A treatment process for high-concentration acrylonitrile wastewater

Abstract

This invention provides a treatment process for high-concentration acrylonitrile wastewater, belonging to the field of water treatment technology, including the following steps: Step S1, preparing a eutectic solvent; Step S2, pumping the pretreated acrylonitrile wastewater and the eutectic solvent into a polyvinylidene fluoride hollow fiber membrane contactor for countercurrent circulation extraction, then introducing the solvent phase into a desorption tank, heating, introducing CO2 gas, bubbling, and then flash evaporation to recover acrylonitrile; injecting the raffinate aqueous phase into an electrolytic cell, simultaneously introducing an O2 / O3 mixed gas, for electrolysis to obtain pretreated wastewater; Step S3, introducing the pretreated wastewater into a moving bed biofilm reactor for two-stage treatment, with the effluent undergoing activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater, obtaining the final effluent. This invention achieves the goals of efficient acrylonitrile recovery, good effluent quality, and low environmental risk.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more specifically to a treatment process for high-concentration acrylonitrile wastewater. Background Technology

[0002] Acrylonitrile, as an important organic chemical raw material, generates large quantities of high-concentration acrylonitrile wastewater during its production and use. This wastewater is complex in composition, highly toxic, chemically stable, and has extremely poor biodegradability. Direct discharge poses a threat to aquatic ecosystems and human health. Traditional physicochemical methods, such as direct distillation or air stripping, are energy-intensive and prone to secondary pollution, while conventional biological treatment is inefficient due to acrylonitrile's strong inhibitory effect on microorganisms. Extraction is an effective way to recover high-concentration acrylonitrile, but traditional extractants such as benzene and halogenated hydrocarbons are highly toxic, volatile, difficult to regenerate, and may remain in the aqueous phase, causing secondary pollution.

[0003] A method for treating acrylonitrile wastewater is disclosed in patent application CN111995187A. The method comprises the following steps: wastewater in a collection tank enters a rapid mixing zone under the action of a booster pump; a first dosing tank adds flocculant to the rapid mixing zone; the flocculant and wastewater mix rapidly in a short time and then enter a slow mixing zone through water holes; a second dosing tank adds coagulant aid to the slow mixing zone; the coagulant aid reacts fully with the wastewater in the slow mixing zone and then flows into a sedimentation zone for sedimentation and separation; the separated supernatant enters a membrane tank; microorganisms in the membrane tank biodegrade organic pollutants in the wastewater; under the suction of an effluent pump, the wastewater in the membrane tank is filtered by various filter membrane components; the clear liquid produced by filtration flows from the inner cavity of the membrane frame into a collection plate and then flows out through an effluent pipe; an aeration device continuously blows air bubbles into the membrane tank; and the suspended packing material in the membrane tank is fluidized and dispersed in the membrane tank. This solution improves membrane separation technology to some extent and removes large particulate pollutants from acrylonitrile wastewater, but the effluent quality is still insufficient, making it difficult to achieve the goal of efficiently removing acrylonitrile and pollutants.

[0004] Therefore, there is a need to provide a treatment process for high-concentration acrylonitrile wastewater to solve the problems existing in the prior art. Summary of the Invention

[0005] In view of this, the present invention provides a treatment process for high-concentration acrylonitrile wastewater, which can achieve efficient acrylonitrile recovery, good effluent quality and low environmental risk.

[0006] To achieve the above objectives, the present invention provides a treatment process for high-concentration acrylonitrile wastewater, comprising the following steps:

[0007] Step S1: Add choline chloride and ethylene glycol to the reaction vessel, heat and stir, then cool and add triethylamine and deionized water, stir, and let stand to obtain a eutectic solvent.

[0008] Step S2: The pretreated acrylonitrile wastewater and eutectic solvent are pumped into a polyvinylidene fluoride hollow fiber membrane contactor for countercurrent circulation extraction. Then, the solvent phase is introduced into a desorption tank, heated, CO2 gas is introduced, bubbling is performed, and then flash evaporation is carried out to recover acrylonitrile. The raffinate aqueous phase is injected into an electrolytic cell, and O2 / O3 mixed gas is introduced at the same time for electrolysis to obtain pre-treated wastewater.

