A method for recovering pet enzymolysis waste liquid

Abstract

This invention proposes a method for recycling PET enzymatic hydrolysis waste liquid, comprising: acidifying and crystallizing the depolymerization liquid from waste PET enzymatic hydrolysis to obtain crude TPA and waste mother liquor containing ethylene glycol, sodium sulfate, and impurities; passing the mother liquor into a nanofiltration system to separate ethylene glycol, and removing organic residues and metal ion impurities through advanced oxidation and ion exchange resins; converting the terminal Na2SO4 wastewater into NaOH and H2SO4 required at the front end through a bipolar membrane electrodialysis system, forming an internal cycle of waste-to-waste treatment and turning waste into treasure, eliminating the procurement costs of fresh acids and alkalis and the treatment costs of saline wastewater, reducing the consumption of the two main chemicals NaOH and H2SO4 in the PET enzymatic hydrolysis process, and producing EG as a byproduct, thereby improving the economic efficiency of the entire process.

Description

Technical Field

[0001] This invention relates to the field of waste recycling, and more particularly to a method for recycling PET enzymatic hydrolysis waste liquid. Background Technology

[0002] Enzymatic depolymerization of PET is an environmentally friendly plastic recycling technology. The process is usually carried out in an alkaline aqueous solution to maintain the optimal activity of the hydrolytic enzymes. The end products are terephthalic acid (TPA) and ethylene glycol (EG). However, TPA is an acidic substance, and its continuous generation consumes the alkali in the system, which requires continuous replenishment of alkali during the reaction to maintain pH stability, resulting in a large consumption of alkali.

[0003] After the reaction is complete, the reaction solution needs to be acidified to acidic conditions by adding acid to allow TPA to precipitate and crystallize. This step consumes a large amount of acid and produces complex wastewater, mainly composed of sodium sulfate, containing residual ethylene glycol, enzyme protein fragments, trace metal ions, and other organic byproducts. This wastewater is difficult to treat, has low value, and direct discharge or treatment will result in resource waste and environmental pollution. The cost of acid and alkali consumption is high, and the pressure on end-of-pipe wastewater treatment is significant. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a method for recycling PET enzymatic hydrolysis waste liquid.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for recovering PET enzymatic hydrolysis waste liquid, comprising: S1. Waste PET is enzymatically depolymerized under alkaline conditions. After the reaction, solid and liquid are separated. The resulting depolymerization solution is acidified and crystallized to obtain crude TPA and mother liquor containing ethylene glycol, sodium sulfate and impurities. S2. Wash and dry the obtained crude TPA to obtain the refined TPA product; S3. Pass the obtained mother liquor into a nanofiltration system for separation to obtain a permeate containing ethylene glycol and a retentate containing sodium sulfate. S4. The obtained retentate is subjected to advanced oxidation treatment to reduce the organic matter content, resulting in a treated sodium sulfate solution. S5. Pass the obtained permeate into the ethylene glycol distillation system to recover ethylene glycol; S6. Pass the obtained treated sodium sulfate solution into an ion exchange resin system to remove polyvalent metal cations and obtain a purified sodium sulfate solution. S7. Pass the obtained purified sodium sulfate solution into a bipolar membrane electrodialysis system to convert it into sulfuric acid solution and sodium hydroxide solution; S8. The generated sodium hydroxide solution is reused in the enzymatic depolymerization process of step S1 as a replenishing alkali solution; the generated sulfuric acid solution is reused in the acidification crystallization precipitation process of step S1 for the precipitation and crystallization of TPA.

[0006] Preferably, in step S1, the reaction conditions for enzymatic depolymerization are: maintaining the pH of the reaction system at 7.5-9.0 by adding sodium hydroxide solution, the reaction temperature at 60-70℃, and the reaction time at 10-14h.

[0007] Preferably, in step S1, after solid-liquid separation and before acidification and crystallization precipitation, the depolymerization solution is first passed into an ultrafiltration system to separate and recover the depolymerization enzyme. The molecular weight cutoff of the ultrafiltration system is 5-15 kDa, and the recovered depolymerization enzyme is reused in the enzymatic depolymerization process.

