Separation and decolorization method for oxalic acid electrolyte prepared by oxalic acid electrolysis using electrodialysis method

Abstract

The application provides a separation and decolorization method for preparing glyoxylic acid electrolyte by oxalic acid electrolysis through an electrodialysis method, and the method comprises the following steps: freezing treatment is performed on the glyoxylic acid electrolyte, so that oxalic acid is crystallized and separated out, and after solid-liquid separation, pretreated electrolyte is obtained; and the pretreated electrolyte is subjected to electrodialysis treatment, so that residual oxalic acid is removed and decolorization is realized, and high-purity glyoxylic acid product is obtained. The separation and decolorization method solves the problems of over-standard chroma of glyoxylic acid product, incomplete separation of oxalic acid and glyoxylic acid, and unstable product quality in the two-step crystallization process of the existing method for preparing glyoxylic acid by oxalic acid electrolysis.

Description

Technical Field

[0001] This invention relates to the field of purification and decolorization technology, and in particular to a separation and decolorization method for preparing glyoxylic acid electrolyte by oxalic acid electrolysis using electrodialysis. Background Technology

[0002] Glyoxylic acid is a high-value-added core intermediate in fine chemicals, possessing both aldehyde and carboxyl group reactivity. It is widely used in pharmaceuticals (synthetic antibiotics, wound healing drugs), chemicals (fragrances, biodegradable materials), agriculture (low-toxicity herbicides), and cosmetics (moisturizing and skincare raw materials), with downstream products commanding significant premiums. There are numerous methods for synthesizing glyoxylic acid, the mainstream ones being the glyoxal-nitric acid oxidation method, the ozone oxidation of maleic anhydride method, and the oxalic acid electrolytic reduction method. The glyoxal-nitric acid oxidation method is relatively mature, with mild reaction conditions but significant pollution, suitable for large-scale production of low-quality products. The ozone oxidation of maleic anhydride method produces high-quality, high-purity products, but requires higher equipment investment and consumes more electricity.

[0003] The oxalic acid electrolytic reduction method is a promising technical route in the current field of glyoxylic acid synthesis. It uses inexpensive and abundant oxalic acid as a raw material, electrolytically reducing it at the cathode of an electrolytic cell to produce a glyoxylic acid electrolyte with a glyoxylic acid content of 4%–8% and an oxalic acid content of 1%–9%. This is then followed by a two-step crystallization process of "vacuum evaporation + cooling crystallization," followed by filtration to obtain a glyoxylic acid product with a purity of 45%–55%. This process has significant advantages in terms of being environmentally friendly and using readily available raw materials. However, the existing two-step crystallization process has two major drawbacks: First, during industrial vacuum evaporation, the electrolyte contains both glyoxylic acid and oxalic acid, making precise temperature control difficult. This can easily lead to high-temperature deterioration and discoloration of the glyoxylic acid, and also results in high energy consumption, increasing economic costs. Second, cooling crystallization relies solely on the difference in solubility of oxalic acid at different temperatures for separation, making it difficult to completely remove oxalic acid impurities from the glyoxylic acid solution. This results in substandard product purity, which in turn affects the quality and application effects of downstream products. Therefore, developing a new process is of paramount importance to solve the core problems of excessive color and incomplete separation of oxalic acid and glyoxylic acid in the two-step crystallization process. Summary of the Invention

[0004] Based on the technical problems existing in the background art, the present invention proposes an electrodialysis method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis. This solves the problems of excessive color of glyoxylic acid product, incomplete separation of oxalic acid and glyoxylic acid, and unstable product quality in the existing two-step crystallization process for preparing glyoxylic acid by oxalic acid electrolysis.

[0005] This invention proposes an electrodialysis method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis, comprising the following steps: S1. The glyoxylic acid electrolyte is frozen to cause oxalic acid to crystallize out. After solid-liquid separation, a pretreated electrolyte is obtained. S2. The pretreated electrolyte is subjected to electrodialysis to remove residual oxalic acid and achieve decolorization, thereby obtaining a high-purity glyoxylic acid product.

