Paramagnetic additive method of optimizing cell electrohydrodynamics
Magnetoelectrolysis cells known to operate successfully without utilizing a non-electrogenerated paramagnetic additive added to an aqueous electrolyte solution of such a cell may in some instances be further enhanced by utilizing such an additive. However, excessive amounts of additive are impracticable and formerly proposed transition metal salts used as paramagnetic additives were never demonstrated as effective except when used in large amounts. Now it is disclosed that small amounts of a salt of a paramagnetic lanthanide solve the problem, if methodically applied to enhancing the magnetoelectrolysis cell in accordance with the specified steps of the invention.
1. Technical Field
This invention relates, in general, to utilizing selected chemical additives in fluid electrolyte solutions of electrochemical cells exemplified by types described hereinafter, for the purpose, primarily, though not necessarily exclusively, of initiating and/or increasing a measurable extent of beneficial fluid convection.
More particularly, what is taught and claimed below as new is an improved method of utilizing non-electrogenerated paramagnetic species of inorganic solutes as solution-improving additives added to aqueous electrolyte solutions of electrochemical cells, preexistently designed to operate more effectively, than otherwise, when a suitably strong external magnetic field of permanent magnet or electromagnet origin projects within a volume containing an aqueous electrolyte solution between an anode and a cathode.
Known from background art are several cells made to utilize magnetic phenomena, including both electrolysis cells supplied dc electricity to enact useful non-spontaneous chemical changes, and voltaic cells that produce dc electricity. Magnetically enhanced cells of all kinds are subjects of development in an area of electrochemistry which T. Z. Fahidy, at the University of Waterloo in Canada, suggested in “Magnetoelectrolysis”, J. Appl. Electrochem., v13 (1983) 553, may be called “magnetoelectrolysis”. The same label aptly identifies the technical field to which the present invention most closely pertains.
2. Background Art
The fact that Dr. Fahidy's suggested label acquired in-use currency is shown by: “Applications of Magnetoelectrolysis”; Tacken, R. A. and Jansen, L. J. J.; J. Appl. Electrochem., v25 (1995) 1, in which recognition is present respecting innovative use of special laser interferometry set-ups, introduced at the University of Victoria in Canada by R. N. O'Brien (the present inventor) and colleagues, to obtain visualized evidence of convection adjacent-electrodes in small magnetoelectrolysis cells made into Fabry-Perot interferometers.
Using the investigative tool of interferometry to examine one particular cell led to discovery in the O'Brien laboratory of an occurrence of convection where density layering would normally have made the electrolyte solution stagnant. The cell was configured with a cathode-over-anode (C/A) horizontal plane parallel electrodes orientation, with the direction of the imposed magnetic field parallel with the electrodes. No convective transport of species between the electrodes, to possibly supplement migration and diffusion, could be expected to result from magnetohydrodynamic (MHD) effects commonly explained by invoking the well-known “Lorentz force”. A new postulate became needed, because clearly something differentiable from an MHD force was driving the unexpected convection in the C/A-configured CU/CUSO4/CU cell immersed in a 0.512 T magnetic field. Whatever the “something” force was, it did not occur for a similarly configured Zn/ZnSO4/Zn cell studied in similar magnetic field immersion. The new postulate invoked an internally generated gradient force involving inhomogeneity of volume magnetic susceptibility and a nonuniform induced magnetic field. The applicable underlying principle is that which states free-to-move paramagnetic substances tend to move into a region of higher magnetic field, whereas diamagnetic substances move away therefrom.
The O'Brien laboratory's discovery and new postulate has become of such evident pertinence, in the background of the present invention, as to warrant incorporating the following publications by reference herewith: “Electrochemical hydrodynamics in magnetic fields with laser interferometry: Influence of paramagnetic ions ; O'Brien, R. N. and Santhanam, K. S. V.; J. Appl. Electrochem., v20 (1990) 427; and, “Magnetic field assisted convection in an electrolyte of nonuniform magnetic susceptibility”; O'Brien, R. N. and Santhanam, K. S. V.; J. Appl. Electrochem., v27 (1997) 573. These publications are of key relevance to delineating with permissible hindsight the below-claimed advance over instances of previous inventions for which, respectively, patent applications were filed within the time limits appropriate to the two articles' publication dates. The background art inventions are discussed further below.
