Method for separating lactic acid from kitchen waste lactic acid fermentation liquidTechnical Field
The invention relates to the technical field of recycling of organic solid wastes, in particular to a method for separating lactic acid from kitchen waste lactic acid fermentation broth.
Background
Lactic acid is one of the most common organic acids used in daily life of human beings, is an important biochemical product, is widely used in the fields of food, beverage, daily chemical industry, medicine, petrochemical industry, textile industry, cigarette industry and the like, and meanwhile, polylactic acid which is a polymer of lactic acid is a biodegradable plastic, and is favored as a raw material of modern medical materials due to good biocompatibility. Therefore, lactic acid has wide market demands at home and abroad. Industrial lactic acid production generally uses microbial fermentation methods. The lactic acid fermentation liquid contains a large amount of cells, proteins, saccharides, acetic acid, inorganic salts, and the like in addition to the target product lactic acid, so that the process of extracting lactic acid from the fermentation liquid is difficult and costly.
The traditional method for separating lactic acid from fermentation broth is the "calcium salt method". The method has the defects that the solubility of the calcium lactate is relatively high, the product loss in the crystallization step is caused, the recovery rate of the lactic acid is low, calcium sulfate waste residue with high impurity content is generated, the quality of the lactic acid product is influenced, acid and alkali are greatly consumed, the environment is seriously polluted, the process flow is complex, the operation is time-consuming and labor-consuming, and the method is not suitable for large-scale industrial application. The prior art also reports that lactic acid in fermentation liquor is separated by a membrane separation method, an ion exchange adsorption method and an electrodialysis method, but the purity of the lactic acid is difficult to ensure due to the complex components of the fermentation liquor, and a large amount of acid, alkali and water are consumed for regeneration of the membrane and the resin, so that the energy consumption is high. Therefore, the method for purifying the lactic acid needs to be studied, and the method has the advantages of higher purity and recovery rate of the lactic acid, higher impurity removal rate, higher efficiency and environmental protection.
Disclosure of Invention
The invention aims to provide a method for separating lactic acid from kitchen waste lactic acid fermentation broth, which comprises the following steps:
(1) The kitchen waste lactic acid fermentation liquid is filtered through a microfiltration membrane to obtain microfiltration trapped fluid and microfiltration permeate, and the microfiltration permeate is continuously filtered through the ultrafiltration membrane to obtain ultrafiltration permeate and ultrafiltration trapped fluid;
(2) The ultrafiltration permeate enters an electric regeneration ion exchanger, the electric regeneration ion exchanger consists of a membrane stack and polar chambers at two sides of the membrane stack, and membrane units of the membrane stack are sequentially arranged by a bipolar membrane, a cation exchange membrane, a bipolar membrane, an anion exchange membrane and a bipolar membrane, and an alkali chamber, a cation resin chamber, a anion resin chamber and an acid chamber are formed at intervals;
Introducing ultrafiltration permeate into a cation resin chamber, introducing water discharged from the cation resin chamber into an alkali chamber, introducing water discharged from the alkali chamber into the cation resin chamber again, and circulating between the cation resin chamber and the alkali chamber;
Introducing the effluent of the positive resin chamber into the negative resin chamber, introducing the effluent of the negative resin chamber into the acid chamber, and introducing the effluent of the acid chamber into the negative resin chamber again, circulating between the negative resin chamber and the acid chamber, stopping circulating when the lactic acid concentration of the effluent of the negative resin chamber is lower than 5g/L, collecting the effluent of the negative resin chamber, and refluxing the effluent of the negative resin chamber into the ultrafiltration permeate in the step (2);
(3) Starting a power supply of the electric regeneration ion exchanger, introducing pure water into the cation resin chamber for repeated circulation in the cation resin chamber, introducing pure water into the anion resin chamber for repeated circulation in the anion resin chamber, introducing alkali liquor into the alkali chamber for repeated circulation in the alkali chamber, introducing lactic acid solution into the acid chamber for repeated circulation in the acid chamber, electrically regenerating for 1-10 h under the condition of working voltage of 30-40V, switching off the power supply, collecting effluent of the acid chamber, and concentrating in vacuum to obtain a final product.
In the preferred technical scheme of the invention, the concentration of lactic acid in the lactic acid fermentation broth is 30-100 g/L, preferably 40-90 g/L.
In the preferred technical scheme of the invention, the concentration of acetic acid in the lactic acid fermentation broth is 1-10 g/L, preferably 2-8 g/L.
