Treatment method of alkylene diarylamine wastewater

Abstract

The invention discloses a treatment method of alkylene diarylamine wastewater, which comprises the following steps: adjusting the pH value of the alkylene diarylamine wastewater to 6-7, adding polyaluminum chloride and a self-made amine flocculant into the alkylene diarylamine wastewater, stirring the alkylene diarylamine wastewater, coagulating and settling to obtain an alkylene diarylamine wastewater supernatant, and filtering to obtain the alkylene diarylamine wastewater. The method comprises the following steps: preparing an alkylene diarylamine wastewater supernatant, introducing the alkylene diarylamine wastewater supernatant into a nitric acid modified activated carbon fiber device for adsorption, adding the adsorbed alkylene diarylamine wastewater supernatant into MVR (Mechanical Vapor Recompression) for evaporation to realize saline-water separation, and using the obtained evaporation condensate water as feeding water of alkylene diarylamine. On the basis of analyzing the composition of the alkylene diarylamine wastewater, a practical, efficient and economical method for separating the high-boiling-point organic matters is provided, effective pretreatment of the high-salinity organic wastewater is realized, and a foundation is laid for comprehensive treatment of the high-salinity organic wastewater.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and in particular relates to a method for treating alkylene diarylamine wastewater. Background Art

[0002] Alkylene diarylamine is a commonly used polyurethane chain extender. Representative diamines include 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,3'-diethyl-4,4'-diaminodiphenylmethane (MOEA), and liquid diarylamine prepared from a mixture of aromatic amines such as o-chloroaniline and aniline. It is used to prepare polyurethanes, polyurethane / polyureas, spray polyureas, etc. with excellent performance and has a wide range of uses. The preparation of alkylene diarylamine is obtained by condensation and rearrangement reaction with aromatic amines and formaldehyde as raw materials under the condition of inorganic acids such as hydrochloric acid and sulfuric acid as catalysts, and the finished product is obtained by post-treatment such as neutralization, water washing, drying, and filtration. The acidic catalyst used in the preparation of the alkylene diarylamine described in this patent is hydrochloric acid, and the solvent used for neutralization is sodium hydroxide solution. The sodium chloride content in the wastewater generated during neutralization and water washing is 8% to 15%, and it contains trace amounts of diarylamine, which is a difficult-to-degrade organic wastewater.

[0003] Su Hong introduced a wastewater treatment method for 4,4'-diaminodiphenylmethane production wastewater in "Research on Treatment Methods for 4,4'-diaminodiphenylmethane Production Wastewater": First, the high-salt organic wastewater is subjected to reduced pressure distillation to concentrate the sodium chloride content in the wastewater to 16% to 18%, and then the concentrated high-salt wastewater is adsorbed by activated carbon. The adsorbed wastewater can be used as supplementary water for the electrolytic sodium chloride brine in the chlor-alkali workshop. The wastewater treatment process is simple and can meet the needs of the chlor-alkali workshop, but the conventional activated carbon particles used for adsorption in this process are difficult to desorb and reuse after adsorption saturation, and the adsorption saturated activated carbon forms solid waste and is treated as hazardous waste. CN118026477A introduces a method for deep treatment of high-salt and high-COD wastewater, which has five steps. The first step is to discharge the wastewater into a sedimentation tank for coagulation and precipitation and filtration. The second step is to perform ozone + ultrasonic oxidation treatment on the filtered wastewater. The third step is to continue to perform Fenton oxidation treatment on the wastewater with hydrogen peroxide + ferrous sulfate. The fourth step is to use powdered activated carbon to adsorb the wastewater after oxidation degradation. The fifth step is to perform MVR evaporation on the wastewater to separate the salt water and complete the resource utilization of the wastewater. This wastewater treatment process has many steps and involves advanced oxidation degradation devices such as ozone preparation and Fenton oxidation, and has high production costs.