[0006] In this invention, the electrolyte for the electrolytic preparation of glyoxylic acid from oxalic acid is first pretreated. Utilizing the principle that the solubility of oxalic acid decreases rapidly with decreasing temperature, a reaction electrolyte containing a large amount of oxalic acid crystals is obtained through freezing. The oxalic acid crystals are then removed by centrifugation, resulting in a pretreated electrolyte containing glyoxylic acid and a small amount of oxalic acid. This prevents oxalic acid precipitation from clogging the electrodialysis membrane and improves electrodialysis separation efficiency. Subsequently, the pretreated electrolyte is purified for glyoxylic acid using electrodialysis. This method is simple to operate, has low energy consumption, and a high impurity removal rate, achieving effective removal of oxalic acid with a glyoxylic acid recovery rate greater than or equal to 70 wt%.

[0007] Preferably, in step S1, the freezing process is carried out using a freezing device; Specifically, the freezing temperature of the freezing device is -5 to -20°C, and the freezing time is 2 to 6 hours.

[0008] Preferably, the concentration of oxalic acid in the pretreated electrolyte is not higher than 2 wt%. Preferably, the pretreated electrolyte has a pH of 0.5 to 1.5, a glyoxylic acid concentration of 4 to 7 wt%, and an oxalic acid concentration of 1 to 2 wt%.

[0009] Preferably, in step S2, the electrodialysis treatment is performed using an electrodialysis device; Specifically, the pretreatment electrolyte is added to the desalination tank, ultrapure water is added to the concentrate tank, and the electrode solution is added to the electrode water tank. After starting the electrodialysis device for the first electrodialysis, the concentrate product 1 in the concentrate tank is exported. Then, ultrapure water is added to the concentrate tank, and the electrodialysis device is started for the second electrodialysis. The concentrate product 2 in the concentrate tank and the desalination product in the desalination tank are exported.

[0010] Preferably, the aqueous solution is a sodium chloride, sodium sulfate, or dilute sulfuric acid solution; Preferably, the concentration of the extreme aqueous solution is 3 to 10 wt%.

[0011] In this invention, the sodium chloride electrode aqueous solution is consumed at a relatively high rate during electrodialysis, and frequent replenishment of sodium chloride can ensure stable use; the sodium sulfate electrode aqueous solution is consumed at a relatively low rate during electrodialysis, and regular replenishment of sodium sulfate and water can ensure stable use; the dilute sulfuric acid electrode aqueous solution is consumed at an extremely low rate during electrodialysis, and regular monitoring and replenishment of sulfuric acid can ensure stable use.

[0012] In this invention, during the electrodialysis process, the conductivity and pH of the desalinated water and the concentrated water are continuously measured. When the conductivity of the desalinated water continuously decreases and the conductivity of the concentrated water continuously increases to the highest point and tends to stabilize, the operation is stopped, and the concentrated water is taken out as concentrated water product 1. After the concentrated water is drained, ultrapure water is added again to the concentrated water tank. Under the same voltage and flow conditions, the pretreatment electrolyte is electrodialyzed again. The conductivity of the desalinated water continues to decrease. When the conductivity of the concentrated water continuously increases to the highest point and tends to stabilize, the operation is stopped, and the desalinated water product and concentrated water product 2 are taken out.

[0013] Preferably, in both the first and second electrodialysis processes, the voltage of the electrodialysis device is controlled at 4–14V, and the flow rate is controlled at 50–90L / h.

[0014] Preferably, the freshwater product has a pH of 1.2-2, a glyoxylic acid concentration of 4-6 wt%, and an oxalic acid concentration of 0-0.05 wt%; the concentrated water product 1 has a pH of 1-1.5, a glyoxylic acid concentration of 0.5-1.5 wt%, and an oxalic acid concentration of 1.5-3 wt%; and the concentrated water product 2 has a pH of 1.2-2, a glyoxylic acid concentration of 0.8-1.8 wt%, and an oxalic acid concentration of 0.5-1.5 wt%.

