CN117059730A - Preparation method of electrode material and treatment method of MDI waste brine - Google Patents

Preparation method of electrode material and treatment method of MDI waste brine Download PDF

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CN117059730A
CN117059730A CN202310914422.9A CN202310914422A CN117059730A CN 117059730 A CN117059730 A CN 117059730A CN 202310914422 A CN202310914422 A CN 202310914422A CN 117059730 A CN117059730 A CN 117059730A
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electrode
brine
polyamine
washing wastewater
washing
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陈杨
李永锋
赵东科
黄怀炜
章靓
张严
林飞腾
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Wanhua Chemical Group Fujian Isocyanate Co ltd
Wanhua Chemical Group Co Ltd
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Wanhua Chemical Group Fujian Isocyanate Co ltd
Wanhua Chemical Group Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46133—Electrodes characterised by the material
    • C02F2001/46138—Electrodes comprising a substrate and a coating
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds

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  • Water Treatment By Electricity Or Magnetism (AREA)

Abstract

The invention discloses a preparation method of an electrode material and a treatment method of MDI waste brine. The electrode material is used for treating washing wastewater generated in the production of diamines and polyamines (DAM) of the diphenylmethane series. And constructing a protective coating on the surface of the electrode. By introducing the nano particles, the hydrophilicity of the coating is improved. By introducing polyethylene glycol, the uniform dispersion of the nano particles is promoted, the hydrophilicity of the coating is further improved and the adsorption behavior of the macromolecular polymer on the surface of the electrode is inhibited by the cooperation of the polyethylene glycol and the nano particles. High-concentration brine with the sodium chloride concentration of 21-25wt% can be obtained, and chlor-alkali can be fully recycled. Meanwhile, the energy consumption of the electric adsorption treatment of polyamine washing wastewater is low, and the wastewater treatment cost is reduced.

Description

Preparation method of electrode material and treatment method of MDI waste brine
Technical Field
The invention belongs to the technical field of low-concentration salt-containing water treatment in the DAM production process, and particularly relates to a preparation method of an electro-adsorption electrode material, which is used for treating washing wastewater generated in the production of diamines and polyamines (DAM) of diphenylmethane series.
Background
The diphenylmethane series of isocyanates (MDI) are the main raw material for polyurethane production, and the preparation methods of DAM and phosgene reaction synthesis are well known in the industry. In the production of DAM, aniline is typically reacted with hydrochloric acid to produce aniline hydrochloride, followed by formaldehyde to produce diamines and polyamines, alkali to neutralize and separate the layers, yielding an organic phase (polyamine) and an aqueous phase (brine). The organic phase contains a small amount of salt substances and alkali, and the salt substances or the alkali are required to be washed and removed by water, so that the separation of the salt substances or the alkali in a downstream process is avoided, the process stability is influenced, and meanwhile, the sodium content in the DAM and the MDI products is ensured to meet the downstream application requirements.
The general treatment mode of the waste brine produced in the DAM production process is that the strong brine obtained by neutralization and delamination is mixed with polyamine washing wastewater, and then the extraction, rectification and TOC removal processes are carried out, so that the TOC content in the waste brine reaches the corresponding index, and then the waste brine is discharged from the sea or used as a chlor-alkali raw material.
Patent CN101801909a discloses a treatment process of combining neutralized brine with polyamine washing wastewater followed by extraction and rectification. However, since the polyamine wash wastewater has a very low salt content, the total sodium chloride content is reduced after mixing with the neutralized brine. On the one hand, the concentration of the brine for delivering chlor-alkali is low, and the chlor-alkali is limited by water balance and only can receive part of the brine. On the other hand, the waste water to be treated is large in quantity, and a large quantity of steam is consumed, so that the economic benefit is reduced.
Patent CN112827365a mentions a method for removing amine organics in polyamine washing wastewater by using super hydrophobic membrane to reduce steam consumption. However, the treated wastewater still contains 63mg/L of aniline, and needs to be discharged after further treatment in a biochemical tank.
The purpose of the polyamine washing process is to remove inorganic substances, mainly sodium chloride and sodium hydroxide, from the polyamine. Thus, if sodium chloride and sodium hydroxide in the polyamine washing wastewater are separated, the washing wastewater can be regenerated and used for polyamine washing. The method has the advantages that 1) the mixing of washing wastewater with low salt concentration and neutral brine is avoided, and the concentration of the chlor-alkali-conveying brine is improved; 2) The washing wastewater does not need complex post-treatment processes such as extraction, rectification, biochemistry and the like, so that the equipment is simplified, and the energy consumption is reduced.
The electro-adsorption method is widely used in the field of wastewater desalination. However, as described in patent CN109438254a and patent CN112126030a, the production of macromolecular organic polymers is unavoidable during polyamine production, a portion of which is transferred to the brine phase. In practice, it has been found that this class of polymers tends to contaminate the electrodes, thereby reducing the electroadsorption efficiency.