In the preferred technical scheme of the invention, the concentration of chloride ions in the lactic acid fermentation broth is 1-10 g/L, preferably 2-8 g/L.
In the preferred technical scheme of the invention, the pH of the lactic acid fermentation broth is 5.0-8.0, and the pH is preferably 6.0-7.0.
In the preferred technical scheme of the invention, the lactic acid fermentation broth is subjected to pretreatment to remove grease and thallus residues, and then subjected to membrane separation treatment.
In the preferred technical scheme of the invention, the kitchen waste lactic acid fermentation broth is fermentation broth obtained by inoculating kitchen waste with lactic acid bacteria for anaerobic fermentation.
In a preferred technical scheme of the invention, the micro-filtration membrane is made of polyvinylidene fluoride (PVDF) and has a pore diameter of 0.1 μm.
In the preferred technical scheme of the invention, the operation pressure of the microfiltration is 0.06-0.12 MPa, and the pH value of the lactic acid fermentation liquor is adjusted to 5.0-8.0 before the microfiltration.
In a preferred embodiment of the invention, the microfiltration retentate is returned to the lactic acid fermentation broth.
In a preferred technical scheme of the invention, the pH of the microfiltration permeation solution is 5.0-8.0, and preferably the pH is 6.0-7.0.
In a preferred embodiment of the present invention, the microfiltration membrane may be cleaned with any one of deionized water, HCl, naOH, naClO or a combination thereof.
In the preferred technical scheme of the invention, after the membrane flux of the microfiltration is reduced by 90%, deionized water can be used for cleaning, reverse cleaning is carried out for 3min under the condition that the operating pressure is 0.10MPa, and the microfiltration is carried out after the membrane flux is recovered.
In the preferred technical scheme of the invention, the ultrafiltration membrane is any one of a Regenerated Cellulose (RC) ultrafiltration membrane and a polyether sulfone (PES) ultrafiltration membrane, and the molecular weight cut-off is 30-100 kDa.
In the preferred technical scheme of the invention, the ultrafiltration operation pressure is 0.080-0.14 MPa, and the pH value of the microfiltration permeate is adjusted to 5.0-8.0 before ultrafiltration.
In a preferred embodiment of the present invention, the ultrafiltration membrane may be cleaned with any one of deionized water, HCl, naOH, naClO, or a combination thereof.
In the preferred technical scheme of the invention, after the ultrafiltration membrane flux is reduced by 90%, 1% NaClO can be used for cleaning, reverse cleaning is carried out for 1.5min and forward cleaning is carried out for 1.5min under the condition that the operating pressure is 0.10MPa, and ultrafiltration is carried out after the membrane flux is recovered.
In a preferred embodiment of the present invention, the cation exchange resin is a strong acid cation exchange resin, preferably any one of 732 type, D001 type, HD-8 type resins, or a combination thereof.
In a preferred embodiment of the present invention, the anion exchange resin is a weakly basic anion exchange resin, preferably any one of D311 type, D301G type, D330 type resins, or a combination thereof.
In the preferred technical scheme of the invention, the alkali liquor in the step (3) is any one of NaOH and KOH with the concentration of 0.05-0.1 mol/L.
In a preferred technical scheme of the invention, the concentration of the lactic acid solution in the step (3) is 0.05-0.1mol/L.
In a preferred embodiment of the present invention, the electrical regeneration time in the step (3) is 2-8 hours, preferably 4-6 hours.
In a preferred technical scheme of the invention, the concentration in the step (3) is 10-15 times of vacuum reduced pressure concentration.
In the preferred technical scheme of the invention, in the step (3), the effluent of the collecting alkali chamber can be used as a neutralizer to flow back to the fermentation reaction.
In a preferred embodiment of the invention, the purity of lactic acid in the final product is greater than 90%, preferably greater than 95%, more preferably greater than 97%.
In a preferred embodiment of the invention, the recovery of lactic acid in the final product is greater than 90%, preferably greater than 92%, more preferably greater than 95%.
In a preferred embodiment of the invention, the removal of acetic acid in the final product is greater than 85%, preferably greater than 88%, more preferably greater than 90%.
In a preferred embodiment of the invention, the chloride ion removal rate in the final product is greater than 90%, preferably greater than 93%, more preferably greater than 96%.