[0015] Preferably, the recovery rate of glyoxylic acid in the freshwater product is 70-85%, and the recovery rate of oxalic acid in the concentrated water products 1 and 2 is 90-100%.

[0016] In this invention, the decolorization rate is higher than 99% when comparing freshwater products with the reaction electrolyte. The calculation methods for the decolorization rate, glyoxylic acid recovery rate, and oxalic acid recovery rate are as follows:

[0017] In the formula, C represents platinum-cobalt colorimetry, and m represents mass.

[0018] In this invention, the freshwater product can be further dehydrated to obtain a glyoxylic acid product with a concentration of 45-55 wt%. Compared with the glyoxylic acid product obtained by the two-step crystallization process of "vacuum evaporation + cooling crystallization", the former product has a significantly lower color and more thorough oxalic acid separation, which can obtain a high-quality glyoxylic acid product. At the same time, the concentrated water product can be collected and reused in the process of preparing glyoxylic acid by oxalic acid electrolysis.

[0019] Preferably, after the first electrodialysis, in addition to exporting the concentrated product 1 from the concentrated water tank, the process also includes exporting the fresh water product from the fresh water tank, loading the fresh water product onto a weakly basic anion exchange resin for adsorption and elution, adding the eluent to the fresh water tank, adding ultrapure water to the concentrated water tank, and starting the electrodialysis device for the second electrodialysis.

[0020] Preferably, the weakly basic anion exchange resin is an anion exchange resin with styrene-divinylbenzene copolymer as the inert backbone and polyol amine groups as functional groups.

[0021] In this invention, the separation effect of glyoxylic acid can be further improved by chromatographic separation between the first and second electrodialysis processes; and compared with general weakly basic anion exchange resins, anion exchange resins with styrene-divinylbenzene copolymer as inert backbone and polyol amine groups as functional groups can achieve more effective separation and purification of glyoxylic acid and obtain higher recovery efficiency.

[0022] In this invention, the weakly basic anion exchange resin is obtained by nucleophilic substitution reaction of tertiary amine anion exchange resin D301 and epichlorohydrin, followed by branching modification reaction with triethylenetetramine. The reaction route is shown below:

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Excellent separation and decolorization effect, good repeatability, and can effectively overcome the defects of "vacuum evaporation + cooling crystallization" process such as excessive product color and incomplete oxalic acid separation, forming an efficient alternative solution; (2) The process is simple, no complex supporting equipment is required, the equipment investment cost is controllable, and it is easy to promote industrialization; (3) The freshwater product obtained after treatment can be used directly as the product solution of glyoxylic acid. After simple dehydration, a high-quality product with a purity of 45-55% and color meeting the standard can be obtained, thereby realizing product value-added. (4) The oxalic acid crystals recovered from the pretreatment of the reaction electrolyte and the concentrated water product obtained after electrodialysis can be recycled and reused as electrolytic raw materials to achieve resource recycling and have the dual benefits of green environmental protection and cost reduction and efficiency improvement. Attached Figure Description

[0024] Figure 1 This is a flowchart of the separation and decolorization process of the electrodialysis method used in the preparation of glyoxylic acid electrolyte by oxalic acid electrolysis according to the present invention; Figure 2 This is a flowchart of the existing two-step crystallization process of "vacuum evaporation + cooling crystallization". Detailed Implementation

