A device for treating (meth)acrylic acid wastewater and a method for treating the same

Abstract

The invention discloses a device for treating (meth) acrylic acid wastewater and a treatment method thereof, comprising a screw extruder, wherein the input end of the screw extruder is connected to a material conveying pipeline, wherein the conveying pipeline is used to convey untreated or treated (meth) acrylic acid wastewater, and a light source is arranged at the input end of the screw extruder to form a light source area at the entrance of the screw extruder, wherein the (meth) acrylic acid wastewater undergoes a photopolymerization reaction in the light source area of ​​the screw extruder. The invention utilizes a photoreaction tube and a screw extruder in series and coupling, so that photopolymerization and thermally initiated polymerization are carried out in sequence, and can continuously treat and produce ecological and environmentally friendly materials with excellent performance, which is not only highly efficient and easy to operate, but also fully utilizes polymerization heat, saves energy consumption, and reduces the treatment cost of wastewater, and has a particularly obvious energy-saving effect when treating a large amount of (meth) acrylic acid wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of (meth)acrylic acid wastewater treatment, and in particular to a device for treating (meth)acrylic acid wastewater and a treatment method thereof. Background Art

[0002] The (meth)acrylic acid contained in the industrial wastewater generated during the production of (meth)acrylates is difficult to biodegrade and cannot be discharged directly, so it needs to be treated harmlessly. The current treatment methods include physical, chemical and biological methods, which are not only time-consuming and costly, but also fail to make good use of the wastewater.

[0003] CN107473456 A discloses a comprehensive treatment method for wastewater produced by acrylic acid esterification, wherein a chain transfer agent and at least two free radical initiators are used to polymerize at 45-85°C for 4-9 hours, and then the polymer is filtered with a sodium filter / ultrafiltration membrane, or an organic solvent is used to precipitate the polymer, and the solid obtained by filtration and separation is used as a scale inhibitor. Since (meth)acrylic acid wastewater contains many impurities, the molecular weight of the polyacrylic acid obtained by chemical treatment is not high and it is difficult to separate it from the wastewater.

[0004] CN 105129906 A discloses a method for photocatalytic treatment of acrylic acid wastewater, using persulfate or hydrogen peroxide as an initiator, using a high-pressure mercury lamp or a KrF ultraviolet excimer laser with a wavelength of 185-350nm and a main wavelength of 254nm to treat the wastewater by light radiation polymerization, and then using a multivalent metal ion compound as a precipitant to flocculate the polymer of acrylic acid and its salts in the wastewater, and then filtering out the precipitate, and the removal rate of acrylic acid in the wastewater is about 77%-88%. Although the treatment process of this treatment method has been greatly simplified, the acrylic acid or its salts in the wastewater are still not used as resources.

[0005] CN 108946750 A discloses a method for preparing organic bentonite from acrylic acid production wastewater, wherein acrylic acid and acetic acid in the wastewater are absorbed into bentonite as a modifier. Since the components of acrylic acid wastewater are complex and contain acid and copper ion catalysts as esterification reactions, they are also easily absorbed into bentonite, which brings uncertainty to some applications. Summary of the invention

[0006] The purpose of the present invention is to provide a continuous treatment method for wastewater resource application in view of the problem of (meth)acrylic acid wastewater treatment, in particular to provide a device and method for treating (meth)acrylic acid wastewater by using photo-thermal reaction. The present invention uses a screw-type photo-thermal reaction device and a photo-thermal polymerization method to convert methacrylic acid, acrylic acid, methacrylate or acrylate and other added components in (meth)acrylic acid wastewater into a gel product in one step. The gel product is then dehydrated and dried to obtain a water-absorbing or water-retaining material. The obtained water-absorbing or water-retaining material can be used as a moisture-retaining, water-absorbing, waterproof and highly water-absorbent material required for environmental protection, agriculture, forestry, green space, road slopes and engineering, thereby solving the shortcomings of the prior art.

[0007] The technical solution adopted by the present invention is as follows: a device for treating (meth)acrylic acid wastewater, comprising a screw extruder, characterized in that the input end of the screw extruder is connected to a material conveying pipeline, the conveying pipeline is used to convey untreated or treated (meth)acrylic acid wastewater, a light source is arranged at the input end of the screw extruder to form a light source area at the inlet of the screw extruder, and the (meth)acrylic acid wastewater undergoes a photopolymerization reaction in the light source area of ​​the screw extruder.

