WO2024257086A1 - Procédé et système de récupération d'hydroxyde de métal alcalin et d'autres produits chimiques à partir de déchets - Google Patents

Procédé et système de récupération d'hydroxyde de métal alcalin et d'autres produits chimiques à partir de déchets Download PDF

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WO2024257086A1
WO2024257086A1 PCT/IL2024/050561 IL2024050561W WO2024257086A1 WO 2024257086 A1 WO2024257086 A1 WO 2024257086A1 IL 2024050561 W IL2024050561 W IL 2024050561W WO 2024257086 A1 WO2024257086 A1 WO 2024257086A1
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xoh
unit
compartment
boric acid
cathode
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Dmitry LISITSIN
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Electriq Global Energy Solutions Ltd
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Electriq Global Energy Solutions Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/422—Electrodialysis
    • B01D61/423—Electrodialysis comprising multiple electrodialysis steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/422—Electrodialysis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/445—Ion-selective electrodialysis with bipolar membranes; Water splitting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/46—Apparatus therefor
    • B01D61/466—Apparatus therefor comprising the membrane sequence BC or CB
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/14—Alkali metal compounds
    • C25B1/16—Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/18—Alkaline earth metal compounds or magnesium compounds
    • C25B1/20—Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/22—Inorganic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/21—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms two or more diaphragms
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/70—Assemblies comprising two or more cells
    • C25B9/73—Assemblies comprising two or more cells of the filter-press type
    • C25B9/75—Assemblies comprising two or more cells of the filter-press type having bipolar electrodes

Definitions

  • the present disclosure relates to electrodialysis and the use of electrodialysis for recovery of chemical substances from waste.
  • Hydrogen is emerging as a new energy vector outside of its traditional role and gaining more recognition internationally as a viable fuel route.
  • borohydrides are being considered as a low-cost hydrogen storage material with high hydrogen generation capacity.
  • the preparation of sodium borohydride from boric acid was originally described by Schlesinger et al. in 1953 in a process called Brown- Schlesinger process.
  • the Brown-Schlesinger process comprises the preparation of trimethylborate B(OCH 3 ) 3 from a boric acid with a consecutive reaction of sodium hydride NaH, with B(OCH 3 ) 3 , to make the product NaBH 4 and the by-product sodium methoxide NaOCH 3 .
  • Other borohydrides such as LiBH 4 and KBH 4 can be prepared by the same route by addition of LiOH and KOH to react with the NaBH 4 at the last step of the Brown-Schlesinger process.
  • the borohydrides have the potential to be used as hydrogen carriers thanks to the easy and efficient process of catalytic hydrogen release upon contacting these carriers with water in a dedicated reactor.
  • the by-product of the hydrogen release process is metaborate salt of alkali metal dissolved in water.
  • the metaborate salt of the alkali metal can be regenerated back to its borohydride salt via the Brown-Schlesinger process.
  • the first step of this route is transforming the metaborate salt to the boric acid by its acidification as described by Pradyot Patnaik. Then, the Brown-Schlesinger process can be applied.
  • the presently disclosed subject matter provides, in accordance with a first of its aspects, a method for recovering alkali metal hydroxide (XOH) from waste comprising aqueous XBO 2 solution, X representing an alkali metal cation.
  • XOH alkali metal hydroxide
  • the method comprises, according to its broadest scope: subjecting a waste comprising aqueous XBO 2 solution, to a first electrodialysis process within a first electrodialysis unit that comprises at least one bipolar membrane, under conditions that provide a first XOH stream and a stream of dealkalized waste and discharging the first XOH stream; and optionally mixing the de-alkalized waste with an acid H n Y, n being an integer to form a slurry mixture of boric acid and X n Y; removing solids from said slurry mixture of boric acid and X n Y to form a solid-free aqueous mixture of boric acid and X n Y; and subjecting the solid-free aqueous mixture of boric acid and X n Y to a second electrodialysis process within a second electrodialysis unit comprising at least one bipolar membrane, the second electrodialysis unit being different from the first electrodialysis unit, under conditions that provides
  • the presently disclosed method and system allow also for the recovery of H n Y from the same receiving waste comprising aqueous XBO 2 solution, as further detailed hereinbelow.
  • the presently disclosed method and system allow also for the recovery of residual BA from the second electrodialysis unit to be further used in the recovery of BA.
  • Figures 1A-1B provides schematic illustrations of components of a first electrodialysis unit (Figure 1A) and its compartments during operation (Figure IB), in accordance with a non-limiting example of the presently disclosed subject matter.
  • Figures 2A-2B provides schematic illustrations of components of a first electrodialysis unit ( Figure 2A) and its compartments during operation ( Figure 2B), in accordance with another non-limiting example of the presently disclosed subject matter.
  • Figures 3A-3B provides schematic illustrations of components of a second electrodialysis unit (Figure 3A) and its compartments during operation ( Figure 3B), in accordance with a non-limiting example of the presently disclosed subject matter.
  • Figure 4 provides schematic flow chart illustrating the operation of a system according to a non-limiting example of the presently disclosed subject matter.
  • Figures 5A-5B are images of a lab scale system according to a non-limiting Example of the presently disclosed subject matter, including whole unit (Figure 5 A) and the membrane assembly unit (stack) (Figure 5B).
  • the present disclosure is based on the development of a technology that allows the recovery of an alkali metal containing base, e.g. KOH, and preferably also acids, e.g. H 2 SO 4 , via electrodialysis processes that utilizes, inter alia, bipolar membranes.
  • an alkali metal containing base e.g. KOH
  • acids e.g. H 2 SO 4
  • the present technology is directed to the recovery of KOH or NaOH and H 2 SO 4 from spent fuel.
  • Spent fuel is an aqueous solution produced after completion of hydrogen release process from KBH 4 , LiBH 4 or NaBH 4 (referred further as XBH 4 ) according to the following simplified reaction:
  • the first step of the recycling process is the acidification of the spent fuel (e.g. by H 2 SO 4 ) to produce boric acid which is the starting point of the XBH 4 synthesis:
  • the spent fuel is characterized by high pH due to the presence of XBO 2 in aqueous solutions, at high concentrations, near the solubility limit. Without being bound by theory, such high concentration creates a complex of tetraborate structure balanced by the X + cations, having the following general structure:
  • the formation of the tetraborate structure results in a high alkaline pH of the waste that results in the formation of also XOH.