[0009] Step S3: The pre-treated wastewater is introduced into a moving bed biofilm reactor for aerobic and anoxic two-stage treatment. The effluent is then subjected to activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0010] Choline chloride and ethylene glycol form a eutectic solvent, which enhances the solvent's solubility for acrylonitrile through hydrogen bonding networks, ion-dipole interactions, and high polarity. During desorption, carbon dioxide is introduced, and under aqueous conditions, it reacts with triethylamine to form triethylammonium bicarbonate, increasing the solvent's ionic strength and viscosity, thereby reducing its solubility for acrylonitrile. The solvent, combined with a membrane contactor, performs selective extraction of acrylonitrile. A hydrophobic polyvinylidene fluoride hollow fiber membrane is used as the liquid-liquid interface. Due to the membrane's hydrophobicity, the aqueous phase cannot permeate, while acrylonitrile molecules can diffuse through the membrane, transferring from the aqueous phase to the solvent phase. When the acrylonitrile-rich solvent phase enters the desorption tank, CO2 is introduced. Under aqueous conditions, it reacts with triethylamine to form triethylammonium bicarbonate, which increases the ionic strength of the solvent, disrupts the polar environment for dissolving acrylonitrile, and produces a salting-out effect. This leads to a decrease in the solubility of acrylonitrile, which is then carried out by the bubbling CO2. Combined with flash evaporation, the CO2 and residual acrylonitrile in the solvent are removed, and the system returns to its initial state, achieving the recovery of acrylonitrile and the recycling of the eutectic solvent.

[0011] By employing a combination of electrochemical and ozone catalysis, the oxidation effect is made more significant. This method can mineralize large, difficult-to-degrade organic molecules in wastewater into CO2 and H2O, or break them down into easily biodegradable small molecules, facilitating subsequent biological treatment.

[0012] A two-stage treatment process was implemented using a moving bed biofilm reactor. In the first aerobic stage, heterotrophic aerobic bacteria dominated, which were able to degrade most of the remaining COD in the wastewater. At the same time, nitrifying bacteria could reduce NH4+. + Oxidized to NO2 - and NO3 - In the second stage of anoxic treatment, the dissolved oxygen level is low, leading to membrane stratification: the outer layer is slightly oxygen-rich, while the inner layer is anoxic. This allows denitrifying bacteria to eliminate NO2. - and NO3 -The nitrogen is reduced to N2, thus achieving nitrogen removal. Finally, activated carbon is used for adsorption to remove trace amounts of microbial products and extremely difficult-to-degrade organic matter produced by biological metabolism, achieving a highly efficient chemical-biological synergistic effect.

[0013] Preferably, in step S2, the preparation of pretreated acrylonitrile wastewater includes the following steps:

[0014] High-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 250-300 rpm at 25-30℃. p-hydroxyanisole was added, and a negative pressure of -80 Pa to -200 Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0015] Acrylonitrile molecules contain carbon-carbon double bonds and cyano groups, making them highly susceptible to free radical chain polymerization. However, p-hydroxyanisole can terminate chain growth by capturing free radicals, inhibiting acrylonitrile self-polymerization, thus facilitating subsequent processes. At the same time, it can absorb exhaust gases and reduce VOC emissions.

[0016] Preferably, in step S2, the volume ratio of pretreated acrylonitrile wastewater to eutectic solvent is 4:1.

[0017] Preferably, in step S2, the heating temperature is 35-40℃; the CO2 pressure is 1.2-1.5 bar; and the bubbling time is 20-30 min.

[0018] Preferably, in step S2, the current density of the electrolysis reaction is 12-18 mA / cm². 2 The time is 40-50 min; the concentration of O3 in the O2 / O3 mixed gas is 3 wt%.

[0019] Preferably, in step S3, after the pre-treated wastewater is introduced into the moving bed biofilm reactor, surface-quaternized porous ceramic particles are added; the preparation of the surface-quaternized porous ceramic particles includes the following steps:

[0020] Bromododecane was dissolved in anhydrous acetonitrile, and then porous ceramic particles with tertiary amine groups on the surface were added. The mixture was heated to 60-70℃ and stirred for 5-7 hours. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0021] By reacting dodecane bromide with porous ceramic particles containing tertiary amine groups on their surface, quaternized porous ceramic particles are obtained, giving the particle surface a permanent positive charge in a near-neutral aquatic environment. Since the cell membranes of most bacteria and microorganisms are negatively charged under natural conditions, according to the principle of electrostatic attraction, the positively charged ceramic particle surface strongly adsorbs the negatively charged microbial cells, firmly fixing the microorganisms to the ceramic particle surface and greatly promoting the initial adhesion of the biofilm and the proliferation of new cells. This avoids the problems of slow biofilm adhesion and easy detachment found in traditional packing materials.