Unless otherwise indicated, the invention relates to percentages between liquids which are volume/volume percentages, between liquids which are volume/weight percentages, between solids which are weight/volume percentages, between solids and liquids which are weight/volume percentages, and the balance being weight/weight percentages.
Unless otherwise indicated, the present invention was tested using the following method:
1. Lactic acid detection method (high performance liquid chromatograph, LC-20 AT) comprises centrifuging sample to be detected in 12000rpm high speed centrifuge for 10min, filtering supernatant with 0.45 μm filter membrane, and subjecting to liquid chromatography. Samples were separated using a Shodex Sugar SH1011 liquid chromatography column (8.0 mm. Times.300 mm) and then entered into a RID detector for detection. The chromatographic conditions were column temperature 60 ℃, mobile phase 5mM H2SO4, flow rate 1.0mL/min, and sample volume 10. Mu.L.
Cl ion measurement method (ion chromatograph, ICS 600) the sample to be measured is centrifuged in a 12000r/min high-speed centrifuge for 10min, and the supernatant is filtered through a 0.22 μm filter membrane and diluted by a proper factor and then enters the ion chromatograph. The sample was separated using a Dionex IonPac AS22 ion chromatography column and then entered into the RID detector for detection. The chromatographic conditions were column temperature 30 ℃, mobile phase 4.5mM Na2CO3/1.4mM NaHCO3, flow rate 1.2mL/min, and sample volume 10. Mu.L.
3. Lactic acid purity: lactic acid mass in final product/final product mass X100%
4. Acetic acid removal rate (mass of acetic acid in lactic acid fermentation broth-mass of acetic acid in final product)/mass of acetic acid in lactic acid fermentation broth ×100%
5. Chlorine ion removal rate (mass of Cl- in lactic acid fermentation broth-mass of Cl- in final product)/mass of Cl- in lactic acid fermentation broth ×100%
6. Lactic acid recovery rate: lactic acid mass in final product/lactic acid mass in lactic acid fermentation broth. Times.100%
Compared with the prior art, the invention has the following beneficial technical effects:
1. The invention combines a membrane separation method with ion exchange adsorption-electrochemical regeneration integrated equipment, is used for purifying the lactic acid in the kitchen waste fermentation liquor, and has high impurity removal rate, thus obtaining the lactic acid with high purity and high recovery rate.
2. The invention can realize resin adsorption-electrochemical in-situ regeneration, does not consume acid-base chemical agents, does not produce waste liquid and waste residues, only consumes a small amount of electric energy and pure water, can directly analyze lactic acid from resin to obtain purified liquid, and simultaneously, the regenerated alkali liquid is recycled to the lactic acid fermentation process, so that the whole process realizes closed cycle, shortens the reaction time, realizes the resource utilization, and meets the production requirements of green and environment protection.
3. The method has the advantages of simple and convenient operation, low energy consumption and cost, and suitability for industrial production.
Drawings
FIG. 1 is a schematic diagram of a method for separating lactic acid from kitchen waste lactic acid fermentation broth;
FIG. 2 is a schematic diagram of an electrically regenerated ion exchanger of the present invention, in which BPM is bipolar membrane, CM is cation membrane, and AM is anion membrane.
FIG. 3 shows a comparison of the various indices of the end products obtained in examples 1-4.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The preparation method of the kitchen waste fermentation liquid comprises the steps of mixing 3kg of kitchen waste with 3kg of pure water, stirring, pulping, loading into a fermentation tank, inoculating lactobacillus seed liquid according to 10% of inoculum size, carrying out anaerobic fermentation, maintaining the fermentation temperature at 43 ℃, and regulating the pH value to 6.8-7.0 by using NaOH solution (10 mol/L) every 12 h. After 84h of fermentation, the fermentation product is centrifugally separated to obtain a liquid phase and a solid phase, the liquid phase is separated to obtain an oil phase through an extraction funnel, and the remainder is the lactic acid fermentation liquid to be separated in the embodiment of the invention. The lactic acid fermentation liquid contains 63.9g/L of lactic acid, 2.5g/L, cl- 2.4.4 g/L of acetic acid, 0.21g/L of protein and 3.33g/L of total sugar through detection.