  • the presently disclosed subject matter thus provides methods and systems for recovery of XOH (which can then be used for production of XBH 4 ) and further of H n Y (which can then be used for production of boric acid and further XBH 4 ), from waste containing XBO 2 , by the electrodialysis process aided by a series of membranes, including bi-polar membranes.
  • Table 1 shows that the presently disclosed methods and systems reduce the chemical consumption almost by an order of magnitude, thereby, significantly reducing the cost of the method and the carbon footprint of produced KBH 4 .
  • the presently disclosed subject matter broadly provides a method comprising: subjecting the waste comprising aqueous XBO 2 solution, to a first electrodialysis process within a first electrodialysis unit that comprises at least one bipolar membrane, under conditions that provide a first XOH stream and a stream of dealkalized waste and discharging the first XOH stream; and optionally, mixing the dealkalized aqueous waste with an acid H n Y, n being an integer to form a slurry mixture of boric acid and X n Y; removing solids from said slurry mixture of boric acid and X n Y to form a solid-free mixture of boric acid and X n Y; and subjecting the solid-free aqueous mixture of boric acid and X n Y to a second electrodialysis process within a second electrodialysis unit comprising at least one bipolar membrane,
  • the method also provides regeneration/recovery of H n Y as further described hereinbelow.
  • the presently disclosed subject matter broadly provides a system comprising a first electrodialysis unit configured for receiving waste comprising aqueous XBO 2 solution, and for separately discharging a first XOH stream and de-alkalized waste; and optionally a second electrodialysis unit, downstream to said first electrodialysis unit, configured for receiving saline boric acid comprising dissolved boric acid and X n Y, X representing an alkali metal cation, n representing an integer and Y representing an anion to said alkali metal cation, and for separately discharging, a second XOH stream and aqueous solution of H n Y and optionally or preferably also a stream of residual (desalinated) BA.
  • aqueous XBO2 waste or to "waste comprising aqueous XBO2 solution” it is to be understood to refer to any aqueous based liquid that contains dissolved XBO 2 , X representing any alkali metal cation.
  • de- alkalized waste it is to be understood to refer to any aqueous based liquid that contains dissolved XBO 2 , X representing any alkali metal cation, yet, with a pH that is lower than the pH of the aqueous XBO 2 waste introduced into the first electrodialysis unit.
  • the waste comprising aqueous XBO 2 solution is spent fuel having the meaning as described above, i.e. the aqueous solution produced during hydrogen release processes from KBH 4 , NaBH 4 or LiBH 4 (referred further as XBH 4 ).
  • X represents potassium
  • the spent fuel is thus one comprising KBO 2 .
  • X represents sodium, and the spent fuel is thus one comprising NaBO 2 .
  • X represents lithium, and the spent fuel is thus one comprising LiBO 2 .
  • the waste comprises dissolved XBO 2 at a concentration close to XBO2 solubility limit.
  • the term "solubility limit” should be understood to refer to the maximum concentration at which XBO 2 can dissolve in water at the method temperature and pressure and represents the point at which no more XBO 2 can be dissolved in water under the given temperature/pressure conditions.
  • the term "close to XBO2 solubility limit” should be understood to refer a concentration that is about l-2wt% below the maximum concentration (solubility limit) of XBO2 in water.
  • the waste comprising aqueous XBO 2 solution is subjected to at least one, preferably two electrodialysis processes, each electrodialysis process involves the use of one or more bipolar membrane (BPM) in the respective electrodialysis cell.
  • BPM bipolar membrane
  • the first electrodialysis unit combines BPMs with cationic membranes (CMs) while the second electrodialysis unit combines BPMs with CMs and anionic membranes (AMs), each unit having a specifically selected arrangement of BPMs, CMs and, in case of the second unit, also AMs.
  • CMs cationic membranes
  • AMs anionic membranes
  • the presently disclosed subject matter can be executed using commercially available BPM, CM and AM.
  • the BPM, CM and/or AM can be any commercially available heterogeneous CM, AM and BPM membranes such as RALEX membranes by Mega Group Ltd.
  • the BPM, CM and/or AM can be any commercially available homogeneous CM, AM and BPM membranes such as any one selected from NEOSEPTA, SELEMION, FUJIFILM® and Nafion membranes or other membranes having the same or similar functionality.
  • the electrodialysis units also include a cathode and an anode.
  • the cathode can be selected from SS316 and Ni based materials.
  • the cathode can be in a form of for example, a plate, foam, mesh structure.
  • the anode since no corrosive gases, such as chlorine, are produced thereon, the anode can be of any type known in the art.
  • the anode is Graphite, or DSA ⁇ or Platinized Nickel, all being well known and commercially available anodes.
  • the first electrodialysis unit comprises an electrodialysis cell including a membrane arrangement that receives the waste including at least aqueous dissolved XBO 2 and results in recovery of a first XOH stream that is collected, and a stream of a stream of dealkalized waste.
  • the first electrodialysis unit comprises a first electrodialysis cell including a first membrane arrangement including a cathode-paired CM and from the anode end of the cell, a repeating set of CM-BPM or a repeating set of CM-BPM-CM.
  • a repeating set it is to be understood to refer to a set of membranes which are sequentially repeated in the membrane arrangement.
  • the membrane arrangement comprises more than one set of CM-BPM.
  • the repeating unit is CM-BPM the entire membrane arrangement can be defined as Anode-(CM-BPM) i -CM-Cathode, where i represents and integer.
  • an electrodialysis cell comprising 3 repeating sets of CM-BPM, namely, i is equal to 3, the cell has the arrangement Anode-CM-BPM- CM-BPM- CM-BPM-CM-Catho e.
  • CM-BPM-CM the membrane arrangement comprises more than one set of CM-BPM-CM.
  • the repeating unit is CM-BPM-CM
  • the entire membrane arrangement can be defined as Anode-(CM-BPM- CM) i -CM-Cathode, where i represents and integer.
  • an electrodialysis cell comprising 3 repeating sets of CM-BPM-CM, namely, i is equal to 3, the cell has the arrangement Anode-CM-BPM-CM-CM-BPM-CM-CM-BPM-CM-CM- Cathode.
  • a second electrodialysis unit is included and the second electrodialysis unit comprises a second electrodialysis cell including a second membrane arrangement that receives an aqueous mixture of boric acid (BA) and X n Y and provides a second XOH stream and a stream of H n Y, and optionally or preferably a stream of residual/ desalinated boric acid.
