Process for treating an amino acid mother liquor

Abstract

The application relates to the technical field of wastewater treatment, and discloses a treatment process for amino acid mother liquor, which comprises the following steps: adding a flocculating agent into the amino acid mother liquor, filtering, electrodialysis, concentrating, crystallizing, and recovering amino acid; the amino acid mother liquor is L-threonine mother liquor; and the flocculating agent comprises N, N-dialkyl chitosan. Through the technical scheme, the problem of insufficient recovery rate when recovering L-threonine from L-threonine mother liquor in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a treatment process for amino acid mother liquor. Background Technology

[0002] L-Threonine is an essential amino acid for humans and animals, widely used in feed additives, pharmaceuticals, food, and nutritional supplements. L-Threonine mother liquor is the waste liquid remaining after crystallization during its microbial fermentation production process. It contains a certain amount of L-Threonine, but is also mixed with various impurities such as bacterial residues, protein impurities, and hydrophobic organic impurities. Recovering and utilizing the L-Threonine in the mother liquor can improve raw material utilization and reduce production costs.

[0003] Currently, the treatment of L-threonine mother liquor generally employs methods such as centrifugation combined with membrane filtration, ion exchange, or bipolar membrane electrodialysis. These methods can initially separate bacterial residues and some impurities from the mother liquor, but the recovery rate still falls short of standards, hindering the improvement of industrial efficiency. Summary of the Invention

[0004] This invention proposes a process for treating amino acid mother liquor, which solves the problem of insufficient recovery rate when recovering L-threonine from L-threonine mother liquor in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a treatment process for amino acid mother liquor, comprising the following steps: Flocculant was added to the amino acid mother liquor, followed by filtration, electrodialysis, concentration, and crystallization to recover the amino acids. The amino acid mother liquor is L-threonine mother liquor; The flocculant includes N,N-dialkyl chitosan.

[0006] As a further technical solution, the preparation method of the N,N-dialkyl chitosan includes the following steps: Acetic acid solution and ethanol are mixed, chitosan is added, and the mixture swells to obtain a transparent viscous liquid; Decalaldehyde solution and sodium cyanoborohydride were added sequentially to the transparent viscous liquid. The reaction was carried out, the pH was adjusted to 7-8, and the mixture was filtered, washed, and dried to obtain N,N-dialkyl chitosan.

[0007] As a further technical solution, the mass-to-volume ratio of chitosan, acetic acid solution and ethanol is 2.8~3.2g:100mL:80mL.

[0008] As a further technical solution, the acetic acid solution is an aqueous solution of acetic acid.

[0009] As a further technical solution, the decanal solution is a decanal ethanol solution.

[0010] As a further technical solution, the molar ratio of chitosan to decanal in the decanal solution is 1:3~3.5.

[0011] As a further technical solution, the molar ratio of decanal to sodium cyanoborohydride in the decanal solution is 1:1 to 1.2.

[0012] As a further technical solution, the reaction rotation speed is 200~300 rpm.

[0013] As a further technical solution, the amount of flocculant added is 0.7% to 0.9% of the mass fraction of the amino acid mother liquor.

[0014] As a further technical solution, the pore size of the filter membrane used in the filtration process is 0.1~0.5μm.

[0015] As a further technical solution, the flow rate of the electrodialysis is 20~30 L / h, and the current density is 10~15 mA / cm². 2 .

[0016] As a further technical solution, the concentration is evaporation concentration, with a vacuum degree of -0.09MPa, a temperature of 50~60℃, and a concentration factor of 4~6 times.

[0017] As a further technical solution, the crystallization is a cooling crystallization, wherein the cooling crystallization is cooled to 10-12°C at a cooling rate of 5-8°C / h.

[0018] As a further technical solution, the flocculant also includes one of nonionic polyacrylamide and polyaluminum chloride.

[0019] As a further technical solution, the flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 2~3:1.

[0020] In this invention, the use of N,N-dialkyl chitosan and nonionic polyacrylamide in combination as flocculants can further improve the recovery rate of L-threonine. N,N-dialkyl chitosan adsorbs hydrophobic impurities in the mother liquor and maintains the stability of the flocculant. The addition of nonionic polyacrylamide does not introduce inorganic ions into the mother liquor, but rather causes small particles in the mother liquor to aggregate into large flocs, accelerating sedimentation and separation, resulting in more thorough impurity removal. The recovery rate of L-threonine is optimal when the mass ratio of N,N-dialkyl chitosan to nonionic polyacrylamide is 2-3:1. When the amount of nonionic polyacrylamide added is too small, the content of large flocs formed decreases, reducing the impurity removal effect and thus lowering the recovery rate. When the amount of nonionic polyacrylamide added is too large, the formed flocs are loose, causing some L-threonine to be encapsulated within the flocs, leading to a decrease in the recovery rate of L-threonine.