Disclosure of Invention
The invention aims to provide a preparation method of an electrode material, which regenerates polyamine washing wastewater generated in the MDI production process by an electro-adsorption technology, can reduce the energy consumption of wastewater treatment and simultaneously reduce wastewater discharge.
To achieve the above technical object, the specific embodiments of the present invention are as follows:
a method for preparing an electrode material, comprising the steps of:
i. dispersing nanocellulose in water to obtain colloid, and then rapidly freezing the colloid;
ii. Freeze-drying the product in the step i, and then carrying out heating pretreatment;
heating and carbonizing the sample obtained in the step ii in an ammonia atmosphere to obtain a nitrogen-doped carbon nano rod;
iv, uniformly mixing the nitrogen-doped carbon nanorods obtained in the step iii with conductive acetylene black and polyvinyl alcohol, adding water, stirring to obtain uniform slurry, coating the uniform slurry on a graphite substrate, and vacuum drying;
and v, mixing the nano particles with NMP, sequentially adding PVDF and PEG, uniformly mixing to obtain a coating solution, coating the coating solution on the surface of an electrode, and soaking in water to remove redundant solvent.
According to the method provided by the invention, in step i, the nanocellulose is rod-shaped, preferably with a diameter of 20-80nm and a length of 150-2500nm, more preferably with a diameter of 20-60nm and a length of 150-1000nm.
In some examples, the nanocellulose is uniformly dispersed in water, wherein the mass fraction of nanocellulose is 2.0-3.0wt%.
In the step i, the temperature range of the quick freezing is-40 to-55 ℃, and the freezing time is 48-64h.
According to the method provided by the invention, in the step ii, freeze drying is carried out under a low-temperature and low-pressure environment, preferably, the freezing temperature is in the range of-50 to-55 ℃ and the pressure is less than or equal to 15Pa. In some examples, the sample is maintained in the freeze dryer for 48-60 hours.
According to the method provided by the invention, in the step ii, the freeze-dried sample is taken out for heating pretreatment, heating is generally selected in a muffle furnace, heating is set at a speed of 4-6 ℃/min, and the temperature is stopped after the temperature is raised to the target temperature. Preferably, the target temperature is 230-260 ℃, e.g. 250 ℃; in some examples, after increasing to the target temperature, the sample is incubated for a further 1.5-2.5 hours at the target temperature.
According to the method provided by the invention, in the step iii, the temperature is raised at the temperature raising rate of 8-12 ℃/min under the ammonia atmosphere, and the process is stopped after reaching the target temperature. Preferably, the target temperature is 700-900 ℃. And after the temperature is increased to the target temperature, continuing to keep the temperature for 2-2.5h.
According to the method provided by the invention, in the step iv, preferably, the mass ratio of the nitrogen-doped carbon nanorods to the polyvinyl alcohol is 7-9, and the mass ratio of the nitrogen-doped carbon nanorods to the conductive acetylene black is 7-9. The adding amount of deionized water is 1.1-1.3 times of the mass of the nitrogen-doped carbon nano rod.
In some examples, nitrogen doped carbon nanorods, conductive acetylene black, polyvinyl alcohol, and deionized water are mixed well at 75-80 ℃.
In some preferred embodiments, in step iv, the vacuum drying process is carried out at 80-85 ℃ and a pressure of less than or equal to 5kPa for a period of time of 1.5-2 hours.
According to the method provided by the invention, in step v, the thickness of the electrode surface coating is preferably 100-150 micrometers.
In some preferred embodiments, in step v, the mass ratio of PVDF added to PEG is 3-4 and the mass ratio of PVDF to nanoparticles is 7-9.
Preferably, in the step v, the nanoparticle material used is Al 2 O 3 、TiO 2 、SiO 2 、CeO 2 One or more of the following.
In some preferred embodiments, in said step v, after the surface coating is completed, the electrode is exposed to air for 20-30s and then immersed in deionized water for 24-36 hours.
In another aspect, there is provided a method of treating MDI waste brine, comprising the steps of:
1) Catalyzing aniline and formaldehyde to react by using hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, adding alkali solution to neutralize and phase-separate to obtain an organic phase containing polyamine and a water phase containing strong brine;
2) Washing the organic phase obtained in step 1) with a washing liquid, and separating phases to obtain an organic phase (polyamine after washing) and an aqueous phase (polyamine washing wastewater);
3) Removing sodium chloride and sodium hydroxide in the water phase obtained in the step 2) by adopting an electro-adsorption method, and taking the regenerated washing wastewater obtained as the washing liquid in the step 2);
4) And (3) desorbing the electrode to obtain high-concentration brine, merging the high-concentration brine with the aqueous phase containing the strong brine obtained in the step (1) to obtain a brine mixed solution, and taking the brine mixed solution as a raw material of a chlor-alkali process after aniline extraction, rectification and TOC removal.