[0004] The composition of organic wastewater varies greatly, and the specific treatment process needs to be determined according to the actual composition of the wastewater. Wastewater with a salt content of >1% is considered high-salt wastewater, and high-salt wastewater is often separated from salt water using MVR / multi-effect evaporation. If the high-salt wastewater also contains trace amounts of high-boiling-point organic matter, it is necessary to separate the organic matter before evaporation. Otherwise, as the high-boiling-point organic matter accumulates in the MVR / multi-effect evaporation device, it will affect the quality of the crystallized salt, making the purity and appearance of the salt fail to meet the relevant standards for by-product salt, forming solid waste or requiring the crystallized salt to be purified again, which will increase the treatment cost. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for treating alkylene diarylamine wastewater. Specifically, based on the analysis of the composition of alkylene diarylamine wastewater, a practical, efficient and economical method for separating high-boiling point organic matter is proposed, which realizes the effective pretreatment of high-salt organic wastewater and lays a foundation for the comprehensive treatment of this high-salt organic wastewater.

[0006] To achieve the above object, one embodiment of the present invention provides a method for treating alkylene diarylamine wastewater, comprising:

[0007] Step S1: adjusting the pH value of the alkylene diarylamine wastewater to be between 6 and 7, adding polyaluminium chloride and a homemade amine flocculant to the alkylene diarylamine wastewater, and subjecting the alkylene diarylamine wastewater to the addition of the polyaluminium chloride and the homemade amine flocculant to stirring, coagulation and sedimentation to obtain a supernatant of the alkylene diarylamine wastewater;

[0008] Step S2: passing the supernatant of the alkylene diarylamine wastewater into an activated carbon fiber device containing nitric acid modified carbon fiber for adsorption;

[0009] Step S3: adding the supernatant of the alkylene diarylamine wastewater after adsorption to MVR for evaporation to achieve brine separation, and the obtained evaporation condensed water is used as the feed water of the alkylene diarylamine, and the industrial salt sodium chloride is sold as a by-product.

[0010] According to one embodiment of the present invention, the alkylene diarylamine wastewater comes from the production process of methylene-linked diphenylamine compounds or mixtures prepared by condensation and rearrangement reactions using aniline compounds and formaldehyde as raw materials.

[0011] According to one embodiment of the present invention, the aniline compounds include but are not limited to aniline, o-chloroaniline, and o-ethylaniline.

[0012] According to one embodiment of the present invention, the homemade amine flocculant is made of o-chloroaniline aqueous solution, formaldehyde aqueous solution and hydrochloric acid as raw materials, and the molar ratio of o-chloroaniline: formaldehyde: hydrochloric acid is 1:0.9~1.1:0.9~1.1, the reaction temperature is between 20~40°C, and the condensation time is between 0.5~1h.

[0013] According to one embodiment of the present invention, the mass fraction of the o-chloroaniline aqueous solution is between 20% and 30%, the mass fraction of the formaldehyde aqueous solution is between 2% and 5%, the mass fraction of hydrochloric acid is between 5% and 10%, and the mass fraction of the self-made amine flocculant obtained after the reaction is between 7% and 10%.

[0014] According to one embodiment of the present invention, the activated carbon fiber is based on polyacrylonitrile, and the concentration of nitric acid used to modify the activated carbon fiber is between 60% and 68%.

[0015] According to one embodiment of the present invention, the desorption solvent of the saturated activated carbon fiber is a sodium hydroxide solution with a mass fraction of 5% to 10%, and the desorbed activated carbon fiber is soaked in a hydrochloric acid solution with a mass fraction of 5% to 10% for 30 to 60 minutes, and then washed with clean water until the pH of the washing water is 7 and then reused;

[0016] The desorbed sodium hydroxide solution is used in a neutralization process for preparing the alkylene diarylamine using the o-chloroaniline as a raw material.

