Electrodialysis for processing of sugar acid solutions

Abstract

A method for metal ion reduction may comprise introducing a sugar acid solution to a system that may include an electrodialysis unit. The sugar acid solution may include a sugar acid, one or more initial cations, and a solvent. The method may also include subjecting the sugar acid solution to electrodialysis under conditions suitable for removal of the initial cation and formation of a sugar free acid. The method may also include recovering the sugar free acid wherein the sugar free acid has a purity of from about 60% to about 90%.

Description

ELECTRODIALYSIS FOR PROCESSING OF SUGAR ACID SOLUTIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The application claims priority to U.S. Provisional Application Serial No. 63 / 510,554 filed on June 27, 2023 and entitled “Electrodialysis for Processing of Sugar Acid Solutions,” which is incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.FIELD

[0003] The present disclosure relates generally to the methods for reducing metal ion concentration of solution. More particularly, the present disclosure relates to methods for the reducing metal ion concentration of sugar acid solutions.BACKGROUND

[0004] Electrodialysis (also referred to as “ED”) is a separation process that utilizes an electrical potential difference as a driving force to move ions through a semipermeable membrane. The membrane is selectively permeable in that the passage of only anions or only cations is permitted, but not both. Thus, separation on the basis of ED is due to differences in charge rather than differences in size. For example, ED is based on the principle that most salts dissolved in water are ionic, being either positively charged (for example, a cation such as Na+, Ca2+, Mg2+) or negatively charged (for example, an anion, such as Cl; CO32). These ions are attracted to electrodes with an opposite electric charge; that is, anions being attracted to a cathode or positively-charged electrode, and cations being attracted to an anode or negatively-charged electrode.

[0005] The ion-exchange membranes in ED units generally contain charged groups which are attached to a polymer backbone of the material forming the membrane. The fixed charged groups partially or completely exclude ions of the same charge from the membrane. This means that an anionic membrane with fixed positive groups excludes positive ions but is freely permeable to negatively charged ions. Similarly, a cationic membrane with fixed negative groups excludes negative ions but is freely permeable to positively charged ions. However, challenges with the use ofconventional ion exchange technologies include difficulties in membrane regeneration, resin cost, resin footprint, and slow throughput. Consequently, an ongoing need exists for improved ED methods.BRIEF DESCRIPTION OF THE DISCLOSURE

[0006] Disclosed herein is a method for metal ion reduction. The method may comprise introducing a sugar acid solution to a system comprising an electrodialysis unit. The sugar acid solution may comprise (i) a sugar acid (ii) one or more initial cations and (iii) a solvent. The method may also comprise subjecting the sugar acid solution to electrodialysis under conditions suitable for removal of the initial cation and formation of a sugar free acid. The method may also comprise recovering the sugar free acid wherein the sugar free acid has a purity of from about 60% to about 90%.

[0007] Additionally or alternatively, disclosed herein is a method for metal ion exchange. The method may comprise introducing a sugar acid solution to a system comprising an electrodialysis unit. The sugar acid solution may comprise (i) a sugar acid (ii) one or more initial cations and (iii) a solvent. The method may also comprise subjecting the sugar acid solution to electrodialysis under conditions suitable for exchanging of the initial cation with a desired cation to form a desired salt complex. The method may also comprise recovering the desired salt complex.

[0008] Additionally or alternatively, disclosed herein is a method for metal ion reduction. The method may comprise introducing a sugar acid solution to a system comprising an electrodialysis unit. The sugar acid solution may comprise (i) a sugar acid-sodium complex and (ii) a solvent. The method may also comprise subjecting the sugar acid solution to electrodialysis under conditions suitable for removal of a sodium cation and formation of a sugar acid-potassium complex. The method may also comprise recovering the sugar acid-potassium complex wherein the sugar acid- potassium complex has a purity of from about 60% to about 90%.

