Process for directional recovery of fractionally purified mixed extractants from industrial wastewater

Abstract

The application discloses a kind of industrial wastewater mixed extractant grading purification directional recovery process, comprising the following steps: industrial wastewater is passed into the adsorption device of amine group-phosphonic acid group modified graphene adsorption material, and the adsorption of specific impurities is strengthened by regulating and controlling bifunctional group mole ratio;Into the adsorption saturated device containing amino phosphonic acid type chelating agent complex desorption agent, using non-overlapping subsection desorption mode directional desorption of n-octanol and N235 and sulfonated kerosene;Mixed desorption liquid is separated after complex desorption agent by rectification, and each extractant component is purified by gradient vacuum distillation;Amine salt waste liquid is reused to adsorption device, and amine salt decomposition and adsorption material functional group in situ regeneration are completed under acidic conditions.The above steps solve the problems of poor adsorption selectivity, desorption interference and material activity attenuation in existing process, realize efficient directional recovery of mixed extractant, and significantly improve the cycle stability of adsorption material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a fractional purification and directional recovery process of mixed extractants in industrial wastewater. BACKGROUND

[0002] In the field of industrial wastewater treatment, extraction method is widely used due to its high efficiency in separating non-degradable pollutants. The core of the method is to realize separation through the selective combination of mixed extractants such as 2-octanol, N235 and sulfonated kerosene with pollutants. However, part of the mixed extractants will be lost with the wastewater during the extraction process, which not only increases the treatment cost, but also causes secondary pollution of water bodies due to the chemical stability of the extractant components. Therefore, the efficient recovery of mixed extractants is crucial to the economy and environmental protection of industrial wastewater treatment.

[0003] In the existing recovery process of mixed extractants, adsorption materials are mostly dependent on traditional carriers such as activated carbon and conventional resins. These materials lack specific functional groups and have poor adsorption selectivity for each component of the mixed extractants, which easily adsorbs suspended impurities and ionic pollutants in the wastewater at the same time, resulting in mixed components in the subsequent desorption liquid and significantly increasing the difficulty of separation. At the same time, the desorption process mostly uses a single temperature or a single desorption agent system, which cannot realize directional desorption according to the differences in the interaction between different extractant components and adsorption materials, causing incomplete desorption or co-desorption of components, further reducing the recovery purity. In the separation link, the existing technology often uses single rectification or simple distillation method, which is difficult to solve the separation problem of 2-octanol and N235, sulfonated kerosene with close boiling points in the mixed extractants, and is easy to form azeotropic system or overlapping distillation, resulting in insufficient purity of the target component. In addition, the amine salt-containing waste liquid generated during the desorption process is mostly directly discharged, which not only wastes resources such as diethanolamine, but also causes water body acid-base imbalance; the surface functional groups of the adsorption material are prone to deprotonation or loss of hydroxyl groups after use, and the activity decays quickly, making it difficult to realize stable recycling use.

[0004] Therefore, it is necessary to provide a fractional purification and directional recovery process of mixed extractants in industrial wastewater to solve the above technical problems. SUMMARY

[0005] The present application relates to the technical field of industrial wastewater treatment, in particular to a fractional purification and directional recovery process of mixed extractants in industrial wastewater.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a fractional purification and directional recovery process of mixed extractants in industrial wastewater, comprising the following steps:

[0007] 1) pass industrial wastewater into an adsorption device, the adsorption device is filled with graphene adsorption material, which introduces amine group and phosphonic acid group by covalent grafting method, to obtain amine group-phosphonic acid group modified graphene adsorption material, the molar ratio of amine group and phosphonic acid group is 0.8:1-1.2:1;

[0008] 2) pass the adsorption saturated adsorption device in step 1) into a composite desorption agent, the composite desorption agent is made by mixing ethanol and diethanolamine at a volume ratio of 85-95:5-15, the pH of the composite desorption agent is 8.0-9.0;

[0009] Using the segmented desorption mode, the secondary octanol on the graphene adsorption material is desorbed at 58-61 DEG C, and the N235 and sulfonated kerosene on the graphene adsorption material are desorbed at 64-66 DEG C;

[0010] During the desorption process, the diethanolamine in the composite desorption agent reacts with the acidic substances in the industrial wastewater and the residual acidic substances on the surface of the adsorption material to generate amine salt, and a mixed desorption liquid containing the composite desorption agent, the secondary octanol, the N235, the sulfonated kerosene and the amine salt is collected;

[0011] 3) pass the mixed desorption liquid obtained in step 2) into a rectifying column, control the top temperature of the column to be 73-80 DEG C and the bottom temperature to be 155-175 DEG C, the composite desorption agent is separated from the top of the column, the secondary octanol, the N235 and the sulfonated kerosene form a mixed extractant and remain in the lower part of the column and are separated, and the amine salt remains in the bottom of the rectifying column to form an amine salt-containing waste liquid;

[0012] Pass the mixed extractant into a gradient vacuum distillation device, and separate the secondary octanol, the N235 and the sulfonated kerosene by gradient vacuum distillation;

[0013] 4) pass the amine salt-containing waste liquid at the bottom of the rectifying column in step 3) into the adsorption device in step 1), and adjust the pH of the system to 2.0-3.0.

[0014] The hierarchical purification and directional recovery process of the mixed extractant in the industrial wastewater provided by the application introduces amine group and phosphonic acid group on the surface of the graphene substrate by covalent grafting method to form a double functional group structure of fixed adsorption site and pH response site. In other words, the amine group acts as a fixed adsorption site, the loading amount is controlled by reaction time, the extractant components are selectively combined by means of hydrogen bond and hydrophobic interaction, and the loading amount density is accurately optimized to avoid site congestion or insufficient adsorption capacity; the phosphonic acid group acts as a pH response site, the loading amount is controlled by reaction temperature, and the core characteristic is the pH response transformation ability of protonation and deprotonation, which provides structural support for the switching of adsorption auxiliary catalytic function; at the same time, the molar ratio of the double functional groups is strictly controlled to be 0.8:1-1.2:1, which is the core parameter of balancing adsorption selectivity and function switching efficiency.