[0021] The working principle and beneficial effects of this invention are as follows: In this invention, N,N-dialkyl chitosan is used as a flocculant to improve the recovery rate of L-threonine from the mother liquor. After modification, long-chain alkyl groups are introduced into the molecular chain of chitosan, giving it a certain degree of hydrophobicity, which can adsorb hydrophobic impurities in the mother liquor. At the same time, N,N-dialkyl chitosan retains a certain degree of hydrophilicity, which can maintain good dispersibility in the mother liquor. Furthermore, the small molecular weight of L-threonine makes it difficult to be captured by the large-molecule chitosan flocculation network, ultimately resulting in a significant improvement in the recovery rate of L-threonine. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following examples and comparative examples, the chitosan had a particle size of 120 mesh and a degree of deacetylation of 94.3 wt%.

[0024] Example 1 A process for treating L-threonine mother liquor includes the following steps: Add 0.7% (w / w) of flocculant to the L-threonine mother liquor, then filter through a 0.1 μm pore size membrane, and finally pass it through an electrodialysis device with a flow rate of 20 L / h and a current density of 10 mA / cm³. 2The obtained mother liquor was evaporated and concentrated under a vacuum of -0.09 MPa and a temperature of 50 °C, with a concentration factor of 4 times. Finally, it was cooled to 10 °C at a cooling rate of 5 °C / h to recover L-threonine; the flocculant was N,N-dialkyl chitosan. The preparation method of N,N-dialkyl chitosan includes the following steps: Mix 0.2 mol / L acetic acid aqueous solution and anhydrous ethanol, add chitosan (the mass-volume ratio of chitosan, acetic acid aqueous solution and anhydrous ethanol is 2.8 g: 100 mL: 80 mL), and swell for 1 h to obtain a transparent viscous liquid; A decaldehyde ethanol solution (the molar ratio of chitosan to decaldehyde in the decaldehyde solution is 1:3, and the concentration of the decaldehyde ethanol solution is 0.5 mol / L) and sodium cyanoborohydride (the molar ratio of decaldehyde to sodium cyanoborohydride in the decaldehyde solution is 1:1) were added sequentially to a transparent viscous liquid. The mixture was reacted at 200 rpm for 24 h, the pH was adjusted to 7, and the mixture was filtered, washed, and dried at 100 °C to obtain N,N-dialkyl chitosan.

[0025] Example 2 A process for treating L-threonine mother liquor includes the following steps: Add 0.8% (w / w) of flocculant to the L-threonine mother liquor, then filter through a 0.5 μm pore size membrane, followed by electrodialysis at a flow rate of 25 L / h and a current density of 15 mA / cm³. 2 The obtained mother liquor was evaporated and concentrated under a vacuum of -0.09 MPa and a temperature of 55°C, with a concentration factor of 5 times. Finally, it was cooled to 10°C at a cooling rate of 6°C / h to recover L-threonine; the flocculant was N,N-dialkyl chitosan. The preparation method of N,N-dialkyl chitosan includes the following steps: Mix 0.2 mol / L acetic acid aqueous solution and anhydrous ethanol, add chitosan (the mass-volume ratio of chitosan, acetic acid aqueous solution and anhydrous ethanol is 3.0 g: 100 mL: 80 mL), and swell for 1 h to obtain a transparent viscous liquid; A decaldehyde ethanol solution (the molar ratio of decaldehyde to chitosan in the decaldehyde solution was 1:3.5, and the concentration of the decaldehyde ethanol solution was 0.5 mol / L) and sodium cyanoborohydride (the molar ratio of decaldehyde to sodium cyanoborohydride was 1:1.1) were added sequentially to a transparent viscous liquid. The mixture was reacted at 250 rpm for 24 h, the pH was adjusted to 8, and the mixture was filtered, washed, and dried at 100 °C to obtain N,N-dialkyl chitosan.

[0026] Example 3 A process for treating L-threonine mother liquor includes the following steps: Add 0.9% (w / w) of flocculant to the L-threonine mother liquor, then filter through a 0.5 μm pore size membrane, followed by electrodialysis at a flow rate of 30 L / h and a current density of 15 mA / cm³. 2 The obtained mother liquor was evaporated and concentrated under a vacuum of -0.09 MPa and a temperature of 60 °C, with a concentration factor of 6 times. Finally, it was cooled to 12 °C at a cooling rate of 8 °C / h to recover L-threonine; the flocculant was N,N-dialkyl chitosan. The preparation method of N,N-dialkyl chitosan includes the following steps: Mix 0.2 mol / L acetic acid aqueous solution and anhydrous ethanol, add chitosan (the mass-volume ratio of chitosan, acetic acid aqueous solution and anhydrous ethanol is 3.2 g: 100 mL: 80 mL), and swell for 1 h to obtain a transparent viscous liquid; A decaldehyde ethanol solution (the molar ratio of chitosan to decaldehyde in the decaldehyde solution was 1:3, and the concentration of the decaldehyde ethanol solution was 0.5 mol / L) and sodium cyanoborohydride (the molar ratio of decaldehyde to sodium cyanoborohydride in the decaldehyde solution was 1:1.2) were added sequentially to a transparent viscous liquid. The mixture was reacted at 300 rpm for 24 h, the pH was adjusted to 8, and the mixture was filtered, washed, and dried at 100 °C to obtain N,N-dialkyl chitosan.