[0025] Example 1

[0026] Reference Figure 1 This embodiment proposes an electrodialysis method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis, specifically including the following steps: (1) The reaction electrolyte (platinum cobalt color of 286.5, pH of 0.862, glyoxylic acid concentration of 4.45wt%, oxalic acid concentration of 4.95wt%) prepared by oxalic acid electrolysis device is frozen in a freezing device at a freezing temperature of -10℃ for 3h to obtain an electrolyte with a large amount of oxalic acid crystals precipitated. After removing the oxalic acid crystals by centrifugation, a pretreated electrolyte (glyoxylic acid concentration of 5.93wt%, oxalic acid concentration of 1.60wt%, pH of 1.142, conductivity of 21.8mS / cm) is obtained. (2) The pretreated electrolyte was subjected to electrodialysis using an electrodialysis device. Specifically, 1L of pretreated electrolyte was added to the desalination tank, 0.5L of ultrapure water was added to the concentrate tank, and 1L of sodium chloride solution (5wt% sodium chloride concentration) was added to the electrode water tank. The desalination pump, concentrate pump, and electrode water pump were turned on to ensure stable circulation of the pretreated electrolyte, concentrate, and electrode water. The voltage of the electrodialysis device was controlled at 12V and the flow rate at 50L / h. The pretreated electrolyte was subjected to the first electrodialysis treatment. During the electrodialysis process, the desalination and concentrate concentrations were continuously measured. The conductivity and pH of the water were measured. The conductivity of the fresh water decreased continuously. When the conductivity of the concentrate increased to a maximum of 28.1 mS / cm and then stabilized, the operation was stopped, and concentrate product 1 was discharged. After the concentrate was drained, the same volume of ultrapure water was added to the concentrate tank again. Under the same voltage and flow conditions, the pretreatment electrolyte was subjected to a second electrodialysis treatment. The conductivity of the fresh water continued to decrease. When the conductivity of the concentrate increased again to a maximum of 11.36 mS / cm and then stabilized, the operation was stopped, and fresh water product 2 and concentrate product 2 were discharged respectively. The concentration composition of the above-mentioned freshwater products and concentrated water products 1 and 2 was measured and recorded in Table 1: Table 1 Concentration composition of freshwater and concentrated water products in Example 1

[0027] Based on the calculations in Table 1 above, the decolorization rate is 100%, the glyoxylic acid recovery rate in the freshwater product is 79.70%, and the oxalic acid recovery rate in the concentrated water product is 99.46%.

[0028] Example 2 Reference Figure 1 This embodiment proposes an electrodialysis method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis, specifically including the following steps: (1) The reaction electrolyte (platinum cobalt color value of 286.5, pH of 0.862, glyoxylic acid concentration of 4.45wt%, oxalic acid concentration of 4.95wt%) was treated according to step (1) of Example 1 to obtain a pretreated electrolyte; (2) The pretreated electrolyte was subjected to electrodialysis using an electrodialysis device. Specifically, 1L of pretreated electrolyte was added to the desalination tank, 0.5L of ultrapure water to the concentrate tank, and 1L of sodium sulfate solution (5wt% sodium sulfate concentration) to the electrode water tank. The desalination pump, concentrate pump, and electrode water pump were turned on to ensure stable circulation of the pretreated electrolyte, concentrate, and electrode water. The voltage of the electrodialysis device was controlled at 8V and the flow rate at 90L / h. The pretreated electrolyte was subjected to the first electrodialysis treatment. During the electrodialysis process, the concentrations of the desalination water and concentrate were continuously measured. Conductivity and pH: The conductivity of the freshwater continuously decreases. When the conductivity of the concentrate continuously increases to the highest point of 27.4 mS / cm and tends to stabilize, the operation is stopped, and concentrate product 1 is discharged. After the concentrate is drained, the same volume of ultrapure water is added back to the concentrate tank. Under the same voltage and flow conditions, the pretreatment electrolyte is subjected to a second electrodialysis treatment. The conductivity of the freshwater continues to decrease. When the conductivity of the concentrate again continuously increases to the highest point of 16.86 mS / cm and tends to stabilize, the operation is stopped, and freshwater product and concentrate product 2 are discharged respectively. The concentration composition of the above-mentioned freshwater products and concentrated water products 1 and 2 was measured and recorded in Table 2: Table 2 Concentration composition of freshwater and concentrated water products in Example 2

[0029] According to Table 2 above, the decolorization rate is 100%, the glyoxylic acid recovery rate in freshwater products is 77.14%, and the oxalic acid recovery rate in concentrated water products is 98.17%.