[0008] Preferably, in step S1, after solid-liquid separation and before acidification and crystallization precipitation, the depolymerization solution is first decolorized. The decolorization treatment uses activated carbon adsorption to remove colored impurities.

[0009] Preferably, in step S3, the nanofiltration membrane of the nanofiltration system has a molecular weight cutoff of 150-250 Da and an operating pressure of 1.5-2.5 MPa.

[0010] Preferably, after separation by the nanofiltration system described in step S3, the mass fraction of sodium sulfate in the retentate containing sodium sulfate is concentrated to 8%–12%.

[0011] Preferably, in step S4, the advanced oxidation treatment employs one or more combinations of Fenton oxidation, ozone oxidation, or ultraviolet catalytic oxidation, and the total organic carbon content of the sodium sulfate solution after treatment is less than 50 mg / L.

[0012] Preferably, in step S6, the ion exchange resin system includes a chelating resin, which is used to deeply remove polyvalent metal cations such as calcium, magnesium, and iron, and the total concentration of polyvalent metal cations in the purified sodium sulfate solution after treatment is less than 1 mg / L.

[0013] Preferably, in step S7, the operating current density of the bipolar membrane electrodialysis system is 30-45 mA / m 2 The resulting sodium hydroxide solution has a concentration of 8%-12%, and the resulting sulfuric acid solution has a concentration of 10%-15%.

[0014] Preferably, in step S8, according to the process requirements of step S1, the generated sodium hydroxide solution and sulfuric acid solution are diluted or concentrated by adjusting the operating current and flow rate of the bipolar membrane electrodialysis system, so that the concentration of the recycled sodium hydroxide solution is adjusted to 8%-12% and the concentration of the sulfuric acid solution is adjusted to 10%-15%.

[0015] Compared with existing technologies, the beneficial effects of this invention include: by converting the terminal Na2SO4 wastewater into the required NaOH and H2SO4 at the front end, an internal cycle of treating waste with waste and turning waste into treasure is formed, eliminating the procurement costs of fresh acids and alkalis and the treatment costs of saline wastewater, reducing the consumption of the two main chemicals NaOH and H2SO4 in the PET enzymatic hydrolysis process, and producing EG as a byproduct, which improves the economic efficiency of the entire process. Through a combination of processes such as nanofiltration, advanced oxidation, and resin adsorption, deep purification and resource utilization of wastewater are achieved, greatly reducing wastewater discharge and environmental burden, which is in line with the concepts of green chemistry and circular economy. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Wherein: Figure 1 The diagram illustrates a process flow chart of a PET enzymatic hydrolysis waste liquid recovery method according to an embodiment of the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] Example 1 One kilogram of waste PET textiles was added to a depolymerization reactor, along with PET (polyethylene terephthalate) hydrolase (Leaf-branch Compost Cutinase, LCC variant enzyme, or Fast-PETase, or an equivalent PET hydrolase with catalytic efficiency, added at 0.5% of the PET mass) and 8 L of pure water. The enzymatic depolymerization reaction was then carried out. The pH of the reaction system was maintained at 8.0 ± 0.2 by adding 10% sodium hydroxide solution. The reaction temperature was controlled at 64 ± 2℃, the stirring rate at 150 r / min, and the reaction time at 12 h. This allowed the PET molecular chains to be fully broken and depolymerized into disodium terephthalate and ethylene glycol, yielding a reaction mixture containing depolymerization products and unreacted residues. In different specific implementations, the amount of PET hydrolase used in this step can be adjusted within the range of 5-50 g / kg PET, the pH of the reaction system can be adjusted within the range of 7.5-9.0, the reaction temperature can be adjusted within the range of 60-70℃, and the reaction time can be adjusted within the range of 10-14 h. Adaptive optimization can be made according to the characteristics of the specific PET raw material and the different types of depolymerization enzymes used.