  • BA boric acid
  • X n Y a second electrodialysis cell including a second membrane arrangement that receives an aqueous mixture of boric acid (BA) and X n Y and provides a second XOH stream and a stream of H n Y, and optionally or preferably a stream of residual/ desalinated boric acid.
  • the second electrodialysis unit comprises a second electrodialysis cell including a membrane arrangement including a cathode-paired CM and from the anode end of the cell, a repeating set of CM-BPM-AM.
  • CM-BPM-AM the membrane arrangement comprises more than one set of CM-BPM-AM.
  • the repeating unit is CM-BPM-AM the entire membrane arrangement can be defined as Anode-(CM-BPM-AM) i -CM-Cathode, where i represents and integer.
  • an electrodialysis cell comprising 3 repeating sets of CM-BPM-AM has the arrangement Anode-CM-B PM- AM-CM-BPM-AM-CM-BPM-AM-CM-Catho e.
  • the first XOH stream and the second XOH stream are preferably combined.
  • H n Y is recovered, which can be then utilized to produce boric acid, as further described hereinbelow.
  • the presently disclosed method provides at least the recovery of XOH and the method comprises:
  • a first electrodialysis unit comprising a first unit inlet end and a first unit outlet end, and extending therebetween a first electrodialysis cell comprising: an anode a cathode paired with a cathode-end CM, a membrane arrangement stacked between the anode and the cathode-end CM, the membrane arrangement comprising, from the anode end, a repeating set of CM-BPM or a repeating set of CM-BPM-CM; a power source configured for applying a voltage across said cell, the anode, the cathode-end CM and the membrane arrangement providing an array of electrolyte flow compartments, each electrolyte flow compartment having a fluid inlet at the first unit inlet end and fluid outlet at the first unit outlet end, the array of electrolyte flow compartments including: an electrode wash compartment between the anode and an anode end-CM and between the cathode and the cathode-end CM, waste treatment
  • This high alkaline solution is fed into the first electrodialysis unit for dealkalization.
  • the operation of the first electrodialysis unit involves the flow of different liquids into the different compartments of the first electrodialysis unit.
  • the flow is from the first unit inlet end towards the first unit outlet end.
  • the electrode wash solution is a solution that contains dissolved XkZ, X having the same meaning as above, namely, an alkali metal cation, k being an integer and Z being a counter anion.
  • the cathode-end CM is has very low permeability (i.e. essentially impermeable) to the Z k '.
  • the low permeability can be understood to mean that at least 99% of the Z k " anions will be kept in the wash solution after a considerable period of operation of the system.
  • the wash solution has a concentration that provides sufficient conductivity to avoid energy losses and yet a minimal conductivity that will not add to the overall resistance of the system. Higher conductivities are less preferable to avoid excessive chemical loss upon replacement of the solution.
  • the wash solution has a conductivity of > 10 mS/cm.
  • the alkali metal cation of the wash solution is identical to the alkali metal cation in the waste, i.e. in the dissolved XBO 2 of the aqueous waste.
  • the wash solution comprises XOH.
  • the wash solution comprises X2SO 4 .
  • lean XOH solution is to be understood to mean a solution of dissolved XOH having a concentration which is lower than final XOH concentration achieved at the end of the treatment process (concentrated XOH solution leaving the XOH compartment outlet).
  • concentration difference between the lean XOH solution and concentrated XOH solution depends on the overall system configuration. In the BPM systems operating in recycle mode with recycling tank, the concentration difference can be as low as 0.1%wt while in once through systems without recycling the concentration difference can reach 5-10%wt.
  • diluted H n Y solution is to be understood to mean a solution of dissolved H n Y having a concentration that provides minimal conductivity such that it will note add to the overall resistance of the membranes and on the other hand provide sufficient conductivity to avoid energy losses.
  • the diluted H n Y solution has a concentration that provides a conductivity of > 10 mS/cm.
  • H n Y refers to a strong acid. In some examples of the presently disclosed subject matter, H n Y is H 2 SO 4 .
  • H n Y is HC1.
  • the different solutions are introduced into the first electrodialysis cell while voltage is applied between the anode and the cathode.
  • the applied voltage is selected to cause transfer of X + across the CMs and generate OH" by the BPM, to thereby form a XOH liquid in the XOH compartment and to generate H + by the BPM in the waste treatment compartment to balance the transfer of X + to the XOH compartment.
  • a first stream of XOH is generated (being a concentrated XOH solution) and is discharged from the cell.
  • concentration of the XOH in the discharged XOH stream is greater than the concentration of XOH in the lean XOH solution.
  • the first unit stream discharged XOH comprises a concentration that is at least 5wt%; at times, at least 7wt%; at times, at least 9wt%; at times, at least 10wt%; at times, at least 12wt%; at times, at least 14wt%. It is to be appreciated that the concentration of XOH in this first stream of XOH discharged from the first electrodialysis unit can be higher, depending on the performance of the ion selective membranes used.
  • the XOH concentration in the first stream of concentrated XOH discharged from the first electrodialysis unit is between about 10wt% and 30wt%; at times, between 10wt% and 25wt%; at times, between 15wt% and 25wt%; at times, between 10wt% and 20wt%; at times, between 10wt% and 15wt%.
  • Figure 1A provides a schematic illustration of a first electrodialysis unit 100, comprising a first unit inlet end 102 and a first unit outlet end 104, and extending therebetween an electrolytic cell 106 including an anode 108, a cathode 110 paired with a cathode-end CM 112, and a membrane arrangement stacked between the anode 108 and the cathode-end CM 112.
  • the membrane arrangement comprises in this non-limiting example, from the anode end, a plurality of i repeating sets (CM (150)-BPM (152)-CM (150))z, 114(i), 114(2)... 114 ( i).
  • Figure 1A also illustrates a power source 120 connected to anode 108 and cathode 110, configured for applying a voltage across the electrolytic cell 102, so as to cause the transfer of charged species as explained hereinabove and below and generation of H + and OH' in BPM.
  • Figure 1A also illustrates the various array of electrolyte flow compartments as follows: an electrode wash compartment 122 between anode 108 and anode side (end) CM 124 and between cathode 110 and the cathode-end/paired CM 112; waste treatment compartments 128 between two facing CM (between two repeating sets) in said membrane arrangement;
  • XOH compartment 130 between a CM and a BPM within a repeating set; and a block loop compartment 132 between BPM and its cathode-side facing CM.
  • Figure IB schematically illustrates the electrodialysis unit of Figure 1A, in operation.
  • anode 108 in Figure IB is the same anode 108 in Figure 1 A.