The postulate and explanation conveyed in the abovecited two key references gained currency, ie., recognition, in the art, as these articles ultimately became subjects of footnotes 25 and 26 in a more recent publication of others, namely: “Electrochemically Generated Magnetic Forces. Enhanced Transport of a Paramagnetic Redox Species in Large, Nonuniform Magnetic Fields”; Ragsdale, S. R.; Grant, K. M.; and White, H. S.; J. Am. Chem. Soc., v120 (1998) 13461. By 1998 these University of Utah chemists had advanced into an area of the art of magnetoelectrolysis perceived as existing but then not well understood, back in 1990 when Dr. O'Brien and Dr. Santhanam wrote: “There is a clearly demonstrated paramagnetic effect interacting in a way, as yet unknown in detail, with the magnetohydrodynamic effect”. (From the Summary in “Electrochemical hydrodynamics . . . influence of paramagnetic ions”.)
Dr. White and Univ. of Utah colleagues published isolation of the paramagnetic effect.
Drs. O'Brien and Santhanam, even as late as 1997, did not have a suitable investigatory tool to assure studying the paramagnetic effect in definite isolation from any possible intermingling of MHD effect, whereas Dr. White and Univ. of Utah colleagues lately found how to do it, with introduction of using modified NMR (nuclear magnetic resonance) tubes for experimental magnetoelectrolysis cells having electrolyte solutions containing highly concentrated organic species such as the nitrobenzene radical anion. A well polished platinum microdisk electrode was found ideal for studying how an inhomogeneous susceptibilities-related gradient force, “without interference from the masking effects of Fmhd”, by itself “may result in a significant enhancement in electrochemical current.” (Abovecited J. Am. Chem. Soc. article, Ragsdale et al., 1998)
Older Magnetoelectrolysis Patents
An early patent disclosing a purpose-built magnetic field enhanced cell, although without proposing a paramagnetic additive to optimize its electrolyte solution, is U.S. Pat. No. 1,658,872 issued to YEAGER (February, 1928) for a then unique “ELECTROLYTIC APPARATUS”. The simpler-constructed of two versions devised for electrodeposition of a metal under the influence of a magnetic field was shown in a drawing figure, the significant righthand portion of which is reproduced herewith as “PRIOR ART”
Another leading example of a patented invention featuring magnetic field assisted stirring of an electrolyte solution, again without proposing a paramagnetic additive to increase stirring, is an “ELECTROLYTIC CELL COMPRISING MEANS FOR CREATING A MAGNETIC FIELD WITHIN THE CELL” for which U.S. Pat. No. 3,597,278 (August, 1971) issued to VON BRIMER. To enable retrofitting the present invention to the modified lead-acid battery of VON BRIMER, one of its figures of drawing is reproduced herewith as “PRIOR ART”
Another cell designed for magnetic field enhancement was disclosed by KAWAKAMI ET AL in U.S. Pat. No. 5,728,182 issued March, 1998 for a “SECONDARY BATTERY AND METHOD FOR MANUFACTURING THE SAME.” A figure illustrating a coin-shaped embodiment is reproduced herewith as “PRIOR ART”
Nearer Related Patents
In part more closely related to the present invention than are the three abovecited patents, are three forming a group, the first of which issued September 1991 to O'BRIEN ET AL for a “SPACER FOR AN ELECTROCHEMICAL APPARATUS”, U.S. Pat. No. 5,051,157. The 1990 published J. Appl. Electrochem. article partly entitled “influence of paramagnetic ions”, cited above, was one of four “OTHER PUBLICATIONS” identified as relevant. Manganous and chromic ions were the only specifically named examples of “suitable” paramagnetic ions whose addition to electrolyte solutions was proposed “to further increase the stirring and to lower internal resistance (concentration polarization)”, and it is no coincidence that these were the ions used in the O'Brien laboratory's interferometric investigations.
The second nearer art patent in the group of three is U.S. Pat. No. 6,194,093 B1 issued February, 2001 to O'BRIEN for “MAGNETIZED CURRENT COLLECTORS COMBINED WITH MAGNETIC SHIELDING MEANS”. This patent too incorporates the proposal that advantage can be gained by adding, to the peculiarly constructed various cells' electrolyte solutions, indifferent paramagnetic ions again exemplified by manganous and chromic ions.
