Glycine mother liquor treatment process

Abstract

The 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 value of glycine mother liquor to 3.5-4.5, adding a flocculating agent, filtering for the first time, filtering for the second time, and then separating and purifying by a membrane to obtain a glycine solution; the flocculating agent comprises chitosan, and the adding amount of the flocculating agent is 0.5%-1.5% of the mass of the glycine mother liquor. Through the technical scheme, the problems of low purity and low yield of glycine recovered from the glycine mother liquor in related technologies are solved.

Description

Technical Field

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

[0002] Glycine is an important organic chemical raw material, widely used in medicine, food, pesticides and other fields. There are many kinds of impurities in glycine mother liquor, including incompletely reacted raw materials, large molecular organic pigments, activated carbon and other impurities. If the glycine mother liquor is not treated and directly discharged, it will cause serious harm to the environment.

[0003] The macromolecular pigments and activated carbon contained in the mother liquor are discharged directly into the water body without treatment. The macromolecular pigments will change the color of the water and affect the light transmittance of the water, which will hinder the photosynthesis of aquatic plants and reduce the content of dissolved oxygen in the water, thereby destroying 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 and affecting the air permeability and water permeability of the soil. The activated carbon may adsorb nutrients and microorganisms in the soil and reduce soil fertility. Moreover, these substances may further spread with processes such as rain erosion, polluting the surrounding soil and groundwater.

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

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

[0006] The technical scheme of the present invention is as follows: The present invention proposes a glycine mother liquor treatment process, comprising the following steps: adjusting the pH of the glycine mother liquor to 3.5-4.5, adding a flocculant, filtering for the first time, filtering for the second time, and then separating and purifying by membrane to obtain a glycine solution; the flocculant comprises chitosan, and the amount of the flocculant added 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 of deionized water and filtration of industrial-grade glycine, and the glycine mother liquor contains a large amount of pigment components after recycling.

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

[0009] In the present invention, a filter membrane with a molecular weight range of 100 to 300 is selected so that glycine molecules can pass through the membrane smoothly. Impurities such as organic pigments are effectively retained on one side of the membrane because their molecular weight is as high as tens of thousands, far exceeding the range allowed by the membrane pore size. 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 uses a bag filter and the second filtration uses a security filter.

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

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

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

[0014] In the present invention, chitosan and kaolin are added as flocculants at the same time, and the synergistic effect of the two is brought into play, the adsorption effect of the flocculants on impurities is enhanced, the formation of a more compact flocculation structure is promoted, the flocculation efficiency is improved, the impurities such as organic pigments in the glycine mother liquor are further removed, and the purity and yield of glycine recovered from the glycine mother liquor are improved.

[0015] As a further technical solution, the kaolin is modified kaolin, and the modified kaolin is kaolin modified by a modifier, and the modifier is a pyrrolecarboxamide compound.

[0016] In the present invention, pyrrole carboxamide compounds are used to modify kaolin to obtain modified kaolin. The modified kaolin has stronger selective adsorption of impurities, helps to accurately 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 3-4:50.

[0018] As a further technical solution, the pyrrolecarboxamide 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 comprises the following steps: dispersing the modifier in a solvent, adding kaolin, filtering and drying after modification to obtain the modified kaolin.

[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: In the present invention, membrane filtration separation technology is adopted to achieve screening according to the molecular weight of the substance. Before membrane filtration, chitosan is added as a flocculant to the organic pigment impurities, and a large number of impurity particles are aggregated to form a larger floc structure through electrostatic adsorption and bridging effects, 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. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the following examples and comparative examples: Chitosan: particle size 120 mesh, deacetylation degree 94.3wt%; Kaolin: particle size is 325 mesh; Bentonite: sodium bentonite, particle size 325 mesh, manufactured by Lingshou County Baifeng Mineral Products Processing Plant; Bag filter: pore size 0.5μm; Security filter: pore size is 0.5μm.