[0017] Compared with the prior art, the beneficial effects of the embodiments of the present application are:

[0018] The invention provides a method for treating alkylene diarylamine wastewater. Based on the analysis of the composition of alkylene diarylamine wastewater, a practical, efficient and economical method for separating high-boiling point organic matter is proposed, which realizes the effective pretreatment of high-salt organic wastewater and lays a foundation for the comprehensive treatment of the high-salt organic wastewater.

[0019] The present invention provides a method for treating alkylene diarylamine wastewater, wherein organic matter in the wastewater is separated by coagulation and adsorption, and then MVR evaporation and desalination are used to separate salt water. The organic matter flocculation precipitation produced by pretreatment is used as a chain extender for polyurethane paving materials with low quality requirements, MVR evaporation condensed water is used as raw material water for alkylene diarylamine, and industrial by-product salt is sold, thereby realizing comprehensive utilization of wastewater, saving resources, and reducing enterprise production costs.

[0020] In order to more clearly understand the technical means of the present invention, which can be implemented according to the contents of the specification, and to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with the accompanying drawings. Other features and advantages of the present invention will be explained in the subsequent description, and part of them will become obvious from the description, or be reflected by implementing the present invention. The purposes and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The present invention provides a schematic diagram of a resource development route for alkylene diarylamine wastewater according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0024] An embodiment of the present invention provides a method for treating alkylene diarylamine wastewater, wherein the method comprises:

[0025] Step S1: adjusting the pH value of the alkylene diarylamine wastewater to be between 6 and 7, adding polyaluminium chloride and a homemade amine flocculant to the alkylene diarylamine wastewater, and subjecting the alkylene diarylamine wastewater to the addition of the polyaluminium chloride and the homemade amine flocculant to stirring, coagulation and sedimentation to obtain a supernatant of the alkylene diarylamine wastewater;

[0026] Step S2: passing the supernatant of the alkylene diarylamine wastewater into an activated carbon fiber device containing nitric acid modified carbon fiber for adsorption;

[0027] Step S3: adding the supernatant of the alkylene diarylamine wastewater after adsorption to MVR for evaporation to achieve brine separation, and the obtained evaporation condensed water is used as the feed water of the alkylene diarylamine, and the industrial salt sodium chloride is sold as a by-product.

[0028] According to one embodiment of the present invention, the alkylene diarylamine wastewater comes from the production process of methylene-linked diphenylamine compounds or mixtures prepared by condensation and rearrangement reactions using aniline compounds and formaldehyde as raw materials.

[0029] According to one embodiment of the present invention, the aniline compounds include but are not limited to aniline, o-chloroaniline, and o-ethylaniline.

[0030] According to one embodiment of the present invention, the homemade amine flocculant is made of o-chloroaniline aqueous solution, formaldehyde aqueous solution and hydrochloric acid as raw materials, and the molar ratio of o-chloroaniline: formaldehyde: hydrochloric acid is 1:0.9~1.1:0.9~1.1, the reaction temperature is between 20~40°C, and the condensation time is between 0.5~1h.

[0031] According to one embodiment of the present invention, the mass fraction of the o-chloroaniline aqueous solution is between 20% and 30%, the mass fraction of the formaldehyde aqueous solution is between 2% and 5%, the mass fraction of hydrochloric acid is between 5% and 10%, and the mass fraction of the self-made amine flocculant obtained after the reaction is between 7% and 10%.

[0032] According to one embodiment of the present invention, the activated carbon fiber is based on polyacrylonitrile, and the concentration of nitric acid used to modify the activated carbon fiber is between 60% and 68%.

[0033] According to one embodiment of the present invention, the desorption solvent of the saturated activated carbon fiber is a sodium hydroxide solution with a mass fraction of 5% to 10%, and the desorbed activated carbon fiber is soaked in a hydrochloric acid solution with a mass fraction of 5% to 10% for 30 to 60 minutes, and then washed with clean water until the pH of the washing water is 7 and then reused;

[0034] The desorbed sodium hydroxide solution is used in a neutralization process for preparing the alkylene diarylamine using the o-chloroaniline as a raw material.

