A process for treating glycine mother liquor

Abstract

The present invention relates to the technical field of wastewater treatment, and provides a glycine mother liquor treatment process, which comprises the following steps: adjusting the pH of the glycine mother liquor to 3.5 - 4.5, adding a flocculant, filtering for the first time and the second time, and then performing membrane separation and purification to obtain a glycine solution; the flocculant comprises chitosan, and the addition amount of the flocculant is 0.5% - 1.5% of the mass of the glycine mother liquor. Through the above technical solution, the problems of low purity and low yield of glycine recovered from the glycine mother liquor in the related art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and specifically, to a process for treating glycine mother liquor. Background Art

[0002] Glycine is an important organic chemical raw material, which is widely used in many fields such as medicine, food, and pesticides. There are various impurities in glycine mother liquor. In addition to the unreacted raw materials, it also includes impurities such as macromolecular organic pigments and activated carbon. If the glycine mother liquor is directly discharged without treatment, it will cause serious harm to the environment.

[0003] The macromolecular pigments and activated carbon contained in the mother liquor are directly discharged into the water body without treatment. The macromolecular pigments will change the color of the water body, affecting the light transmittance of the water body, which will hinder the photosynthesis of plants in the water, reduce the dissolved oxygen content in the water, and then damage the aquatic ecosystem; if the mother liquor is used for irrigation or enters the soil through other channels, the macromolecular pigments may accumulate in the soil, changing the color and structure of the soil, affecting the air permeability and water permeability of the soil. The activated carbon may adsorb nutrients and microorganisms in the soil, reducing the soil fertility. Moreover, these substances may further spread with processes such as rainwater scouring, polluting the surrounding soil and groundwater.

[0004] Secondly, the low purity and low yield of glycine are also the main problems in the mother liquor recovery process. The glycine with low yield and unqualified purity will seriously affect its reuse value. Therefore, the research and application of the glycine mother liquor treatment process are crucial for the green development of the chemical industry and environmental protection. It is very necessary to propose a treatment process for glycine mother liquor. Summary of the Invention

[0005] The present invention proposes a process for treating glycine mother liquor, which solves the problems of low purity and low yield of glycine recovered from glycine mother liquor in the related art.

[0006] The technical solution of the present invention is as follows: The present invention proposes a process for treating glycine mother liquor, including the following steps: adjusting the pH of the glycine mother liquor to 3.5 - 4.5, adding a flocculant, after the first filtration and the second filtration, and then through membrane separation and purification to obtain a glycine solution; the flocculant includes chitosan, and the addition amount of the flocculant is 0.5% - 1.5% of the mass of the glycine mother liquor.

[0007] As a further technical solution, the glycine mother liquor is obtained by supersaturated crystallization and filtration of industrial-grade glycine with deionized water, and the glycine mother liquor contains a large amount of pigment components after being recycled.

[0008] As a further technical solution, the molecular weight of the filtration membrane for membrane separation is 100 - 300.

[0009] In the present invention, a filtration membrane with a molecular weight range of 100 to 300 is selected, enabling glycine molecules to smoothly pass through the membrane. Impurities such as organic pigments, due to their molecular weight being as high as tens of thousands or more, far exceeding the range allowed to pass through the membrane pore size, are effectively intercepted on one side of the membrane. This precise screening mechanism greatly reduces the impurity content in the glycine product and significantly improves the purity of glycine.

[0010] As a further technical solution, the first filtration is carried out using a bag filter, and the second filtration is carried out using a cartridge filter.

[0011] As a further technical solution, the pore sizes of the bag filter and the cartridge filter are independently 0.1 to 1 μm.

[0012] As a further technical solution, the solution used for adjusting the pH is a hydrochloric acid solution with a mass concentration of 30 wt%.

[0013] As a further technical solution, the flocculant further includes kaolin, and the mass ratio of the chitosan to the kaolin is 2 to 3:1.

[0014] In the present invention, chitosan and kaolin are added simultaneously as flocculants to exert their synergistic effect, enhance the adsorption of the flocculant to impurities, promote the formation of a more compact floc structure, improve the flocculation efficiency, further remove impurities such as organic pigments in the glycine mother liquor, and improve the purity and yield of the recovered glycine in the glycine mother liquor.

[0015] As a further technical solution, the kaolin is modified kaolin, and the modified kaolin is obtained by modifying kaolin with a modifier, and the modifier is a pyrrole carboxamide compound.

[0016] In the present invention, kaolin is modified with a pyrrole carboxamide compound to obtain modified kaolin. The modified kaolin has a stronger selective adsorption for impurities, helps to precisely remove impurities, avoids the loss of glycine, and further improves the purity and yield of glycine.

[0017] As a further technical solution, in the raw material of the modified kaolin, the mass ratio of the modifier to the kaolin is 3 to 4:50.