[0015] Preferably, in step 1), the step of introducing amine groups and phosphonic acid groups to the graphene adsorption material by the covalent grafting method comprises:

[0016] 1a) dispersing the graphene substrate in a N,N-dimethylformamide solvent, ultrasonic treatment for 1-3 h, adding an amine group precursor and a catalyst triethylamine, the mass ratio of the amine group precursor to the graphene substrate being 1:8-1:12, stirring and reacting at 60-80 DEG C for 4-6 h to obtain amine group modified graphene; wherein the amine group functional group loading of the amine group precursor is regulated by the reaction time: the amine group loading is 0.3-0.4 mmol / g when the reaction time is 4 h, and the amine group loading is 0.5-0.6 mmol / g when the reaction time is 6 h;

[0017] 1b) adding a phosphonic acid group precursor to the amine group modified graphene dispersion, the mass ratio of the phosphonic acid group precursor to the amine group modified graphene being 1:5-1:7, heating to 80-100 DEG C, stirring and reacting for 6-8 h to generate phosphonic acid groups through ester hydrolysis reaction; wherein the phosphonic acid group loading is regulated by the reaction temperature: the phosphonic acid group loading is 0.4-0.5 mmol / g when the reaction temperature is 80 DEG C, and the phosphonic acid group loading is 0.6-0.7 mmol / g when the reaction temperature is 100 DEG C;

[0018] 1c) after the reaction is completed, washing with deionized water and ethanol alternately for 3-5 times, and vacuum drying for 6-12 h to obtain the amine group-phosphonic acid group modified graphene adsorption material; by adjusting the reaction time of step 1a) and the reaction temperature of step 1b), the molar ratio of the amine group to the phosphonic acid group in the final material is 0.8:1-1.2:1.

[0019] The industrial wastewater mixed extractant fractional purification directional recovery process provided by the application, in the adsorption stage, the pH of the industrial wastewater influent is controlled in the acidic interval of 2.0-3.0, triggering the protonation conversion of the phosphonic acid group, forming a synergistic adsorption system with the amine group, the amine group selectively adsorbs the extractant components, the phosphonic acid group enhances the balance of the hydrophilic and hydrophobic levels after protonation, assists in weakening the interaction between the extractant and the wastewater, simultaneously repels the ionic impurities in the wastewater, reduces the competitive adsorption, improves the adsorption selectivity, and the linkage regulation of the influent water temperature and flow further guarantees the sufficient contact between the adsorption material and the wastewater, avoids the adsorption equilibrium deviation caused by high temperature, and ensures the stability of the dual functional group synergistic adsorption efficiency.

[0020] In the desorption stage, the pH of the composite desorption agent is adjusted to the alkaline range of 8.0-9.0, triggering the deprotonation of the phosphonic acid group, and the function is switched from adsorption assistance to catalytic weakening. The deprotonated phosphonic acid group weakens the binding force between the adsorbent and the extractant components through charge repulsion, and cooperates with the solubilization of ethanol and the alkaline environment of diethanolamine in the composite desorption agent to reduce the desorption energy barrier of the extractant. The amino phosphonic acid chelating agent ethylenediaminetetramethylene phosphonic acid introduced synchronously captures the residual metal ions in the industrial wastewater through strong complexation, avoids the formation of stable complexes between metal ions and extractants to hinder desorption, and prevents metal ions from occupying adsorption sites to ensure the directionality of the desorption process. The non-overlapping design of the staged desorption temperature realizes the step-by-step desorption of sec-octanol, N235 and sulfonated kerosene according to the difference in the interaction energy between different extractant components and adsorbent materials, and avoids the mixing of components caused by co-desorption.

[0021] In the regeneration stage, after the amine salt-containing waste liquid is reused to the adsorption device, the pH of the system is adjusted to the acidic range of 2.0-3.0, the function of the phosphonic acid group is reset, and the material is regenerated. The acidic working condition triggers the decomposition of amine salt into diethanolamine and organic acid, the concentration of diethanolamine is adjusted to 0.05-0.15 mol / L, the hydroxyl defects on the surface of the adsorbent are repaired through amino exchange reaction, the adsorption activity of amine group is restored, and at the same time, diethanolamine and residual organic acid undergo esterification reaction to eliminate impurity interference. The organic acid produced by the decomposition of amine salt transfers protons to promote the re-protonation of deprotonated phosphonic acid group, complete the reversible switching of catalytic site to adsorption auxiliary site, and the pH fluctuation is strictly controlled within ±0.3 to ensure that the protonation ratio is ≥90%, realizing the in-situ regeneration of adsorbent and providing stable performance for the next adsorption cycle.

[0022] Preferably, in step 1), the pH of the industrial wastewater is 2.0-3.0, the inflow is 20-50 L / h, and the water temperature is 25-45℃. When the water temperature is ≥30℃, the inflow is reduced by 10-30%.

[0023] Preferably, in step 2), the composite desorption agent further comprises an amino phosphonic acid chelating agent, and the volume ratio of ethanol, diethanolamine and amino phosphonic acid chelating agent is 85-95:5-12:1-3.