[0035] Example 1

[0036] Preparation of amine flocculants

[0037] To a 1L three-necked flask, add 200g of 8% hydrochloric acid solution, then add 210g of o-chloroaniline aqueous solution, wherein the mass of o-chloroaniline is 53.2g. After stirring for 15min, add 315g of 4% formaldehyde solution from the feeding hopper, and react for 40min at a temperature of 25-30°C and a stirring rate of 140-160r / min to obtain an amine flocculant.

[0038] Example 2

[0039] Add hydrochloric acid / sodium hydroxide solution to the wastewater regulating tank to adjust the pH value of the wastewater to 6-7, then pump the wastewater into the reaction zone 1 of the sedimentation tank, add a 3% mass fraction of polyaluminium chloride aqueous solution into zone 1 to ensure that the concentration of polyaluminium chloride in the wastewater is 30ppm, and stir at a speed of 130-150r / min. The residence time of the wastewater in reaction zone 1 is about 3-4min, and then enter the reaction zone 2, add a homemade amine flocculant in the reaction zone 2, the concentration of the amine flocculant in the wastewater is 20ppm, the stirring speed is 90-110r / min, and the residence time of the wastewater in reaction zone 2 is about 5-6min. Next, the wastewater enters the sedimentation zone and stays in the sedimentation zone for about 40min. The supernatant of the sedimentation tank overflows from the outlet into the buffer tank and is pumped at a speed of 0.1-0.15m 3 / min is passed into an adsorption device filled with activated carbon fiber to adsorb organic matter; the organic matter below the sedimentation tank can be used as a chain extender for paving materials after being collected. The effluent after adsorption is preheated to 90°C and enters the heater, and the water is evaporated under the condition of steam temperature of 95°C. The vapor-liquid mixture enters the separation crystallization chamber, and the slurry flows out from the lower part of the crystallization chamber and enters the centrifuge to separate sodium chloride. After the solid sodium chloride is dried, a snow-white finished salt is obtained, and the purity can meet the standard of GB / T5462-2015 "Industrial Salt" wet salt superior grade. The slurry mother liquor is mixed with the raw material liquid and preheated again and forced to circulate and evaporate and desalt. The MVR is continuously operated without the phenomenon of the finished salt color deepening. When the MVR condensed water is used as the feed water for 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), the purity and appearance of the obtained MOCA are the same as those of MOCA prepared with pure water as raw materials.

[0040] Example 3

[0041] Regarding the high-salt, hard-to-degrade organic wastewater produced during the production of alkylene diarylamines, the COD is 8000-15000 mg / L, the sodium chloride content is 8%-15%, and there are also trace amounts of aromatic amines that cannot be precipitated. Based on the analysis of the wastewater composition, please refer to Figure 1 The present invention proposes a treatment method suitable for such wastewater, that is, using coagulation and adsorption methods to separate organic matter in the wastewater, and then using MVR evaporation and desalination to achieve brine separation. The organic matter flocculation precipitation produced by pretreatment can be used as a chain extender for polyurethane paving materials with low quality requirements, MVR evaporation condensed water is used as raw material water for alkylene diarylamine, and industrial by-product salt can be sold, thereby realizing the comprehensive utilization of wastewater, saving resources, and reducing enterprise production costs.