  • Figure IB adds to Figure 1A in illustrating different liquid streams introduced into different compartments, upon activation of a voltage across the cell.
  • Figure IB illustrates the first electrodialysis unit 100 including the first unit inlet end 102, the first unit outlet end 104, and extending therebetween the electrolytic cell 106 including the anode 108, the cathode 110 paired with the cathode- end CM 112, and the membrane arrangement stacked between the anode 108 and the cathode-end CM 112.
  • power source applies voltage between the anode 108 and the cathode 110 and the following streams of liquids are introduced into the cell: a stream of an electrode wash solution 140 flow from the first unit inlet end 102, into the anode side electrode wash compartment 122 and into a cathode-side electrode wash compartment 125 and is discharged from the first unit outlet end 104 via streamline 142 and can be circulated back into the electrode wash compartment; streams of the liquid waste 144 comprising aqueous XBO 2 solution flow from the first unit inlet end 102, into the waste treatment compartments 128, and are discharges as a stream of de-alkalized waste 146; streams of lean XOH solution 148 flow from the first unit inlet end 102 into the XOH compartments 130, and is discharged from the cell, via first unit outlet end, as the first stream of XOH 180; streams of diluted acid solution H n Y 152 flow from the first unit inlet end 102 into the block loop compartments 132
  • the stream of waste comprising the aqueous XBO 2 solution has a pH of between 12 and 14 and as a result of treatment within the first electrodialysis unit, the pH of the de-alkalized steam of waste is reduced, at times, to a pH of between 9 and 12.
  • the stream of waste comprising the aqueous dissolved XBO 2 has a pH of about 14 and as a result of treatment within the first electrodialysis unit, the pH of the de-alkalized steam of waste is reduced, at times, to a pH below 11.
  • the recirculating of the wash solution comprises mixing the electrode wash solution discharged from the unit outlet ends, prior to being re-introduced into each electrode wash compartment.
  • Figure IB is the ions transfer that takes place in the electrodialysis cell upon application of the voltage, including: the transfer of X + across each CMs into the XOH compartment and the generation of OH" by the BPM in the XOH compartment, which together provide a XOH solute in the XOH compartment; and the generation of H + by the BPM in each waste treatment compartment to balance said transfer of X + to the XOH compartment; and the prevention of boron compounds leakage from the liquid waste to the XOH compartment due to the presence of the block loop compartment.
  • block loop compartment may be relevant when using BPM that may be insufficient to prevent penetration of the tetraborate anions (B4O 7 2 ') to the XOH stream. This may cause loss of boron containing compounds and decrease yield of production of boric acid, which is processed as further described hereinbelow.
  • B 4 O 7 2 ' anions face a CM which is typically more selective than BPM and thus prevents any significant leak of the boron compounds to the XOH compartment (XOH stream).
  • the waste when using a block loop compartment, is fed to compartments that are bound by CM from both the anode side and the cathode side.
  • the depletion of positively charged X + from the waste comprising the aqueous XBO 2 solution is balanced by H + ions transfer from the adjacent block loop.
  • the X + ions are transferred to the XOH compartments which are bound by CM from the anode side and by BPM from the cathode side.
  • the X + cations transferred from the liquid waste compartments are captured in XOH compartments since their further migration towards cathode is blocked by the anion part of the BPM.
  • the captured X + cations are balanced by OH" anions generated by BPM. In this way the concentration of XOH is increased.
  • the block loop is bound by BPM from the anode side and by the CM from the cathode side.
  • the streams of diluted acid solution H n Y 152 comprise a diprotic or triprotic acid.
  • the acid in the diluted solution H n Y 152 comprise an anion Y n " that is sufficiently large to prevent its penetration to the XOH compartments via the CM.
  • the streams of diluted acid solution H n Y 152 comprise H 2 SO 4 acid.
  • the streams of diluted acid solution H n Y 152 comprise an organic acid.
  • organic acids can be used given that the anion part has very low permeability through the cation part of the BPM.
  • H + cations from the steam of diluted acid solution H n Y move towards the liquid waste compartments through the cathode-side CM.
  • the depletion of H + ions in the block loop compartment is compensated by the H + cations generation by the BPM.
  • FIG. 2A and 2B providing a schematic illustration of a first electrodialysis unit in accordance with another non-limiting example of the presently disclosed subject matter.
  • anode 208 in Figures 2A-2B is an anode having the same function as anode 108 in Figures 1A-1B.
  • Figure 2A illustrates a first electrodialysis unit 200, comprising a first unit inlet end 202 and a first unit outlet end 204, and extending therebetween an electrolytic cell 206 including an anode 208, a cathode 210 paired with a cathode-end CM 212, and a membrane arrangement stacked between the anode 208 and the cathode-end CM 212.
  • Membrane arrangement comprises in this non-limiting example, from the anode end, a plurality of repeating set of CM (250)-BPM (252), 214(i), 214(2)... 214 (l) .
  • Figure 2A also illustrates a power source 220 connected to the anode 208 and the cathode 210, configured for applying a voltage across the electrolytic cell 202, so as to cause the transfer of charged species as described herein and generation of H + and OH" in BPM.
  • a power source 220 connected to the anode 208 and the cathode 210, configured for applying a voltage across the electrolytic cell 202, so as to cause the transfer of charged species as described herein and generation of H + and OH" in BPM.
  • Figure 2A also illustrates similar arrays of electrolyte flow compartments including an electrode (anode) wash compartment 222 between anode 208 and an anode-side CM 224 and a further electrode (cathode) wash compartment 225 between cathode 210 and cathode-end/paired CM 212; waste treatment compartments 228 between the cation part of the BPM and a cathode-side CM (the CM of a next repeating set or of the cathode paired CM); and the XOH compartments 230 between a CM and anion part of BPM (i.e. of the BPM of the same repeating set).
  • an electrode anode
  • cathode wash compartment 225 between cathode 210 and cathode-end/paired CM 212
  • waste treatment compartments 228 between the cation part of the BPM and a cathode-side CM (the CM of a next repeating set or of the cathode
  • Figure 2B schematically illustrates the electrodialysis unit of Figure 2A, in operation.
  • anode 208 in Figure 2B is the same anode 208 in Figure 2A.
  • Figure 2B adds to Figure 2A in illustrating the different liquid streams introduced into the different compartments, upon activation of a voltage across the cell by the power supply (not illustrated in Figure 2B).