[0027] Example 4 The only difference between this embodiment and Example 2 is that the flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 4:1.

[0028] Example 5 The only difference between this embodiment and Example 2 is that the flocculant is N,N-dialkyl chitosan and polyaluminum chloride in a mass ratio of 4:1.

[0029] Example 6 The only difference between this embodiment and Example 4 is that the flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 3:1.

[0030] Example 7 The only difference between this embodiment and Example 4 is that the flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 2:1.

[0031] Example 8 The only difference between this embodiment and Example 4 is that the flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 1:1.

[0032] Comparative Example 1 The only difference between this comparative example and Example 2 is that the flocculant is chitosan.

[0033] Comparative Example 2 The only difference between this comparative example and Example 2 is that the flocculant is nonionic polyacrylamide.

[0034] Comparative Example 3 The only difference between this comparative example and Example 2 is that the flocculant is chitosan and nonionic polyacrylamide in a mass ratio of 4:1.

[0035] Experimental Example The yields of L-threonine obtained in Examples 1-8 and Comparative Examples 1-3 were calculated using the formula: Recovery rate = (Actual yield / Theoretical yield) × 100%, and the results are shown in Table 1. Table 1. Recovery results of L-threonine obtained in Examples 1-8 and Comparative Examples 1-3

[0036] 1. Compared with Comparative Examples 1-3, the recovery rate of L-threonine obtained in Examples 1-8 was significantly higher than that in Comparative Examples 1-3, indicating that N,N-dialkylchitosan as a flocculant can improve the recovery rate of L-threonine from L-threonine mother liquor.

[0037] 2. Comparing Examples 2 and 4-8, the recovery rate of L-threonine obtained in Example 4 was higher than that in Examples 2 and 5, indicating that the combined use of N,N-dialkyl chitosan and nonionic polyacrylamide can further improve the recovery rate of L-threonine from the L-threonine mother liquor; the recovery rate of L-threonine obtained in Examples 6-7 was higher than that in Examples 4 and 8, indicating that limiting the mass ratio of N,N-dialkyl chitosan and nonionic polyacrylamide to 2-3:1 further improves the recovery rate of L-threonine.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for treating amino acid mother liquor, characterized in that, Includes the following steps: Flocculant was added to the amino acid mother liquor, followed by filtration, electrodialysis, concentration, and crystallization to recover the amino acids. The amino acid mother liquor is L-threonine mother liquor; The flocculant includes N,N-dialkyl chitosan.

2. The process for treating amino acid mother liquor according to claim 1, characterized in that, The preparation method of the N,N-dialkyl chitosan includes the following steps: Acetic acid solution and ethanol are mixed, chitosan is added, and the mixture swells to obtain a transparent viscous liquid; Decalaldehyde solution and sodium cyanoborohydride were added sequentially to the transparent viscous liquid. The reaction was carried out, the pH was adjusted to 7-8, and the mixture was filtered, washed, and dried to obtain N,N-dialkyl chitosan.

3. The process for treating amino acid mother liquor according to claim 2, characterized in that, The mass-to-volume ratio of chitosan, acetic acid solution, and ethanol is 2.8~3.2g:100mL:80mL; The molar ratio of chitosan to decanal in the decanal solution is 1:3~3.5; The molar ratio of decanal to sodium cyanoborohydride in the decanal solution is 1:1 to 1.

2.

4. The process for treating amino acid mother liquor according to claim 1, characterized in that, The amount of flocculant added is 0.7% to 0.9% of the mass fraction of the amino acid mother liquor.

5. The treatment process for amino acid mother liquor according to claim 1, characterized in that, The filter membrane used in the filtration process has a pore size of 0.1~0.5μm.

6. The process for treating amino acid mother liquor according to claim 1, characterized in that, The flow rate of the electrodialysis is 20-30 L / h, and the current density is 10-15 mA / cm². 2 .

7. The process for treating amino acid mother liquor according to claim 1, characterized in that, The concentration is an evaporative concentration, with a vacuum degree of -0.09 MPa, a temperature of 50~60℃, and a concentration factor of 4~6 times.

8. The process for treating amino acid mother liquor according to claim 1, characterized in that, The crystallization is a cooling crystallization, wherein the cooling crystallization is carried out at a cooling rate of 5~8℃ / h to 10~12℃.

9. The process for treating amino acid mother liquor according to claim 1, characterized in that, The flocculant also includes one of nonionic polyacrylamide and polyaluminum chloride.

10. The process for treating amino acid mother liquor according to claim 1, characterized in that, The flocculant is N,N-dialkyl chitosan and nonionic polyacrylamide in a mass ratio of 2~3:1.

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