[0020] After the reaction, the reaction mixture is passed through a plate and frame filter press for solid-liquid separation, retaining the depolymerization residue. The permeate is used as the depolymerization solution for subsequent processing. This depolymerization solution is then processed through an ultrafiltration system. The ultrafiltration membrane has a molecular weight cutoff of 10 kDa, is made of polyethersulfone (PES), and operates at a pressure of 0.2 MPa. Depolymerization enzymes with molecular weights greater than 10 kDa are retained on the concentration side of the ultrafiltration membrane and recovered for reuse in the next batch of enzymatic depolymerization reaction, thereby reducing enzyme consumption costs during the enzymatic depolymerization process. Soluble components with molecular weights less than 10 kDa permeate through the ultrafiltration membrane into the permeate side. In different specific embodiments, the molecular weight cutoff of the ultrafiltration membrane can be selected within the range of 5-15 kDa.

[0021] The ultrafiltration permeate then enters the activated carbon decolorization unit, where colored impurities and some dissolved organic pollutants are removed through physical adsorption in the activated carbon adsorption tower. The activated carbon loading is 50 g / L of permeate, and the contact time is 30 min. After decolorization, the liquid is pale yellow and clear. A 30% sulfuric acid solution is slowly added to the decolorized liquid for acidification and crystallization precipitation treatment. The pH of the system is adjusted to the range of 2.0-3.0. Under acidic conditions, disodium terephthalate is converted into terephthalic acid and precipitates out, forming crude TPA crystals. The suspension containing crude TPA crystals is passed through a centrifuge for solid-liquid separation to obtain crude TPA filter cake and mother liquor. The mother liquor mainly contains ethylene glycol, sodium sulfate, and a small amount of unprecipitated organic impurities.

[0022] The obtained crude TPA filter cake was washed three times with pure water, each time using three times the mass of the filter cake, to remove soluble substances such as sodium sulfate and ethylene glycol entrained in the filter cake. The washed filter cake was then vacuum dried at 105°C for 4 hours to obtain a white refined TPA product with a purity of over 99.9% and a yield of 95.8%. In different specific embodiments, the drying temperature can be adjusted within the range of 90-120°C, and the drying time can be adjusted within the range of 3-6 hours.

[0023] Next, the mother liquor is further separated and processed for resource utilization. The mother liquor is passed into a nanofiltration system. The nanofiltration membrane has a molecular weight cutoff of 200 Da, is made of composite polyamide, and the operating pressure is controlled at 2.0 MPa with a cross-flow velocity of 3 m / s. Based on the nanofiltration membrane's ability to retain charged salts such as sodium sulfate and its high permeability to small-molecule non-electrolytes such as ethylene glycol, a permeate containing ethylene glycol and a concentrated sodium sulfate retentate are obtained after separation. The permeate contains approximately 5% ethylene glycol and a small amount of low-molecular-weight organic matter. The retentate contains sodium sulfate at a mass fraction concentrated to approximately 10%, while retaining some organic impurities. In different specific embodiments, the molecular weight cutoff of the nanofiltration membrane can be selected within the range of 150-250 Da, the operating pressure can be adjusted within the range of 1.5-2.5 MPa, and the corresponding concentration of sodium sulfate in the retentate can be within the range of 8%-12%.

[0024] The nanofiltration permeate and the sodium sulfate-containing retentate were subsequently treated separately. On one hand, the sodium sulfate-containing retentate was passed into a Fenton advanced oxidation system for treatment, and ferrous sulfate was added to the reactor. ) and hydrogen peroxide ( ),in The dosage was 0.5 mmol / L. The dosage was 5 mmol / L. and The molar ratio was 1:10, the pH of the system was adjusted to within the range of 3-4, the reaction temperature was 25-30℃, and the reaction time was 2 hours. During the reaction, the hydroxyl radicals generated oxidized and mineralized residual enzyme protein fragments, organic debris, and small organic molecules in the solution, decomposing them into carbon dioxide and water. After treatment, the total organic carbon (TOC) content of the solution was reduced to 32 mg / L. In different specific embodiments, the TOC content of the solution after advanced oxidation treatment can be controlled below 50 mg / L to meet the requirements of subsequent processes.