[0022] Surface-quaternized porous ceramsite supports the coexistence of aerobic, facultative, and anaerobic bacteria within the same biofilm, enabling efficient simultaneous nitrification and denitrification in the two-stage treatment of a moving bed biofilm reactor, achieving deep nitrogen removal. Furthermore, quaternary ammonium salts possess antibacterial properties, selectively inhibiting the excessive proliferation of harmful bacteria such as filamentous bacteria that easily cause sludge and clogging, while allowing beneficial bacteria to survive and form a stable biofilm, ensuring treatment efficiency while avoiding clogging problems. In addition, porous ceramsite can accelerate biodegradation rates through adsorption, achieving highly efficient treatment.

[0023] Preferably, the preparation of the porous ceramic particles containing tertiary amine groups includes the following steps:

[0024] 3-(dimethylamino)methacrylate, deionized water, isopropanol and sodium dodecyl sulfate were mixed evenly, and nitrogen gas was bubbled in. Modified porous ceramic particles were added, and the mixture was heated to 55-60℃. Ammonium persulfate and sodium metabisulfite were added, and the mixture was stirred and reacted for 45-60 min. The mixture was then filtered, washed, and dried to obtain porous ceramic particles with tertiary amine groups on the surface.

[0025] In-situ grafting polymerization was carried out on the surface of modified porous ceramic particles by initiation with ammonium persulfate and sodium metabisulfite to obtain an organic polymer brush surface with a large number of tertiary amine groups.

[0026] Preferably, the preparation of the modified porous ceramsite includes the following steps: mixing anhydrous ethanol, deionized water and glacial acetic acid evenly, adding 3-(methacryloyloxy)propyltrimethoxysilane and stirring, then adding activated porous ceramsite, ultrasonically treating, impregnating, filtering, drying and curing to obtain modified porous ceramsite; the preparation of the activated porous ceramsite includes the following steps: using hydrochloric acid solution to impregnate and activate porous ceramsite with a diameter of 3-5 mm, washing and drying to obtain activated porous ceramsite.

[0027] Porous ceramsite with a diameter of 3-5 mm can balance specific surface area and mass transfer pathway, resulting in low pressure drop and erosion resistance. After activation, it is further cleaned and the microporous structure is expanded. Surface modification with 3-(methacryloyloxy)propyltrimethoxysilane forms a hydrolysis-resistant covalent anchoring layer with exposed polymerizable double bonds, facilitating subsequent grafting.

[0028] Preferably, in step S3, the dissolved oxygen concentration in the reactor during the first aerobic treatment is 1.5-2 mg / L, and the residence time is 2-3 h; the dissolved oxygen concentration in the reactor during the second anoxic treatment is 0.2-0.5 mg / L, and the residence time is 2-3 h.

[0029] Preferably, the raw material of the eutectic solvent comprises the following components in parts by weight:

[0030] Choline chloride 140-210 parts, ethylene glycol 124-186 parts, triethylamine 12-18 parts, and deionized water 10-15 parts.

[0031] The eutectic solvent prepared using the above proportions can achieve better extraction results, which is helpful for the treatment of acrylonitrile wastewater.

[0032] The above-described technical solution of the present invention has at least the following beneficial effects:

[0033] 1. Choline chloride and ethylene glycol are used to form a eutectic solvent, which is used in conjunction with a membrane contactor to selectively extract acrylonitrile. CO2 reacts with triethylamine and water to increase the ionic strength of the solvent, which leads to a decrease in the solubility of acrylonitrile. As a result, acrylonitrile is carried out by the bubbling CO2 and precipitated, thus realizing the recovery of acrylonitrile and the recycling of the eutectic solvent.

[0034] 2. By employing electrochemical and ozone catalysis, the oxidation effect is more significant, which can mineralize large, difficult-to-degrade organic molecules in wastewater into CO2 and H2O, or break them down into easily biodegradable small molecules, facilitating subsequent biological treatment.