The third nearer art patent is U.S. Pat. No. 6,556,424 issued April, 2003 to O'BRIEN for a “SUPERCAPACITOR HAVING MAGNETIZED PARTS”, wherein again appeared the proposal of an electrolyte solution changed by adding indifferent paramagnetic ions, eg., the manganous and chromic ones of the original influence of paramagnetic ions article by this time (2003) dating back thirteen years.
From none of these three closely related patents, nor from them all cumulatively, did a presented reason emerge for specifically always naming manganous and chromic ions. An informed artisan could, however, from attending to “OTHER PUBLICATIONS” cited, find and read the only explicitly stated reason where it once was published, viz., in the 1990-dated “influence of paramagnetic ions” article. Out of a truly vast number of all potentially usable paramagnetic ions, the reason for selecting manganous and chromic ions was capability on their part to satisfy “thermodynamic considerations” related to those of the otherwise stagnant Zn/ZnSO4/Zn cell modified. See the criterion set forth at about the middle of the second column of text in the article's Introduction.
In the O'BRIEN ET AL patent, first in the nearer art group of three, the prospect that additive paramagnetic ions may lose potency for the method via undesired coordination with certain ligands was left unconsidered.
Moreover, although not a specifically claimed aspect of teachings, a teaching in the only paragraph teaching the paramagnetic additive method suggested to the artisans that even ions which are not indifferent”, and even which may be included in “the deposition”, may be used—qualifying this aspect of the teaching with the phrase: “as long as the deposition on an electrode does not cause detrimental effect, e.g. pressure discharge, loss of active material, etc.” With candid permissible hindsight of an artisan today, reviewing that single paragraph of paramagnetic additive method teaching, particularly in view of its “etc.”, more likely than not elicits an impression of an invitation to experiment, at indefinite length, to discover whatever the actual practicable scope encompassed by the method might be.
The second and third already identified nearer art patents substantially re-instituted the aforesaid teaching from O'BRIEN ET AL, with the one exception of including a caution regarding possible “corrosive shuttle mechanisms”. What was there intended to be conveyed concerns the fact that many ions are capable of changing in solution from one valency to another, if not by chemical reaction with other solute species, then possibly by being brought by diffusion or convection into contact with an oxidizing or reducing electrode. Such undesired electrodes-discharging “shuttles” or “redox couples” are described by H. Bode, page 321, Lead-Acid Batteries, Wiley-Interscience (1977). Electrolyte solution “impurities” named as likely to create the problem in a lead-acid battery include chromium, manganese, and chlorine. These, it happens, are constituents of the compounds which, for reason of “thermodynamics considerations”, were selected to supply paramagnetic ions to add to the electrolyte solution of the Zn/ZnSO4/Zn cell featured in the background art's “influence of paramagnetic ions” reference—not very like the lead-acid cell which was one of three illustrated embodiments in U.S. Pat. No. 5,051,157.
Deposition of a coating on a well designed electrode for the second illustrated embodiment of O'BRIEN ET AL would impair that cell's intended efficient production of gases. It was designed to electrolyze an aqueous solution, not change electrode active materials. A drawing figure showing the saltwater-electrolyzing cell of U.S. Pat. No. 5,051,157 is re-shown herewith as “PRIOR ART”
Wherever in the detailed description below there is a method step appropriately carried out using a known methodology and/or item of testing apparatus, known specifically from previously use in the background art area of magnetoelectrolysis, the originators of the method or apparatus (if known) will be credited, further background information thereby appearing at places elsewhere than under the BACKGROUND OF THE INVENTION main heading here concluded.
BRIEF SUMMARY OF THE INVENTIONOne object of the present invention is to avoid making any kinds of changes to an electrolyte solution that are likely to damage prospects for procuring usual recognized advantages of electrochemical cells featuring performance affected by imposed magnetic fields, such as the following advantages: reducing internal resistance by reducing thickness of the diffusion layer at an electrode, and by decreasing concentration polarization; increasing mass transport and raising the limiting current density for a given electrolytic process in a given cell; achieving (for plating cells) uniformly smooth deposition of the intended plating species on an electrode; lengthening secondary battery life-cycles by suppressing formation of dendrites; effectively lowering the specific resistance of the electrolyte solution; and enabling substantially all active sites on an electrode to be used, rather than just the most active sites.