[0008] In the treatment device of the present invention, (meth)acrylic acid wastewater undergoes photopolymerization reaction in the light source area of ​​the screw extruder, that is, (meth)acrylic acid wastewater containing an initiator (especially containing a photoinitiator) is directly sent into the light source area of ​​the screw extruder through a conveying pipeline. Under the irradiation of the light source, the (meth)acrylic acid wastewater undergoes photopolymerization reaction. Since the photopolymerization speed is particularly fast, especially for (meth)acrylic acid wastewater without fillers or powder, it can form a gel material within a few seconds, which is convenient for the screw extruder to transmit the material. Then, under the push of the screw extruder, the material reaches the heating area of ​​the screw extruder, that is, enters the thermal reaction area with a temperature of 50-110°C. The remaining monomers in the material can also undergo further thermal polymerization reaction under the initiation of the thermal initiator until it is extruded from the outlet of the screw extruder to finally obtain a gel product.

[0009] Further, in order to better implement the device of the present invention, in the screw extruder, photopolymerization and thermal polymerization can be carried out simultaneously, and the relative proportion of the two reactions can be adjusted by the length of the light source area, and the total polymerization reaction time is adjusted by the screw length. The longer the screw is, the longer the material polymerization reaction time is. The light source area can almost cover the entire screw area, that is, complete photopolymerization reaction; the light source area can also occupy a part of the screw length, for example, at least 15%, and the thermal reaction area occupies 85% of the screw length, so that the material continues to undergo thermal polymerization after photopolymerization, which is particularly suitable for materials with powder added and light transparency that is not too high. The length of the screw is determined by the aspect ratio of the screw. The larger the aspect ratio, the longer the screw, and the longer the total reaction time. It is preferred that the aspect ratio of the screw extruder is greater than 40, and the light source area occupies at least 20% of the screw length, so that the thermal reaction has a longer time, the monomer conversion is more complete, and the treatment effect is better. Those skilled in the art can set the length of the appropriate light source area and the relative proportion of the photothermal reaction according to parameters such as the length, aspect ratio, and heating temperature of the screw machine. In conclusion, the use of a screw extruder can simultaneously complete the photoreaction, thermal reaction and continuous transportation of gel-state materials, thereby achieving the purpose of continuous treatment of (meth)acrylic acid wastewater and production of gel products.

[0010] In the present invention, in order to achieve better technical effects, the input end of the delivery pipeline is connected to the output end of the photoreaction tube, that is, after the (meth)acrylic acid wastewater undergoes photopolymerization reaction in the photoreaction tube, it is then transported to the screw extruder through the delivery pipeline. In this way, the photoreaction tube provides a first reaction site for the photopolymerization reaction of the (meth)acrylic acid wastewater, that is, when the reaction liquid passes through the photoreaction tube, it is irradiated by the light source and a partial photopolymerization reaction occurs.

[0011] Furthermore, the photoreaction tube has at least one layer of transparent tube. When the photoreaction tube has a multi-layer transparent tube structure, a reflective layer is provided on the side of the outermost transparent tube of the photoreaction tube opposite to the inner transparent tube. The reflective layer can be made of a metal plate, preferably an aluminum metal plate.

[0012] Preferably, before irradiation, an inert gas such as nitrogen, argon, etc. can be introduced from an air inlet of the photoreaction tube or the air inlet of the screw feed port to remove oxygen, and a lid is placed at the outlet of the screw extruder to vent air. The air is ventilated for more than 10 minutes to remove oxygen. When the oxygen content is lower than 100 ppm, especially lower than 50 ppm, the material is pumped for photothermal reaction, and the lid of the discharge port is removed when the material starts to be discharged from the discharge port.

[0013] In the present invention, the light source used for the light irradiation to initiate polymerization includes UV lamps and LED lamps, etc., preferably UV lamps or LED lamps with an emission wavelength of 280-415 nm.

[0014] The present invention also includes a method for treating (meth)acrylic acid wastewater, characterized in that the method comprises the following steps:

[0015] S1, preparing a reaction solution by mixing an initiator, a vinyl monomer, an optional powder and (meth)acrylic acid wastewater according to a designed ratio;

[0016] S2, conveying the reaction liquid to a screw extruder for photopolymerization and thermal polymerization, and finally extruding through the screw extruder.