[0042] The flocculants used in the coagulation stage of the present invention are polyaluminium chloride and a self-made amine flocculant. Polyaluminium chloride needs to be dissolved in water before use to prepare a polyaluminium chloride solution with a mass fraction of 2% to 3%. The self-made amine flocculant belongs to the same type as the organic matter in the wastewater, and the raw materials are the same as alkylene diarylamine, so the addition of the self-made amine flocculant will not cause the coagulation and precipitation of the wastewater to add additional new types of substances. The raw materials used for the amine flocculant are formaldehyde, hydrochloric acid and o-chloroaniline, and o-chloroaniline and formaldehyde are condensed under the action of hydrochloric acid catalyst to generate polymers, wherein the mass fraction of formaldehyde is 2% to 5%, the mass fraction of hydrochloric acid is 5% to 10%, and the mass fraction of o-chloroaniline aqueous solution is 20% to 30%. The reaction temperature is room temperature to 40°C, o-chloroaniline: formaldehyde: hydrochloric acid: =1:0.9-1.1:0.9-1.1 (molar ratio), the reaction time is 0.5-1h, and the mass fraction of the amine flocculant aqueous solution after the reaction is completed is 7%-10%.

[0043] Before coagulation, hydrochloric acid or sodium hydroxide solution can be added to the wastewater to adjust the pH value of the wastewater to 6-7, and then a 2%-3% polyaluminium chloride solution is added thereto, and the amount of polyaluminium chloride added to the wastewater is 30-50ppm. After rapid stirring for 3-5 minutes, an amine flocculant is added, and the amount of the amine flocculant added is 10-20ppm. After rapid stirring and uniformity, the liquid is allowed to stand and settle for 0.5-2h. A small amount of flocculent precipitate can be observed in the liquid. The flocculent precipitate can be collected and used as a chain extender for paving materials with low quality requirements, and the clear supernatant is further subjected to adsorption pretreatment.

[0044] Adsorption is a simple operation when treating large amounts of wastewater. Traditional adsorbents include granular / powdered / columnar activated carbon, etc., which can be sourced from fruit shells, coconut shells, coal, etc. They are cheap and widely used in industrial water treatment, gas deodorization, gold purification, etc. This type of activated carbon granules is convenient to use, but it is difficult to reuse after use, and solid waste is formed after use. The activated carbon fiber developed on the basis of granular activated carbon has a higher specific surface area and higher strength than granular activated carbon, and can be reused many times. It is a new material with great development prospects. The activated carbon fiber used in the present invention for treating wastewater is an activated carbon fiber based on polyacrylonitrile. The activated carbon fiber is oxidized and modified with nitric acid with a concentration of 60% to 68% before use. The oxidation time is 2 to 3 hours. The modified activated carbon fiber is rinsed with clean water until the pH value of the outflowing water is neutral. When using activated carbon fiber to adsorb the supernatant after coagulation and precipitation, intermittent or continuous methods can be used, and neither will affect the adsorption effect. The adsorption saturated activated carbon fiber can be desorbed and reused by water vapor and alkali solution. The present invention uses a sodium hydroxide solution with a mass fraction of 5% to 10% to desorb the adsorption saturated activated carbon fiber. The desorbed sodium hydroxide solution is merged into the sodium hydroxide solution for neutralization of alkylene diarylamine. The desorption can be carried out at room temperature to 80°C. The desorbed activated carbon fiber is soaked in dilute hydrochloric acid with a mass fraction of 5% to 10% and then washed with clean water until the washed water is neutral. At this time, the activated carbon fiber can be reused.

[0045] After the high-salt organic wastewater produced in the preparation process of alkylene diarylamines is pretreated by coagulation and activated carbon fiber adsorption, the high-boiling point organic matter in the original wastewater that is difficult to remove by gravity sedimentation can be effectively separated. The wastewater is passed into the MVR device for evaporation and desalination, and white sodium chloride crystals that meet the GB / T 5462-2015 "Industrial Salt" wet salt premium standard can be obtained. During the continuous operation of the MVR, no yellowish low-quality sodium chloride will be produced.

[0046] The beneficial effects of the method for treating alkylene diarylamine wastewater provided by the present invention are:

[0047] Firstly, based on the analysis of the composition of alkylene diarylamine wastewater, the present invention proposes a practical, efficient and economical method for separating high-boiling point organic matter, realizes the effective pretreatment of high-salt organic wastewater, and lays a foundation for the comprehensive treatment of this high-salt organic wastewater.