[0035] 3. A moving bed biofilm reactor is used for two-stage treatment. In the first aerobic stage, heterotrophic aerobic bacteria dominate, which can degrade most of the remaining COD in the wastewater. At the same time, nitrifying bacteria can reduce NH4+. + Oxidized to NO2 - and NO3 - In the second stage of anoxic treatment, the dissolved oxygen level is low, and denitrifying bacteria convert NO2 into oxygen. - and NO3 - It is reduced to N2, thereby achieving nitrogen removal. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0037] Example 1

[0038] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 300rpm at 25℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0039] Add 140g of choline chloride and 124g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 300rpm for 20min, then cool to 30°C and add 12g of triethylamine, then add 10g of deionized water, continue stirring for 15min, and let stand to obtain a eutectic solvent.

[0040] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2 The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 35 °C, and CO2 gas at a pressure of 1.2 bar was introduced. Bubbling was performed for 30 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0041] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 15 mA / cm³. 2 Simultaneously, a mixed gas of O2 / O3 with an ozone concentration of 3wt% is introduced, the pH is maintained at 6.0-6.5, the temperature is 25-30℃, and the electrolysis reaction is carried out continuously for 45 minutes to obtain pre-treated wastewater.

[0042] 700g of porous ceramsite with a diameter of 3-5mm was immersed in 0.1mol / L hydrochloric acid solution for 10min to activate it, washed with deionized water, and dried to obtain activated porous ceramsite.

[0043] Mix 950 mL of anhydrous ethanol, 40 mL of deionized water and 10 mL of glacial acetic acid evenly, add 10 g of 3-(methacryloyloxy)propyltrimethoxysilane, stir for 30 min, add 700 g of activated porous ceramsite, sonicate for 3 min, impregnate for 20 min, filter, dry, and cure at 110 °C for 1 h to obtain modified porous ceramsite.

[0044] Mix 20g of 3-(dimethylamino)methacrylate, 180g of deionized water, 10g of isopropanol and 0.1g of sodium dodecyl sulfate evenly, bubble with nitrogen, add 600g of modified porous ceramsite, heat to 55℃, add 0.5g of ammonium persulfate and 0.25g of sodium metabisulfite, stir and react for 60min, filter, wash and dry to obtain porous ceramsite containing tertiary amine groups.

[0045] 10g of bromododecane was dissolved in 200mL of anhydrous acetonitrile, and 600g of porous ceramic particles containing tertiary amine groups were added. The mixture was heated to 70℃ and stirred for 5h. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0046] The pre-treated wastewater is introduced into a moving bed biofilm reactor, and porous ceramsite with quaternized surface is added. In the first stage, the dissolved oxygen in the reactor is controlled at 2 mg / L, and the residence time is 2 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.5 mg / L, and the residence time is 3 h. The temperature is 30℃, and the pH is 7-7.5. The effluent undergoes activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0047] Example 2

[0048] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 250rpm at 30℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0049] Add 210g of choline chloride and 186g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 200rpm for 30min, then cool to 30°C and add 18g of triethylamine, then add 15g of deionized water, continue stirring for 15min, and let stand to obtain a eutectic solvent.

[0050] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2 The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 40 °C, and CO2 gas at a pressure of 1.5 bar was introduced. Bubbling was performed for 20 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0051] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 12 mA / cm³. 2 Simultaneously, a 3wt% O2 / O3 mixed gas is introduced, maintaining the pH at 6.0-6.5 and the temperature at 25-30℃, and the electrolysis reaction is carried out continuously for 50 minutes to obtain pre-treated wastewater.

[0052] 700g of porous ceramsite with a diameter of 3-5mm was immersed in 0.1mol / L hydrochloric acid solution for 10min to activate it, washed with deionized water, and dried to obtain activated porous ceramsite.

[0053] Mix 950 mL of anhydrous ethanol, 40 mL of deionized water and 10 mL of glacial acetic acid evenly, add 10 g of 3-(methacryloyloxy)propyltrimethoxysilane, stir for 30 min, add 700 g of activated porous ceramsite, sonicate for 3 min, impregnate for 20 min, filter, dry, and cure at 110 °C for 1 h to obtain modified porous ceramsite.