[0009] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.BRIEF DESCRIPTION OF DRAWINGS

[0010] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0011] Figure 1 is a schematic depiction of systems and methods for removal of potassium from potassium glucarate according to one or more aspects of the present disclosure;

[0012] Figure 2 is a schematic depiction of systems and methods for removal of potassium from potassium gluconate according to one or more aspects of the present disclosure;

[0013] Figure 3 is a schematic depiction of systems and methods for separating sugar diacids from glucaric acid using electrodialysis according to one or more aspects of the present disclosure;

[0014] Figure 4 is a schematic depiction of systems and methods for separating sugar monoacids from glucaric acid using electrodialysis according to one or more aspects of the present disclosure;

[0015] Figure 5 is a schematic depiction of systems and methods for removal of metal ion from chelated sugar acid using bipolar membranes according to one or more aspects of the present disclosure; and

[0016] Figure 6 is a schematic depiction of systems and methods for removal of metal ion from chelated sugar acid using cation exchange membranes according to one or more aspects of the present disclosure.DETAILED DESCRIPTION

[0017] Disclosed herein are systems and methods for reducing the concentration of metal ions in a solution, for example, a solution comprising sugar acids. In one or more aspects, the sugar acid comprises aldaric acid, uronic acid, glucaric acid, gluconic acid, glucuronic acid, gluconic acid oxidation galactonic acid, galactaric acid, glutamic acid, or combinations thereof. As will be disclosed further herein, the disclosed methods advantageously provide for an economical and high throughput method for separating metal ions from sugar chelates without the need for ion exchange resins or other methods such as precipitation.

[0018] Also disclosed herein are systems and methods for the formation of high-purity acids from acid salts. In one or more aspects, the high-purity acid is a sugar acid, for example, aldaric acid, uronic acid, glucaric acid, gluconic acid, glucuronic acid, gluconic acid oxidation galactonic acid, galactaric acid, glutamic acid, or combinations thereof. In various aspects, as will be disclosed herein, the systems and methods utilize ED, for example, to yield the high-purity acids.

[0019] Referring to Figure 1 , an embodiment of a system and method for the purification of glucaricacid from an acid mixture 102, for example, a mixture of gluconic acid, glucaric acid, dextrose, and other organic acids is depicted schematically. The system for the purification of glucaric acid from the acid mixture generally comprises a system 100 in which the method may be carried out.

[0020] In some embodiments disclosed with reference to Figure 1 , the acid mixture may be introduced into a moisture vapor recompression (MVR) unit 110. In the MVR unit 110, the acid mixture may be concentrated to form a concentrated acid mixture 112. For example, in various aspects, the concentrated acid mixture 112 in which the water present in the concentrated acid mixture 112 is reduced, relative to the acid mixture 102, by at least about 5% by weight, additionally or alternatively, at least about 10% by weight, additionally or alternatively, at least about 15% by weight, additionally or alternatively, at least about 20% by weight, additionally or alternatively, at least about 25% by weight, additionally or alternatively, at least about 30% by weight, additionally or alternatively, at least about 35% by weight, additionally or alternatively, at least about 40% by weight, additionally or alternatively, at least about 45% by weight, additionally or alternatively, at least about 50% by weight, additionally or alternatively, at least about 60% by weight, additionally or alternatively, at least about 70% by weight, additionally or alternatively, at least about 80% by weight, additionally or alternatively, at least about 90% by weight.

[0021] In one or more aspects, the concentrated acid mixture 112 and potassium hydroxide 113 may then be directed to a mixer 115 where the concentrated acid mixture 112 and the potassium hydroxide 113 are comingled to yield formation of the potassium salt of the sugar acids (PSOA) stream 117. The PSOA stream 117 may comprise, for example, potassium gluconate, potassium glucarate, potassium glucuronate, potassium guluronate, and / or other potassium salts of organic acid salts, in varying proportions. In various aspects, the concentrated acid mixture and potassium hydroxide may be mixed at a ratio of at least about 10:1 , by wt., additionally or alternatively, at least about 5:1 , by wt., additionally or alternatively, at least about 4:1 , by wt., additionally or alternatively, at least about 3:1 , by wt., additionally or alternatively, at least about 2.5:1 , by wt., additionally or alternatively, at least about 2:1 , by wt, additionally or alternatively, at least about 1.5:1 , by wt., and / or not more than about 1 :1.5, by wt., additionally or alternatively, not more than about 1 :2, by wt., additionally or alternatively, not more than about 1 :2.5, by wt, additionally oralternatively, not more than about 1 :3, by wt., additionally or alternatively, not more than about 1 :3.5, by wt., additionally or alternatively, not more than about 1 :4, by wt., additionally or alternatively, not more than about 1 :4.5, by wt., additionally or alternatively, not more than about 1 :5, by wt.