More positively, a motivating intention—or, ie., object of introducing the invention is to extend the range of magnetically enhanced cells having electrolyte solutions optimized by addition of paramagnetic ions, and also to extend the range of paramagnetic ions clearly identifiable as desirably used for such addition. In the three patent-based chief references above (O'BRIEN ET AL; O'BRIEN; O'BRIEN), the now old pre-cursor paramagnetic additive method was only taught as being closely tied to particular new cells, each featuring a unique plan of construction which artisans may well have thought had been conceived in contemplation of utilizing additive-enhanced electrolyte solutions. In contrast thereto, what presently is to be taught is a method more clearly applicable to pre-designed cells certainly not originally made in contemplation of the present invention, since it did not then exist.
Another important object of the invention is to minimize the amount of electrolyte solution additive used, since otherwise there may occur a counter-productive increase in specific resistance of the electrolyte solution, or even degradation of as-designed ratios of free water to the electroactive species of ions native to the modified cells concerned. Furthermore, potential users of the method are apt to doubt its real world value unless, by minimizing materials needed, manufacturing costs are kept reasonable. In the tiny cell reported in the O'Brien/Santhanam journal article, J. Appl. Electrochem., v. 20 (1990) p. 427 et seq, equal portions of two aqueous electrolyte solutions were combined: 0.1 M zinc sulphate, and 0.1 M manganous chloride, which made the mixed end-solution's whole molarity for each of them 0.5 M, ie., a half-and-half mixture clearly containing too much special additive for any industrially applicable zinc plating cell.
Fortunately, after a long course of unpublished non-routine experiments, the present inventor recently discovered that systematic steps of applying the present invention resulted in finding surprising effectiveness of a paramagnetic salt of a lanthanide element, which worked as a low-concentration additive to a nickel-metal hydride cell's aqueous potassium hydroxide electrolyte solution of about 5M, at just under about 0.04 M whole solution molarity, or a molarity ratio of about 100:1 instead of the equimolar previously cited solutions.
Grouping steps of this method into stages is for convenient presentation, rather than to dictate a chronological sequence. To fix ideas, the invention's method is organized into four stages, called “cell analysis”, “flux plotting”, “stability assurance”, and “additive concentration”, each of which comprises specified method steps, ie., actions required of the method-practicing artisan to do. While the preponderance of work for most steps requires no testing, certain steps do call for routine tests, methodologies and means for which will be clearly indicated.
All method steps are presented in detail hereinafter, but, by way of summary, one key step for each stage will immediately be indicated.
A step at Stage 1, cell analysis, is to ascertain whether or not the cell is amenable to increasing its limiting current density beyond the demonstrable level attainable by mechanical stirring at a rate producing a result equivalent to that of the magnetic enhancement means already built into the cell. If mechanical stirring faster than this rate produces a further increase of limiting current density, then the cell meets a criterion of being amenable to improving its magnetic enhancement effect without changing its given magnetic field producing means, but instead by implementing addition of selected paramagnetic ions to the cell's electrolyte solution, in the specified manner arrived at in light of combined information acquired at other method steps to be described. Results of the mechanical stirring analogizing process may in some cases raise need for a non-“a priori” justification for the proposed paramagnetic additive utilization, and contingencies of such other plausible justifications are describe below.
A step at Stage 2, flux plotting, is to ascertain how generally planar patterns of rationally envisaged imposed magnetic flux lines may be expected by interaction with the contemplated paramagnetic susceptibilities effect to be modified, with probable inducing of a resulting non-uniform magnetic field of secondary origin but primary importance. Extent of masking, if any, of the paramagnetic gradient effect by a true MHD effect is here assessed.
A step at Stage 3, stability assurance, requires ruling out in-solution valence changes and/or ligand-associated coordinations likely to degrade effectiveness of an added paramagnetic solute.
A step at Stage 4, additive concentration, involves routine testing to find whether a desirably small amount of highly paramagnetic additive provides sufficient paramagnetic/diamagnetic contrast in the modified electrolyte solution to procure the desired susceptibilities gradient effect to complement an existing true MHD effect, if any.