[0054] Mix 20g of 3-(dimethylamino)methacrylate, 180g of deionized water, 10g of isopropanol and 0.1g of sodium dodecyl sulfate evenly, bubble with nitrogen, add 600g of modified porous ceramsite, heat to 60℃, add 0.5g of ammonium persulfate and 0.25g of sodium metabisulfite, stir and react for 45min, filter, wash and dry to obtain porous ceramsite containing tertiary amine groups.

[0055] 10g of bromododecane was dissolved in 200mL of anhydrous acetonitrile, and 600g of porous ceramic particles containing tertiary amine groups were added. The mixture was heated to 65℃ and stirred for 6h. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0056] The pre-treated wastewater is introduced into a moving bed biofilm reactor, and porous ceramsite with quaternized surface is added. In the first stage, the dissolved oxygen in the reactor is controlled at 1.5 mg / L, and the residence time is 3 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.2 mg / L, and the residence time is 2 h. The temperature is 30℃, and the pH is 7-7.5. The effluent is then subjected to activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0057] Example 3

[0058] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 300rpm at 25℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0059] Add 175g of choline chloride and 155g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 250rpm for 25min, then cool to 30°C and add 15g of triethylamine and 12.5g of deionized water, continue stirring for 15min, and let stand to obtain a eutectic solvent.

[0060] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 40 °C, and CO2 gas at a pressure of 1.35 bar was introduced. Bubbling was performed for 25 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0061] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 18 mA / cm³. 2 Simultaneously, a 3wt% O2 / O3 mixed gas is introduced, maintaining the pH at 6.0-6.5 and the temperature at 25-30℃, and the electrolysis reaction is carried out continuously for 40 minutes to obtain pre-treated wastewater.

[0062] 700g of porous ceramsite with a diameter of 3-5mm was immersed in 0.1mol / L hydrochloric acid solution for 10min to activate it, washed with deionized water, and dried to obtain activated porous ceramsite.

[0063] Mix 950 mL of anhydrous ethanol, 40 mL of deionized water and 10 mL of glacial acetic acid evenly, add 10 g of 3-(methacryloyloxy)propyltrimethoxysilane, stir for 30 min, add 700 g of activated porous ceramsite, sonicate for 3 min, impregnate for 20 min, filter, dry, and cure at 110 °C for 1 h to obtain modified porous ceramsite.

[0064] Mix 20g of 3-(dimethylamino)methacrylate, 180g of deionized water, 10g of isopropanol and 0.1g of sodium dodecyl sulfate evenly, bubble with nitrogen, add 600g of modified porous ceramsite, heat to 60℃, add 0.5g of ammonium persulfate and 0.25g of sodium metabisulfite, stir and react for 50min, filter, wash and dry to obtain porous ceramsite containing tertiary amine groups.

[0065] 10g of bromododecane was dissolved in 200mL of anhydrous acetonitrile, and 600g of porous ceramic particles containing tertiary amine groups were added. The mixture was heated to 70℃ and stirred for 5h. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0066] The pre-treated wastewater is introduced into a moving bed biofilm reactor, and porous quaternized ceramic particles are added to the surface. In the first stage, the dissolved oxygen in the reactor is controlled at 1.8 mg / L, and the residence time is 2.5 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.3 mg / L, the residence time is 2.5 h, the temperature is 30℃, and the pH is 7-7.5. The effluent is then subjected to activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0067] Example 4

[0068] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 250rpm at 30℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0069] Add 140g of choline chloride and 124g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 350rpm for 20min, then cool to 30°C and add 12g of triethylamine, then add 10g of deionized water, continue stirring for 15min, and let stand to obtain a eutectic solvent.

[0070] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2 The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 35 °C, and CO2 gas at a pressure of 1.5 bar was introduced. Bubbling was performed for 20 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0071] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 12 mA / cm³. 2 Simultaneously, a 3wt% O2 / O3 mixed gas is introduced, maintaining the pH at 6.0-6.5 and the temperature at 25-30℃, and the electrolysis reaction is carried out continuously for 50 minutes to obtain pre-treated wastewater.

[0072] 700g of porous ceramsite with a diameter of 3-5mm was immersed in 0.1mol / L hydrochloric acid solution for 10min to activate it, washed with deionized water, and dried to obtain activated porous ceramsite.