[0022] Referring again to Figure 1 , the PSOA stream 117 may be conveyed to a crystallizer 120. Generally, the crystallizer 120 may be configured to cause the PSOA stream 117 to be cooled and mixed, while cooling, so as to form a crystalline potassium glucarate (CPG)-containing stream 122, for example, to cause at least a portion of the potassium glucarate in the PSOA stream 117 to be crystalized. For example, and not intending to be bound by theory, potassium glucarate may be readily precipitated as crystalline potassium glucarate from the CPG-containing stream, while other, more soluble potassium salts of organic acids having relatively higher solubility may remain in solution.

[0023] As shown in Figure 1 , the CPG-containing stream 122 may be conveyed to a centrifuge 130. In the centrifuge 130, the crystalized potassium glucarate may be separated from the remainder of the CPG-containing stream 122 to form a potassium salt slurry stream 132 and a solid potassium glucarate stream 136. Generally, the solid potassium glucarate stream 136 may comprise substantially pure potassium glucarate, for example, at least about 80%, by weight, potassium glucarate, additionally or alternatively, at least about 85%, by weight, potassium glucarate, additionally or alternatively, at least about 90% by weight, potassium glucarate, additionally or alternatively, at least about 95%, by weight, potassium glucarate, additionally or alternatively, at least about 96%, by weight, potassium glucarate, additionally or alternatively, at least about 97%, by weight, potassium glucarate, additionally or alternatively, at least about 98%, by weight, potassium glucarate, additionally or alternatively, at least about 99%, by weight, potassium glucarate, additionally or alternatively, at least about 99.5%, by weight, potassium glucarate. The potassium salt slurry stream 132 may generally comprise, for example, potassium gluconate, potassium glucarate, potassium glucuronate, potassium guluronate, and / or other organic acids in varying proportions. Generally, the proportion of potassium glucarate in the potassium salt slurry stream 132 may be may be substantially reduced relative to the PSOA stream 117, for example, such that at least about 50%, by weight, of the potassium glucarate present in the PSOA stream 117 is removed in the solid potassium glucarate stream 136, additionally or alternatively, at least about 60%, byweight, of the potassium glucarate, additionally or alternatively, at least about 70%, by weight, of the potassium glucarate, additionally or alternatively, at least about 80%, by weight, of the potassium glucarate, additionally or alternatively, at least about 85%, by weight, of the potassium glucarate, additionally or alternatively, at least about 90%, by weight, of the potassium glucarate, additionally or alternatively, at least about 95%, by weight, of the potassium glucarate present in the PSOA stream 117 is removed in the solid potassium glucarate stream 136.

[0024] In some embodiments, a first portion of the potassium salt slurry stream 132 may returned to the crystallizer 120 as a potassium salt slurry recycle stream 134. For example, as shown in Figure 1 , the potassium salt slurry recycle stream 134 may be mixed with the PSOA stream 117 prior to introduction into the crystallizer 120; alternatively, the potassium salt slurry recycle stream 134 may be introduced directly in the crystallizer 120. Not intending to be bound by theory, returning the first portion of the potassium salt slurry stream 132 to the crystallizer (for example, as the potassium salt slurry recycle stream 134), may provide the opportunity to recover previously unrecovered potassium glucarate originally present in the PSOA stream 117.

[0025] Additionally or alternatively, in some embodiments, a second portion of the potassium salt slurry stream 133 may, optionally, be directed to a processing system 125 for further processing, for example, such as one or more oxidation steps, so as to yield one or more by-products comprising potassium gluconate, potassium glucarate, potassium glucuronate, potassium guluronate, and / or other potassium salts of organic acid salts, in varying proportions. One or more embodiments of such additional processing are disclosed with respect to Figure 2, as disclosed herein. Generally, the proportion of the potassium salt slurry 132 directed towards the first and second portions of the potassium salt slurry stream 132, respectively, may vary based upon factors including, but not limited to, proportion of the amount of potassium glucarate in the potassium salt slurry stream 133. For example, where relative little potassium glucarate remains in the potassium salt slurry stream 133 (for example, where the potassium salt slurry stream 133 comprises at least about 80%, by weight, of components other than potassium glucarate, additionally or alternatively, at least about 85%, by weight, of components other than potassium glucarate, additionally or alternatively, at least about 90%, by weight, of components other than potassium glucarate, additionally or alternatively, at least about 95%, by weight, of componentsother than potassium glucarate) most or all of the potassium salt slurry stream may be directed to the processing system 125.