[0024] The amino phosphonic acid chelating agent is ethylenediaminetetramethylene phosphonic acid, and the preparation steps thereof include:

[0025] 2a) add 1 part of ethylenediamine and 3-7 parts of deionized water into a four-necked flask, the ethylenediamine is in parts by mass and the deionized water is in parts by volume, stir until the ethylenediamine is completely dissolved, control the system temperature to be 15-30℃, slowly add 37% formaldehyde aqueous solution to it, the molar ratio of formaldehyde to ethylenediamine is 3-6:1, the dropwise adding time is controlled to be 20-40 min, continue stirring for 10-20 min after the dropwise adding is completed, and an ethylenediamine-formaldehyde condensate solution is formed;

[0026] 2b) pass a cooling medium into the condensate solution obtained in step 2a) to reduce the system temperature to 3-12℃, slowly add phosphorus trichloride, the molar ratio of phosphorus trichloride to ethylenediamine is 2.5-4:1, the system temperature is controlled to be ≤18℃ during the dropwise adding process, the dropwise adding time is 1-2.5 h, the temperature is increased to 35-55℃ after the dropwise adding is completed, and stirring reaction is carried out for 1.5-2.5 h to obtain a phosphonate intermediate;

[0027] 2c) add deionized water to the phosphonate intermediate obtained in step 2b), the volume ratio of the deionized water added to the deionized water in step 2a) is 1.2-2:1, the temperature is increased to 85-100℃, reflux hydrolysis reaction is carried out for 2.5-4.5 h, after the reaction is completed, the system pH is neutralized to 5.5-7.5 with 30% sodium hydroxide solution, and after concentration by reduced pressure distillation, crystallization and drying, ethylenediamine tetramethylene phosphonic acid is obtained.

[0028] As preferred, in step 3), the process parameters of the gradient vacuum distillation are as follows: the secondary octanol is separated at a vacuum degree of 0.06-0.09 MPa and a temperature of 78-88℃, and when the purity of the secondary octanol in the distillate is ≤90%, the separation endpoint is determined; the N235 and sulfonated kerosene are separated at a vacuum degree of 0.001-0.005 MPa and a temperature of 105-125℃, and the distillation is stopped when the total purity of the N235 and sulfonated kerosene in the distillate is ≤90%.

[0029] As preferred, in step 3), the temperature increasing rate of the gradient vacuum distillation equipment is 2-6℃ / h, the time for increasing the temperature from the first stage endpoint temperature of 88℃ to the second stage starting temperature of 105℃ is 3-8.5 h, and the temperature maintaining time of each stage of distillation is 0.5-2 h.

[0030] The provided industrial wastewater mixed extractant fractional purification directional recovery process aims at the separation difficulty of secondary octanol and N235, and sulfonated kerosene with close boiling points, and adopts two-stage vacuum degree and temperature gradient for regulation and control, the first stage separates secondary octanol, the second stage separates N235 and sulfonated kerosene, through the combination of the gradient reduction of vacuum degree and the increase of temperature, the boiling point of components is reduced to avoid degradation, the overlapping problem of distillation is solved, and the purity of the distillate is ≤ 90% as the separation endpoint, the slow heating rate of 2-6 ℃ / h and the holding time of 0.5-2 h are matched to ensure the full separation of each component. The amine salt-containing waste liquid at the bottom of the rectifying tower is not directly discharged, but is reused as a regeneration medium, the amine salt is efficiently decomposed under acidic conditions, the recovered diethanolamine is used to repair the hydroxyl defects of the adsorption material, and the organic acid is used to promote the resetting of the phosphonic acid group, so that the resources are maximally utilized. It not only avoids water pollution caused by direct discharge of amine salt-containing waste liquid from the source, but more importantly, it provides a chemical environment and key substance support for the switching of the pH response site of the phosphonic acid group in the graphene adsorption material: after the reuse of the amine salt-containing waste liquid, the system is regulated to an acidic interval of 2.0-3.0, which exactly matches the pH condition required for the protonation of the phosphonic acid group, and the organic acid generated by the decomposition of the amine salt in the waste liquid can provide sufficient protons through proton transfer for the resetting of the deprotonated phosphonic acid group, while the diethanolamine generated by the decomposition can repair the aged amine group sites on the surface of the adsorption material, so that the synergistic structure of the phosphonic acid group and the amine group can be restored, fundamentally solving the problem of functional group activity attenuation of the adsorption material after use, and greatly improving the stability of long-term cyclic use.

[0031] As preferred, in step 3), after the separated composite desorption agent is filtered to remove trace impurities, the volume ratio of ethanol to diethanolamine is detected and supplemented to 85-95:5-15, and the pH is adjusted back to 8-9 for reuse in step 2).

[0032] As preferred, in step 4), the amine salt in the amine salt-containing waste liquid is decomposed into diethanolamine and organic acid under acidic conditions, the decomposition reaction time is 40-80 min, and the concentration of diethanolamine in the system is regulated to 0.05-0.15 mol / L.

[0033] As preferred, in step 4), when the diethanolamine reacts with the hydroxyl groups generated by the hydrolysis of the graphene adsorption material surface through amino exchange reaction, it also reacts with the residual organic acid impurities through esterification reaction, the reaction temperature is controlled at 30-40 ℃, and the reaction time is 30-50 min.

[0034] As preferred, in step 4), the organic acid generated by the decomposition of the amine salt forms a concentration of 0.03-0.08 mol / L in the system, which promotes the resetting of the deprotonated phosphonic acid group through proton transfer, the pH fluctuation range of this process is ≤ ± 0.3, and the proportion of protonated phosphonic acid group is ≥ 90%.