  • Figure 2B illustrates the first electrodialysis unit 200 including the first unit inlet end 202, the first unit outlet end 204, the and extending therebetween the electrolytic cell 206 including the anode 208, the cathode 210 paired with the cathodeend CM 212, and the membrane arrangement stacked between the anode 208 and the cathode-end CM 212.
  • power source applies voltage between the anode 208 and the cathode 210 and the following streams of liquid are introduced into the cell: a stream of an electrode wash solution 240 flow from the first unit inlet end 202, into the anode side electrode wash compartment 222 and into a cathode-side electrode wash compartment 225 and is discharged from the first unit outlet end 204 via streamline 242 and can be circulated back into the electrode wash compartment as described above; streams of the liquid waste 244 comprising aqueous XBO 2 solution flow from the first unit inlet end 202, into the waste treatment compartments 228, and are discharges as a stream of de-alkalized waste 246; and streams of lean XOH solution 248 flow from the first unit inlet end 202 into the XOH compartments 230, and is discharged from the cell, via first unit outlet end, as the first stream of XOH 280.
  • a stream of an electrode wash solution 240 flow from the first unit inlet end 202, into the anode side electrode wash compartment 222
  • the first electrodialysis unit of Figure 2B is lacking the block loop compartments.
  • the X + cations move towards cathode through the CM while the ECO 7 2 ' anions migration towards anode is blocked by the cation part of the BPM.
  • the depletion of positively charged X + from the solution is balanced by H + ions generated by BPM.
  • the X + ions are transferred to the XOH compartments which are bound by CM from the anode side and by anion part of BPM from the cathode side.
  • the X + cations transferred from the liquid waste compartments are captured in XOH compartments since their further migration towards cathode is blocked by the anion part of the BPM.
  • the captured X + cations are balanced by OH" anions generated by BPM.
  • the concentration of XOH is increased.
  • the anode and cathode are bound by CM and are washed (preferably by diluted XOH solution) to close the electrical circuit.
  • the XOH washing solution is split and feed both anode and cathode compartments.
  • the outlet XOH washing solution is mixed after exiting the compartments and is recycled back to the process.
  • a first stream of XOH is recovered.
  • the first stream of XOH is subjected to a least one evaporating process to provide a first unit concentrated XOH that can be stored in a dedicated tank or communicated for further use, e.g. in XBH 4 production processes.
  • the first electrodialysis unit discharges de-alkalized liquid waste.
  • dealkalized waste it is to be understood to refer to the aqueous waste solution comprising dissolved XBO 2 with a pH that is lower than the pH of the aqueous waste comprising the dissolved XBO 2 introduced into the first electrodialysis unit.
  • the waste introduced into the first electrodialysis unit has high alkalinity.
  • the stream of aqueous waste comprising the dissolved XBO 2 has a pH of between 12 and 14 and as a result of treatment within the first electrodialysis unit, the pH of the de-alkalized steam of waste is reduced, at times, to a pH of between 9 and 12.
  • the stream of aqueous waste comprising the dissolved XBO 2 has a pH of about 14 and as a result of treatment within the first electrodialysis unit, the pH of the de-alkalized steam of waste is reduced, at times, to a pH of less than 11.
  • the dealkalized liquid/aqueous waste is subjected to a process resulting in the regeneration of boric acid.
  • the generation comprises a reaction between the dealkalized liquid waste and a strong acid H n Y, n being an integer and Y representing an anion to form boric acid and X n Y slurry.
  • the generation of boric acid can be represented by the following equation:
  • the boric acid and X n Y salt are in a form of a slurry. This is due to the limited solubility of boric acid and X n Y, resulting in their partial precipitation. Yet, some of the boric acid and the X n Y salt remain dissolved and can be separated from the precipitated matter.
  • the dissolved boric acid and X n Y are separated from the precipitated matter.
  • the dissolved aqueous boric acid/ X n Y comprises water saturated with dissolved boric acid and dissolved X n Y.
  • the solids comprising the boric acid and X n Y are dried, i.e. the method further comprises drying the solids.
  • Separation between the boric acid and the X n Y can be achieved by the selective dissolution of boric acid.
  • the dried boric acid is selectively dissolved in an organic solvent.
  • the boric acid organic solvent is selected from the group consisting of short chain alcohols, such as methanol, ethanol, 1 -propanol.
  • boric acid organic solvent is methanol.
  • solid X n Y salt is dissolved in water.
  • the water dissolved boric acid / X n Y obtained from the solidliquid separator is combined with the water dissolved X n Y, in a boric acid tank.
  • the boric acid tank thus comprises a mixture of dissolved boric acid and dissolved X n Y, at times, referred to herein by the term "saline boric acid” or "saline BA" .
  • This mixture can be further processed to recover further XOH and acid H n Y.
  • the saline BA is subjected to a second electrodialysis process utilizing a second electrodialysis unit that is different in the membrane arrangement from that used in the first electrodialysis unit.
  • the method thus further comprises subjecting the saline BA to an electrodialysis reaction within a second electrodialysis unit.
  • the second electrodialysis unit forming part of the presently disclosed method and system comprises a second unit inlet end and a second unit outlet end, and extending therebetween a second electrodialysis cell comprising: an anode, a cathode paired with a cathode-end CM, a second unit membrane arrangement stacked between the anode and the cathodeend CM, the second unit membrane arrangement comprising, from the anode, a repeating set of CM-BPM-AM; a power source configured for applying a voltage across the second cell, the cathode end CM and the second unit membrane arrangement providing an array of electrolyte flow compartments, each electrolyte flow compartment having a fluid inlet at the second unit inlet end and fluid outlet at the second unit outlet end, the array of electrolyte flow compartments providing: an electrode wash compartment between the anode and an anode side/end CM and between the cathode and the cathode-end CM;
  • CM-BPM-AM XOH compartment between CM and BPM of a repeating set
  • CM-BPM-AM a repeating set
  • saline boric acid compartment between an AM and a CM
  • the subjecting of the saline BA to an electrodialysis reaction within a second electrodialysis unit comprises
  • the wash solution of the passing through the electrode compartment of the second electrodialysis unit can be the same or different from the wash solution employed in the first electrodialysis unit, as long as the alkali metal cation is the same as that present in the waste to be treated (i.e. of the XBO 2 ).
  • lean H n Y solution that is being introduced into the H n Y compartment of the second electrodialysis unit is to be understood to mean the solution having low H n Y concentration.