[0026] Referring again to Figure 1 , in some embodiments, solid potassium glucarate stream 136 may be conveyed to a dissolution tank 140. In the dissolution tank, the solid, crystalline potassium glucarate may be mixed with water to form dissolved potassium glucarate stream 142.

[0027] As shown in Figure 1 , the dissolved potassium glucarate stream 142 may be conveyed to an electrodialysis stack 150. In the electrodialysis stack 150, the potassium ion may be replaced and / or removed, as will be disclosed herein. Removal of potassium ion results in free potassium which can form a salt with hydroxide ions and be recycled into the system of potassium hydroxide recycle stream 154. For example, the potassium hydroxide recycle stream 154 may form at least a portion of the potassium hydroxide 113 introduced into the mixer 115. As such, the electrodialysis stack 150 may yield a free acid, that is, a glucaric acid stream 152. In some embodiments, a portion of the glucaric acid stream 152 may be recycled to the dissolution tank 140.

[0028] In one or more embodiments, electrodialysis, such as via an electrodialysis stack, may also be effective to convert a potassium gluconate stream into either gluconic acid or sodium gluconate. Not intending to be bound by theory, since potassium gluconate is used far less often the gluconic acid or sodium gluconate, this converts a side stream to higher one or more higher value products, while regenerating more of the potassium hydroxide used.

[0029] For example, referring to Figure 2, additional or alternative embodiments of a system 200 and method for the purification of an acid mixture 202, for example, a mixture of gluconic acid, guluronic acid and glucaric acid, is depicted schematically. Generally, the embodiment of Figure 2 utilities one or more components, streams, and / or process steps of Figure 1 and, as such, the discussion of analogous components, streams, and / or process steps disclosed with respect to Figure 1 is likewise be applicable to the disclosure with respect to Figure 2.

[0030] With reference to Figure 2, in some embodiments, the second portion of the potassium salt slurry stream 133 may, optionally, be directed to a processing system 125 for further processing, and may be conveyed to an electrodialysis stack 230. In some embodiments, optionally, sodium hydroxide 228 may be introduced into the electrodialysis stack 230. In one or more aspects, in the electrodialysis stack 230, thepotassium salts of organic acids present in the second portion of the potassium salt slurry stream 233 may be converted to the corresponding sodium salts of organic acids, via the operation of the electrodialysis stack 230. Additionally, a second potassium hydroxide recycle stream 234 formed in the electrodialysis stack 230 may form at least a portion of the potassium hydroxide 113 introduced into the mixer 115, as similarly discussed with respect to Figure 1 .

[0031] In some embodiments, electrodialysis may be used to fractionate gluconic acid from glucaric acid via a cascade of electrodialysis membranes that are configured to selectively separate mono-carboxylic acids (for example, gluconic acid) and dicarboxylic acids (for example, glucaric acid). Gluconic acid and glucaric acid anions have a negative charge (coupled to the hydrogen / hydronium ion’s positive charge), but the magnitude differs by a factor of 2. This may lead to an imperfect separation for each electrodialysis stack, so a series of cascades may be employed to achieve a desired degree of separation, for example, analogous to a multistage distillation, multistage liquid-liquid extraction, or multi-stage ultrafiltration. Examples of such configurations may be achieved by selecting for diacids (i.e. glucaric acid), as in the configuration of Figure 3, or by selecting for the monoacid (i.e. gluconic), as in the configuration of Figure 4.

[0032] For example, Figure 3 is a system 300 comprising a plurality of electrodialysis stages. The system 300 of Figure 3 illustrates the use of electrodialysis to separate (e.g., fractionate) gluconic acid from glucaric acid via a cascade of electrodialysis membranes that select between mono-carboxylic acids (for example, gluconic acid) and di-carboxylic acids (for example, glucaric acid).