[0035] Compared with the prior art, the application has the beneficial effects that:

[0036] 1、The application constructs amine group-phosphonic acid group bifunctional system on the surface of graphene substrate by covalent grafting method, utilizes the synergistic effect of hydrogen bond, hydrophobic effect and electrostatic adsorption between the two types of functional groups and each component of mixed extractant, strengthens the selective adsorption of target components, reduces the competitive adsorption of impurities in wastewater, and improves the adsorption selectivity and capacity. The non-overlapping temperature interval of step 2) is combined with the pH regulation of the composite desorption agent, and the directional desorption is realized according to the interaction energy difference between different extractant components and the adsorption material, so that the co-desorption phenomenon is avoided, and high-purity desorption liquid is provided for subsequent separation.

[0037] 2、The amino phosphonic acid type chelating agent introduced in the composite desorption agent can complex the metal ions in industrial wastewater, eliminate the hidden danger of forming stable complexes with the extractant, and ensure the desorption efficiency and the cleanliness of the separation system. The rectification and gradient vacuum distillation process of step 3) realizes accurate separation by regulating the temperature and vacuum degree according to the boiling point characteristics of each extractant component, effectively solves the separation problem of components with close boiling points, and improves the purity of the recovered products.

[0038] 3、The amine salt waste liquid is reused to the adsorption device, and the amine salt is decomposed under acidic conditions to generate diethanolamine, which repairs the hydroxyl defects on the surface of the adsorption material through amino exchange reaction, and the organic acid promotes the deprotonation of the phosphonic acid group by proton transfer, realizing in-situ regeneration of the adsorption material, prolonging its cycle use period, strengthening the recovery effect of the mixed extractant, realizing the cyclic stable use of the adsorption material, and reducing resource waste and pollutant emission. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The columnar analysis chart for testing the adsorption capacity performance of the adsorption material used in the processes provided in examples 1-3 and comparative examples 1-6 of the application;

[0040] Figure 2 The columnar analysis chart for testing the desorption rate of sec-octyl alcohol in the processes provided in examples 1-3 and comparative examples 1-6 of the application;

[0041] Figure 3 The columnar analysis chart for testing the desorption rate of N235 and sulfonated kerosene in the processes provided in examples 1-3 and comparative examples 1-6 of the application;

[0042] Figure 4 The columnar analysis chart for testing the purity of sec-octyl alcohol in the processes provided in examples 1-3 and comparative examples 1-6 of the application;

[0043] Figure 5 The columnar analysis chart for testing the purity performance of N235 and sulfonated kerosene in the processes provided in examples 1-3 and comparative examples 1-6 of the application;

[0044] Figure 6 Columnar analysis chart for 10-cycle capacity retention test of adsorption material used in the process provided for Examples 1-3 and Comparative Examples 1-6 of the present application. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be clearly and completely described below in combination with specific examples. Obviously, the described examples are only some of the embodiments of the present application, but not all the embodiments. Based on the examples in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0046] Example 1

[0047] The present example provides a fractional purification and directional recovery process of mixed extractants in industrial wastewater, and the specific steps are as follows:

[0048] 1) The industrial wastewater with pH of 2.5, water temperature of 30℃ and COD of 500 mg / L is introduced into an adsorption device, the water inlet flow is 35 L / h, and the adsorption device is filled with modified graphene adsorption material;

[0049] The above-mentioned modified graphene adsorption material is to introduce amine group and phosphonic acid group into graphene adsorption material, and the specific steps are as follows: graphene substrate is dispersed in N,N-dimethylformamide solvent, the mass-volume ratio of graphene substrate to solvent is 1:70, and ultrasonic treatment is performed for 2 h; amine precursor 3-aminopropyl triethoxysilane and catalyst triethylamine are added, the mass ratio of amine precursor to graphene substrate is 1:10, the molar ratio of triethylamine to amine precursor is 1:1, stirring reaction is performed at 70℃ for 5 h, and the loading amount of amine group is 0.45 mmol / g; phosphonic acid precursor 3-glycidyl ether oxypropyl trimethoxysilane is added to the dispersion, the mass ratio of phosphonic acid precursor to amine modified graphene is 1:6, the temperature is raised to 90℃ for stirring reaction for 7 h, and the loading amount of phosphonic acid group is 0.55 mmol / g; deionized water and ethanol are alternately washed for 4 times, and vacuum drying is performed for 9 h to obtain modified graphene adsorption material with a molar ratio of amine group to phosphonic acid group of 1:1.

[0050] 2) After adsorption saturation, composite desorption agent (volume ratio of ethanol, diethanolamine and ethylenediamine tetramethylene phosphonic acid is 90:8:2, pH is 8.5) is introduced, and secondary octanol is desorbed at 59℃, and after the desorption rate of secondary octanol is ≥95%, N235 and sulfonated kerosene are desorbed at 65℃, and the mixed desorption liquid is collected.

[0051] 3) The mixed desorption liquid is introduced into the rectification tower, the tower top temperature is 76℃, the tower bottom temperature is 165℃, and the composite desorption agent is separated; the mixed extractant is introduced into the gradient vacuum distillation equipment, the secondary octanol is separated at a vacuum degree of 0.07 MPa and 83℃, and the distillate purity is greater than or equal to 90% when the temperature is stopped to rise at a rate of 4℃ / h from 88℃ to 105℃ for 4.25h, and the N235 and sulfonated kerosene are separated at a vacuum degree of 0.003 MPa and 115℃, and the total purity is greater than or equal to 90% when the temperature of each stage is kept for 1h; the composite desorption agent is filtered, and then ethanol and diethanolamine are supplemented to a set proportion, and the pH is adjusted back to 8.5 before reuse.

[0052] 4) The amine salt-containing waste liquid at the bottom of the rectification tower is introduced into the adsorption device, the pH is adjusted to 2.5, the amine salt decomposition reaction time is 60 min, the diethanolamine concentration is controlled to 0.1 mol / L, the organic acid concentration is 0.05 mol / L at 35℃ for 40 min, the pH fluctuation is less than or equal to ±0.2, and the proportion of protonated phosphonic acid group is greater than or equal to 92%.