[0048] Secondly, the present invention uses coagulation and adsorption methods to separate organic matter from wastewater, and then uses MVR evaporation and desalination to achieve brine separation. The organic matter flocculation precipitation produced by pretreatment is used as a chain extender for polyurethane paving materials with low quality requirements, and the MVR evaporation condensed water is used as raw material water for alkylene diarylamine. The industrial by-product salt can be sold, thereby realizing the comprehensive utilization of wastewater, saving resources, and reducing the production cost of enterprises.

[0049] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the disclosure scope involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) by each other.

[0050] In addition, although each operation is described in a specific order, this should not be construed as requiring these operations to be performed in the specific order shown or in a sequential order. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present invention. Some features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination mode.

[0051] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

[0052] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for treating alkylene diarylamine wastewater, characterized in that: include: Step S1: adjusting the pH value of the alkylene diarylamine wastewater to be between 6 and 7, adding polyaluminium chloride and a homemade amine flocculant to the alkylene diarylamine wastewater, and subjecting the alkylene diarylamine wastewater to the addition of the polyaluminium chloride and the homemade amine flocculant to stirring, coagulation and sedimentation to obtain a supernatant of the alkylene diarylamine wastewater; Step S2: passing the supernatant of the alkylene diarylamine wastewater into an activated carbon fiber device containing nitric acid modified carbon fiber for adsorption; Step S3: adding the supernatant of the alkylene diarylamine wastewater after adsorption to MVR for evaporation to achieve brine separation, and the obtained evaporation condensed water is used as the feed water of the alkylene diarylamine, and the industrial salt sodium chloride is sold as a by-product.

2. The method for treating alkylene diarylamine wastewater according to claim 1, characterized in that: The alkylene diarylamine wastewater comes from the production process of diphenylamine compounds or mixtures connected by methylene, which are prepared by condensation and rearrangement reaction using aniline compounds and formaldehyde as raw materials.

3. The method for treating alkylene diarylamine wastewater according to claim 2, characterized in that: The aniline compounds include but are not limited to aniline, o-chloroaniline, and o-ethylaniline.

4. The method for treating alkylene diarylamine wastewater according to claim 1, characterized in that: The self-made amine flocculant uses o-chloroaniline aqueous solution, formaldehyde aqueous solution and hydrochloric acid as raw materials, and the molar ratio of o-chloroaniline:formaldehyde:hydrochloric acid is 1:0.9-1.1:0.9-1.1, the reaction temperature is between 20-40°C, and the condensation time is between 0.5-1h.

5. The method for treating alkylene diarylamine wastewater according to claim 4, characterized in that: The mass fraction of the o-chloroaniline aqueous solution is between 20% and 30%, the mass fraction of the formaldehyde aqueous solution is between 2% and 5%, the mass fraction of the hydrochloric acid is between 5% and 10%, and the mass fraction of the self-made amine flocculant obtained after the reaction is between 7% and 10%.

6. The method for treating alkylene diarylamine wastewater according to claim 1, characterized in that: The activated carbon fiber is a fiber based on polyacrylonitrile, and the concentration of nitric acid used to modify the activated carbon fiber is between 60% and 68%.

7. The method for treating alkylene diarylamine wastewater according to claim 6, characterized in that: The desorption solvent of the saturated activated carbon fiber is a sodium hydroxide solution with a mass fraction of 5% to 10%. The desorbed activated carbon fiber is soaked in a hydrochloric acid solution with a mass fraction of 5% to 10% for 30 to 60 minutes, and then washed with clean water until the pH of the washing water is 7 before being reused; The desorbed sodium hydroxide solution is used in a neutralization process for preparing the alkylene diarylamine using the o-chloroaniline as a raw material.

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