According to the method provided by the invention, in the step 1), aniline and formaldehyde are subjected to a precondensation reaction and rearrangement and transposition are carried out in the presence of an acid catalyst, which are familiar to the person skilled in the art and are not repeated here.
In the step 1), the obtained mixed solution containing DAM and hydrochloride thereof needs to be added with alkali liquor to neutralize the mixed solution in order to prevent hydrochloric acid from entering downstream corrosion equipment. Preferably, an aqueous sodium hydroxide solution having a concentration of 48 to 50wt% is used; in some examples, the aqueous phase containing strong brine obtained in step 1) has a sodium chloride content of 19-21wt%.
According to the method provided by the invention, in the step 2), the washing liquid is the regenerated washing wastewater in the step 3). Typically, the volume ratio of the washing liquid to the organic phase obtained in step 1) is between 0.4 and 0.8:1, the temperature of the washing operation is higher than 80 ℃.
The total of sodium chloride and sodium hydroxide content in the composition of the organic phase (polyamine after washing) obtained in step 2) is less than 5ppm.
The composition of the water phase (polyamine washing wastewater) obtained in the step 2) contains one or more of aniline, MDA, cyclohexanol, cyclohexylamine, cyclohexanone, sodium chloride and sodium hydroxide, wherein the concentration of sodium chloride is less than 1200ppm, and the concentration of sodium hydroxide is less than 300ppm.
According to the method provided by the invention, in step 3), the electric adsorption treatment is carried out in an electric adsorption device, and conventional electric adsorption equipment can be optionally used. The electrode material is characterized in that the electrode of the electro-adsorption extraction equipment is made of the electrode material.
In some preferred embodiments, a quartz sand filter having a particle size of 0.5-1.0mm is provided at the inlet of the electro-adsorption device.
In the electro-adsorption treatment of the step 3), water phase (polyamine washing wastewater) to be treated is introduced between two electrode plates of the electro-adsorption equipment, so that sodium chloride and sodium hydroxide are adsorbed by the electrode material rich in micropores.
In the step 3), it is preferable that the electrode voltage is 1.5 to 2V.
In the step 3), after the electro-adsorption treatment, the composition of the regenerated washing wastewater obtained can be less than 35ppm of sodium chloride and less than 15ppm of sodium hydroxide. The remaining components of the polyamine washing wastewater, such as organic substances, e.g. aniline, MDA, cyclohexanol, cyclohexylamine, etc., do not significantly change in content relative to the aqueous phase obtained in step 2).
In step 4), as the electro-adsorption process continues, the concentration of the ions adsorbed on the electrode increases, and the adsorption rate of the electrode to the anions and cations in the wastewater decreases due to the ion-exclusion effect. Preferably, after the operation is performed for 1.8-2.2 hours, the direct current power supply is reversely connected with the electrode, so that the ions adsorbed by the electrode are quickly desorbed. Preferably, the desorption time is 4-7min, and the reverse connection voltage is 1.0-1.4V. Meanwhile, high-concentration brine generated in the desorption process is received into a buffer tank, mixed with the water phase containing the concentrated brine in the step 1), and then subjected to treatments of aniline extraction, rectification and TOC removal.
The invention develops a process for recycling polyamine washing wastewater. The most widely used treatment of the brine waste produced in MDI production is aniline extraction and rectification, as is well known. Compared with the existing technology, in the new development technology, the load of treating the waste brine is reduced by recycling the water phase (polyamine washing wastewater) in the step 2). Therefore, on one hand, the novel process can effectively reduce the consumption of the extractant aniline, and the correspondingly generated extraction phase (recovered aniline) is also greatly reduced, so that the situation that the aniline recovery amount is larger than the aniline consumption amount in the reaction and the aniline amount entering the system overflows can be effectively avoided. On the other hand, the consumption of steam in the distillation process can be effectively reduced, and the production cost is greatly reduced.
The invention does not need to blend the aqueous phase containing strong brine obtained after neutralization and delamination in the step 1) with the aqueous phase (polyamine washing wastewater) in the step 2).
In the step 4), in the aniline extraction process, the high salt concentration in the brine mixed solution can maintain the oil-water two-phase density difference, and the risk of unstable oil-water interface control is reduced.
The salt concentration of the brine (step 4) product sent to the chlor-alkali process can be maintained at 21-25wt%. And the chlor-alkali can be completely recycled, so that a part of chlor-alkali is prevented from being recycled and a part of chlor-alkali is prevented from being discharged, and the economic benefit is improved.