Changing original as-designed electrolyte solutions of off-the-shelf magnetically enhanced cells, into new mixed electrolyte solutions containing specially selected added paramagnetic ions, particularly such ions as have not previously been specifically named as among those suitable, risks ruining a given magnetoelectrolysis cell's designed-for functions and pre-existing mode of magnetic enhancement, unless the fully described method of solution optimization that is this invention is carried out with the care advisedly always taken in a highly specialized step-by-step practical “retrofit”, ie., modification. Other highly expert investigators, aside from the present inventor and former colleagues, have published much useful information to which artisans in this area should consult, including evidence from the abovecited group of University of Utah chemists on the point that significant diminishment of electrochemical current can occur, under slightly different conditions from when significant enhancement occurs. Basically, although the invention as claimed below is not an apparatus, the present inventor considers proper teaching of the method, that the invention is, to require reference to figures of drawing illustrating representative magnetoelectrolysis cells regarding which the instructed artisans do well to take as suitable subjects to which to apply this new method taught them. Accordingly such figures of drawing are next briefly described, before the whole detailed description of the present invention is set forth.
BRIEF DESCRIPTION OF THE DRAWING
With reference first to the
Stage 1, cell analysis, encompasses acquiring confirmation of qualifying and informative basic matters that should not be neglected when contemplating changing the electrolyte solution design for a given magnetically enhanced cell.
Locating in the cell a solid-phase anode and counterpart solid-phase cathode is the cell analysis stage 3 s a. step, functioning like other steps in Stages 1 and 2, insofar as serving cell-qualifying and subsequent acts-informing functions, both. All contemporary cells do not use classical solid-phase electrodes. Regarding those which do not, the present invention is not intended for application thereto. A basically competent, yet non-expert artisan, apprised of what scant background information has previously existed concerning electrolyte solution optimization in magnetoelectrolysis cells, if left unguided, might err in either of two ways: assuming that all magnetoelectrolysis cells encountered will have solid-phase electrodes, or else assuming that electrolyte solution optimization by the method of the invention will work irrespective of cell electrodes' physical phase status.
The “b.” step at the cell analysis stage, called “active materials identification” will be substantially self-explanatory to those of skill in the art, who also will understand that in some instances the electrodes are inert and intended to remain so. As an example here, there is the saltwater electrolyzing apparatus described as magnetically enhanced in the abovecited O'BRIEN ET AL patent, wherein it was assumed that artisans would perceive necessity of avoiding to do anything, eg., by using inappropriate additives, that would plate the carbon and the steel electrodes.
The “c.” step of Stage 1, called electrolyte solution characterization”, requires finding that between the anode and cathode is a liquid-phase aqueous electrolyte solution of identified chemical constitution and electrochemical properties. Like the “a.” step above, this step too serves both qualifying and informative functions. The method of the invention does not work for solid-phase electrolytes, for example; and, without learning what chemicals are in the solution, a later-described step of “assuring paramagnetic additive stability” could not be performed.
At the first stage's “d.” step occurs routine testing, or equivalent determination from existing information, when available, to ascertain that either (1) the limiting current density of the analyzed cell can be increased by stirring the electrolyte solution at a rate faster than that equivalent in result to already present magnetic field assisted stirring, or else that (2) another reason justifies changing the electrolyte solution by addition of paramagnetic ions thereto. This step is called “applicability testing”, and is included because there are likely instances where as much as can possibly be done to improve convective transport of electroactive species to active sites for their reduction or oxidation may already have been done.
The method of the present invention has not been designed to over-ride reaction kinetics intrinsic to a given electrochemical cell, and future work of investigation needs to be directed to that issue in magnetochemistry.
An already recognized mechanical stirring equivalency test that is easily adapted to satisfying Stage 1, step “d”, was described by S. Mohanta and T. Z. Fahidy, in “The Effect of a Uniform Magnetic Field on Mass Transfer in Electrolysis”, S. Mohanta and T. Z. Fahidy; Can. J. Chem. Eng., v. 50 (1972) 248. These University of Waterloo magnetoelectrolysis investigators specifically compared results of mechanical stirring to “the relative strength of magnetic stirring”. Although their test was done absent contemplation of paramagnetic additives to further increase “magnetic stirring”, the old test is easily slightly modified as follows. After finding what the limiting current density of the cell under analysis is, when operated with its integral magnetic enhancement means intact, afterwards the amount of mechanical stirring needed to produce the same result, but without the magnetic field producing means, is found. Then, stirring mechanically to an even greater extent can be used to find whether an attempt to procure additional increase of limiting current density would be pointless, for reason of having already done as much as can possibly be done to improve convective transport of electroactive species to active sites for their reduction or oxidation.