[0053] Example 2

[0054] The embodiment provides a fractional purification and directional recovery process for mixed extractants in industrial wastewater, and the specific steps are as follows:

[0055] 1) The industrial wastewater with a pH of 2.0, a water temperature of 25℃, and a COD of 300 mg / L is introduced into the adsorption device, and the water inlet flow is 50 L / h, and the adsorption device is filled with modified graphene adsorption material;

[0056] The modified graphene adsorption material is to introduce amine groups and phosphonic acid groups into the graphene adsorption material, and the specific steps are as follows: the graphene substrate is dispersed in N,N-dimethylformamide solvent, the mass-volume ratio of the graphene substrate to the solvent is 1:50, and ultrasonic treatment is performed for 1h; amine precursor 3-aminopropyltriethoxysilane and catalyst triethylamine are added, the mass ratio of amine precursor to graphene substrate is 1:8, the molar ratio of triethylamine to amine precursor is 0.5:1, stirring reaction is performed at 60℃ for 4h, the amine group loading is 0.35 mmol / g; 3-glycidyl ether oxypropyl trimethoxysilane is added to the dispersion, the mass ratio of phosphonic acid precursor to amine modified graphene is 1:5, the temperature is raised to 80℃, and stirring reaction is performed for 6h, the phosphonic acid group loading is 0.45 mmol / g; the modified graphene adsorption material with a mole ratio of amine groups to phosphonic acid groups of 0.8:1 is obtained after alternating washing with deionized water and ethanol for 3 times and vacuum drying for 6h.

[0057] 2) After adsorption saturation, the composite desorption agent (volume ratio of ethanol, diethanolamine, and ethylenediamine tetramethylene phosphonic acid is 85:12:3, and pH is 8.0) is introduced, and the secondary octanol is desorbed at 58°C. After the desorption rate of the secondary octanol is ≥95%, the temperature is increased to 64°C to desorb N235 and sulfonated kerosene, and the mixed desorption liquid is collected.

[0058] 3) The mixed desorption liquid is introduced into a rectifying column, the top temperature is 73°C, the bottom temperature is 155°C, and the composite desorption agent is separated; the mixed extractant is introduced into a gradient vacuum distillation device, the secondary octanol is separated at a vacuum degree of 0.06 MPa and a temperature of 78°C in the first stage, and the distillate purity is ≥90% when stopped, the temperature is increased at a rate of 2°C / h, and the time from 88°C to 105°C is 8.5 h, the N235 and sulfonated kerosene are separated at a vacuum degree of 0.001 MPa and a temperature of 105°C in the second stage, and the total purity is ≥90% when stopped, and the temperature is maintained for 0.5 h in each stage; the composite desorption agent is filtered, and ethanol and diethanolamine are supplemented to the set ratio, and the pH is adjusted to 8.0 before reuse.

[0059] 4) The amine salt-containing waste liquid at the bottom of the rectifying column is introduced into an adsorption device, the pH is adjusted to 2.0, the amine salt decomposition reaction time is 40 min, the diethanolamine concentration is controlled to 0.05 mol / L, the reaction is carried out at 30°C for 30 min, the organic acid concentration is 0.03 mol / L, the pH fluctuation is ≤±0.2, and the proportion of protonated phosphonic acid group is ≥90%.

[0060] Example 3

[0061] The embodiment provides a step-by-step purification and directional recovery process for mixed extractants in industrial wastewater, and the specific steps are as follows:

[0062] 1) The industrial wastewater with pH of 3.0, water temperature of 45°C, and COD of 800 mg / L is introduced into an adsorption device, the water temperature is ≥30°C, the inlet flow is reduced by 30% to 20 L / h, and the adsorption device is filled with modified graphene adsorption material;

[0063] The modified graphene adsorption material is obtained by introducing amine groups and phosphonic acid groups into the graphene adsorption material. The specific steps are as follows: graphene substrate is dispersed in N,N-dimethylformamide solvent, the mass-volume ratio of graphene substrate to solvent is 1:100, and ultrasonic treatment is performed for 3 hours; amine precursor 3-aminopropyltriethoxysilane and catalyst triethylamine are added, the mass ratio of amine precursor to graphene substrate is 1:12, the molar ratio of triethylamine to amine precursor is 1.5:1, stirring reaction is performed at 80°C for 6 hours, the loading amount of amine groups is 0.55 mmol / g; phosphonic acid precursor 3-glycidyl ether oxypropyl trimethoxysilane is added to the dispersion, the mass ratio of phosphonic acid precursor to amine modified graphene is 1:7, the temperature is raised to 100°C, and stirring reaction is performed for 8 hours, the loading amount of phosphonic acid groups is 0.65 mmol / g; deionized water and ethanol are alternately washed for 5 times, and vacuum drying is performed for 12 hours, to obtain a modified graphene adsorption material with a molar ratio of amine groups to phosphonic acid groups of 1.2:1.

[0064] 2) After adsorption saturation, the composite desorption agent (ethanol, diethanolamine, and ethylenediamine tetramethylene phosphonic acid with a volume ratio of 95:5:1, and pH of 9.0) is introduced, and the secondary octyl alcohol is desorbed at 61°C; after the desorption rate of the secondary octyl alcohol is ≥95%, the temperature is raised to 66°C to desorb N235 and sulfonated kerosene, and the mixed desorption liquid is collected.