[0073] Mix 950 mL of anhydrous ethanol, 40 mL of deionized water and 10 mL of glacial acetic acid evenly, add 10 g of 3-(methacryloyloxy)propyltrimethoxysilane, stir for 30 min, add 700 g of activated porous ceramsite, sonicate for 3 min, impregnate for 20 min, filter, dry, and cure at 110 °C for 1 h to obtain modified porous ceramsite.

[0074] Mix 20g of 3-(dimethylamino)methacrylate, 180g of deionized water, 10g of isopropanol and 0.1g of sodium dodecyl sulfate evenly, bubble with nitrogen, add 600g of modified porous ceramsite, heat to 55℃, add 0.5g of ammonium persulfate and 0.25g of sodium metabisulfite, stir and react for 55min, filter, wash and dry to obtain porous ceramsite containing tertiary amine groups.

[0075] 10g of bromododecane was dissolved in 200mL of anhydrous acetonitrile, and 600g of porous ceramic particles containing tertiary amine groups were added. The mixture was heated to 60℃ and stirred for 7h. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0076] The pre-treated wastewater is introduced into a moving bed biofilm reactor, and porous ceramsite with quaternized surface is added. In the first stage, the dissolved oxygen in the reactor is controlled at 2 mg / L, and the residence time is 2.5 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.5 mg / L, the residence time is 2.5 h, the temperature is 30℃, and the pH is 7-7.5. The effluent undergoes activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0077] Example 5

[0078] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 300rpm at 25℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0079] Add 175g of choline chloride and 155g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 250 rpm for 30 min, then cool to 30°C and add 15g of triethylamine and 12.5g of deionized water, continue stirring for 15 min, and let stand to obtain a eutectic solvent.

[0080] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2 The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 40 °C, and CO2 gas at a pressure of 1.2 bar was introduced. Bubbling was performed for 30 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0081] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 15 mA / cm³. 2 Simultaneously, a mixed gas of O2 / O3 with an ozone concentration of 3wt% is introduced, the pH is maintained at 6.0-6.5, the temperature is 25-30℃, and the electrolysis reaction is carried out continuously for 45 minutes to obtain pre-treated wastewater.

[0082] 700g of porous ceramsite with a diameter of 3-5mm was immersed in 0.1mol / L hydrochloric acid solution for 10min to activate it, washed with deionized water, and dried to obtain activated porous ceramsite.

[0083] Mix 950 mL of anhydrous ethanol, 40 mL of deionized water and 10 mL of glacial acetic acid evenly, add 10 g of 3-(methacryloyloxy)propyltrimethoxysilane, stir for 30 min, add 700 g of activated porous ceramsite, sonicate for 3 min, impregnate for 20 min, filter, dry, and cure at 110 °C for 1 h to obtain modified porous ceramsite.

[0084] Mix 20g of 3-(dimethylamino)methacrylate, 180g of deionized water, 10g of isopropanol and 0.1g of sodium dodecyl sulfate evenly, bubble with nitrogen, add 600g of modified porous ceramsite, heat to 60℃, add 0.5g of ammonium persulfate and 0.25g of sodium metabisulfite, stir and react for 50min, filter, wash and dry to obtain porous ceramsite containing tertiary amine groups.

[0085] 10g of bromododecane was dissolved in 200mL of anhydrous acetonitrile, and 600g of porous ceramic particles containing tertiary amine groups were added. The mixture was heated to 65℃ and stirred for 6h. After filtration, washing, and drying, the surface-quaternized porous ceramic particles were obtained.

[0086] The pre-treated wastewater is introduced into a moving bed biofilm reactor, and porous ceramsite with quaternized surface is added. In the first stage, the dissolved oxygen in the reactor is controlled at 1.8 mg / L, and the residence time is 3 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.5 mg / L, and the residence time is 3 h. The temperature is 30℃, and the pH is 7-7.5. The effluent undergoes activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0087] Example 6

[0088] 1L of high-concentration acrylonitrile wastewater was added to a closed homogenizing tank and stirred at 300rpm at 25℃. 20mg of p-hydroxyanisole was added, and a negative pressure of -80Pa to -200Pa was applied. Stirring was continued for 2 hours to obtain pretreated acrylonitrile wastewater.