The present inventor has long regarded increased stirring, without changing to a stronger source of magnetic field as an important benefit of resorting to paramagnetic additives in electrolyte solutions of magnetically enhanced cells. This does not mean, however, that no other justification for the same resort is recognizable, as will be seen in taking the battery shown in
To illustrate how conveniently the method of the present invention applies to an art-recognized magnetically enhanced cell already pre-designed, attention is drawn to a coin-shaped nickel-zinc secondary battery shown in “PRIOR ART”
Referring now to enumerated figure elements disclosing this battery's parts: made of titanium-clad stainless steel are an anode cap 305 and a cathode can 306, sealed together via a polypropylene gasket 310 to form a housing, the exterior top and bottom of which are integral terminals. Inside and below cap 305 are anode-active-material layer 301 and magnetic-material layer 315, containing powdered zinc and zinc oxide in the anode, and magnetized barium ferrite particles in layer 315. Inside and above cathode can 306 at the cell's base is cathode-active-material layer 303 comprising nickel powder and nickel hydroxide filled into a foamed nickel member. Separator/electrolyte solution 307, between the cell's anode and cathode is an aqueous solution of potassium hydroxide. The coin-shaped nickel-zinc battery of KAWAKAMI ET AL analyzes regarding first stage steps a., b., and c., merely by consulting the patented battery's specification. Solid-phase anode 301, which is the cathode at which metal reduction occurs during charging, is parallel with and above solid-phase “cathode 303. The active materials have been identified, and the electrolyte solution is aqueous and liquid-phase.
Step d. of stage 1 is where, in many instances, the routine mechanical stirring equivalency test is advised. However, in this particular instance of the KAWAKAMI ET AL coin-shaped nickel-zinc battery, step d. is resolved adequately without an actual test, for reasons next explained in connection with stage 2, “flux plotting”.
The KAWAKAMI ET AL cell shown herewith by
KAWAKAMI ET AL do not specifically address the subject of convection, but those informed in contemporary magnetoelectrolysis art will infer, after considering the coin-shaped nickel-zinc battery's magnetic field, parallel with horizontal electrodes, that solution motion should occur in a like manner to that of the C/A zinc cell to the electrolyte solution of which Drs. O'Brien and Santhanam added paramagnetic ions, because an induced non-uniform field will occur.
Whereas stage 2's step a. is imposed magnetic field flux plotting, which can often be done on the basis of mere inspection of magnetically enchanced batteries' plans or specifications, step b. is non-uniform induced magnetic field flux plotting. A non-uniform induced magnetic field is expected to occur in all instances of using the present invention, because of regional dissimilarities of average local magnetic susceptibility in the electrolyte solution. Magnetic flux lines are conventionally drawn more closely spaced when crossing through a region containing paramagnetic material, an effect of which is to make permeability in that region higher than in air. Flux lines are drawn more widely spaced when crossing through a region that is of lesser permeability than air because of containing diamagnetic material.
Contemporary equipment exists which can and should be used to detect and plot induced non-uniform magnetic fields, whenever it may not be readily apparent by inspection of magnetoelectrolysis cell lay-out of where differentially permeable regions within an electrolyte solution locate during cell operation. Hall probe gaussmeters of high sensitivity and small dimensions may be inserted at appropriately selected points. Plotting of induced magnetic fields can also be done using medical imaging technology, such as described in U.S. Pat. No. 5,073,858 (December, 1991) to MILL for MAGNETIC SUSCEPTIBILITY IMAGING (MSI).
U.S. Pat. No. 5,738,837 issued Apr. 1998 to KLAVENESS ET AL for LANTHANIDE PARAMAGNETIC AGENTS FOR MAGNETOMETRIC IMAGING is one of many disclosures of medical imaging techniques and devices which are readily adapted to mapping magnetic susceptibilities gradients that drive convection in magnetically enhanced cells and batteries featuring intentionally increased extent of paramagnetic/diamagnetic contrast in their electrolyte solutions, as is the case for the present invention.