[0065] 3) The mixed desorption liquid is introduced into a rectifying column, the top temperature is 80°C, and the bottom temperature is 175°C, and the composite desorption agent is separated; the mixed extractant is introduced into a gradient vacuum distillation device, the secondary octyl alcohol is separated at a vacuum degree of 0.09 MPa and 88°C in the first stage, and the distillate purity is ≥90% when stopped, the temperature rising rate is 6°C / h, and it takes 3h to rise from 88°C to 105°C, the N235 and sulfonated kerosene are separated at a vacuum degree of 0.005 MPa and 125°C in the second stage, and the total purity is ≥90% when stopped, and each stage temperature is maintained for 2h; the composite desorption agent is filtered, and ethanol and diethanolamine are supplemented to the set proportion, and the pH is adjusted to 9.0 for reuse.

[0066] 4) The amine salt waste liquid at the bottom of the rectifying column is introduced into the adsorption device, the pH is adjusted to 3.0, the amine salt decomposition reaction time is 80 min, the diethanolamine concentration is controlled to be 0.15 mol / L, the organic acid concentration is 0.08 mol / L after reaction at 40°C for 50 min, the pH fluctuation is ≤±0.3, and the proportion of protonated phosphonic acid groups is ≥91%.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is only that the adsorption material is ordinary graphene without modification, that is, without introducing amine groups and phosphonic acid groups by covalent grafting method.

[0069] Expected performance: Ordinary graphene has poor adsorption selectivity for each component of the mixed extractant, and simultaneously adsorbs impurities in wastewater. The impurity content in the mixed desorption liquid increases significantly, the recovery purity of each component decreases, and the adsorption capacity decreases significantly.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is only that the temperature of the staged desorption is 58-63°C and 62-66°C, and there is a temperature overlap interval.

[0072] Expected performance: Temperature overlap causes secondary octanol to be co-desorbed with N235 and sulfonated kerosene, resulting in mixed components in the desorption liquid, significantly increasing the difficulty of subsequent separation, invalidating the effect of fractional directional recovery, and decreasing the recovery purity of each component.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is only that the amino phosphonic acid chelating agent is not added to the composite desorption agent.

[0075] Expected performance: Residual metal ions in industrial wastewater cannot be complexed to form stable complexes with extractants, resulting in decreased desorption efficiency, metal ions entering the rectification system, causing equipment corrosion and reduced separation precision.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is only that the gradient vacuum distillation has no clear separation endpoint determination, and the temperature rise rate is too fast.

[0078] Expected performance: A too-fast temperature rise rate results in insufficient separation of components, with secondary octanol and N235 and sulfonated kerosene appearing in overlapping distillates, resulting in decreased recovery purity. The absence of a separation endpoint determination causes loss of target components or mixing of impurities, resulting in reduced recovery yield.

[0079] Comparative Example 5

[0080] The difference between this comparative example and Example 1 is only that the amine salt-containing waste liquid at the bottom of the rectification tower is directly discharged without being recycled through the adsorption device.

[0081] Expected performance: The deprotonated phosphonic acid group on the surface of the adsorption material cannot be reset, and the residual hydroxyl group causes continuous decay of adsorption activity, resulting in a significant decrease in adsorption capacity after multiple uses. Discharging amine salt waste liquid causes resource waste and environmental pollution, significantly reducing process economy and environmental friendliness.

[0082] Comparative Example 6

[0083] The difference between this comparative example and Example 1 is only that the pH of the system is adjusted to 3.5-4.0 in Step 4, without controlling the pH fluctuation range.

[0084] Expected performance: The pH deviates from the appropriate interval of phosphonic acid group protonation, the proton transfer efficiency of organic acid decreases, the proportion of protonated phosphonic acid group is insufficient, the synergistic effect of the dual functional groups of the adsorption material is weakened, the subsequent adsorption capacity decreases, the pH fluctuation leads to instability of the reaction system, the amine salt decomposition is incomplete, and the diethanolamine utilization rate decreases.

[0085] Performance test method:

[0086] 1. Adsorption performance test

[0087] Test instrument: ultraviolet-visible spectrophotometer, electronic balance, constant temperature water bath, peristaltic pump

[0088] Test steps: Take 0.5 g of adsorption material in the examples and comparative examples, and add 50 mL of simulated industrial wastewater containing secondary octanol, N235, and sulfonated kerosene (the initial concentration of each component is 100 mg / L, pH = 2.5, and the water temperature is 30°C); use a peristaltic pump to control the water inflow of 35 L / h, and after the adsorption reaches saturation, filter the supernatant through a 0.45 μm filter membrane, and measure the equilibrium concentration of each component by ultraviolet-visible spectrophotometer.

[0089] Calculation method: adsorption capacity (q) = (C0-C e ) × V / m, wherein C0 is the initial concentration, C e is the equilibrium concentration, V is the solution volume, and m is the mass of the adsorption material.

[0090] 2. Desorption performance test

[0091] Test instrument: gas chromatograph, constant temperature water bath heating device, condensation recovery device

[0092] Test steps: After the adsorption is saturated, the material is packed in a fixed bed adsorption column, and the corresponding composite desorption agent is introduced, and the desorption is carried out in stages according to the set temperature; collect the desorption liquid of each temperature stage, and measure the concentration of each extractant component in the desorption liquid by gas chromatograph, and calculate the desorption amount.

[0093] Calculation method: desorption rate (η) = desorption amount / adsorption amount × 100%.

[0094] 3. Separation purity test

[0095] Test instrument: high performance liquid chromatograph, gas chromatograph-mass spectrometer

[0096] Test steps: Take each component distillate after rectification and gradient vacuum distillation, and measure the peak area of the target component and the impurity peak area by high performance liquid chromatograph and gas chromatograph-mass spectrometer, and calculate the purity.

[0097] Calculation method: purity (P) = target component peak area / total peak area × 100%.