In the invention, only inorganic matters in the polyamine washing wastewater are removed, and organic matters such as aniline and DAM are reserved. The recycled and regenerated washing wastewater can not bring new impurities into the system, and the dissolved DAM in the regenerated washing wastewater is saturated, so that the DAM loss can not be caused. The polyamine washing wastewater is basically and completely recycled, so that the water supplementing amount of the system can be effectively reduced.
In order to solve the problem that the electrode is polluted by macromolecule polymers in the wastewater, a protective coating is constructed on the surface of the electrode. By introducing the nano particles, the hydrophilicity of the coating is improved. By introducing polyethylene glycol, the uniform dispersion of the nano particles is promoted, the hydrophilicity of the coating is further improved and the adsorption behavior of the macromolecular polymer on the surface of the electrode is inhibited by the cooperation of the polyethylene glycol and the nano particles.
Detailed Description
In order that the features and aspects of the invention described herein may be fully understood, specific embodiments will be described in further detail. While the preferred embodiments of the present invention have been described in the specific examples, it should be noted that the present invention may be embodied in various forms and should not be construed as being limited to the described embodiments.
Raw material source
Nanocellulose, shanghai Ke Raman Agents Co;
conductive acetylene black, tianjin Yibosui chemical Co., ltd;
n-methylpyrrolidone, ala Ding Shenghua technologies;
polyvinyl alcohol (average relative molecular weight 90000), a science and technology company of ala Ding Shenghua;
nano alumina, a Ding Shenghua science and technology company, inc;
nano titanium dioxide, ala Ding Shenghua technologies limited;
nano silica, ala Ding Shenghua technologies limited;
polyethylene glycol (average relative molecular weight 8000), a science and technology company of ala Ding Shenghua;
polyvinylidene fluoride, acidoma (Shanghai) chemical Co., ltd. Other chemical reagents used in the method of the invention are all conventional reagents in the field, and the purity is more than chemical purity.
Test method
Electro-adsorption device: the electric adsorption device consists of two electric adsorption modules, a rectification power supply cabinet, a quartz sand filter, a precise filter (5 mu m), a water pump and a water tank, wherein each electric adsorption module comprises 200 pairs of electrodes. The precise filter of the quartz sand filter is used for reducing suspended matters in the wastewater and avoiding the electrode from being blocked and polluted.
In each of examples and comparative examples, the content of the components of brine, chlor-alkali-fed brine and polyamine washing wastewater obtained by adding alkali to neutralize and phase-split were measured
The determination method of sodium chloride and sodium hydroxide is a potentiometric titration method;
the measurement method of aniline and DAM is liquid chromatography.
Example 1
(1) The electrode material of the electro-adsorption device is prepared according to the following steps:
i. uniformly dispersing nano carbon cellulose with the diameter of 20-60nm and the length of 150-1000nm in deionized water according to the mass fraction of 2%. Homogenizing for 15min by using a cell breaker to obtain uniform colloid, and then placing the colloid in an ultralow temperature refrigerator and freezing at-55 ℃ for 48h;
ii. The frozen sample was placed in a freeze dryer and dried at-53℃under 15Pa for 60 hours. The sample was taken out and heated to 245℃in a muffle furnace at a rate of 4℃per minute, followed by maintaining at 245℃for 2 hours.
iii, placing the sample obtained in the step ii in a tube furnace, heating to 800 ℃ at a speed of 12 ℃/min under an ammonia atmosphere, and then maintaining at 800 ℃ for 2.5h.
iv, taking 7g of the nitrogen doped carbon nano rod in the step iii, uniformly mixing with 1g of conductive acetylene black and 1g of polyvinyl alcohol, then adding 8.4g of deionized water at 75 ℃ and uniformly stirring to obtain uniform slurry, coating the uniform slurry on a graphite substrate, and drying for 1.5h at 85 ℃ and 3 kPa.
v, 0.9g TiO 2 The nanoparticles were mixed with 39.6g NMP, sonicated for 5min, then 7g PVDF and 2g PEG were added sequentially, and stirring was continued for 4 hours to obtain a coating solution, which was applied to the electrode surface at a thickness of 125 microns using a casting die. Exposing the electrode to airFor 20s, which was then immersed in deionized water for 30h.
(2) And installing the prepared electrode material on an electro-adsorption device for regenerating and recycling the polyamine washing wastewater.
(3) The method for regenerating and recycling the polyamine washing wastewater comprises the following steps:
1) The reaction of aniline and formaldehyde is catalyzed by hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, and then caustic soda with the concentration of 50% is added for neutralization and phase separation to obtain an organic phase containing polyamine and an aqueous phase containing strong brine. The aqueous phase contained 19% sodium chloride, 0.8% sodium hydroxide, 1.5% aniline. Flow rate of aqueous phase 60m 3 /h, organic phase flow 55m 3 /h。
2) Washing the organic phase obtained in step 1) with the post-regeneration wash waste water obtained in step 3) at 95℃with a flow rate of 23m 3 And/h. The phase is separated again to give an organic phase (polyamine after washing) and an aqueous phase (polyamine washing wastewater).