[0017] In the above treatment method, the (meth)acrylic acid wastewater may be pretreated or unpretreated. Specifically, the untreated (meth)acrylic acid wastewater may be directly introduced into a screw extruder for treatment. After being treated by the screw extruder, a gel product meeting the requirements may be obtained. The (meth)acrylic acid wastewater may also be introduced into the screw extruder after being pretreated. For example, when a photoreaction tube is provided, the (meth)acrylic acid wastewater may be subjected to a preliminary photopolymerization reaction by using the photoreaction tube to improve the treatment effect. When the photoreaction tube is not provided, the (meth)acrylic acid wastewater may also be subjected to a partial thermal polymerization reaction to obtain a viscous body having a certain viscosity, and then introduced into the screw extruder. Finally, a gel product meeting the requirements may be obtained after being treated by the screw extruder. The main advantage of pre-treating the (meth)acrylic acid wastewater with thermal polymerization is that the photoreaction tube is omitted, and the entire treatment device may be simplified.

[0018] In the present invention, (meth) acrylic acid wastewater refers to the fractionated wastewater produced during the esterification reaction of acrylic acid or methacrylic acid, and the washing liquid produced by washing the esterification reaction product with caustic soda, soda ash or potassium hydroxide solution, which mainly contains one or more of methacrylic acid, acrylic acid, methacrylate or acrylate, and methacrylate or acrylate mainly refers to their sodium salt or potassium salt. In addition to methacrylic acid, acrylic acid, methacrylate or acrylate, the wastewater also contains a catalyst, a stabilizer, a raw material alcohol and a product (meth) acrylic acid ester for the esterification reaction, and the composition is complex. If direct thermal polymerization is performed, less gel is generated and it is difficult to separate directly. The inventors have found that by adding a suitable vinyl monomer and an optional powder, the wastewater can be easily and efficiently converted into a solid gel product through polymerization reaction treatment, and the block or split product after drying and crushing has a higher water absorption. It can be used as an ecological and environmentally friendly material with water absorption and water retention, realizing the harmless treatment and resource utilization of wastewater, and overcoming the shortcomings of the prior art. Due to the fast speed of photopolymerization, the heat released by the polymerization reaction, and the increase in material temperature, photopolymerization is combined with thermal polymerization and carried out sequentially, so that the photoinitiator and thermal initiator work together synergistically, thereby increasing the degree of polymerization and completely converting the raw materials into products.

[0019] In the present invention, the content of methacrylic acid, acrylic acid, methacrylate or acrylate in the (meth)acrylic acid wastewater is 2.5-30w% (w% represents mass fraction) of the mass of the water liquid. The content of methacrylic acid, acrylic acid, methacrylate or acrylate varies greatly due to the production process and the raw materials used in the esterification reaction. Adding at least one or more vinyl monomers with similar properties, especially water-soluble, can promote the photopolymerization reaction of methacrylic acid, acrylic acid, methacrylate or acrylate in the wastewater, and regulate the water absorption and water retention properties, especially the water absorption and temperature resistance of salt water.

[0020] In the present invention, the photoinitiator is a photoinitiator that generates free radicals after illumination, including aromatic ketones, substituted and unsubstituted benzoin ethers, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc., and combinations thereof. Preferably, the photoinitiator is sensitive to the wavelength range of 280-410nm. The amount of the photoinitiator is generally 0.08-2w% of the wastewater mass.

[0021] In the present invention, the initiator also includes a thermal initiator, and the thermal initiator includes a water-soluble or soluble thermal initiator, including persulfate, such as ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, and a water-soluble azo initiator, such as azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, azobisisopropylimidazoline, etc., and the dosage is generally 0.08-2w% of the wastewater mass. For persulfate and hydrogen peroxide, a reducing agent can also be used to appropriately reduce the onset temperature of the thermal initiator. The available reducing agents include sulfite and ferrous chloride, etc. Those skilled in the art can inquire about their use methods and dosages from relevant materials.

[0022] In the present invention, powder, initiator and vinyl monomer are mixed with (meth) acrylic acid wastewater to form a reaction solution, wherein the powder is attapulgite, bentonite, soluble starch or water-soluble starch, including various types of starch, such as potato flour, sweet potato flour, corn flour, cassava flour, potato flour, konjac flour, sweet potato flour, etc., modified starch, carboxymethyl starch, starch phosphate, and soluble or water-soluble starch treated with soybean meal, grain fermentation lees, etc. In the photo-thermal polymerization reaction, methacrylic acid, acrylic acid, methacrylate, acrylate and vinyl monomer in the wastewater undergo polymerization reaction and graft polymerization reaction to the modified starch agent. The main function of the powder is to improve or improve the temperature resistance and water absorption performance of the product and increase the output. After the powder is added, the photopolymerization is more stable and the water absorption effect of the product is better. The dosage of the powder is preferably 0-10w% of the wastewater. If the dosage is too little, the product will not be able to absorb enough water from salt water. If the dosage is too much, the viscosity of the solution will be too high, the light transmittance will deteriorate, and photopolymerization will be affected. The preferred dosage is 0.5-5w% of the wastewater.