  • concentration difference between the lean H n Y and the discharged final H n Y solution depends on the actual process configuration of the industrial scale electrodialysis unit. In once through operation regime the concentration of lean H n Y can be lower than l%wt. In systems having H n Y stream recirculated through circulation tank, the concentration difference between lean H n Y stream and final H n Y stream can be lower than l%wt.
  • saline BA that is being introduced into the Saline BA compartment of the second electrodialysis unit is to be understood to mean a solution comprising dissolved boric acid and dissolved acid X n Y, the X n Y having the meaning as described herein.
  • the second electrodialysis unit also provides, in addition to the second stream of XOH, discharging of H n Y from the H n Y compartment, to be re-used in the presently disclosed method and system.
  • Figures 3A-3B providing a schematic illustration of a second electrodialysis unit in accordance with a non-limiting example of the presently disclosed subject matter.
  • anode 308 in Figures 3A-3B is an anode having the same function as anode 108 in Figures 1A-1B.
  • FIG. 3A illustrates a second electrodialysis unit 320, comprising a first unit inlet end 302 and a first unit outlet end 304, and extending therebetween an electrolytic cell 306 including an anode 308, a cathode 310 paired with a cathode-end CM 312, and a membrane arrangement stacked between the anode 308 and the cathode-end CM 312.
  • Membrane arrangement comprises in this non-limiting example, from the anode end, a plurality of repeating set of CM (350)-BPM (352)-AM (354), 314 ( i), 314 (2) . . . 314 (i) .
  • Figure 3A also illustrates a power source 320 connected to the anode 308 and the cathode 310, configured for applying a voltage across the electrolytic cell 302, so as to cause the transfer of charged species as described herein and generation of H + and OH" in BPM.
  • a power source 320 connected to the anode 308 and the cathode 310, configured for applying a voltage across the electrolytic cell 302, so as to cause the transfer of charged species as described herein and generation of H + and OH" in BPM.
  • Figure 3A also illustrates an array of electrolyte flow compartments including an electrode (anode) wash compartment 322 between anode 308 and an anode-end CM 325 and a further electrode (cathode) wash compartment 325 between cathode 310 and cathode-paired CM 312; XOH compartments 330 between CM and BPM; acid compartments 360 between the BPM and AM; and saline boric acid compartments 362 between AM and CM.
  • an electrode anode wash compartment 322 between anode 308 and an anode-end CM 325 and a further electrode (cathode) wash compartment 325 between cathode 310 and cathode-paired CM 312
  • XOH compartments 330 between CM and BPM
  • acid compartments 360 between the BPM and AM
  • saline boric acid compartments 362 between AM and CM.
  • Figure 3B schematically illustrates the electrodialysis unit of Figure 3A, in operation.
  • anode 308 in Figure 3B is the same anode 308 in Figure 3 A.
  • Figure 3B illustrates the different liquid streams introduced into the different compartments illustrated in Figure 3A, upon activation of a voltage across the cell by the source of power supply (not illustrated in Figure 3B).
  • Figure 3B illustrates, inter alia, the second electrodialysis unit 300 including the second unit inlet end 302, the second unit outlet end 304, and extending therebetween the electrolytic cell 306 including the anode 308, the cathode 310 paired with the cathode-end CM 312, and the membrane arrangement stacked between the anode 308 and the cathode-end CM 312.
  • H n Y compartments receive H + generated from the BPM and Y n " anion transferred through the AM from the saline BA compartment 362 thus resulting in an increase in the acid H n Y concentration in the H n Y compartment 360.
  • the saline BA compartments receive the mixture of dissolve boric acid and dissolved X n Y and as a result of the applied potential, the cation X + is transferred, via CM, to the XOH compartments 330 and the anion Y n " is transferred, via the AM, to the H n Y compartments 360, such that in the stream passing through the saline BA compartments loose most of X n Y while maintaining BA .
  • the latter can be explained by the fact that the weekly charged boric acid, B(OH)3, is almost not attracted to the electrodes and most of it remains in the compartment’s outlet stream which is then directed for further boric acid recovery.
  • wash solution As also explained above, passing through the electrode compartment it is to be noted that it can be the same or different from the wash solution employed in the first electrodialysis unit, as long as the alkali metal cation is the same.
  • the wash solution in the first electrodialysis unit can be XOH, e.g. KOH
  • the wash solution in the second electrodialysis unit can be X2SO 4 , e.g. K2SO 4 .
  • the concentration of the second unit XOH being discharged is greater than the concentration of XOH in the lean XOH solution.
  • the XOH discharged from the second electrodialysis unit comprises a concentration that is at least 5wt%; at times, at least 7 wt%; at times, at least 9wt%; at times, at least 10wt%; at times, at least 12wt%; at times, at least 14wt%. It is to be appreciated that the concentration of XOH in this second unit discharged XOH can be higher than 12wt%, depending on the performance of the ion selective membranes used.
  • the XOH concentration discharged from the second electrodialysis unit is between about 5wt% and 20wt%; at times, between 5wt% and 15wt%; at times, between 10wt% and 20wt%; at times, between 5wt% and 10wt%; at times, between 8wt% and 15wt%.
  • the XOH discharged from the second electrodialysis unit is concentrated. Accordingly, the disclosed method also comprises subjecting the second unit XOH from the second unit outlet end to at least one evaporating process to provide second unit concentrated XOH.
  • the second unit XOH from the second unit outlet end is combined with the first unit XOH (from the first electrodialysis unit) prior to being introduced into an evaporator, i.e. the combined XOH is subjected to at least one evaporating process to provide a combined concentrated XOH.
  • the concentrated XOH is collected in a XOH tank.
  • the method also comprises collecting the concentrated H n Y generated in the second electrodialysis unit. This allows for the recovery of H n Y which can then be reused in for the boric acid production. Thus, in the context of the presently disclosed subject matter, the method also provides recovery of H n Y from the H n Y compartment of the second electrodialysis unit.
  • H n Y represents H 2 SO 4 and thus, the method provides recovery of H 2 SO 4 .
  • the presently disclosed subject matter also provides a system for regeneration of at least XOH.
  • the system comprises: a first electrodialysis unit configured for receiving waste comprising aqueous XBO 2 solution, and for separately discharging a first XOH stream and dealkalized waste; and optionally, a second electrodialysis unit, downstream to said first electrodialysis unit, configured for receiving saline boric acid comprising dissolved boric acid and X n Y, X representing an alkali metal cation, n representing an integer and Y representing an anion to said alkali metal cation, and for separately discharging a second XOH stream and aqueous solution of H n Y.