3) The aqueous phase (polyamine washing wastewater) was sent to an electric adsorption device for regeneration, and the electrode voltage of the electric adsorption device was 1.8V.
4) Every 1.8h interval, the positive electrode and the negative electrode are reversely connected for 7min, and the reverse connection voltage is 1.2V. And (3) desorbing ions adsorbed by the electrode, mixing high-concentration brine produced in the desorption process with the water phase containing the concentrated brine in the step (1) to obtain brine mixed solution, and removing the step (5). The primary adsorption-desorption is a cycle, and after 100 cycles, the regenerated washing wastewater contains 29ppm of sodium chloride and 13ppm of sodium hydroxide. The organic phase containing polyamine of step 1) was washed with the regenerated washing wastewater, and the organic phase (washed polyamine) obtained in step 2) contained 0.8ppm of sodium chloride and 0.2ppm of sodium hydroxide.
5) Sequentially adopting aniline extraction, distillation and catalytic oxidation to treat the salt water mixed liquor in the step 4), wherein the extraction process is carried out in a tower type extractor, and the feeding mass ratio of the aniline to the mixed liquor is 0.22; the distillation process is carried out in a distillation tower, and the mass ratio of the steam addition amount of the tower kettle to the mixed liquid is 0.23; the catalytic oxidation process is carried out in a fixed bed tower reactor, the oxidant is 12% sodium hypochlorite aqueous solution, and the mass ratio of the oxidant to the mixed solution is 0.01.The salt concentration in the treated brine is 21wt%, the TOC content is lower than 10ppm, and the flow is 47m 3 And/h, sending to chlor-alkali as a raw material.
Example 2
(1) The electrode material of the electro-adsorption device is prepared according to the following steps:
i. uniformly dispersing nano carbon cellulose with the diameter of 20-60nm and the length of 150-1000nm in deionized water according to the mass fraction of 2.5%. Homogenizing for 15min by using a cell breaker to obtain uniform colloid, and then placing the colloid in an ultralow temperature refrigerator to freeze for 56h at-47 ℃;
ii. The frozen sample was placed in a freeze dryer and dried at-50℃under 15Pa for 54 hours. The sample was taken out and heated to 260℃in a muffle furnace at a rate of 5℃per minute, followed by a 2-hour hold at 260 ℃.
iii, placing the sample obtained in the step ii in a tube furnace, heating to 900 ℃ at a speed of 10 ℃/min under an ammonia atmosphere, and then maintaining at 900 ℃ for 2.5h.
iv, taking 8g of the nitrogen doped carbon nano rod in the step iii, uniformly mixing with 1g of conductive acetylene black and 1g of polyvinyl alcohol, then adding 10.4g of deionized water at 77 ℃ to uniformly stir, obtaining uniform slurry, coating the uniform slurry on a graphite substrate, and drying for 1.7h at 83 ℃ and 5 kPa.
v, 1g Al 2 O 3 The nanoparticles were mixed with 39.6g NMP, sonicated for 5min, then 7g PVDF and 2.3g PEG were added sequentially, and stirring was continued for 4h to obtain a coating solution, which was applied to the electrode surface at a thickness of 150 μm using a casting mold. The electrode was exposed to air for 25s and then immersed in deionized water for 24h.
(2) And installing the prepared electrode material on an electro-adsorption device for regenerating and recycling the polyamine washing wastewater.
(3) The method for regenerating and recycling the polyamine washing wastewater comprises the following steps:
1) The reaction of aniline and formaldehyde is catalyzed by hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, and then caustic soda with the concentration of 50% is added for neutralization and phase separation to obtain an organic phase containing polyamine and an aqueous phase containing strong brine.The aqueous phase contained 19% sodium chloride, 0.8% sodium hydroxide, 1.5% aniline. Flow rate of aqueous phase 60m 3 /h, organic phase flow 55m 3 /h。
2) Washing the organic phase obtained in step 1) with the post-regeneration wash waste water obtained in step 3) at 95℃with a flow rate of 23m 3 And/h. The phase is separated again to give an organic phase (polyamine after washing) and an aqueous phase (polyamine washing wastewater).
3) The aqueous phase (polyamine washing wastewater) was sent to an electric adsorption device for regeneration, and the electrode voltage of the electric adsorption device was 2V.