[0030] Example 3 Reference Figure 1 This embodiment proposes an electrodialysis method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis, specifically including the following steps: (1) The reaction electrolyte (platinum cobalt color value of 286.5, pH of 0.862, glyoxylic acid concentration of 4.45wt%, oxalic acid concentration of 4.95wt%) was treated according to step (1) of Example 1 to obtain a pretreated electrolyte; (2) The pretreated electrolyte was subjected to electrodialysis using an electrodialysis device. Specifically, 1L of pretreated electrolyte was added to the desalination tank, 0.5L of ultrapure water to the concentrate tank, and 1L of sulfuric acid solution (3wt% sulfuric acid concentration) to the electrode water tank. The desalination pump, concentrate pump, and electrode water pump were turned on to ensure stable circulation of the pretreated electrolyte, concentrate, and electrode water. The voltage of the electrodialysis device was controlled at 14V and the flow rate at 60L / h. The pretreated electrolyte was subjected to the first electrodialysis treatment. During the electrodialysis process, the concentrations of the desalination water and concentrate were continuously measured. Conductivity and pH: The conductivity of the freshwater continuously decreases. When the conductivity of the concentrate continuously increases to the highest point of 27.2 mS / cm and tends to stabilize, the operation is stopped, and concentrate product 1 is discharged. After the concentrate is drained, the same volume of ultrapure water is added back to the concentrate tank. Under the same voltage and flow conditions, the pretreatment electrolyte is subjected to a second electrodialysis treatment. The conductivity of the freshwater continues to decrease. When the conductivity of the concentrate again continuously increases to the highest point of 14.75 mS / cm and tends to stabilize, the operation is stopped, and freshwater product and concentrate product 2 are discharged separately. The concentration composition of the above-mentioned freshwater products and concentrated water products 1 and 2 was measured and recorded in Table 3: Table 3 Concentration composition of freshwater and concentrated water products in Example 3

[0031] Based on the calculations in Table 1 above, the decolorization rate is 100%, the glyoxylic acid recovery rate in the freshwater product is 82.59%, and the oxalic acid recovery rate in the concentrated water product is 98.88%.

[0032] 1 L of decolorized freshwater product after electrodialysis was collected and evaporated to remove water, yielding glyoxylic acid product with a concentration of 50.45 wt%, an oxalic acid concentration of 0.11 wt%, and a platinum-cobalt color of 227.3.

[0033] Example 4 This embodiment proposes a separation and decolorization method using electrodialysis for preparing glyoxylic acid electrolyte by oxalic acid electrolysis, specifically including the following steps: (1) The reaction electrolyte (platinum cobalt color value of 286.5, pH of 0.862, glyoxylic acid concentration of 4.45wt%, oxalic acid concentration of 4.95wt%) was treated according to step (1) of Example 1 to obtain a pretreated electrolyte; (2) The pretreated electrolyte was subjected to electrodialysis using an electrodialysis device. Specifically, 1L of pretreated electrolyte was added to the desalination tank, 0.5L of ultrapure water was added to the concentrate tank, and 1L of sulfuric acid solution (sulfuric acid concentration of 3wt%) was added to the electrode water tank. The desalination pump, concentrate pump, and electrode water pump were turned on to ensure stable circulation of the pretreated electrolyte, concentrate, and electrode water. The voltage of the electrodialysis device was controlled at 14V and the flow rate at 60L / h. The pretreated electrolyte was subjected to the first electrodialysis treatment. During the electrodialysis process, the conductivity and pH of the desalination and concentrate were continuously measured. The conductivity of the desalination continuously decreased, and the conductivity of the concentrate continuously increased to its maximum. When the conductivity reaches 27.2 mS / cm and tends to stabilize, the operation is stopped, and concentrated product 1 and desalinated intermediate are exported. The desalinated intermediate is fed into the exchange column of a weakly basic anion exchange resin for ion exchange at a flow rate of 1.0 BV / h. The resulting ion exchange solution is added back to the desalinated tank, and the same volume of ultrapure water is added back to the concentrated tank. Under the same voltage and flow conditions, the pretreated electrolyte is subjected to a second electrodialysis treatment. The conductivity of the desalinated water continues to decrease. When the conductivity of the concentrated water increases again to the highest point of 10.12 mS / cm and tends to stabilize, the operation is stopped, and the desalinated product and concentrated product 2 are exported respectively. The aforementioned weakly basic anion exchange resin is an anion exchange resin with styrene-divinylbenzene copolymer as the inert backbone and polyol amine groups as functional groups. Its specific preparation method includes: Macroporous weakly basic anion exchange resin (D301 resin) was added to N-methylpyrrolidone and swollen completely. Then, epichlorohydrin (20 wt% of D301 resin) was added to carry out a nucleophilic substitution reaction. The mixture was heated to 60°C and stirred for 12 h. Then, triethylenetetramine (10 wt% of D301 resin) was added to carry out branching modification. The mixture was heated to 80°C and stirred for 24 h. After the reaction was completed, the resin was poured into acetone to precipitate. After filtration, the precipitate was dried under vacuum to obtain the weakly basic anion exchange resin.

