     2     CO     3   . This was experimentally verified in the measured thermogravimetric analysis of Li 2 CO 3 , shown in  FIG. 5 , and when Li 2 O was dissolved in molten Li 2 CO 3 , and injected with CO 2  (gas). Through the measured mass gain, a rapid reaction to Li 2 CO 3  was observed. When CO 2  was flowed into a solution of 5% by weight Li 2 O in molten Li 2 CO 3  at 750° C., the rate of mass gain was only limited by the flow rate of CO 2  into the cell (using an Omega FMA 5508 mass flow controller) to react one equivalent of CO 2  per dissolved Li 2 O. As seen in the thermogrametric analysis in the second figure below, the mass loss over time of heated lithium carbonate heated in an open atmosphere (−0.03% CO 2 ) was slow up to 850° C., but accelerated at 950° C. However the mass loss falls to nearly zero when heated under pure (1 atm) CO 2 . Also without being bound by any theory, in accord with Li 2 O+CO 2 →Li 2 CO 3 , added Li 2 O shifts the equlibrium to the left and inhibits carbonate decomposition. As seen in  FIG. 5  in the open atmosphere molten 100% Li 2 CO 3  at 850° C. loses mass, while a mixture of 90% by weight Li 2 CO 3  and 10% Li 2 O exhibits little mass loss over time. 
       Example 5 
       [0042]    Experiments were conducted and calculations performed to demonstrate that carbon may be formed in molten carbonate electrolyte, thus allowing the codeposition of iron and carbon (steel) at high electrowinning potentials. 
         [0043]    Steel, rather than iron, was directly formed from iron oxide salts, such as the commonly occurring salts Fe 2 O 3  or Fe 3 O 4 , by applying higher electrowinning potentials to co-deposit iron and carbon from molten carbonates. For example, without being bound by theory, carbon is formed by the electrolysis of lithium carbonate as: 
         [0000]      Li 2 CO 3 →C+Li 2 O+O 2  
 
         [0000]    Carbonate was replenished with carbon dioxide, without being bound by theory in accord with: 
         [0000]      Li 2 O+CO 2 →Li 2 CO 3  
 
         [0000]    At higher electrowinning potentials in molten carbonate containing iron oxide, without being bound by theory, steel containing carbon was formed as: 
         [0000]      Fe 2 O 3   +x CO 2 →2FeC x/2 +(3/2 +x )O 2  
 
         [0044]    Using the known thermochemical data provided by the US National Institute of Standards and Technology Chemweb for Li 2 O, CO 2 , C, CO, and the alkali oxides and carbonates the reaction free-energy of Li 2 O+CO 2 →Li 2 CO 3 , was calculated to determine the thermodynamic equilibrium constant as a function of temperature, and is presented in  FIG. 6 . As summarized in the  FIG. 6 , molten lithium carbonate, Li 2 CO 3 , provides a preferred, low energy route compared to Na 2 CO 3  or K 2 CO 3 , for the conversion of CO 2 , via a Li 2 O intermediate, to carbon. 
         [0045]    As seen in the photograph inset of the  FIG. 7 , at 750° C., carbon dioxide is electrolytically reduced in molten lithium carbonate electrolyte to solid carbon. The carbon formed in the electrolysis in molten Li 2 CO 3  at 750° C. is quantitative in accord with the 4 e-reduction of carbon dioxide. As seen in the cyclic voltammetry in  FIG. 7 , the transition to a carbon monoxide product is observed with increasing temperature. Specifically, while at 750° C. solid carbon is the main product at 950° C. the CO is the sole product. Hence, switching between the C or CO product is temperature programmable. The electrolysis potential to reduce lithium carbonate, is recorded in  FIG. 7  as a function of either cathode (with an oversized anode) current density or anode (with an oversized cathode) current density. 
       Example 6 
       [0046]    Experiments were conducted to demonstrate effective anodes in the molten carbonate electrolyte. The oxygen product at the anode will occur during electrolysis in molten lithium carbonate with or without (as in the previous example) dissolved iron oxide. In the  FIG. 7  above, the anode is platinum, and in addition a variety of other materials are effective anodes as summarized below. The anode can be made of any inert material which is stable under the operating conditions of the cell. The inert anode can be designed to promote an oxygen evolution reaction at low electrolysis potentials. Effective materials include metals, such as nickel, platinum or iridium, as shown in Table 3, metal oxides such as nickel oxide, metal alloys such as monel and inconel, and conductive carbon based materials such as glassy carbon and graphite. The data in Table 3 was obtained with smooth anodes. The nickel crucible walls were used as an oversized cathode. Enhanced anode surface area, such as with screen or spongy materials, by physical roughening, by chemical or electrochemical etching, or as deposited on a conductive support, will decrease electrolysis potential. Metals, such as nickel, when employed as oxygen generating anodes are effectively also metal oxides, quickly forming a thin nickel oxide layer which promotes oxygen formation. Hence, when a 62 micron thick nickel foil was immersed and used as an anode for electrolysis at 100 mA/cm 2  in 1.77 m Fe 2 O 3 , 7.08 m Li 2 O at 750° C. in molten lithium carbonate for 90 seconds, approximately 2 micron of the nickel was converted to the oxide, and this value was unchanged after 2 hours of continuous electrolysis. However, the nickel anode becomes unstable at higher temperature, for example after two hours of 100 mA/cm 2  electrolysis in the same electrolyte, at 850° C. or 950° C., respectively 7 or 9 microns of nickel are converted to the oxide. Inconel and monel nickel alloys are also active as anodes, however at 950° C. the monel alloy anode quickly corrodes, presumably due to oxidation of the copper component of the alloy. The stability of an iridium anode was measured at high temperature, 850° C., before, and after long term electrolysis at higher current density, 1000 mA/cm 2 , and showed no deformation or observable change. Specifically, the experiment was conducted with a 0.473 cm 2  iridium wire at 1000 mA/cm 2  in an Li 2 CO 3  electrolyte containing as 1.77 m Fe 2 O 3  and 3.54 m Li 2 O for 8 hours at 850° C. The diameter and integrity of the iridium was the same before and after the extended electrolysis. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Potential 
                 J/mA cm −2   
                   