[0033] With reference to Figure 3, in one or more aspects, a mixed organic acid stream 318 comprising, for example, gluconic acid, glucoronic acid, guluronic acid, glucaric acid, and water may be conveyed to a first electrodialysis stage 320 that is configured to separate monoacids (for example, mono-carboxylic acids) from diacids (for example, di-carboxylic acids). In the embodiment of Figure 3, the first electrodialysis stage 320 produces a first diacid-rich stream 324 and a first diacid-lean stream 322. A first portion of the first diacid-rich stream 324 may be conveyed back into the mixed organic acid stream 318 to be recycled through the first electrodialysis stage 320. A second portion of the first diacid-rich stream 324 may be withdrawn as a diacid product stream 326. The diacid product stream 326 may comprise generally comprise substantially pure diacids and trace amounts of monoacids. For example, the diacidproduct stream 326 may comprise at least about 80%, by weight, glucaric acid, additionally or alternatively, at least about 85%, by weight, additionally or alternatively, at least about 90%, by weight, additionally or alternatively, at least about 95%, by weight, additionally or alternatively, at least about 96%, by weight, additionally or alternatively, at least about 97%, by weight, additionally or alternatively, at least about 98%, by weight, additionally or alternatively, at least about 99%, by weight, glucaric acid.

[0034] Referring again to Figure 3, the first diacid-lean stream 322 may be conveyed to a second electrodialysis stage 340 that is also configured to separate monoacids (for example, mono-carboxylic acids) from diacids (for example, di-carboxylic acids). In the embodiment of Figure 3, the second electrodialysis stage 340 produces a second diacid-rich stream 344 and a monoacid product stream 342. A portion of the second diacid-rich stream 344 may be conveyed back into the first diacid-lean stream 322 to be recycled through the second electrodialysis stage 340 and a portion of the second diacid-rich stream 344 may be conveyed back into the mixed organic acid stream 318 to be recycled through the first electrodialysis stage 320. Additionally or alternatively, a portion of the second diacid-rich stream 344 may be withdrawn as a purge-stream 346, for example, to prevent accumulation of diacids. The monoacid product stream 342 may comprise generally comprise substantially pure monoacids and trace amounts of diacids. For example, the monoacid product stream 342 may comprise at least about 80%, by weight, gluconic acid, glucuronic acid, and / or guluronic acid, additionally or alternatively, at least about 85%, by weight, additionally or alternatively, at least about 90%, by weight, additionally or alternatively, at least about 95%, by weight, additionally or alternatively, at least about 96%, by weight, additionally or alternatively, at least about 97%, by weight, additionally or alternatively, at least about 98%, by weight, additionally or alternatively, at least about 99%, by weight, gluconic acid, glucuronic acid, and / or guluronic acid.

[0035] Figure 4 is another system 400 comprising a plurality of electrodialysis stages. Similar to the system 300 of Figure 3, the system 400 of Figure illustrates the use of electrodialysis to separate (e.g., fractionate) gluconic acid from glucaric acid via a cascade of electrodialysis membranes that select between mono-carboxylic acids (for example, gluconic acid) and di-carboxylic acids (for example, glucaric acid).

[0036] With reference to Figure 4, in one or more aspects, a mixed organic acid stream 418 comprising, for example, gluconic acid, glucoronic acid, guluronic acid,glucaric acid, and water may be conveyed to a first electrodialysis stage 420 that is configured to separate monoacids (for example, mono-carboxylic acids) from diacids (for example, di-carboxylic acids). In the embodiment of Figure 4, the first electrodialysis stage 420 produces a first monoacid-rich stream 424 and a first monoacid-lean stream 422. A first portion of the first monoacid-rich stream 424 may be conveyed back into the mixed organic acid stream 418 to be recycled through the first electrodialysis stage 420. A second portion of the first monoacid-rich stream 424 may be withdrawn as a monoacid product stream 426. The monoacid product stream 426 may comprise generally comprise substantially pure monoacids and trace amounts of diacids. For example, the monoacid product stream 426 may comprise at least about 80%, by weight, gluconic acid, glucuronic acid, and / or guluronic acid, additionally or alternatively, at least about 85%, by weight, additionally or alternatively, at least about 90%, by weight, additionally or alternatively, at least about 95%, by weight, additionally or alternatively, at least about 96%, by weight, additionally or alternatively, at least about 97%, by weight, additionally or alternatively, at least about 98%, by weight, additionally or alternatively, at least about 99%, by weight, glucaric acid.