[0089] Add 175g of choline chloride and 155g of ethylene glycol to a reaction vessel, heat to 50°C, stir at 250 rpm for 30 min, then cool to 30°C and add 15g of triethylamine and 12.5g of deionized water, continue stirring for 15 min, and let stand to obtain a eutectic solvent.

[0090] Pretreated acrylonitrile wastewater and a eutectic solvent were pumped into a polyvinylidene fluoride hollow fiber membrane contactor at a volume ratio of 4:1 for countercurrent circulation extraction. The membrane area was 0.5 m². 2The membrane had a pore size of 0.1 μm, a transmembrane pressure difference of 0.08 bar, and an aqueous phase cross-flow rate of 0.3 m / s. The membrane was circulated for 25 min. The solvent phase was then introduced into a desorption vessel, heated to 40 °C, and CO2 gas at a pressure of 1.2 bar was introduced. Bubbling was performed for 30 min to release acrylonitrile. Subsequently, the mixture was flash-evaporated under a vacuum of -0.05 MPa for 10 min to recover acrylonitrile, and the eutectic solvent was regenerated and returned to the circulation extraction.

[0091] The raffinate aqueous phase was injected into the electrolytic cell, and the current density was controlled at 15 mA / cm³. 2 Simultaneously, a mixed gas of O2 / O3 with an ozone concentration of 3wt% is introduced, the pH is maintained at 6.0-6.5, the temperature is 25-30℃, and the electrolysis reaction is carried out continuously for 45 minutes to obtain pre-treated wastewater.

[0092] The pre-treated wastewater is introduced into a moving bed biofilm reactor. In the first stage, the dissolved oxygen in the reactor is controlled at 1.8 mg / L, and the residence time is 3 h. In the second stage, the dissolved oxygen in the reactor is controlled at 0.5 mg / L, and the residence time is 3 h. The temperature is 30℃, and the pH is 7-7.5. The effluent undergoes activated carbon adsorption to complete the treatment of high-concentration acrylonitrile wastewater and obtain the final effluent.

[0093] The present invention also includes comparative examples and related experiments.

[0094] Comparative Example 1

[0095] The only difference between Comparative Example 1 and Example 1 is that no eutectic solvent was prepared in Comparative Example 1, while the other processing steps were the same as in Example 1.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 1 is that ozone was not used when electrolyzing the raffinate aqueous phase in Comparative Example 2, while the other treatment processes were the same as in Example 1.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Example 1 is that the moving bed biofilm reactor in Comparative Example 3 did not undergo two-stage treatment (aerobic and anoxic), but only one-stage treatment. The dissolved oxygen concentration was 1 mg / L and the residence time was 5 h. Other treatment processes were the same as in Example 1.

[0100] Performance testing

[0101] In the high-concentration acrylonitrile wastewater described in Examples 1-6 and Comparative Examples 1-3, the acrylonitrile (AN) concentration was 1480 mg / L; the COD (chemical oxygen demand) concentration was 6800 mg / L; the TOC (total organic carbon) concentration was 2150 mg / L; and the TN (total nitrogen) concentration was 180 mg / L. The final effluents obtained from the treatment processes described in Examples 1-6 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0102] Table 1

[0103]

[0104] As shown in Table 1, Comparative Example 1, without the preparation of a eutectic solvent, had an AN concentration of 3.4 in its final effluent, which was significantly higher than that in the final effluent of Example 1. This indicates that the eutectic solvent helps to selectively extract acrylonitrile and improve treatment efficiency. The COD and TOC concentrations in the final effluent of Comparative Example 2 increased significantly compared to Example 1, indicating that the synergistic catalytic method of electrochemistry and ozone can make the oxidation more significant, promote the mineralization of organic matter in wastewater, and convert it into CO2 and H2O. The TN concentration in the final effluent of Comparative Example 3 increased significantly, indicating that the two-stage treatment of aerobic and anoxic processes can achieve nitrification and denitrification, thus removing nitrogen.

[0105] Compared with Example 5, Example 6 did not prepare surface quaternized porous ceramic particles, but all data in the final effluent increased, indicating that surface quaternized porous ceramic particles help adsorb microorganisms, achieve simultaneous nitrification and denitrification, and promote the improvement of treatment efficiency.