[0025] Example 1 A glycine mother liquor treatment process comprises the following steps: using 30wt% hydrochloric acid solution to adjust the pH value of the glycine mother liquor to 3.5, adding 0.5% flocculant by mass fraction of the mother liquor, lifting the mother liquor by a mother liquor lifting pump, filtering by a bag filter, removing flocculated particles and suspended matter, filtering by a security filter, and entering a membrane separation and purification device to obtain a glycine solution after purification; wherein the flocculant is chitosan.

[0026] Example 2 A glycine mother liquor treatment process comprises the following steps: using 30wt% hydrochloric acid solution to adjust the pH value of the glycine mother liquor to 4, adding 1% flocculant by mass fraction of the mother liquor, lifting the mother liquor by a mother liquor lifting pump, filtering by a bag filter, removing flocculated particles and suspended matter, filtering by a security filter, entering a membrane separation and purification device, and obtaining a glycine solution after purification; wherein the flocculant is chitosan.

[0027] Example 3 A glycine mother liquor treatment process comprises the following steps: using 30wt% hydrochloric acid solution to adjust the pH value of the glycine mother liquor to 4.5, adding a flocculant with a mass fraction of 1.5% of the mother liquor, lifting the mother liquor through a mother liquor lifting pump, filtering through a bag filter, removing flocculated particles and suspended matter, filtering through a security filter, entering a membrane separation and purification device, and obtaining a glycine solution after purification; wherein the flocculant is chitosan.

[0028] Example 4 Compared with Example 3, the difference in Example 4 is that the flocculant is kaolin.

[0029] Example 5 Compared with Example 3, the difference of Example 5 is that the flocculant consists of chitosan and kaolin in a mass ratio of 2:1.

[0030] Example 6 Compared with Example 3, the difference of Example 6 is that the flocculant consists of chitosan and kaolin in a mass ratio of 5:2.

[0031] Example 7 Compared with Example 3, the difference of Example 7 is that the flocculant consists of chitosan and kaolin in a mass ratio of 3:1.

[0032] Example 8 The preparation method of modified kaolin includes the following steps: weighing 3 parts of 1-methylpyrrole-2-carboxamide, adding it into 500 parts of ethanol, adding 50 parts of kaolin, heating to 60°C and stirring for 7 hours, filtering and drying to obtain modified kaolin.

[0033] Compared with Example 6, the difference of Example 8 is that kaolin is replaced by an equal amount of modified kaolin obtained by the above preparation method.

[0034] Example 9 The preparation method of modified kaolin includes the following steps: weighing 3.5 parts of 1-methylpyrrole-2-carboxamide, adding it into 500 parts of ethanol, adding 50 parts of kaolin, heating to 70°C and stirring for 6 hours, filtering and drying to obtain modified kaolin.

[0035] Compared with Example 6, the difference in Example 9 is that kaolin is replaced by an equal amount of modified kaolin obtained by the above preparation method.

[0036] Example 10 The preparation method of modified kaolin includes the following steps: weighing 4 parts of 1-methylpyrrole-2-carboxamide, adding it into 500 parts of ethanol, adding 50 parts of kaolin, heating to 80°C and stirring for 5 hours, filtering and drying to obtain modified kaolin.

[0037] Compared with Example 6, the difference in Example 10 is that kaolin is replaced by an equal amount of modified kaolin obtained by the above preparation method.

[0038] Embodiment 11 Compared with Example 9, Example 11 is different in that 1-methylpyrrole-2-carboxamide is replaced by an equal amount of 2-amino-1H-pyrrole-3-carboxamide.

[0039] Comparative Example 1 Compared with Example 3, the difference in Comparative Example 1 is that no flocculant is added.

[0040] Comparative Example 2 Compared with Example 6, the difference in Comparative Example 2 is that kaolin is replaced by an equal amount of bentonite.