The lactic acid bacteria seed liquid culturing step is that enterococcus mundtii Enterococcus mundtii (CGMCC 22227) preserved under the condition of-80 ℃ is inoculated into a lactic acid bacteria culture medium according to the inoculation amount of 10 percent, cultured for 12 hours at 43 ℃ and used as an activated seed liquid, and then 10 percent of the activated seed liquid is inoculated into the lactic acid bacteria culture medium and cultured for 9 hours at 43 ℃ to obtain the lactic acid bacteria seed liquid. The lactobacillus culture medium comprises 10.0g of peptone, 8.0g of beef extract, 4.0g of yeast powder, 20.0g of glucose, 5.0g of sodium acetate trihydrate and tri-ammonium citrate added into each liter of deionized water 2.0g,Tween 80 1.0mL,K2HPO4 2.0g,MgSO4.7H2O 0.2g,MnSO4.H2O 0.05g,pH 7.0.
The dual stage membranes of the examples were purchased from FuMA-Tech company, germanyFBM, male membrane selected from and female membrane available from eastern tenwei membrane technologies, inc. Of shandong, each membrane having an area of 7cm2 and an effective area of about 95% of the actual area, resins are commercially available.
Example 1
(1) Taking 500mL of lactic acid fermentation liquor, adjusting the pH value to 6.0, filtering a microfiltration membrane, wherein the material of the microfiltration membrane is polyvinylidene fluoride (PVDF), the aperture is 0.1 mu m, the operating pressure is 0.10Mpa, and collecting microfiltration permeate and microfiltration retentate, and refluxing the microfiltration retentate into fermentation reaction;
(2) Regulating the pH value of the microfiltration permeate prepared in the step (1) to be 6.0, passing through an ultrafiltration membrane, wherein the ultrafiltration membrane is a polyether sulfone (PES) ultrafiltration membrane with the molecular weight cutoff of 50kDa, and the operating pressure is 0.12Mpa to obtain ultrafiltration permeate and ultrafiltration retentate, and refluxing the ultrafiltration retentate into a fermentation reaction;
(3) The ultrafiltration permeate liquid prepared in the step (2) is sent into an electric regeneration ion exchanger with a power supply turned off at a flow rate of 8ml/s, wherein a membrane unit in the electric regeneration ion exchanger is sequentially provided with a bipolar membrane, a positive membrane, a double-stage membrane, a negative membrane and a bipolar membrane, and an alkali chamber, a positive resin chamber (filled with 732 type strong acid cation exchange resin), a negative resin chamber (filled with D311 type macroporous weak alkaline acrylic acid anion exchange resin) and an acid chamber are formed at intervals;
Introducing ultrafiltration permeate into a cation resin chamber (the working temperature of cation exchange resin is 25 ℃), introducing water discharged from the cation resin chamber into an alkali chamber, introducing water discharged from the alkali chamber into the cation resin chamber again, and circulating between the cation resin chamber and the alkali chamber;
Introducing the effluent of the positive resin chamber into a negative resin chamber (the working temperature of anion exchange resin is 25 ℃), introducing the effluent of the negative resin chamber into an acid chamber, and introducing the effluent of the acid chamber into the negative resin chamber again, circulating between the negative resin chamber and the acid chamber;
(4) Starting the power supply of the electric regeneration ion exchanger, respectively introducing pure water into the positive resin chamber at a flow rate of 8ml/s, repeatedly circulating the pure water in the positive resin chamber, introducing pure water into the negative resin chamber, repeatedly circulating the pure water in the negative resin chamber, introducing NaOH solution with a concentration of 0.05mol/L into the alkali chamber, repeatedly circulating the NaOH solution in the alkali chamber, introducing lactic acid solution with a concentration of 0.05mol/L into the acid chamber, repeatedly circulating the lactic acid solution in the acid chamber, electrically regenerating the lactic acid solution for 6 hours under the condition of an operating voltage of 30V, closing the power supply, collecting effluent of the acid chamber, distilling and concentrating the effluent for 13 times under the vacuum condition that the pressure is reduced to 2.67KPa (20 mmHg) to obtain a final product, and collecting the effluent of the alkali chamber, wherein the effluent can be used as a neutralizer to flow back to a fermentation reaction, as shown in figures 1-2.