  • the applied voltage between the anode and the cathode provide for: transfer of X + across each CMs; generation of OH" by the BPM, to thereby form a XOH liquid in the XOH compartment generation of H + by the BPM in the waste treatment compartment to balance the transfer of X + to the XOH compartment; and separate discharge of a first steam of XOH and a stream of de-alkalized waste.
  • the system comprises a step of subjecting the dealkalized liquid/aqueous waste to a process resulting in the regeneration of boric acid.
  • the system comprises a first mixing chamber configured for mixing the stream of de-alkalized waste with H n Y acid (e.g. H 2 SO 4 ), prior to introducing the aqueous boric acid into the solid-liquid separator.
  • H n Y acid e.g. H 2 SO 4
  • the generation of boric acid comprises a reaction between the dealkalized liquid waste and a strong acid H n Y, n being an integer and Y representing an anion to form boric acid and X n Y slurry.
  • the system comprises a solid-liquid separator (as described hereinabove) configured to receive the boric acid and X n Y slurry and to separate between solution saline boric acid and X n Y salt (liquid part) and solid boric acid and X n Y containing matter (solid part).
  • a solid-liquid separator as described hereinabove
  • the solid boric acid and X n Y containing matter is subjected to drying.
  • the system comprises a drying unit configured to dry the solid boric acid-containing matter received from the (boric acid and X n Y slurry) solid-liquid separator and second electrodialysis unit.
  • the system comprises boric acid separation unit downstream to the drying unit, the separation unit being configured to selectively dissolve the dried solid boric acid containing matter in an organic solvent and discharge/recover dissolved boric acid, and discharge solid X n Y.
  • the system comprises a X n Y dissolution unit configured to dissolve solid X n Y received from the boric acid separation unit.
  • the system comprises a second mixing chamber configured to mix saline boric acid discharged from the solidliquid separator with the dissolved X n Y received from the X n Y dissolution unit, the second mixing chamber being upstream to said second electrodialysis unit and is configured to communicate the mixed dissolved boric acid and X n Y into the second electrodialysis unit.
  • the liquid saline boric acid containing dissolved X n Y salt is collected for further treatment by the second electrodialysis unit, as further described hereinabove and below.
  • the applied voltage between the anode and the cathode provides for: transfer of X + across each CM, transfer of Y n " across each AM, generation of OH" by said BPM in the XOH compartment generation of H + by said BPM in the H n Y compartment; and separate discharge of a second stream of concentrated XOH and a stream of H n Y.
  • the second electrodialysis unit as defined hereinabove the applied voltage between the anode and the cathode also allows to keep a weakly charged boric acid in residual boric acid waste stream for further utilization.
  • the system also comprises a first evaporator (as described hereinabove), which is configured to evaporate water from the aqueous solution of XOH discharged from the first electrodialysis unit and to discharge first unit concentrated XOH.
  • a first evaporator as described hereinabove, which is configured to evaporate water from the aqueous solution of XOH discharged from the first electrodialysis unit and to discharge first unit concentrated XOH.
  • the system comprises a second evaporator configured to evaporate water from the aqueous solution of H n Y received from the second electrodialysis unit and to discharge concentrated H n Y.
  • the system comprises a third evaporator between said second electrodialysis unit and said drying unit, said third evaporator being configured to evaporate water from said residual boric acid.
  • FIG. 4 providing a schematic illustration of a system comprising all the above-described optional system elements and is configured for recovery of XOH and preferably also H n Y from aqueous XBO 2 waste solution, such as spent fuel, according to some examples of the presently disclosed subject matter.
  • Figure 4 shows a schematic illustration of a system according to some examples of the presently disclosed subject matter, constructed to allow the recovery of XOH from waste containing the aqueous dissolved XBO 2 and preferably also recovery of H n Y utilized in the process of XOH recovery.
  • waste comprising the aqueous dissolved XBO 2
  • XBO2 Waste waste comprising the aqueous dissolved XBO 2
  • 1 st ED Unit waste comprising the aqueous dissolved XBO 2
  • the XBO 2 containing waste is an aqueous solution of XBO 2 at high concentration near the solubility limit.
  • Such a solution creates a complex tetraborate structure balanced by X + cations. This process results in a highly alkaline pH of the XBO 2 waste due to consecutive liberation of XOH according to the following route:
  • This solution is fed to the 1 st ED Unit composed of the power source, cathode and anode and ion selective membranes arranged in a stack between the cathode and anode.
  • the membrane arrangement in the 1 st ED Unit can have a repeating sequence of CM-BPM-CM as schematically illustrated in Figure 1 A (in case of working with a block loop) or a sequence of CM-BPM as schematically illustrated in Figure 2A (in case of working without a block loop).
  • the 1 st ED Unit generates two main process streams.
  • the first stream is a first XOH stream.
  • the first XOH stream is sent to a 1 st Evaporator to increase the XOH concentration to a desired level (e.g. 40wt%-45wt%) and stored in dedicated tank ("XOH Tank” , e.g. for later use in XBH 4 production process.
  • a desired level e.g. 40wt%-45wt%
  • XOH Tank dedicated tank
  • the second stream discharged from the 1 st ED Unit is de-alkalized waste which is sent to a boric acid production stage in a BA reactor ("BA Reactor").
  • BA Reactor concentrated acid H n Y is added to the dealkalized waste to produce boric acid slurry.
  • boric acid has limited solubility and it is precipitated together with the generated salt X n Y. Part of the boric acid and X n Y salt remain in dissolved form.
  • Solid-Liquid Separator Solid-Liquid Separator
  • BA + X n Y solid BA + X n Y
  • Boric Acid Drying liquid boric acid production waste
  • Dry boric acid and X n Y are contacted by methanol in boric acid dissolution (" Boric Acid Dissolution”).
  • boric acid dissolution methanol selectively dissolves the boric acid leaving most of the X n Y salt in solid form.
  • the methanol dissolved BA is sent to further use, e.g. in XBH 4 production processes, while the solid X n Y is sent to water dissolution step ("X n Y Dissolution").
  • the dissolved X n Y salt is transferred to the same Waste Collection Tank into which the liquid BA waste is sent (“ Waste Collection Tank") and is thus mixed with waste from boric acid production step.
  • Waste Collection Tank Waste Collection Tank
  • the total waste stream from the Waste Collection Tank is sent to a 2 nd electrodialysis unit ("2 nd ED Unit") to recover a second XOH stream, the boric acid and also H n Y.
  • the 2 nd ED unit operational principle is detailed hereinabove.