[0034] 1 L of decolorized freshwater product after electrodialysis was collected and evaporated to remove water, yielding glyoxylic acid product with a concentration of 50.49 wt%, an oxalic acid concentration of 0.03 wt%, and a platinum-cobalt color of 198.2.

[0035] In the above embodiments, if a macroporous weakly basic anion exchange resin (D301 resin) is directly used instead of the weakly basic anion exchange resin column described in Example 4 for ion exchange, the glyoxylic acid product obtained has a glyoxylic acid concentration of 50.37 wt%, an oxalic acid concentration of 0.10 wt%, and a platinum-cobalt color of 219.4.

[0036] Therefore, it can be seen that the separation effect of glyoxylic acid can be further improved by chromatographic separation between the first and second electrodialysis. Moreover, compared with general weakly basic anion exchange resins, anion exchange resins with styrene-divinylbenzene copolymer as inert backbone and polyol amine groups as functional groups can achieve more effective separation and purification of glyoxylic acid and obtain higher recovery efficiency.

[0037] Comparative Example 1 Reference Figure 2 This comparative example proposes a two-step crystallization method for the separation and decolorization of glyoxylic acid electrolyte prepared by oxalic acid electrolysis, specifically including the following steps: The reaction electrolyte (platinum-cobalt color value 286.5, pH 0.862, glyoxylic acid concentration 4.45 wt%, oxalic acid concentration 4.95 wt%) was evaporated using a vacuum evaporator at a controlled temperature of 50°C. After evaporation to remove water, crystallization was carried out using a freezing device. Specifically, ethylene glycol was used as the refrigerant, and crystallization was performed at -10°C. After centrifugation and filtration, the process of "vacuum evaporation + cooling crystallization + centrifugation" was repeated. When the glyoxylic acid concentration in the reaction material reached approximately 50 wt%, the glyoxylic acid product was taken out, with a glyoxylic acid concentration of 50.44 wt%, an oxalic acid concentration of 1.46 wt%, and a platinum-cobalt color value of 847.5.

[0038] The concentration composition of the glyoxylic acid products obtained in Example 3 and Comparative Example 1 is recorded in Table 4: Table 4 Concentration composition of glyoxylic acid products obtained in Example 3 and Comparative Example 1

[0039] As shown in Table 4 above, compared with the glyoxylic acid product obtained by the two-step crystallization process of "vacuum evaporation + cooling crystallization" in Comparative Example 1, the color of the product in Example 3 is greatly reduced, the oxalic acid is completely separated, and a high-quality glyoxylic acid product is obtained; the concentrated water product is collected and reused in the process of preparing glyoxylic acid by oxalic acid electrolysis, realizing resource recycling and green environmental protection.