4) Every interval is 2.2h, the positive electrode and the negative electrode are reversely connected for 5min, and the reverse connection voltage is 1.0V. And (3) desorbing ions adsorbed by the electrode, mixing high-concentration brine produced in the desorption process with the water phase containing the concentrated brine in the step (1) to obtain brine mixed solution, and removing the step (5). The primary adsorption-desorption is a cycle, and after 100 cycles, the regenerated washing wastewater contains 38ppm of sodium chloride and 16ppm of sodium hydroxide. The organic phase containing polyamine of step 1) was washed with the regenerated washing wastewater, and the organic phase (washed polyamine) obtained in step 2) contained 1.6ppm of sodium chloride and 0.5ppm of sodium hydroxide.
5) Sequentially adopting aniline extraction, distillation and catalytic oxidation to treat the salt water mixed liquor in the step 4), wherein the extraction process is carried out in a tower type extractor, and the feeding mass ratio of the aniline to the mixed liquor is 0.22; the distillation process is carried out in a distillation tower, and the mass ratio of the steam addition amount of the tower kettle to the mixed liquid is 0.23; the catalytic oxidation process is carried out in a fixed bed tower reactor, the oxidant is 12% sodium hypochlorite aqueous solution, and the mass ratio of the oxidant to the mixed solution is 0.01. The salt concentration in the treated brine is 21wt%, the TOC content is lower than 10ppm, and the flow is 47m 3 And/h, sending to chlor-alkali as a raw material.
Example 3
(1) The electrode material of the electro-adsorption device is prepared according to the following steps:
i. uniformly dispersing nano carbon cellulose with the diameter of 20-60nm and the length of 150-1000nm in deionized water according to the mass fraction of 3%. Homogenizing for 15min by using a cell breaker to obtain uniform colloid, and then placing the colloid in an ultralow temperature refrigerator to freeze for 64h at-40 ℃;
ii. The frozen sample was placed in a freeze dryer and dried at-55℃under 15Pa for 48 hours. The sample was taken out and heated to 230℃in a muffle furnace at a rate of 6℃per minute, followed by a 2h hold at 230 ℃.
iii, placing the sample obtained in the step ii in a tube furnace, heating to 700 ℃ at a speed of 8 ℃/min under an ammonia atmosphere, and then maintaining at 700 ℃ for 2.5h.
iv, taking 9g of the nitrogen doped carbon nano rod in the step iii, uniformly mixing the carbon nano rod with 1g of conductive acetylene black and 1g of polyvinyl alcohol, then adding 9.9g of deionized water at 80 ℃ to uniformly stir and mix, obtaining uniform slurry, coating the uniform slurry on a graphite substrate, and drying for 2 hours at 80 ℃ and 4 kPa.
v, 0.8g SiO 2 The nanoparticles were mixed with 39.6g NMP, sonicated for 5min, then 7g PVDF and 1.8g PEG were added sequentially, and stirring was continued for 4 hours to obtain a coating solution, which was applied to the electrode surface at a thickness of 100 μm using a casting mold. The electrode was exposed to air for 30s and then immersed in deionized water for 36h.
(2) And installing the prepared electrode material on an electro-adsorption device for regenerating and recycling the polyamine washing wastewater.
(3) The method for regenerating and recycling the polyamine washing wastewater comprises the following steps:
1) The reaction of aniline and formaldehyde is catalyzed by hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, and then caustic soda with the concentration of 50% is added for neutralization and phase separation to obtain an organic phase containing polyamine and an aqueous phase containing strong brine. The aqueous phase contained 19% sodium chloride, 0.8% sodium hydroxide, 1.5% aniline. Flow rate of aqueous phase 60m 3 /h, organic phase flow 55m 3 /h。
2) Washing the organic phase obtained in step 1) with the post-regeneration wash waste water obtained in step 3) at 95℃with a flow rate of 23m 3 And/h. The phase is separated again to give an organic phase (polyamine after washing) and an aqueous phase (polyamine washing wastewater).
3) The aqueous phase (polyamine washing wastewater) was sent to an electric adsorption device for regeneration, and the electrode voltage of the electric adsorption device was 1.5V.
4) Every interval is 2h, the positive electrode and the negative electrode are reversely connected for 4min, and the reverse connection voltage is 1.4V. And (3) desorbing ions adsorbed by the electrode, mixing high-concentration brine produced in the desorption process with the water phase containing the concentrated brine in the step (1) to obtain brine mixed solution, and removing the step (5). The primary adsorption-desorption is a cycle, and after 100 cycles, the regenerated washing wastewater contains 132ppm of sodium chloride and 35ppm of sodium hydroxide. The organic phase containing polyamine of step 1) was washed with the regenerated washing wastewater, and the organic phase (washed polyamine) obtained in step 2) contained 2.3ppm of sodium chloride and 0.8ppm of sodium hydroxide.