[0018] As a further technical solution, the pyrrole carboxamide compound includes one or two of 1-methylpyrrole-2-carboxamide and 2-amino-1H-pyrrole-3-carboxamide.

[0019] As a further technical solution, the preparation method of the modified kaolin includes the following steps: dispersing the modifier in a solvent, adding kaolin, and obtaining the modified kaolin after filtration and drying.

[0020] As a further technical solution, the mass ratio of the kaolin to the solvent is 1:10.

[0021] As a further technical solution, the modification temperature is 60-80°C, and the modification time is 5-7h.

[0022] The working principle and beneficial effects of the present invention are as follows:

[0023] In the present invention, a membrane filtration separation technology is adopted to achieve screening according to the molecular weight of substances. Before membrane filtration, chitosan is added as a flocculant to the organic pigment impurities. Through electrostatic adsorption and bridging effects, numerous impurity particles are aggregated to form larger floc structures, thereby effectively removing impurities such as organic pigments in the glycine mother liquor and improving the purity and yield of glycine recovered from the glycine mother liquor. Specific embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present invention.

[0025] In the following examples and comparative examples:

[0026] Chitosan: particle size 120 mesh, deacetylation degree 94.3 wt%;

[0027] Kaolin: particle size 325 mesh;

[0028] Bentonite: sodium-based bentonite, particle size 325 mesh, manufacturer is Lingshou Baifeng Mineral Products Processing Factory;

[0029] Bag filter: pore size 0.5 μm;

[0030] Security filter: pore size 0.5 μm.

[0031] Example 1

[0032] A glycine mother liquor treatment process includes the following steps: adjusting the pH of the glycine mother liquor to 3.5 with a 30 wt% hydrochloric acid solution, adding a flocculant with a mass fraction of 0.5% of the mother liquor, lifting it by a mother liquor lift pump, filtering it through a bag filter to remove flocculent particles and suspended matters, and then filtering it through a security filter and entering a membrane separation and purification device to obtain a purified glycine solution; the flocculant is chitosan.

[0033] Example 2

[0034] A glycine mother liquor treatment process includes the following steps: adjusting the pH of the glycine mother liquor to 4 with a 30wt% hydrochloric acid solution, adding a flocculant with a mass fraction of 1% of the mother liquor, lifting it by a mother liquor lift pump, filtering it through a bag filter to remove flocculent particles and suspended matter, filtering it through a security filter and then entering a membrane separation and purification device, and obtaining a glycine solution after purification; wherein the flocculant is chitosan.

[0035] Example 3

[0036] A glycine mother liquor treatment process includes the following steps: adjusting the pH of the glycine mother liquor to 4.5 with a 30wt% hydrochloric acid solution, adding a flocculant with a mass fraction of 1.5% of the mother liquor, lifting it by a mother liquor lift pump, filtering it through a bag filter to remove flocculent particles and suspended matter, filtering it through a security filter and then entering a membrane separation and purification device, and obtaining a glycine solution after purification; wherein the flocculant is chitosan.

[0037] Example 4

[0038] Compared with Example 3, the difference in Example 4 is that the flocculant is kaolin.

[0039] Example 5

[0040] Compared with Example 3, the difference in Example 5 is that the flocculant is composed of chitosan and kaolin with a mass ratio of 2:1.

[0041] Example 6

[0042] Compared with Example 3, the difference in Example 6 is that the flocculant is composed of chitosan and kaolin with a mass ratio of 5:2.

[0043] Example 7

[0044] Compared with Example 3, the difference in Example 7 is that the flocculant is composed of chitosan and kaolin with a mass ratio of 3:1.

[0045] Example 8

[0046] The preparation method of modified kaolin includes the following steps: weighing 3 parts of 1-methylpyrrole-2-carboxamide, adding it to 500 parts of ethanol, adding 50 parts of kaolin, heating to 60°C and stirring for 7 hours, and then filtering and drying to obtain modified kaolin.

[0047] Compared with Example 6, the difference in Example 8 is that the kaolin is replaced with an equal amount of modified kaolin obtained by the above preparation method.

[0048] Example 9

[0049] The preparation method of the modified kaolin comprises the following steps: Weigh 3.5 parts of 1-methylpyrrole-2-carboxamide, add it to 500 parts of ethanol, add 50 parts of kaolin, heat up to 70 °C and stir for 6 h, then filter and dry to obtain the modified kaolin.

[0050] Compared with Example 6, Example 9 is different in that the kaolin is replaced with an equal amount of the modified kaolin obtained by the above preparation method.

[0051] Example 10

[0052] The preparation method of the modified kaolin comprises the following steps: Weigh 4 parts of 1-methylpyrrole-2-carboxamide, add it to 500 parts of ethanol, add 50 parts of kaolin, heat up to 80 °C and stir for 5 h, then filter and dry to obtain the modified kaolin.