[0023] Preferably, the wastewater and the aqueous solution after adding vinyl monomers, especially acrylic acid or methacrylic acid, can be neutralized with alkali solution to make the pH value of the wastewater 6-8 to reduce the corrosiveness of the wastewater to the equipment and adjust and control the water absorption rate and water absorption speed of the obtained polymer as a super absorbent resin.

[0024] In the present invention, a chain transfer agent for free radical polymerization reaction can be added to wastewater to control the degree of crosslinking and the morphology of polymer molecular chains. The amount of chain transfer agent is related to the chain transfer agent used and can be 0-20w%. Those skilled in the art can find a suitable amount of chain transfer agent through relevant data and comparative tests.

[0025] The gel material obtained by the method for treating (meth)acrylic acid wastewater of the present invention is characterized in that the water absorption rate of the gel material is not less than 20 times, and the water retention rate is not less than 90%. The preparation of the gel material enables the (meth)acrylic acid wastewater to be fully utilized as a resource, that is, the gel material can be used as a base material for manufacturing water-retaining and water-absorbing materials, or as a basic material for an improver, a water absorbent or a water-retaining agent for agriculture, forestry, planting, green space, road engineering, and slope management and maintenance.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. The present invention couples the photo-thermal polymerization reaction with the screw extruder, so that the photopolymerization and the thermally initiated polymerization as well as the material transportation are carried out simultaneously, and the ecological and environmentally friendly materials with excellent performance can be continuously processed and produced. It is not only highly efficient and easy to operate, but also fully utilizes the polymerization heat, saves energy consumption, and reduces the wastewater treatment cost. In particular, the energy-saving effect is very obvious when treating a large amount of (meth) acrylic acid wastewater;

[0028] 2. The photopolymerization method used in the present invention is fast, usually turning into thermal polymerization within tens of seconds, and the entire reaction process is completed within a few minutes, with high efficiency and high monomer conversion rate of the polymerization reaction;

[0029] 3. By adopting the treatment method of the present invention, the photopolymerization treatment process of (meth)acrylic acid wastewater is easy to control, the product is a gel, and the production process is environmentally friendly;

[0030] 4. The product obtained by photopolymerization treatment has high water absorption characteristics, and the water absorption rate can be greater than 100 times. It can be used as a water-retaining and water-absorbing material, realizing the resource utilization of wastewater. It can be used to manufacture water-retaining and water-absorbing matrix materials, or as a basic material for improvers, water absorbents or water-retaining agents in agriculture, forestry, planting, green space, road engineering, and slope management and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a schematic diagram of the structure of a device for treating (meth)acrylic acid wastewater.

[0032] Markings in the figure: 1 is a material tank, 2 is a metering pump, 3 is a photoreaction tube, 4 is a light source area, and 5 is a screw extruder. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] like Figure 1As shown, a device for treating (meth)acrylic acid wastewater comprises a material tank 1, wherein the material tank 1 is connected to a photoreaction tube 3 with a light source through a conveying pipeline, wherein the photoreaction tube 3 realizes a photopolymerization reaction of a reaction liquid (i.e., (meth)acrylic acid wastewater mixed with an initiator) in the photoreaction tube 3 through the light source, and an output end of the photoreaction tube 3 is connected to an input end of a screw extruder 5 through a conveying pipeline, wherein a light source is provided at the input end of the screw extruder 5 to form a light source area 4 at the inlet, and the reaction liquid in the light source area 4 realizes a photopolymerization reaction under the irradiation of the light source. The material tank 1 is a container for (meth)acrylic acid wastewater and pharmaceutical ingredients, which can be equipped with a stirring device and a liquid level meter to facilitate ingredient preparation and mixing. A metering pump 2 can be arranged on the conveying pipeline to control the flow rate of the reaction liquid formed after ingredient preparation. The metering pump can be in the form of a plunger type or other driving methods. The photoreaction tube 3 preferably has a two-layer transparent tube structure (not shown in the figure, that is, a sleeve type structure). The photoreaction tube 3 is used to provide a reaction place for the photopolymerization reaction. The light source includes a UV lamp or an LED lamp, preferably a UV lamp or an LED lamp with an emission wavelength of 280-415nm. For the photoreaction tube 3 with a double-layer transparent tube structure, when the light source is a UV mercury lamp, the light source can be installed outside the transparent tube of the outer layer of the photoreaction tube 3. When the light source is an LED lamp, the light source can be installed in the gap between the outer and inner transparent tubes. A viscosity sensor (not shown in the figure) can be arranged at the output end of the photoreaction tube to detect the viscosity of the reaction liquid at the outlet end of the photoreaction tube 3. Correspondingly, the light source of the screw extruder 5 is installed at the optical window of the screw extruder. When the light source at the optical window is a UV mercury lamp, it is better to install the light source on the outside of the optical window. When the light source is a low-power lamp or an LED lamp, the light source can be installed on the inside of the optical window to directly irradiate the reaction liquid.