5) Sequentially adopting aniline extraction, distillation and catalytic oxidation to treat the salt water mixed liquor in the step 4), wherein the extraction process is carried out in a tower type extractor, and the feeding mass ratio of the aniline to the mixed liquor is 0.22; the distillation process is carried out in a distillation tower, and the mass ratio of the steam addition amount of the tower kettle to the mixed liquid is 0.23; the catalytic oxidation process is carried out in a fixed bed tower reactor, the oxidant is 12% sodium hypochlorite aqueous solution, and the mass ratio of the oxidant to the mixed solution is 0.01. The salt concentration in the treated brine is 21wt%, the TOC content is lower than 10ppm, and the flow is 47m 3 And/h, sending to chlor-alkali as a raw material.
Comparative example 1
The method of example 1 is referred to, except that the electrode used is not surface-coated, i.e., the electrode is prepared without step v. The other electrode preparation methods, polyamine washing wastewater regeneration and reuse methods, and electrode adsorption-desorption cycle methods were the same as in example 1.
After 100 cycles, the regenerated washing wastewater contains 8663ppm of sodium chloride and 840ppm of sodium hydroxide. The organic phase containing polyamine of step 1) was washed with the regenerated washing wastewater, and the organic phase (washed polyamine) obtained in step 2) contained 45ppm of sodium chloride and 4.7ppm of sodium hydroxide.
Comparative example 2
Referring to the method of example 1, except that in step v, the formulation of the electrode surface film is free of PEG and nanoparticles. Step v was performed by mixing 39.6g NMP and 7g PVDF and stirring for 4 hours to obtain a coating solution, which was applied to the electrode surface at a thickness of 125 μm using a casting die. The electrode was exposed to air for 20s and then immersed in deionized water for 30h. The other electrode preparation methods, polyamine washing wastewater recycling methods, and electrode adsorption-desorption cycle methods were the same as in example 1.
After 100 cycles, the regenerated washing wastewater contains 6438ppm of sodium chloride and 746ppm of sodium hydroxide. The organic phase containing polyamine of step 1) was washed with the regenerated washing wastewater, and the organic phase (washed polyamine) obtained in step 2) contained 37ppm of sodium chloride and 4.3ppm of sodium hydroxide.
Comparative example 3
The treatment method for polyamine washing wastewater is different from example 1 in that polyamine washing wastewater is not treated solely by an electro-adsorption method, but is blended with brine obtained by adding alkali to neutralize and split phases, and aniline extraction, distillation and catalytic oxidation treatment are sequentially adopted, and specifically comprises the following steps.
1) The reaction of aniline and formaldehyde is catalyzed by hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, and then caustic soda with the concentration of 50% is added for neutralization and phase separation to obtain an organic phase containing polyamine and an aqueous phase containing strong brine. The aqueous phase contained 19% sodium chloride, 0.8% sodium hydroxide, 1.5% aniline. Flow rate of aqueous phase 60m 3 /h, organic phase flow 55m 3 /h。
2) At 95℃with 23m 3 Washing the organic phase obtained in step 1) with water and separating again to obtain an organic phase (polyamine after washing) and an aqueous phase (polyamine washing wastewater).
3) Mixing the water phase in the step 1) with the water phase (polyamine washing wastewater) in the step 2), and sequentially adopting aniline extraction, distillation and catalytic oxidation treatment. Wherein, the extraction process is carried out in a tower extractor, and the feeding mass ratio of aniline to mixed liquor is 0.22; the distillation process is carried out in a distillation tower, and the mass ratio of the steam addition amount of the tower kettle to the mixed liquid is 0.23; the catalytic oxidation process is carried out in a fixed bed tower reactor, the oxidant is 12% sodium hypochlorite aqueous solution, and the mass ratio of the oxidant to the mixed solution is 0.01. Salt concentration in the treated brine is 16%, TOC content is lower than 10ppm, and flow is 64m 3 And/h. Because the external water quantity received by the chlor-alkali system is limited, the external water quantity is only 48m 3 And (3) delivering the treated brine to chlor-alkali as a raw material.
As can be seen by comparing the results of the examples and comparative examples:
(1) The carbon electrode material has good adsorption effect on sodium chloride and sodium hydroxide, and can effectively remove sodium chloride and sodium hydroxide in polyamine washing wastewater so as to promote the recycling of the polyamine washing wastewater. By applying a coating containing Al on the surface of the electrode 2 O 3 And the hydrophilic coating of the nano particles and PEG reduces the pollution of macromolecular organic high polymers in the wastewater to the electrode and prolongs the service life of the electrode. In the adsorption-desorption cycle test, the adsorption performance of the electrode was not degraded.
(2) The traditional process mixes the polyamine washing wastewater with the water phase containing strong brine, and the brine concentration after the extraction and rectification treatment is low. Limited by the chloralkali balance, only 75% of the brine can be recovered, resulting in sodium chloride loss. By treating the polyamine washing wastewater alone, the concentration of the chlor-alkali brine is increased, and the chlor-alkali can completely recover the treated brine.