[0025] In other specific embodiments, the advanced oxidation treatment of sodium sulfate retentate can also employ ozone oxidation or ultraviolet catalytic oxidation. The operating parameters for ozone oxidation can be set to an ozone dosage of 3-5 g / L and a reaction time of 1-2 h; the operating parameters for ultraviolet catalytic oxidation can be set to an ultraviolet light intensity of 50-300 mW / cm².2 Catalyst titanium dioxide ( The dosage is 0.5-2 g / L, and the reaction time is 2-4 h. The above three advanced oxidation methods can be used alone, in pairs, or in combination. The TOC content of the treated solution can be controlled below 50 mg / L.

[0026] On the other hand, the nanofiltration permeate is passed into an ethylene glycol distillation column, with the bottom temperature controlled at 197°C and the top temperature at 190°C. Distillation separation is carried out under reduced pressure (top vacuum of -0.09 MPa). During distillation, ethylene glycol separates from water and other small-molecule organic compounds based on their boiling point differences. The ethylene glycol vapor collected from the top or side stream is condensed to obtain the ethylene glycol product with a purity of over 99.0% and a recovery rate of 88.5%.

[0027] The sodium sulfate solution, after Fenton oxidation treatment, is purified by passing it through an ion exchange resin system. The solution first flows at a flow rate of 5 BV / h through a strongly acidic cation exchange resin column (using a sulfonic acid type resin with a styrene-divinylbenzene copolymer matrix) to remove most of the monovalent and divalent metal cations. The effluent then flows at a flow rate of 3 BV / h into a chelating resin column (using an aminophosphonic acid type or iminodiacetic acid type chelating resin). Through the selective adsorption of polyvalent metal cations such as calcium, magnesium, and iron by the specific coordination groups of the chelating resin, the total concentration of polyvalent metal cations is reduced to 0.3 mg / L, resulting in a purified sodium sulfate solution. In different specific embodiments, the total concentration of polyvalent metal cations in the purified sodium sulfate solution after ion exchange treatment can be controlled below 1 mg / L to meet the downstream bipolar membrane electrodialysis requirements for the total concentration of polyvalent metal ions in the feed solution.

[0028] The purified sodium sulfate solution was used as the feed solution and passed into a bipolar membrane electrodialysis device. The device's membrane stack adopted a three-compartment structure of cation exchange membrane-bipolar membrane-anion exchange membrane, and the current density was controlled at 35 mA / m³. 2 The operating temperature is 25-30℃, and the material circulation rate is 2L / min. Under the action of an applied DC electric field, sodium ions in the solution migrate towards the cathode, and sulfate ions migrate towards the anode. Simultaneously, the hydrolysis layer in the middle of the bipolar membrane dissociates water molecules into hydrogen ions and hydroxide ions. In the cathode chamber, sodium ions combine with hydroxide ions to form a sodium hydroxide solution with a concentration of approximately 10%; in the anode chamber, sulfate ions combine with hydrogen ions to form a sulfuric acid solution with a concentration of approximately 12%. In different specific embodiments, the operating current density of the bipolar membrane electrodialysis device can be 30-45 mA / m². 2 The concentration of sodium hydroxide solution produced can be adjusted within the range of 8%-12%, and the concentration of sulfuric acid solution produced can be adjusted within the range of 10%-15%.

[0029] Finally, the generated sodium hydroxide solution is recycled in the PET enzymatic depolymerization reaction process of this embodiment as a supplementary alkali solution to maintain the pH of the reaction system; the generated sulfuric acid solution is recycled in the crude TPA acidification crystallization precipitation process of this embodiment as an acid source for the precipitation of terephthalic acid. During the recycling process, the concentration of sodium hydroxide solution can be adjusted to the range of 8%-12% and the concentration of sulfuric acid solution to the range of 10%-15% by adjusting the operating current and flow rate of the bipolar membrane electrodialysis device according to the actual needs of the upstream process for acid and alkali concentration; and / or the generated sodium hydroxide solution and sulfuric acid solution can be diluted or concentrated to match the needs of the upstream process.