Whereas the electrolyte solution characterization step c. of stage 1 of this method gathers information about chemical constitution and electrochemical properties of the solution particular to a cell which is to be modified, such information must be used at stage 3 termed “stability assurance”, when addressing the major subject matters that allocate to the two method steps of stage 3: a. electroactive species preservation; and, b. assuring stability of additive paramagnetism.
Both steps at stage 3 require of an electrochemistry-trained artisan that he or she at least mentally perform—possibly supplemented by simple routine tests if necessary—a matching and ruling-out process directed to expected chemical results of mixing otherwise not normally mixed chemical solutes into the pre-existing electrolyte solution for the cell concerned. What needs to be done respecting the step “a.”, electroactive species preservation, is considered both clearly within the ordinary skill level of the relevant artisans, and essentially not new regarding needing to consider chemical results of changes to the aqueous solutions dealt with, especially concerning the possibility of changing relative concentrations of H3O+ (hydronium) ions and OH— (hydroxide) ions. The equilibrium-related ion product constant of H2O is valid for all dilute aqueous solutions regardless of sources of the hydronium and hydroxide ions contained. Increasing acidity decreases hydroxide concentration, and increasing alkalinity decreases hydronium concentration
When hydronium and hydroxide ions are important electroactive species, their concentrations need be kept within permissible ranges, found either by existing data consultation or simple experiment, for a given electrochemical cell modified by using a paramagnetic additive. Relatedly, cell-making artisans will also appreciate that the pH of an aqueous electrolyte solution, no less than temperature which affects the ion product constant of H2O, affects the likelihood and rate of chemical changes to constituents therein. Respecting reactions in solution, it is essential that additives to a pre-designed electrolyte solution do not react to form undesired compounds therein.
Assuring paramagnetic additive stability is step b. of stability assurance, and requires ruling out degradation effects from two major factors: (1) in-solution change of valence of the ion used for its paramagnetism; and, (2) in-solution formation of coordinated complexes. Valence-changing “shuttle” forming problems, such as were mentioned above in connection with presence of manganese, chrome, and chlorine species in lead-acid batteries' solutions, are best avoided by using only paramagnetic ions exhibiting only one valence in solution. At the cost of increased complexity, however, stabilization of a given multi-valent ion, so that it stays in one valence, might be feasible. Eg., in aqueous solution, the Mn2+ cation occurs as hexaaquo complex [Mn(H2O)6]2+, and the dissolved divalent Mn cation oxidizes to higher valent oxide hydrates at an accelerated rate if the solution contains a high OH concentration. Control of the solution's alkalinity can preserve the Mn2+0 from change. If Mn3+ were to be used, this ion is stabilized in aqueous solution by sulfuric acid concentrations of about 400-450 g/L.
Control of factor (2) requires ruling out formation of a coordinated complex between the paramagnetic additive ion and any ligand analogous in paramagnetism-decreasing effect to that of cyanide upon Fe species.
Attending to importance of local environment to paramagnetism makes clear, in contrast to sparse information provided in the nearest prior art reference (O'BRIEN ET AL, U.S. Pat. No. 5,051,157), that the mere fact of a substance's paramagnetism in isolation does not ensure its being suitable as a convection-enhancing additive in all practical magnetoelectrolysis-type electrochemical cells. Nor, as will shortly be explained, is it presently recommended practice, for carrying out the method of the present invention, to select a paramagnetic additive ion solely on the basis of how many unpaired electrons it has. That was a selection criterion appropriate to paramagnetic candidates found within the chemical series of transition metals conventionally listed horizontally from Sc through Cu in period 4 of the PERIODIC TABLE OF ELEMENTS and also period 5. The present invention advances beyond this, into periods and members thereof which would not have been immediately envisaged on the basis of the prior art's only specifically named species (Mn and Cr).