[0040] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A separation and decolorization method for glyoxylic acid electrolyte prepared by oxalic acid electrolysis using electrodialysis, characterized in that, Includes the following steps: S1. The glyoxylic acid electrolyte is frozen to cause oxalic acid to crystallize out. After solid-liquid separation, a pretreated electrolyte is obtained. S2. The pretreated electrolyte is subjected to electrodialysis to remove residual oxalic acid and achieve decolorization, thereby obtaining a high-purity glyoxylic acid product.

2. The method for separation and decolorization of glyoxylic acid electrolyte prepared by electrodialysis of oxalic acid according to claim 1, characterized in that, In step S1, the freezing process is carried out using a freezing device; Specifically, the freezing temperature of the freezing device is -5 to -20°C, and the freezing time is 2 to 6 hours.

3. The separation and decolorization method for preparing glyoxylic acid electrolyte by electrodialysis according to claim 2, characterized in that, The concentration of oxalic acid in the pretreated electrolyte is not higher than 2 wt%. Preferably, the pretreated electrolyte has a pH of 0.5 to 1.5, a glyoxylic acid concentration of 4 to 7 wt%, and an oxalic acid concentration of 1 to 2 wt%.

4. The method for separation and decolorization of glyoxylic acid electrolyte prepared by electrodialysis according to any one of claims 1-3, characterized in that, In step S2, the electrodialysis treatment is carried out using an electrodialysis device; Specifically, the pretreatment electrolyte is added to the desalination tank, ultrapure water is added to the concentrate tank, and the electrode solution is added to the electrode water tank. After starting the electrodialysis device for the first electrodialysis, the concentrate product 1 in the concentrate tank is exported. Then, ultrapure water is added to the concentrate tank, and the electrodialysis device is started for the second electrodialysis. The concentrate product 2 in the concentrate tank and the desalination product in the desalination tank are exported.

5. The separation and decolorization method for glyoxylic acid electrolyte preparation by electrodialysis according to claim 4, characterized in that, The polar aqueous solution is a sodium chloride, sodium sulfate, or dilute sulfuric acid solution; Preferably, the concentration of the extreme aqueous solution is 3 to 10 wt%.

6. The separation and decolorization method for preparing glyoxylic acid electrolyte by electrodialysis according to claim 4 or 5, characterized in that, In both the first and second electrodialysis processes, the voltage of the electrodialysis device was controlled at 4–14V, and the flow rate was controlled at 50–90L / h.

7. The method for separation and decolorization of glyoxylic acid electrolyte prepared by electrodialysis according to any one of claims 4-6, characterized in that, The freshwater product has a pH of 1.2–2, a glyoxylic acid concentration of 4–6 wt%, and an oxalic acid concentration of 0–0.05 wt%; the concentrated water product 1 has a pH of 1–1.5, a glyoxylic acid concentration of 0.5–1.5 wt%, and an oxalic acid concentration of 1.5–3 wt%; the concentrated water product 2 has a pH of 1.2–2, a glyoxylic acid concentration of 0.8–1.8 wt%, and an oxalic acid concentration of 0.5–1.5 wt%.

8. The method for separation and decolorization of glyoxylic acid electrolyte prepared by electrodialysis according to any one of claims 4-7, characterized in that, The recovery rate of glyoxylic acid in the freshwater product is 70-85%, and the recovery rate of oxalic acid in the concentrated water products 1 and 2 is 90-100%.

9. The method for separation and decolorization of glyoxylic acid electrolyte prepared by electrodialysis according to any one of claims 4-8, characterized in that, After the first electrodialysis, in addition to exporting the concentrated product 1 from the concentrated water tank, the desalinated product from the desalinated water tank is also exported. The desalinated product is then loaded onto a weakly basic anion exchange resin for adsorption and elution. The eluent is then added to the desalinated water tank, and ultrapure water is added to the concentrated water tank. The electrodialysis device is then started for the second electrodialysis.

10. The separation and decolorization method for preparing glyoxylic acid electrolyte by electrodialysis according to claim 9, characterized in that, The weakly basic anion exchange resin is an anion exchange resin with styrene-divinylbenzene copolymer as the inert backbone and polyol amine groups as functional groups.

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