[0098] 4. Adsorption material cycle stability test

[0099] Test instrument: fixed bed adsorption-desorption device, ultraviolet-visible spectrophotometer

[0100] Test steps: Based on the process conditions of Example 1 and Comparative Example 5, the adsorption-desorption-regeneration cycle was repeated for 10 times, and the adsorption capacity was determined after each cycle according to the adsorption performance test method provided by the application, and the adsorption capacity retention rate of each cycle was recorded.

[0101] Calculation method: capacity retention rate (R n ) = nth adsorption capacity / first adsorption capacity x 100%.

[0102] 5. Amine salt decomposition rate test

[0103] Test instrument: potentiometric titrator, ion chromatograph

[0104] Test steps: Take 10 mL of waste liquid before and after decomposition of the amine salt in step 4), determine the amine salt concentration before and after decomposition by ion chromatograph, calculate the decomposition rate; at the same time, determine the diethanolamine concentration after decomposition by potentiometric titrator, and verify the concentration control effect.

[0105] Calculation method: amine salt decomposition rate (δ) = (initial amine salt concentration - residual amine salt concentration) / initial amine salt concentration x 100%.

[0106] 6. Metal ion removal rate test

[0107] Test instrument: inductively coupled plasma mass spectrometer

[0108] Test steps: Take simulated industrial wastewater containing Fe 3+ , Cu 2+ (concentration is 5 mg / L), after adsorption-desorption process, collect the desorption liquid, and determine the metal ion concentration in the desorption liquid by inductively coupled plasma mass spectrometer, and calculate the removal rate.

[0109] Calculation method: metal ion removal rate (k) = (initial metal ion concentration - residual metal ion concentration) / initial metal ion concentration x 100%.

[0110] Experimental data:

[0111]

[0112] Based on the above data, the adsorption capacity of Examples 1-3 of the application is 81.7 to 88.5 mg / g, which is much higher than that of Comparative Example 1 of unmodified graphene, and by adjusting the molar ratio of the two types of functional groups, the adsorption selectivity is further optimized, and the competitive adsorption of impurities in wastewater is reduced.

[0113] Secondly, the non-temperature overlapping subsection desorption mode realizes directional desorption according to the difference in interaction energy between different extractant components and the adsorbent material, avoids the co-desorption phenomenon, and cooperates with the complex desorption agent containing the amino phosphonic acid type chelating agent to complex the metal ions in the industrial wastewater. The desorption rates of the secondary octanol in examples 1-3 and N235 and sulfonated kerosene are all above 95%, the metal ion removal rates are all above 92%, the desorption rate and the purity of comparative example 2 both decrease by about 10% due to temperature overlap, the metal ion removal rate of comparative example 3 is only 35.7% when no chelating agent is added, and the desorption and separation effects are significantly attenuated. The combination process of rectification and gradient vacuum distillation effectively solves the separation problem of components with close boiling points by adjusting the temperature and vacuum degree, so that the recovery purity of each component in examples 1-3 is above 93%, and the purity of comparative example 4 without a clear separation endpoint and with too fast heating rate is improved by 8%-10%.

[0114] Thirdly, after the amine salt-containing waste liquid is reused to the adsorption device, the amine salt is efficiently decomposed under acidic conditions, the decomposition rates of examples 1-3 are all above 97%, the generated diethanolamine repairs the hydroxyl defects on the surface of the adsorbent material through amino exchange reaction, and the organic acid pushes the deprotonated phosphonic acid group to reset through proton transfer, so as to ensure the cycle stability of the adsorbent material. The 10-cycle capacity retention rates of examples 1-3 are 89.3% to 92.7%, the material cannot be regenerated due to direct discharge of the waste liquid in comparative example 5, and the 10-cycle retention rate is only 58.3%, and the decomposition rate of the amine salt and the cycle stability are both greatly decreased in comparative example 6 because the pH deviates from the appropriate interval and is not controlled to fluctuate.

[0115] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of equivalent elements of the claims are intended to be embraced in the present application.

Claims

1. A process for the fractional purification and directional recovery of mixed extractants in industrial wastewater, characterized in that, The method comprises the following steps: 1) introducing industrial wastewater into an adsorption device filled with amine-phosphonic acid group modified graphene adsorption material, the molar ratio of amine group to phosphonic acid group in the adsorption material being 0.8:1-1.2:1; 2) introducing a composite desorption agent with a pH of 8.0-9.0 into the adsorption-saturated adsorption device in step 1), the composite desorption agent being prepared by mixing ethanol and diethanolamine at a volume ratio of 85-95:5-15, and adopting a staged desorption mode to desorb secondary octanol at 58-61 ℃ and to desorb N235 and sulfonated kerosene at 64-66 ℃, and collecting the mixed desorption liquid; The composite desorption agent further comprises an aminophosphonic acid type chelating agent; 3) introducing the mixed desorption liquid obtained in step 2) into a rectifying column, controlling the top temperature to be 73-80 ℃ and the bottom temperature to be 155-175 ℃, and separating to obtain a composite desorption agent, a mixed extractant and an amine salt-containing waste liquid; the mixed extractant is separated by gradient vacuum distillation to obtain secondary octanol, N235 and sulfonated kerosene; 4) introducing the amine salt-containing waste liquid at the bottom of the rectifying column in step 3) into the adsorption device in step 1), and adjusting the pH of the system to 2.0-3.

0.