[0030] After processing using the method described in Example 1, the purity of the TPA product reached over 99.9%, with a yield of 95.8%; the purity of the ethylene glycol by-product reached over 99.0%, with a recovery rate of 88.5%; the total concentration of polyvalent metal cations was controlled at 0.3 mg / L, and the TOC content of the treated solution was controlled at 32 mg / L; sodium hydroxide and sulfuric acid were basically recycled, the process required virtually no additional acid or alkali reagents, wastewater discharge was near zero, the overall resource recovery rate reached over 90%, and the treatment cost was reduced by 40% compared to traditional processes.

[0031] Comparative Example 1 To illustrate the differences between the method of the present invention and traditional processing techniques, Comparative Example 1 is provided as a reference. The PET enzymatic depolymerization reaction conditions, solid-liquid separation, ultrafiltration, decolorization, and acidification crystallization precipitation steps used in Comparative Example 1 are the same as those in Example 1. The differences are: the mother liquor treatment uses a traditional evaporation and concentration process; the solid sodium sulfate obtained after evaporation is directly disposed of as solid waste; and ethylene glycol is recovered through conventional distillation. Furthermore, the sodium hydroxide required for the enzymatic depolymerization process and the sulfuric acid required for acidification crystallization are both purchased externally and added only once, without recycling.

[0032] The results showed that the TPA product yield in Comparative Example 1 was 90.1%, which was lower than the 95.8% in Example 1; the ethylene glycol recovery rate was 75.2%, which was lower than the 88.5% in Example 1; sodium sulfate was disposed of directly in solid form, and approximately 0.15 kg of hazardous waste was generated for every 1 kg of PET processed; at the same time, since sodium hydroxide and sulfuric acid were purchased and added externally in a one-time manner, the acid and alkali consumption was large, the treatment cost was high, and the pressure of solid waste treatment was high.

[0033] Example 2 To further verify the impact of key process parameters on the treatment effect in the method of this invention, Example 2 is provided for parameter comparison. In Example 2, while keeping other process steps the same as in Example 1, three different combinations of nanofiltration operating pressure and bipolar membrane electrodialysis current density were selected to investigate the changes in sodium sulfate concentration, acid / alkali preparation concentration, TOC removal rate, and ethylene glycol recovery rate. Specific experimental data are shown in the table below.

[0034] Table 1: Effects of different nanofiltration operating pressures and bipolar membrane current densities on sodium sulfate concentration and acid-base preparation efficiency. The experimental data in the table above show that the nanofiltration operating pressure is 1.5-2.5 MPa and the bipolar membrane electrodialysis current density is 30-45 mA / m. 2 Within the specified range, as the nanofiltration pressure increased, the concentration of sodium sulfate in the retentate rose from 8.2% to 11.8%, ensuring that the material concentration for subsequent bipolar membrane electrodialysis was within a suitable operating range. As the current density increased, the concentration of the prepared sodium hydroxide solution rose from 8.1% to 11.9%, and the concentration of the sulfuric acid solution rose from 10.3% to 14.7%, with corresponding increases in TOC removal rate and ethylene glycol recovery rate. Experimental results show that adjusting the process parameters within the range defined in the claims of this invention can achieve the technical effects of recovering resources such as phthalic acid and ethylene glycol, as well as achieving a closed-loop acid-base cycle.

[0035] Based on the above embodiments, those skilled in the art can make various modifications and equivalent substitutions to the process conditions, equipment selection, and operating parameters in the embodiments without departing from the design concept of the present invention. For example, they can change the specific type of PET hydrolytic enzyme, adjust the reaction temperature and time range of each step, change the specific model of the nanofiltration membrane or ion exchange resin, adopt other advanced oxidation methods that can achieve equivalent effects, and adjust the operating mode of the bipolar membrane electrodialysis device. All such modifications and equivalent substitutions fall within the protection scope of the present invention. The protection scope of the present invention is defined by the claims and their equivalents and should not be limited to the specific embodiments disclosed in this specification.