  • the 2 nd ED Unit is generally composed of the power source, cathode and anode and ion selective membranes arranged in a stack between the cathode and anode.
  • the membrane arrangement in the 2 nd ED Unit has a repeating sequence of CM-BPM-AM as schematically illustrated in Figure 3 A.
  • the 2 nd ED unit generates three main process streams.
  • a first stream discharged from the 2 nd ED Unit is a second XOH stream which is sent to a 1 st Evaporator to increase the XOH concentration to the desired level and stored together with the first XOH stream, in the XOH Tank.
  • a second stream discharged from the 2 nd ED Unit is H n Y stream, which is sent to a 2 nd Evaporator to increase the H n Y acid concentration to the desired level, which can then be stored in a H n Y Tank and from the H n Y Tank, communicated to the BA Reactor for reused in the BA production stage.
  • a third stream comprising desalinated solution containing residual boric acid. This stream is sent to a 3 rd Evaporator to produce solid boric acid which can be then dried in the Boric Acid Drying unit together with the boric acid discharged from the Solid- Liquid Separator.
  • a membrane includes one or more membranes.
  • the term “comprising” is intended to mean that the composition include the recited components, e.g. 1 st elecrodialysis unit, but not excluding other elements or components than may form part of the presently disclosed subject matter.
  • the term “consisting essentially of' is used to define methods and systems which include the recited components or elements but exclude other components or elements that may have an essential significance on the performance of the disclsoed methods and systems. " Consisting of' shall thus mean excluding components or elements that are not specifically recited. Embodiments defined by each of these transition terms are within the scope of this invention.
  • CM, AM and BPM membranes RALEX membranes by Mega Group Ltd.
  • the system consisted of 5 independent circulating loops (the "compartments") marked as DI, D2, E, Cl (not in use in the current example) and C2.
  • Each circulating loop includes a respective dedicated circulating vessel, piping, flowmeter and circulating pump (pump and flowmeter are not shown in Figure 5A).
  • the circulating vessels were submerged in a thermal bath to enable constant temperature conditions during the experiment.
  • the system also included a dedicated power source (Power supply) with its Power supply Voltmeter and Power supply Amperemeter.
  • the pumps and the power source were operated from a control panel, also shown in Figure 5A.
  • the system was designed to operate with a single replaceable membrane unit (stack) including a stack of membranes' arrangement that allows the switching between an operation with a block loop circulating stream (D2) and without a block loop circulating stream (where D2 is "not in use”).
  • stack a stack of membranes' arrangement that allows the switching between an operation with a block loop circulating stream (D2) and without a block loop circulating stream (where D2 is "not in use”).
  • the system of Figure 5A can also simulate the operation of the 2 nd electrodialysis unit, as evident from Table 2 below.
  • Figure 5B shows that the shown stack of membranes' arrangements also includes an anode plate and a cathode plate with electrical connections to the power source (the power source not shown).
  • Circulation piping lines were connected to the relevant membrane arrangement port located in electrode plates.
  • the membranes were arranged between the anode and cathode and held by tightening rods.
  • sensing electrodes were used and were located between the electrodes and the membrane adjacent thereto.
  • the purpose of the sensing electrodes is to measure the potential drop on the membranes without the interference of the potential drop related to the reaction occurring on the electrodes and electrical system resistance.
  • the potential difference measured by sensing electrodes serves for determination of process energy consumption used for system scale up.
  • Table 2 summarizes the circulating streams’ designation for different system configurations (e.g. with or without the circulation of a block loop stream). Table 2: Streams designation for different BPM systems configuration
  • the experimental conditions for the different system configurations include the following:
  • the KOH solution recovered reached concentration of up to 7.5%wt at the end of the experiment. Less than 1% of B4O 7 2 ' anions were lost from the treated waste stream. The process energy consumption was estimated as ⁇ 1.5 kWh per 1 kg of recovered KOH.
  • the results obtained without block loop circulation were similar to the results obtained with block loop circulation, except the loss of the B4O 7 2 ' anions in the former configuration.
  • the B4O 7 2 ' anions loss from the treated waste stream to the KOH stream increased without the block loop circulation, from ⁇ 1% to ⁇ 5%.
  • the treated saline Boric Acid waste obtained from operating the 1 st electrodialysis unit (with or without the operation of a block loop) contained ⁇ 60 gr of Boric Acid and ⁇ 120 gr of K2SO 4 in one liter of the solution.

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Abstract

La présente divulgation concerne un procédé et un système de récupération d'hydroxyde de métal alcalin (XOH) à partir de déchets comprenant une solution aqueuse de XBO2, le procédé comprenant les étapes suivantes : (i) soumission des déchets à un premier processus d'électrodialyse à l'intérieur d'une première unité d'électrodialyse qui comprend au moins une membrane bipolaire, dans des conditions qui fournissent un premier flux de XOH et un flux de déchets désalcalinisés et l'évacuation du premier flux XOH; et éventuellement mélange des déchets désalcalinisés avec un HnY acide, n étant un nombre entier et Y un contre-anion du cation de métal alcalin pour former une suspension d'acide borique et de XnY; (ii) élimination des solides de ladite suspension d'acide borique et de XnY pour former un mélange aqueux exempt de solides d'acide borique et de XnY; (iii) soumission du mélange aqueux exempt de solides d'acide borique et de XnY à un second processus d'électrodialyse à l'intérieur d'une seconde unité d'électrodialyse comprenant au moins une membrane bipolaire, la seconde unité d'électrodialyse étant différente de la première unité d'électrodialyse, dans des conditions qui fournissent un second flux de XOH et un flux de HnY; et (iv) collecte du premier flux de XOH et du second flux de XOH. Le système comprend une première unité d'électrodialyse conçue pour recevoir des déchets comprenant une solution aqueuse de XBO2 et pour évacuer séparément un premier flux de XOH et des déchets désalcalinisés; et éventuellement une seconde unité d'électrodialyse, en aval de ladite première unité d'électrodialyse, conçue pour recevoir de l'acide borique salin comprenant de l'acide borique dissous et du XnY, X représentant un cation de métal alcalin, n représentant un nombre entier et Y représentant un anion dudit cation de métal alcalin, et pour évacuer séparément un second flux de XOH et une solution aqueuse de HnY.
PCT/IL2024/050561 2023-06-13 2024-06-06 Procédé et système de récupération d'hydroxyde de métal alcalin et d'autres produits chimiques à partir de déchets Ceased WO2024257086A1 (fr)

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Citations (5)

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