[0037] Referring again to Figure 4, the first monoacid-lean stream 422 may be conveyed to a second electrodialysis stage 440 that is also configured to separate monoacids (for example, mono-carboxylic acids) from diacids (for example, dicarboxylic acids). In the embodiment of Figure 4, the second electrodialysis stage 440 produces a second monoacid-rich stream 444 and a diacid product stream 442. A portion of the second monoacid-rich stream 444 may be conveyed back into the first monoacid-lean stream 422 to be recycled through the second electrodialysis stage 440 and a portion of the second monoacid-rich stream 444 may be conveyed back into the mixed organic acid stream 418 to be recycled through the first electrodialysis stage 420. Additionally or alternatively, a portion of the second monoacid-rich stream 444 may be withdrawn as a purge-stream 446, for example, to prevent accumulation of monoacids. The diacid product stream 442 may comprise generally comprise substantially pure diacids and trace amounts of monoacids. For example, the diacid product stream 442 may comprise at least about 80%, by weight, glucaric acid, additionally or alternatively, at least about 85%, by weight, additionally or alternatively, at least about 90%, by weight, additionally or alternatively, at least about 95%, by weight, additionally or alternatively, at least about 96%, by weight, additionally oralternatively, at least about 97%, by weight, additionally or alternatively, at least about 98%, by weight, additionally or alternatively, at least about 99%, by weight, glucaric acid.

[0038] In one or more embodiments, potassium glucarate may be solubilized (and / or resolubilized) in water, forexample, a high-pH (e.g., greater than about 7.5), hydroxide rich, water. In such aspects, the potassium glucarate solution may comprise soluble (e.g., free-floating) potassium (K+) and glucarate (GA-) ions. In one of more embodiments disclosed herein, the ions may be separated via an electrodialysis membrane stack to produce a potassium free glucaric acid stream, and a potassium hydroxide stream which may be recycled back into the process.

[0039] For example, Figure 5A illustrates an embodiment of an electrodialysis stack 500 which utilizes a bipolar membrane-based configuration. The electrodialysis stack 500 generally comprises a cathode 510, a first bipolar membrane 520, a second bipolar membrane 522, a cation exchange membrane 530, an anion exchange membrane 540, and an anode 550. The first bipolar membrane 520 and bipolar exchange membrane 522 each comprise a cation exchange membrane 530 and an anion exchange membrane 540. In operation, water 502, potassium glucarate 506, and potassium hydroxide are introduced into the electrodialysis stack 500. Glucate (GA-) ions 514 from the potassium glucarate 506 are drawn through the cation exchange membrane 530 toward the cathode 510 and hydrogen (H+) ions migrate through the first bipolar membrane 520 toward the anode 550. The glucarate (GA-) ions 514 and hydrogen (H+) ions yield glucaric acid 508, which may be withdrawn from the electrodialysis stack 500. Also, potassium (K+) ions 516 from the potassium glucarate 506 are drawn through the anion exchange membrane toward the anode 550 and hydroxide (OH-) ions 518 migrate through the second bipolar membrane 522 toward the cathode 510. The potassium (K+) ions 516 and the hydroxide (OH-) ions 518 yield potassium hydroxide 504, which may be withdrawn from the electrodialysis stack 500.

[0040] Figure 5B illustrates an embodiment of an electrodialysis stack 600 which utilizes cation exchange membranes. The electrodialysis stack 600 generally comprises a cathode 610, a first cation exchange membrane 630, a second cation exchange membrane 640, and an anode 550. In operation, water 602 and potassium glucarate 606 are introduced into the electrodialysis stack 600. Hydrogen (H+) ions 612 are drawn through the first cation exchange membrane 630 toward the anode 650and interact with the potassium glucarate to 606 to yield glucaric acid 508. Also, potassium (K+) ions 516 from the potassium glucarate 506 are drawn through the second cation exchange membrane 640 toward the anode 650 to yield potassium hydroxide 616, which may be withdrawn from the electrodialysis stack 600.