Example 2
(1) Taking 500mL of lactic acid fermentation liquor, adjusting the pH value to 6.0, filtering a microfiltration membrane, wherein the material of the microfiltration membrane is polyvinylidene fluoride (PVDF), the aperture is 0.1 mu m, the operating pressure is 0.10Mpa, and collecting microfiltration permeate and microfiltration retentate, and refluxing the microfiltration retentate into fermentation reaction;
(2) Regulating the pH value of the microfiltration permeate prepared in the step (1) to be 6.0, passing through an ultrafiltration membrane, wherein the ultrafiltration membrane is a polyether sulfone (PES) ultrafiltration membrane with the molecular weight cutoff of 50kDa, and the operating pressure is 0.12Mpa to obtain ultrafiltration permeate and ultrafiltration retentate, and refluxing the ultrafiltration retentate into a fermentation reaction;
(3) The ultrafiltration permeate liquid prepared in the step (2) is sent into an electric regeneration ion exchanger with a power supply turned off at a flow rate of 8ml/s, wherein a membrane unit in the electric regeneration ion exchanger is sequentially provided with a bipolar membrane, a positive membrane, a double-stage membrane, a negative membrane and a bipolar membrane, and an alkali chamber, a positive resin chamber (filled with 732 type strong acid cation exchange resin), a negative resin chamber (filled with D345 type macroporous weak alkaline phenolic type anion exchange resin) and an acid chamber are formed at intervals;
Introducing ultrafiltration permeate into a cation resin chamber (the working temperature of cation exchange resin is 25 ℃), introducing water discharged from the cation resin chamber into an alkali chamber, introducing water discharged from the alkali chamber into the cation resin chamber again, and circulating between the cation resin chamber and the alkali chamber;
Introducing the effluent of the positive resin chamber into a negative resin chamber (the working temperature of anion exchange resin is 25 ℃), introducing the effluent of the negative resin chamber into an acid chamber, and introducing the effluent of the acid chamber into the negative resin chamber again, circulating between the negative resin chamber and the acid chamber;
(4) Starting the power supply of the electric regeneration ion exchanger, respectively introducing pure water into the positive resin chamber at a flow rate of 8ml/s, repeatedly circulating the pure water in the positive resin chamber, introducing pure water into the negative resin chamber, repeatedly circulating the pure water in the negative resin chamber, introducing NaOH solution with a concentration of 0.05mol/L into the alkali chamber, repeatedly circulating the NaOH solution in the alkali chamber, introducing lactic acid solution with a concentration of 0.05mol/L into the acid chamber, repeatedly circulating the lactic acid solution in the acid chamber, electrically regenerating the lactic acid solution for 6 hours under the condition of an operating voltage of 30V, closing the power supply, collecting effluent of the acid chamber, distilling and concentrating the effluent for 13 times under the vacuum condition that the pressure is reduced to 2.67KPa (20 mmHg), and collecting the effluent of the alkali chamber, wherein the effluent can be used as a neutralizer to flow back into a fermentation reaction.
Example 3
(1) Taking 500mL of lactic acid fermentation liquor, adjusting the pH value to 6.0, filtering a microfiltration membrane, wherein the material of the microfiltration membrane is polyvinylidene fluoride (PVDF), the aperture is 0.1 mu m, the operating pressure is 0.10Mpa, and collecting microfiltration permeate and microfiltration retentate, and refluxing the microfiltration retentate into fermentation reaction;
(2) Regulating the pH value of the microfiltration permeate prepared in the step (1) to be 6.0, passing through an ultrafiltration membrane, wherein the ultrafiltration membrane is a polyether sulfone (PES) ultrafiltration membrane with the molecular weight cutoff of 50kDa, and the operating pressure is 0.12Mpa to obtain ultrafiltration permeate and ultrafiltration retentate, and refluxing the ultrafiltration retentate into a fermentation reaction;
(3) The ultrafiltration permeate liquid prepared in the step (2) is sent into an electric regeneration ion exchanger with a power supply turned off at a flow rate of 8ml/s, wherein a membrane unit in the electric regeneration ion exchanger is sequentially provided with a bipolar membrane, a positive membrane, a double-stage membrane, a negative membrane and a bipolar membrane, and an alkali chamber, a positive resin chamber (filled with 732-type strong acid cation exchange resin), a negative resin chamber (filled with D301G macroporous weak alkaline styrene anion exchange resin) and an acid chamber are formed at intervals;
Introducing ultrafiltration permeate into a cation resin chamber (the working temperature of cation exchange resin is 25 ℃), introducing water discharged from the cation resin chamber into an alkali chamber, introducing water discharged from the alkali chamber into the cation resin chamber again, and circulating between the cation resin chamber and the alkali chamber;
Introducing the effluent of the positive resin chamber into a negative resin chamber (the working temperature of anion exchange resin is 25 ℃), introducing the effluent of the negative resin chamber into an acid chamber, and introducing the effluent of the acid chamber into the negative resin chamber again, circulating between the negative resin chamber and the acid chamber;
(4) Starting the power supply of the electric regeneration ion exchanger, respectively introducing pure water into the positive resin chamber at a flow rate of 8ml/s, repeatedly circulating the pure water in the positive resin chamber, introducing pure water into the negative resin chamber, repeatedly circulating the pure water in the negative resin chamber, introducing NaOH solution with a concentration of 0.05mol/L into the alkali chamber, repeatedly circulating the NaOH solution in the alkali chamber, introducing lactic acid solution with a concentration of 0.05mol/L into the acid chamber, repeatedly circulating the lactic acid solution in the acid chamber, electrically regenerating the lactic acid solution for 6 hours under the condition of an operating voltage of 30V, closing the power supply, collecting effluent of the acid chamber, distilling and concentrating the effluent for 13 times under the vacuum condition that the pressure is reduced to 2.67KPa (20 mmHg), and collecting the effluent of the alkali chamber, wherein the effluent can be used as a neutralizer to flow back into a fermentation reaction.