[0053] Compared with Example 6, Example 10 is different in that the kaolin is replaced with an equal amount of the modified kaolin obtained by the above preparation method.

[0054] Example 11

[0055] Compared with Example 9, Example 11 is different in that 1-methylpyrrole-2-carboxamide is replaced with an equal amount of 2-amino-1H-pyrrole-3-carboxamide.

[0056] Comparative Example 1

[0057] Compared with Example 3, Comparative Example 1 is different in that no flocculant is added.

[0058] Comparative Example 2

[0059] Compared with Example 6, Comparative Example 2 is different in that the kaolin is replaced with an equal amount of bentonite.

[0060] Comparative Example 3

[0061] Compared with Example 3, Comparative Example 3 is different in that the pH is not adjusted.

[0062] For the glycine prepared in Examples 1 to 11 and Comparative Examples 1 to 3, the purity of the product was tested by high performance liquid chromatography.

[0063] The test results are shown in the following table:

[0064] Table 1 Performance test results of glycine prepared in Examples 1 to 11 and Comparative Examples 1 to 3

[0065]

[0066] Note: In the above table, the yield calculation formula is: (actual output / theoretical output) × 100%.

[0067] Compared with Comparative Example 1, chitosan was added as a flocculant in Example 3. As a result, the yield and purity of Example 3 were both better than those of Comparative Example 1, indicating that the addition of chitosan could improve the yield and purity of glycine.

[0068] Compared with Examples 3 and 4, chitosan and kaolin were added simultaneously as flocculants in Examples 5 - 7. As a result, the yield and purity of Examples 5 - 7 were both better than those of Examples 3 and 4, indicating that chitosan and kaolin played a synergistic role and could further improve the yield and purity of glycine. In Examples 5 - 7, chitosan and kaolin with different mass ratios were added. As a result, the yield and purity of Example 6 were both better than those of Examples 5 and 7, indicating that when the mass ratio of chitosan to kaolin was 5:2, the yield and purity of the obtained glycine were better.

[0069] Compared with Comparative Example 2, modified bentonite was added as a flocculant in Example 6. As a result, the yield and purity of Example 6 were both better than those of Comparative Example 2, indicating that the synergistic effect of kaolin and chitosan was better and the yield and purity of the obtained glycine were higher.

[0070] Compared with Example 6, modified kaolin obtained by modification with a pyrrole carboxamide compound was added as a flocculant in Examples 8 - 11. As a result, the yield and purity of Examples 8 - 11 were both better than those of Example 6, indicating that when modified kaolin modified with a pyrrole carboxamide compound was added, the yield and purity of the obtained glycine were better.

[0071] Compared with Comparative Example 3, the pH was adjusted to 4.5 with hydrochloric acid solution in Example 3. As a result, the yield and purity of Example 3 were both better than those of Comparative Example 3, indicating that after adjusting the pH, the yield and purity of the obtained glycine were higher.

[0072] The above are only the 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 principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A glycine mother liquor treatment process, characterized in that, It includes the following steps: Adjust the pH of the glycine mother liquor to 3.5 - 4.5, add a flocculant, and after the first filtration and the second filtration, then through membrane separation and purification to obtain a glycine solution; the flocculant includes chitosan, and the addition amount of the flocculant is 0.5% - 1.5% of the mass of the glycine mother liquor; The flocculant further includes kaolin, and the mass ratio of the chitosan to the kaolin is 2 - 3:1; The kaolin is modified kaolin, and the modified kaolin is obtained by modifying kaolin with a modifier, and the modifier is a pyrrole carboxamide compound; The pyrrole carboxamide compound includes one or two of 1 - methylpyrrole - 2 - carboxamide and 2 - amino - 1H - pyrrole - 3 - carboxamide; The preparation method of the modified kaolin includes the following steps: disperse the modifier in a solvent, add kaolin, and after modification, filter and dry to obtain the modified kaolin; The temperature of the modification is 60 - 80 °C, and the time of the modification is 5 - 7 h.

2. The glycine mother liquor treatment process according to claim 1, wherein, The first filtration uses a bag filter, and the second filtration uses a cartridge filter.

3. A glycine mother liquor treatment process according to claim 2, wherein, The pore sizes of the bag filter and the cartridge filter are independently 0.1 - 1 μm.

4. A glycine mother liquor treatment process according to claim 1, characterized in that, The solution used to adjust the pH is a hydrochloric acid solution with a mass concentration of 30 wt%.

5. A glycine mother liquor treatment process according to claim 1, characterized in that, In the raw materials of the modified kaolin, the mass ratio of the modifier to the kaolin is 3 - 4:50.

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