[0041] As such, the systems and methods disclosed herein may be utilized to exchange a cation initially associated with a sugar acid with a desired cation as needed to meet some user or process goal. For example, the initial cation may be a Group 1 alkali metal, a Group 2 alkaline earth metal, a Group 8 metal, Group 11 metal, Group 12 metal, or combinations thereof. In one or more aspects the initial cation and final desired cation are selected from the group consisting of a proton, aluminum, calcium, magnesium, ammonium, sodium, potassium, cesium, strontium, zinc, copper, ferric iron, ferrous iron, or combinations thereof.

[0042] In one or more aspects, the methods disclosed herein result in the production of purified sugar acids with purity ranges of from about 60% to about 90%, additionally or alternatively, greater than about 70%, additionally or alternatively, greater than about 80%, additionally or alternatively, greater than about 90% or about 60%, about 61 %, about 62%, about 63%, about 64%, about 65%, about 66%, about 67%, about68%, about 69%, about 70%, about 71 %, about 72%, about 73%, about 74%, about75%, about 76%, about 77%, about 78%, about 79%, about 80%, about 81 %, about82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about89%, about 90%, about 91 %, about 92%, about 93%, about 94%, about 95%, about96%, about 97%, about 98%, or about 99%.

[0043] In one or more aspects, the cation content in sugar acid-containing solution may be reduced from about 10% to about 99% after subjecting the sugar acidcontaining solution to electrodialysis as disclosed herein, alternatively reduction of the cation may range from about 20% to about 99%, additionally or alternatively, from about 25% to about 90%, alternatively from about 30% to about 90%, additionally or alternatively, from about 35% to about 90%, alternatively from about 40% to about 80%, additionally or alternatively, from about 50% to about 75%, additionally or alternatively, from about 50% to about 70%, or about 10%, about 13%, about 16%, about 19%, about 22%, about 25%, about 28%, about 31 %, about 34%, about 37%, about 40%, about 43%, about 46%, about 49%, about 52%, about 55%, about 58%, about 61 %, about 64%, about 67%, about 70%, about 73%, about 76%, about 79%, about 82%, about 85%, about 88%, about 91 %, about 94%, about 97%, or about 99%.EXAMPLES

[0044] The following disclosure is an example of certain aspects disclosed herein. EXAMPLE 1

[0045] Glucose was oxidized in the presence of oxygen and an enzyme catalyst to form a product mixture and the product mixture subjected to electrodialysis. Table 1 provides the weight percent of components identified in the product mixture, initial, and subsequent to electrodialysis, final. The percent removal for each compound or ion investigated is summarized as percent removalTable 1

[0046] The data in Table 1 demonstrates the removal of gluconic acid and inorganic ions from an electrodialysis product stream, with minimal losses of the sugar of interest Electrodialysis can also be used to separate uncharged sugars from organic acids such as gluconic acid and inorganic salts also present in the feed to electrodialysis. Here, the process removes the charged organic acids and salts to the brine, whereas the uncharged sugars, unaffected by electrodialysis, may continue to a diluate stream.

[0047] While aspects of the presently disclosed subject matter have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the subject matter. The aspects described herein are exemplary only and are not intended to be limiting. Many variations and modifications of the subject matter disclosed herein are possible and are within the scope of the disclosed subject matter. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greaterthan 0.10 includes 0.11 , 0.12, 0.13, etc.). Use of the term "optionally" with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should beunderstood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc.

[0048] Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an aspect of the present disclosure. Thus, the claims are a further description and are an addition to the aspects of the presently disclosed subject matter The discussion of a reference herein is not an admission that it is prior art to the presently disclosed subject matter, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural or other details supplementary to those set forth herein.

Claims

CLAIMSWhat is claimed is:

1. A method for metal ion reduction comprising:(i) introducing a sugar acid solution to a system comprising an electrodialysis unit, wherein the sugar acid solution comprises (i) a sugar acid (ii) one or more initial cations and (iii) a solvent;(ii) subjecting the sugar acid solution to electrodialysis under conditions suitable for removal of the initial cation and formation of a sugar free acid; and(iii) recovering the sugar free acid wherein the sugarfree acid has a purity of from about 60% to about 90%.