[0036] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for recovering PET enzymatic hydrolysis waste liquid, characterized in that, include: S1. Waste PET is enzymatically depolymerized under alkaline conditions. After the reaction, solid and liquid are separated. The resulting depolymerization solution is acidified and crystallized to obtain crude TPA and mother liquor containing ethylene glycol, sodium sulfate and impurities. S2. Wash and dry the obtained crude TPA to obtain the refined TPA product; S3. Pass the obtained mother liquor into a nanofiltration system for separation to obtain a permeate containing ethylene glycol and a retentate containing sodium sulfate. S4. The obtained retentate is subjected to advanced oxidation treatment to reduce the organic matter content, resulting in a treated sodium sulfate solution. S5. Pass the obtained permeate into the ethylene glycol distillation system to recover ethylene glycol; S6. Pass the obtained treated sodium sulfate solution into an ion exchange resin system to remove polyvalent metal cations and obtain a purified sodium sulfate solution. S7. Pass the obtained purified sodium sulfate solution into a bipolar membrane electrodialysis system to convert it into sulfuric acid solution and sodium hydroxide solution; S8. The generated sodium hydroxide solution is reused in the enzymatic depolymerization process of step S1 as a replenishing alkali solution; the generated sulfuric acid solution is reused in the acidification crystallization precipitation process of step S1 for the precipitation and crystallization of TPA.

2. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S1, the reaction conditions for enzymatic depolymerization are as follows: the pH of the reaction system is maintained at 7.5-9.0 by adding sodium hydroxide solution, the reaction temperature is 60-70℃, and the reaction time is 10-14h.

3. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S1, after solid-liquid separation and before acidification and crystallization precipitation, the depolymerization solution is first passed into an ultrafiltration system to separate and recover the depolymerization enzyme. The molecular weight cutoff of the ultrafiltration system is 5-15 kDa, and the recovered depolymerization enzyme is reused in the enzymatic depolymerization process.

4. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S1, after solid-liquid separation and before acidification and crystallization precipitation, the depolymerization solution is first decolorized. The decolorization treatment uses activated carbon adsorption to remove colored impurities.

5. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S3, the nanofiltration membrane of the nanofiltration system has a molecular weight cutoff of 150-250 Da and an operating pressure of 1.5-2.5 MPa.

6. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, After separation by the nanofiltration system described in step S3, the mass fraction of sodium sulfate in the retentate containing sodium sulfate is concentrated to 8%-12%.

7. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S4, the advanced oxidation treatment employs one or more combinations of Fenton oxidation, ozone oxidation, or ultraviolet catalytic oxidation, and the total organic carbon content of the sodium sulfate solution after treatment is less than 50 mg / L.

8. The method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S6, the ion exchange resin system includes a chelating resin, which is used to deeply remove polyvalent metal cations such as calcium, magnesium, and iron. The total concentration of polyvalent metal cations in the purified sodium sulfate solution after treatment is less than 1 mg / L.

9. A method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S7, the operating current density of the bipolar membrane electrodialysis system is 30-45 mA / m 2 The resulting sodium hydroxide solution has a concentration of 8%-12%, and the resulting sulfuric acid solution has a concentration of 10%-15%.

10. A method for recovering PET enzymatic hydrolysis waste liquid according to claim 1, characterized in that, In step S8, according to the process requirements of step S1, the sodium hydroxide solution and sulfuric acid solution produced are diluted or concentrated by adjusting the operating current and flow rate of the bipolar membrane electrodialysis system, so that the concentration of the recycled sodium hydroxide solution is adjusted to 8%-12% and the concentration of the sulfuric acid solution is adjusted to 10%-15%.

Images