Example 4
(1) Taking 500mL of lactic acid fermentation liquor, adjusting the pH value to 6.0, filtering a microfiltration membrane, wherein the material of the microfiltration membrane is polyvinylidene fluoride (PVDF), the aperture is 0.1 mu m, the operating pressure is 0.10Mpa, and collecting microfiltration permeate and microfiltration retentate, and refluxing the microfiltration retentate into fermentation reaction;
(2) Regulating the pH value of the microfiltration permeate prepared in the step (1) to be 6.0, passing through an ultrafiltration membrane, wherein the ultrafiltration membrane is a polyether sulfone (PES) ultrafiltration membrane with the molecular weight cutoff of 50kDa, and the operating pressure is 0.12Mpa to obtain ultrafiltration permeate and ultrafiltration retentate, and refluxing the ultrafiltration retentate into a fermentation reaction;
(3) The ultrafiltration permeate liquid prepared in the step (2) is sent into an electric regeneration ion exchanger which is powered off at a flow rate of 8ml/s, wherein a membrane unit in the electric regeneration ion exchanger is formed by a bipolar membrane, a cationic membrane, a two-stage membrane, a negative membrane and a bipolar membrane in sequence, and an alkali chamber, a positive resin chamber (filled with 732 type strong acid cation exchange resin), a negative resin chamber (filled with D330 type weak alkaline epoxy anion exchange resin) and an acid chamber are formed at intervals;
Introducing ultrafiltration permeate into a cation resin chamber (the working temperature of cation exchange resin is 25 ℃), introducing water discharged from the cation resin chamber into an alkali chamber, introducing water discharged from the alkali chamber into the cation resin chamber again, and circulating between the cation resin chamber and the alkali chamber;
Introducing the effluent of the positive resin chamber into a negative resin chamber (the working temperature of anion exchange resin is 25 ℃), introducing the effluent of the negative resin chamber into an acid chamber, and introducing the effluent of the acid chamber into the negative resin chamber again, circulating between the negative resin chamber and the acid chamber;
(4) Starting the power supply of the electric regeneration ion exchanger, respectively introducing pure water into the positive resin chamber at a flow rate of 8ml/s, repeatedly circulating the pure water in the positive resin chamber, introducing pure water into the negative resin chamber, repeatedly circulating the pure water in the negative resin chamber, introducing NaOH solution with a concentration of 0.05mol/L into the alkali chamber, repeatedly circulating the NaOH solution in the alkali chamber, introducing lactic acid solution with a concentration of 0.05mol/L into the acid chamber, repeatedly circulating the lactic acid solution in the acid chamber, electrically regenerating the lactic acid solution for 6 hours under the condition of an operating voltage of 30V, closing the power supply, collecting effluent of the acid chamber, distilling and concentrating the effluent for 13 times under the vacuum condition that the pressure is reduced to 2.67KPa (20 mmHg), and collecting the effluent of the alkali chamber, wherein the effluent can be used as a neutralizer to flow back into a fermentation reaction.
Test example 1
The final products obtained in examples 1-4 were tested for lactic acid purity, lactic acid recovery, acetic acid removal, cl- removal, see FIG. 3 for details.
It should be noted that the above embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solution described in the above embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.