At stage 4 of the presently taught method, for convenience called “additive concentration”, the crucial single step is to select for the addition (entailed to be performed) a highly paramagnetic additive which works, without requiring an undesirably large amount thereof, to provide sufficient paramagnetic/diamagnetic contrast in the electrolyte solution to procure the desired susceptibilities gradient effect which is intended to complement an existing true MHD effect, if any, or else, by itself to initiate the solution motion which has been recognized by RAGSDALE ET AL, cited above. By the present inventor s own lexicography herewith supplied, the phrase “without requiring an undesirably large amount”, when applied to the selected paramagnetic additive, means: a whole solution molarity of the paramagnetic ion of between about 0.02 M and 0.25 M. This is a significantly smaller amount of additive than heretofore reported as effective in abovecited Journal of Applied Electrochemistry articles by O'Brien and Santhanam.
After a long course of unpublished non-routine experiments, the present inventor recently discovered surprising low-concentration effectiveness of a paramagnetic salt of a lanthanide element. It was Dysprosium Chloride which he added to a nickel-metal hydride cell's aqueous potassium hydroxide electrolyte solution, at just under about 0.04 M whole solution molarity, actually 0.0394 M. At molarities in the region of 0.0004 no effect was found. A Dysprosium ion has the same number of unpaired 4f electrons as does Samarium, viz., 5, but the magnetic moment for the latter ion is 1.6 (Bohr magnetons), whereas that for Dysprosium is 10.6. Similarly, Terbium with the same number of unpaired 4f electrons as Europium, viz. 6, has the higher moment of 9.7, compared to Europium's 3.5. Erbium's moment of 9.6 compares to Neodymium's of 3.6, but both have 3 unpaired 4f electrons. In general, the major difference between magnetic moments of any two rare earth metal ions having the same number of 4f unpaired electrons is explained by complicating factors such as Russell-Saunders coupling and variations in radial distances of orbiting electrons from atomic nuclei. The result of significance is that typical “approximations” of magnetic moment based on number of unpaired electrons do not work for lanthanides (or analogous actinides), like such approximations do work for fourth period transition metals.
With reference now to
The test cell's electrodes 1 were a cathode and an anode removed from a commercial cell and magnetized using a “MECHANICALLY PULSED MAGNETIZATION KIT”.
The inventor made and patented the kit for exactly this kind of purpose. See U.S. Pat. No. 6,741,440 (O'BRIEN, May 2004). Comblike plastic separator structure 2 separated electrodes 1 with minimal obstruction to expected vertical flows of the electrolyte solution (unnumbered, as not shown among disassembled components). A suitable plastic casing comprising parts 3 bonded together left the cell open at the top when assembled, and somewhat more than half-filled to the top, from which usual terminal leads extended.
Tests of the experimental test cell shown in
Allowing for minor modifications within the spirit of the invention, its scope shall be defined as follows in the claims.
Claims
1. For a method of utilizing a paramagnetic additive to enhance the performance of a magnetoelectrolysis cell having an aqueous electrolyte solution containing between from about 0.0004 M to about 0.025 M of the additive, the method comprising, in combination:
- a step for locating electrodes in the cell which are a solid-phase anode and a solid-phase cathode;
- a step for ascertaining whether the electrodes are to comprise active materials or else are to be inert;
- a step for ascertaining that an aqueous electrolyte solution of identified electroactive species constitution and properties exists in the liquid phase between the electrodes;
- a step for ascertaining that the magnetoelectrolysis cell is susceptible to enhancement by addition of a non-electrogenerated paramagnetic additive;
- a step for plotting imposed magnetic field flux inherent to the magnetoelectrolysis cell;
- a step for plotting induced non-uniform magnetic field flux resulting in the magnetoelectrolysis cell from presence of regions in the electrolyte solution having different magnetic susceptibilites;
- a step for preserving electroactive species identities in the electrolyte solution;
- a step for assuring stability of paramagnetism of the paramagnetic additive; and,
- a step for selecting, as the paramagnetic additive, a material selected from outside the range of fourth and fifth period transition metals, and of which an undesirably large amount thereof is not required in order to procure intended enhancement of the magnetoelectrolysis cell.
2. The method of claim 1, wherein the paramagnetic additive material selected is a salt of one of the lanthanide elements numbered from 58 through 70 in the PERIODIC TABLE OF THE ELEMENTS.
3. The method of claim 1, wherein the paramagnetic additive material selected is a salt of an actinide element.
Type: Application
Filed: Feb 14, 2005
Publication Date: Aug 17, 2006
Inventor: Robert O'Brien (Victoria)
Application Number: 11/058,494
International Classification: C25C 3/34 (20060101);