                 Li 2 O 
               
             
          
           
               
                 mV 
                 3 
                 20 
                 200 
                 500 
                 1000 
                 Anode 
                 Cathode 
                 molal, m 
               
               
                   
               
             
          
           
               
                 E(750° C.) 
                 — 
                 40 
                 151 
                 260 
                 475 
                 Ni(0.479 cm 2 ) 
                 Ni(28 cm 2 ) 
                 5.31 
               
               
                 E(750° C.) 
                 — 
                 71 
                 196 
                 310 
                 535 
                 Ir(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 5.31 
               
               
                 E(750° C.) 
                 — 
                 57 
                 236 
                 371 
                 778 
                 Pt(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 5.31 
               
               
                 E(750° C.) 
                 — 
                 42 
                 159 
                 310 
                 615 
                 Ni(0.479 cm 2 ) 
                 Ni(28 cm 2 ) 
                 3.71 
               
               
                 E(750° C.) 
                 — 
                 66 
                 212 
                 339 
                 787 
                 Ir(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 3.71 
               
               
                 E(750° C.) 
                 — 
                 71 
                 227 
                 380 
                 947 
                 Pt(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 3.71 
               
               
                 E(750° C.) 
                 — 
                 335 
                 1048 
                 1265 
                 1408 
                 Ni(0.479 cm 2 ) 
                 Ni(28 cm 2 ) 
                 0 
               
               
                 E(750° C.) 
                 155 
                 310 
                 1246 
                 1586 
                 1741 
                 Ir(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 0 
               
               
                 E(750° C.) 
                 — 
                 370 
                 1258 
                 1676 
                 1888 
                 Pt(0.473 cm 2 ) 
                 Ni(28 cm 2 ) 
                 0 
               
               
                   
               
             
          
         
       
     
       Example 7 
       [0047]    Experiments were conducted to demonstrate that common impurities found in iron oxide salts do not prevent high solubility of iron oxides in molten lithium carbonate. These impurities do not dissolve beyond a measured solubility limit, and this facilitates electrowinning of low purity iron oxide ores. The predominant iron ores are hematite (Fe 2 O 3 ) and magnetite (Fe 3 O 4 ). These ores also commonly contain various levels of silica, and alumina. SiO 2  and Al 2 O 3  dissolve in molten lithium carbonate as Li 2 SiO 3  and LiAlO 2 . In 750° C. Li 2 CO 3  the respective solubility was 0.4 m SiO 2  and 0.06 m Al 2 O 3 . Dissolution of 0.4 m SiO 2  in 750° C. molten lithium carbonate decreases the solubility of dissolved Fe(III) (dissolved as Fe 2 O 3 ) by only a small fraction (less than 10 percent). The solubility of either Al 2 O 3  or SiO 2  in molten lithium carbonate increases with increasing temperature, and at 950° C. was 0.6 m Al 2 O 3  and 4 m SiO 2 . High concentrations of dissolved lithium oxide have only a small effect on the solubility of silica or alumina in lithium carbonate. At 750° C. lithium carbonate containing 7 m Li 2 O, the solubility was 0.06 m Al 2 O 3  and 0.5 m SiO 2 . Furthermore, iron tends to electrowin in carbonate melts without contamination due to the reduction of common impurities found in iron oxide salts. Such impurities include, in addition to silicon and aluminium salts, alkali salts, magnesium salts, barium salts, manganese salts, titanium salts, chromium salts, beryllium salts and zinc salts. Specifically, the standard electrode potential for the elements Li, Na, K, Al, Mg, Ba, Mn, Zn, Cr, Ti, Si and Be are each more negative than that of iron, and the salts of these metals tend to require a substantially greater electrolysis potential than those of comparable iron salts. Hence, electrolysis voltage, as well as solubility limitations, also inhibits adverse effects on the iron electrowinning, as common impurities in iron oxides tend to have a high voltage barrier to electrowinning. 
         [0048]    All ranges disclosed herein are inclusive and combinable (e.g., ranges of “up to about 25 wt %, or, more specifically about 5 wt % to about 20 wt %” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt % to about 25 wt %,” etc.). The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 
         [0049]    While the disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.