2. The process according to claim 1, characterized in that, In step 1), the amine-phosphonic acid group modified graphene adsorption material is prepared by a covalent grafting method, and the preparation steps comprise: 1a) dispersing a graphene base material in a N,N-dimethylformamide solvent, ultrasonic treatment for 1-3 h, adding an amine group precursor and a catalyst triethylamine, the mass ratio of the amine group precursor to the graphene base material being 1:8-1:12, stirring and reacting at 60-80 ℃ for 4-6 h to obtain amine group modified graphene; wherein the amine group functional group loading of the amine group precursor is regulated by the reaction time: the amine group loading is 0.3-0.4 mmol / g when the reaction time is 4 h, and the amine group loading is 0.5-0.6 mmol / g when the reaction time is 6 h; 1b) adding a phosphonic acid group precursor to the amine group modified graphene dispersion, the mass ratio of the phosphonic acid group precursor to the amine group modified graphene being 1:5-1:7, heating to 80-100 ℃, stirring and reacting for 6-8 h to generate phosphonic acid groups through ester hydrolysis reaction; wherein the phosphonic acid group loading is regulated by the reaction temperature: the phosphonic acid group loading is 0.4-0.5 mmol / g when the reaction temperature is 80 ℃, and the phosphonic acid group loading is 0.6-0.7 mmol / g when the reaction temperature is 100 ℃; 1c) after the reaction is completed, washing 3-5 times alternately with deionized water and ethanol, and vacuum drying for 6-12 h to obtain the amine-phosphonic acid group modified graphene adsorption material; by adjusting the reaction time in step 1a) and the reaction temperature in step 1b), the molar ratio of amine group to phosphonic acid group in the final material is 0.8:1-1.2:

1.

3. The process of claim 2, wherein, In step 1), the pH of the industrial wastewater is 2.0-3.0, the inflow is 20-50 L / h, and the water temperature is 25-45 ℃; when the water temperature is greater than or equal to 30 ℃, the inflow is reduced by 10-30%.

4. The process of claim 1, wherein, In step 2), the volume ratio of ethanol, diethanolamine and aminophosphonic acid type chelating agent is 85-95:5-12:1-3. The amino phosphonic acid type chelating agent is ethylenediamine tetramethylene phosphonic acid, and the preparation steps thereof include: 2a) 1 part of ethylenediamine and 3-7 parts of deionized water are added into a four-necked flask, the ethylenediamine is in parts by mass, and the deionized water is in parts by volume; after stirring until the ethylenediamine is completely dissolved, the temperature of the system is controlled to be 15-30℃; then 37% formaldehyde aqueous solution is slowly added dropwise, the molar ratio of formaldehyde to ethylenediamine is 3-6:1, the dropwise adding time is controlled to be 20-40 min, after the dropwise adding is completed, stirring is continued for 10-20 min, and an ethylenediamine-formaldehyde condensate solution is formed; 2b) cooling medium is introduced into the condensate solution obtained in step 2a) to reduce the temperature of the system to 3-12℃; then phosphorus trichloride is slowly added dropwise, the molar ratio of phosphorus trichloride to ethylenediamine is 2.5-4:1, the temperature of the system is controlled to be ≤18℃ during the dropwise adding process, the dropwise adding time is 1-2.5 h, after the dropwise adding is completed, the temperature is increased to 35-55℃, and stirring reaction is carried out for 1.5-2.5 h to obtain a phosphonate intermediate; 2c) deionized water is added into the phosphonate intermediate obtained in step 2b), the volume ratio of the deionized water added to the deionized water in step 2a) is 1.2-2:1, the temperature is increased to 85-100℃, reflux hydrolysis reaction is carried out for 2.5-4.5 h, after the reaction is completed, 30% sodium hydroxide solution is used to neutralize the pH of the system to 5.5-7.5, and after concentration by reduced pressure distillation, crystallization and drying, ethylenediamine tetramethylene phosphonic acid is obtained.

5. The process of claim 1, wherein, In step 3), the process parameters of the gradient vacuum distillation are as follows: in the first stage, secondary octanol is separated at a vacuum degree of 0.06-0.09 MPa and a temperature of 78-88℃, and when the purity of the secondary octanol in the distillate is ≤90%, the separation is determined to be completed; in the second stage, N235 and sulfonated kerosene are separated at a vacuum degree of 0.001-0.005 MPa and a temperature of 105-125℃, and when the total purity of N235 and sulfonated kerosene in the distillate is ≤90%, the distillation is stopped.

6. The process of claim 5, wherein, In step 3), the temperature increasing rate of the gradient vacuum distillation is 2-6℃ / h, and the time for increasing the temperature from the terminal temperature of the first stage (88℃) to the initial temperature of the second stage (105℃) is 3-8.5 h, and the temperature of each stage is maintained for 0.5-2 h.

7. The process of claim 6, wherein, In step 3), after the separated composite desorbent is filtered to remove trace impurities, ethanol and diethanolamine are detected and supplemented to a volume ratio of 85-95:5-15 and a pH of 8-9, and the composite desorbent is returned to step 2).

8. The process of claim 1, wherein, In step 4), the amine salt in the amine salt-containing waste liquid is decomposed into diethanolamine and organic acid under acidic conditions, the decomposition reaction time is 40-80 min, and the concentration of diethanolamine in the system is controlled to be 0.05-0.15 mol / L.

9. The process of claim 8, wherein, In step 4), when the amino exchange reaction between diethanolamine and the hydroxyl groups produced by the hydrolysis of graphene adsorption material surface occurs, an esterification reaction between diethanolamine and residual organic acid impurities also occurs, the reaction temperature is controlled to be 30-40℃, and the reaction time is 30-50 min.

10. The process of claim 9, wherein, In step 4), the organic acid produced by the amine salt decomposition forms a concentration of 0.03-0.08 mol / L in the system, and the deprotonated phosphonic acid group is promoted to return by proton transfer, the pH fluctuation range of the process is controlled to be ≤±0.3, and the proportion of the protonated phosphonic acid group is ≥90%.

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