(3) The invention develops a process for recycling polyamine washing wastewater. Compared with the traditional process of blending the washing wastewater and the neutralized brine, in the new development process, the regenerated washing backwater is recycled, so that the load of treating the waste brine is reduced, the steam consumption in the treatment process of the waste brine is reduced, and the economic benefit is improved. The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.

Claims (10)

1. A method for preparing an electrode material, comprising the steps of:
i. dispersing nanocellulose in water to obtain colloid, and then rapidly freezing the colloid;
ii. Freeze-drying the product in the step i, and then carrying out heating pretreatment;
heating and carbonizing the sample obtained in the step ii in an ammonia atmosphere to obtain a nitrogen-doped carbon nano rod;
iv, uniformly mixing the nitrogen-doped carbon nanorods obtained in the step iii with conductive acetylene black and polyvinyl alcohol, adding water, stirring to obtain uniform slurry, coating the uniform slurry on a graphite substrate, and vacuum drying;
and v, mixing the nano particles with NMP, sequentially adding PVDF and PEG, uniformly mixing to obtain a coating solution, coating the coating solution on the surface of an electrode, and soaking in water to remove redundant solvent.
2. The method according to claim 1, characterized in that in step i the nanocellulose is rod-shaped, preferably having a diameter of 20-80nm, a length of 150-2500nm, more preferably having a diameter of 20-60nm, a length of 150-1000nm.
3. The method according to claim 1 or 2, wherein in step ii, the temperature is raised at a rate of 4-6 ℃/min until it reaches 230-260 ℃, and the temperature is kept for 1.5-2.5h.
4. A method according to any one of claims 1-3, characterized in that in step iii, the temperature is raised to 700-900 ℃ at a rate of 8-12 ℃/min under an ammonia atmosphere, and the temperature is maintained for 2-2.5h.
5. The method according to any one of claims 1 to 4, wherein in the step iv, the mass ratio of the nitrogen-doped carbon nanorods to the polyvinyl alcohol is 7 to 9, the mass ratio of the nitrogen-doped carbon nanorods to the conductive acetylene black is 7 to 9, and the deionized water is added in an amount 1.1 to 1.3 times the mass of the nitrogen-doped carbon nanorods.
6. The method of claim 1 to 5, wherein in step v, the thickness of the electrode surface coating is 100 to 150 μm; adding PVDF and PEG with a mass ratio of 3-4, and adding PVDF and nano particles with a mass ratio of 7-9; the nanoparticle material is Al 2 O 3 、TiO 2 、SiO 2 、CeO 2 One of the followingOr a plurality of; after the surface coating is completed, the electrode is exposed to air for 20-30s and then immersed in deionized water for 24-36h.
7. A treatment method of MDI waste brine comprises the following steps:
1) Catalyzing aniline and formaldehyde to react by using hydrochloric acid to prepare a mixed solution containing DAM and hydrochloride thereof, adding alkali solution to neutralize and phase-separate to obtain an organic phase containing polyamine and a water phase containing strong brine;
2) Washing the organic phase obtained in the step 1) with a washing liquid, and separating phases to obtain an organic phase and a water phase, wherein the organic phase and the water phase are respectively marked as polyamine after washing and polyamine washing wastewater;
3) Removing sodium chloride and sodium hydroxide in the aqueous phase obtained in the step 2) by adopting an electro-adsorption method comprising the electrode material prepared by the method of any one of claims 1-6, and taking the regenerated washing wastewater obtained as the washing liquid in the step 2);
4) And (3) desorbing the electrode to obtain high-concentration brine, merging the high-concentration brine with the aqueous phase containing the strong brine obtained in the step (1) to obtain a brine mixed solution, and taking the brine mixed solution as a raw material of a chlor-alkali process after aniline extraction, rectification and TOC removal.
8. The method according to claim 7, wherein the composition of the polyamine washing wastewater obtained in the step 2) contains one or more of aniline, MDA, cyclohexanol, cyclohexylamine, cyclohexanone, sodium chloride and sodium hydroxide, wherein the concentration of sodium chloride is less than 1200ppm, and the concentration of sodium hydroxide is less than 300ppm.
9. The method according to claim 7 or 8, wherein in step 3), the electrode voltage of the electro-adsorption is 1.5-2V.
10. The method according to any one of claims 7 to 9, wherein in step 3), the composition of the regenerated washing wastewater obtained after the electro-adsorption treatment is less than 35ppm of sodium chloride and less than 15ppm of sodium hydroxide.
CN202310914422.9A 2023-07-25 2023-07-25 Preparation method of electrode material and treatment method of MDI waste brine Pending CN117059730A (en)

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