[0106] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for treating high-strength acrylonitrile wastewater, characterized by, The method comprises the following steps: Step S1, choline chloride and ethylene glycol are added into a reaction kettle, and then warmed and stirred, and then cooled and added with triethylamine and deionized water, and then stirred and settled to obtain a eutectic solvent; Step S2, the pretreated acrylonitrile wastewater is pumped into the polyvinylidene fluoride hollow fiber membrane contactor to perform countercurrent circulation extraction with the eutectic solvent, and then the solvent phase is introduced into a desorption tank, warmed, and bubbled with CO2 gas, and then flashed to recover acrylonitrile; the raffinate water phase is injected into an electrolytic cell while being introduced with O2 / O3 mixed gas to perform electrolysis, and thus the preliminary treated wastewater is obtained; Step S3, the preliminary treated wastewater is introduced into a moving bed biofilm reactor to perform aerobic and anoxic two-stage treatment, and the effluent is subjected to activated carbon adsorption to complete the treatment of the high-concentration acrylonitrile wastewater, and thus the final effluent is obtained.

2. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, In the step S2, the preparation of the pretreated acrylonitrile wastewater comprises the following steps: The high-concentration acrylonitrile wastewater is added into a sealed homogenizer tank, and stirred at a speed of 250-300 rpm at 25-30℃ while adding p-hydroxyanisole, and then negative pressure of-80 Pa to-200 Pa is drawn, and the stirring is continued for 2 h to obtain the pretreated acrylonitrile wastewater.

3. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, In the step S2, the volume ratio of the pretreated acrylonitrile wastewater to the eutectic solvent is 4:

1.

4. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, In the step S2, the temperature of the warming is 35-40℃, the pressure of the CO2 is 1.2-1.5 bar, and the bubbling time is 20-30 min.

5. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, The current density of the electrolysis reaction in the step S2 is 12-18 mA / cm 2 , and the time is 40-50 min; the concentration of O3 in the O2 / O3 mixed gas is 3 wt%.

6. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, In the step S3, the surface quaternary ammonium porous ceramsite is further added after the preliminary treated wastewater is introduced into the moving bed biofilm reactor; and the preparation of the surface quaternary ammonium porous ceramsite comprises the following steps: The bromododecane is dissolved in anhydrous acetonitrile, and then the surface tertiary amine group-containing porous ceramsite is added, and then heated to 60-70℃, and then stirred for 5-7 h, and then filtered, washed and dried to obtain the surface quaternary ammonium porous ceramsite.

7. The process for treating high-strength acrylonitrile wastewater according to claim 6, characterized in that, The preparation of the surface tertiary amine group-containing porous ceramsite comprises the following steps: The 3-(dimethylamino) methyl acrylate, deionized water, isopropyl alcohol and sodium dodecyl sulfate are uniformly mixed, and then nitrogen is bubbled, and then the modified porous ceramsite is added, and then heated to 55-60℃, and then ammonium persulfate and sodium metabisulfite are added, and then stirred for 45-60 min, and then filtered, washed and dried to obtain the surface tertiary amine group-containing porous ceramsite.

8. The treatment process of high-concentration acrylonitrile wastewater according to claim 7, characterized in that, The preparation of the modified porous ceramsite comprises the following steps: The anhydrous ethanol, deionized water and glacial acetic acid are uniformly mixed, and then 3-(methacryloyloxy) propyl trimethoxysilane is added for stirring, and then the activated porous ceramsite is added, and then ultrasonic treatment, immersion, filtration, drying, curing are performed to obtain the modified porous ceramsite; The preparation of the activated porous ceramsite comprises the following steps: the porous ceramsite with a diameter of 3-5 mm is immersed and washed with a hydrochloric acid solution for activation, and then washed and dried to obtain the activated porous ceramsite.

9. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, In the step S3, the concentration of dissolved oxygen in the reactor in the first-stage aerobic treatment is 1.5-2 mg / L, and the residence time is 2-3 h; and the concentration of dissolved oxygen in the reactor in the second-stage anoxic treatment is 0.2-0.5 mg / L, and the residence time is 2-3 h.

10. The process for treating high-strength acrylonitrile wastewater according to claim 1, characterized in that, The raw materials of the eutectic solvent comprise the following components in parts by weight: Choline chloride 140-210 parts, ethylene glycol 124-186 parts, triethylamine 12-18 parts and deionized water 10-15 parts.

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