2. The method of claim 1 , wherein the sugar acid comprises aldaric acid, uronic acid, glucaric acid, gluconic acid, glucuronic acid, glucose oxidation products, gluconic acid oxidation products, disaccharides, oxidized disaccharides, n-keto- acids, C2-C6 diacids, galactonic acid, galactaric acid, glutamic acid, glucodialdose, 2-ketoglucose, glucodiamine, glycoaldehyde, glyoxal, salts thereof, lactones thereof, or combinations thereof.

3. The method of claim 1 , wherein the initial cation is selected from the group consisting of a proton, aluminum, calcium, magnesium, ammonium, sodium, potassium, cesium, strontium, zinc, copper, ferric iron, ferrous iron, or combinations thereof4. The method of claim 1 , wherein the sugar acid solution comprises water.

5. The method of claim 1, wherein the sugar acid solution comprises from about 50 wt.% to about 95 wt.% sugar acid based on the total weight of the sugar acid solution.

6. The method of claim 1 , wherein the sugar acid solution has a pH of from about 5.0 to about 8.0.

7. The method of claim 1 , wherein free sugar acid has a purity of greater than about8. The method of claim 1 , wherein a cation content of the sugar acid solution is reduced by from about 20% to about 99%.

9. A method for metal ion exchange comprising:(i) introducing a sugar acid solution to a system comprising an electrodialysis unit, wherein the sugar acid solution comprises (i) a sugar acid (ii) one or more initial cations and (iii) a solvent;(ii) subjecting the sugar acid solution to electrodialysis under conditions suitable for exchanging of the initial cation with a desired cation to form a desired salt complex; and(iii) recovering the desired salt complex.

10. The method of claim 9, wherein the sugar acid comprises aldaric acid, uranic acid, glucaric acid, gluconic acid, glucuronic acid, glucose oxidation products, gluconic acid oxidation products, disaccharides, oxidized disaccharides, n-keto- acids, C2-C6 diacids, galactonic acid, galactaric acid, glutamic acid, glucodialdose, 2-ketoglucose, glucodiamine, glycoaldehyde, glyoxal, salts thereof, lactones thereof, or combinations thereof.11 . The method of claim 9, wherein the initial cation and desired is selected from the group consisting of a proton, aluminum, calcium, magnesium, ammonium, sodium, potassium, cesium, strontium, zinc, copper, ferric iron, ferrous iron, or combinations thereof12. The method of claim 9, wherein the sugar acid solution comprises water.

13. The method of claim 9, wherein the sugar acid solution comprises from about 50 wt.% to about 95 wt.% sugar acid based on the total weight of the sugar acid solution.

14. The method of claim 9, wherein the sugar acid solution has a pH of from about 5.0 to about 8.0.

15. The method of claim 9, wherein desired salt complex has a purity of greater than about 70%.

16. The method of claim 9, wherein the amount of the initial cation is reduced by from about 20% to about 99%.

17. A method for metal ion reduction comprising:(i) introducing a sugar acid solution to a system comprising an electrodialysis unit wherein the sugar acid solution comprises (i) a sugar acid-sodium complex and(ii) a solvent;(ii) subjecting the sugar acid solution to electrodialysis under conditions suitable for removal of a sodium cation and formation of a sugar acid-potassium complex; and(iii) recovering the sugar acid-potassium complex wherein the sugar acid- potassium complex has a purity of from about 60% to about 90%.

18. The method of claim 17, wherein the sugar acid comprises aldaric acid, uronic acid, glucaric acid, gluconic acid, glucuronic acid, glucose oxidation products, gluconic acid oxidation products, disaccharides, oxidized disaccharides, n-keto- acids, C2-C6 diacids, galactonic acid, galactaric acid, glutamic acid, glucodialdose, 2-ketoglucose, glucodiamine, glycoaldehyde, glyoxal, salts thereof, lactones thereof, or combinations thereof.

19. The method of claim 17, wherein the sugar acid comprises gluconate.

20. The method of claim 17, wherein the sugar acid solution comprises from about 50 wt.% to about 95 wt.% sugar acid based on the total weight of the sugar acid solution.

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