[0041] Comparative Example 3 Compared with Example 3, Comparative Example 3 is different in that the pH is not adjusted.

[0042] The glycine obtained in Examples 1 to 11 and Comparative Examples 1 to 3 was tested for purity using high performance liquid chromatography.

[0043] The test results are shown in the following table: Table 1 Performance test results of glycine obtained in Examples 1 to 11 and Comparative Examples 1 to 3

[0044] Note: In the above table, the yield calculation formula is: (actual yield / theoretical yield) × 100%.

[0045] Compared with Comparative Example 1, Example 3 added chitosan as a flocculant. As a result, the yield and purity of Example 3 were better than those of Comparative Example 1, indicating that the addition of chitosan can improve the yield and purity of glycine.

[0046] Compared with Examples 3 and 4, Examples 5 to 7 simultaneously added chitosan and kaolin as flocculants, and the yield and purity of Examples 5 to 7 were better than those of Examples 3 and 4, indicating that chitosan and kaolin play a synergistic role and can further improve the yield and purity of glycine. In Examples 5 to 7, chitosan and kaolin in different mass ratios were added, and the yield and purity of Example 6 were better than those of Examples 5 and 7, indicating that when the mass ratio of chitosan to kaolin is 5:2, the yield and purity of glycine obtained are better.

[0047] Compared with Comparative Example 2, Example 6 added modified bentonite as a flocculant. As a result, the yield and purity of Example 6 were 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.

[0048] Compared with Example 6, Examples 8 to 11 added modified kaolin modified with a pyrrolecarboxamide compound as a flocculant. As a result, the yield and purity of Examples 8 to 11 were better than those of Example 6, indicating that when kaolin modified with a pyrrolecarboxamide compound was added, the yield and purity of the obtained glycine were better.

[0049] Compared with Comparative Example 3, Example 3 used hydrochloric acid solution to adjust the pH to 4.5. As a result, the yield and purity of Example 3 were better than those of Comparative Example 3, indicating that after adjusting the pH, the yield and purity of the obtained glycine were higher.

[0050] The above are only 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 in the protection scope of the present invention.

Claims

1. A glycine mother liquor treatment process, characterized in that: The following steps are involved: The pH of the glycine mother liquor is adjusted to 3.5-4.5, a flocculant is added, and after a first filtration and a second filtration, a glycine solution is obtained by membrane separation and purification; the flocculant includes chitosan, and the amount of the flocculant added is 0.5%-1.5% of the mass of the glycine mother liquor.

2. A glycine mother liquor treatment process according to claim 1, characterized in that: The first filtration uses a bag filter, and the second filtration uses a security filter.

3. A glycine mother liquor treatment process according to claim 2, characterized in that: The pore sizes of the bag filter and the security filter are independently 0.1-1 μm.

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

5. A glycine mother liquor treatment process according to claim 1, characterized in that: The flocculant also includes kaolin, and the mass ratio of the chitosan to the kaolin is 2-3:

1.

6. A glycine mother liquor treatment process according to claim 5, characterized in that: The kaolin is modified kaolin, which is obtained by modifying kaolin with a modifier, and the modifier is a pyrrolecarboxamide compound.

7. A glycine mother liquor treatment process according to claim 6, characterized in that: In the raw material of the modified kaolin, the mass ratio of the modifier to the kaolin is 3-4:

50.

8. A glycine mother liquor treatment process according to claim 6, characterized in that: The pyrrole carboxamide compound includes one or both of 1-methylpyrrole-2-carboxamide and 2-amino-1H-pyrrole-3-carboxamide.

9. A glycine mother liquor treatment process according to claim 6, characterized in that: The preparation method of the modified kaolin comprises the following steps: dispersing a modifier in a solvent, adding kaolin, filtering and drying after modification to obtain the modified kaolin.

10. A glycine mother liquor treatment process according to claim 9, characterized in that: The modification temperature is 60-80° C., and the modification time is 5-7 hours.

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