[0036] Furthermore, the photoreaction tube 3 of the above-mentioned processing device is a selective device, that is, the photoreaction tube 3 may be provided or not provided.

[0037] In order to better illustrate the present invention, specific embodiments are listed below:

[0038] Wastewater indicators of a certain factory: The wastewater comes from a chemical plant that produces acrylates. The sodium acrylate content of the wastewater is about 20w%, the COD value is about 220000, and the pH value is 7-8.

[0039] Example 1

[0040] 50 kg of waste water, 0.8 w% of water-soluble starch, 25 w% of acrylamide, 0.3 w% of sodium methyl allyl sulfonate, 2 w% of acrylic acid, 0.1 w% of photoinitiator 819 and 0.3 w% of azobisisobutylamidine hydrochloride were added into an 80-liter closed stainless steel stirring storage tank (i.e., material tank 1), and nitrogen was bubbled for 15 minutes. The lower outlet of the storage tank was connected to a metering pump, and the metering pump was connected to a glass tube (i.e., photoreaction tube 3) with round tubes at both ends, a flat middle sheet, and an inner hollow of 2 mm x 10 mm by a transparent silicone tube. A high-gloss metal aluminum plate was installed on the back of the glass tube as a reflective plate (i.e., a reflective layer, which can also be made of other reflective materials). The tail end of the glass tube was connected to the inlet of a twin-screw extruder through a hose. The silicone tube, the glass tube and the inlet of the screw machine were all surrounded by cylindrical glass, leaving a nitrogen inlet. The screw extruder has an aspect ratio of 60, with a total of twelve barrel sections, a screw diameter of 35.6 mm, a groove depth of 6 mm, a maximum screw speed of 600 rpm, a total length of 2160 mm, 4 optical windows installed, and a cast aluminum heater for barrel heating. When the reaction starts, the outlet of the screw extruder is first wrapped with a film, and nitrogen is introduced from the nitrogen inlet of the glass tube. After exhausting from the film gap at the outlet of the screw extruder for 15 minutes, the metering pump is started, the flow rate is adjusted, and all the gas in the tube is exhausted. Then, the LED lamp with a total power of 9W, including 6 lamp beads with a wavelength of 365nm and 4 lamp beads with a wavelength of 395nm, is turned on to irradiate the flowing solution through the glass round tube. At the same time, the screw extruder and three sets of LED lights in three optical windows are started to irradiate the screw machine through the windows. The electric heating is started, the temperature is set to 90°C, and the sealing film at the outlet of the screw extruder is removed. After about 2 minutes, a viscous body drips from the outlet, and then the dripping body gradually becomes filamentous. After about 5 minutes, it becomes a gel strip with a certain elasticity and steam. The speed of the metering pump is adjusted to about 50 liters / h to match the speed of the extruder. After about 50 minutes, all the solution is processed.

[0041] 100 g of the obtained gel was fully dried at 120°C, ground and sieved, and 1 g of the fine powder was weighed for measurement according to the standard method. The measurement results showed that the water absorption rate to pure water was 156 times, the water retention rate was 97%, and the weight of the gel after water absorption and re-drying was almost the same as that before water absorption, indicating that no monomer or salt was dissolved in the water and lost weight.

[0042] Example 2

[0043] This embodiment is substantially the same as the embodiment 1, except that the photoreaction tube is removed and a 500W medium pressure mercury lamp is used to replace an LED lamp group in the optical window. The final measurement results are: the above wastewater treatment time is reduced by 5 minutes, the water absorption rate of pure water is 160 times, and the water retention rate is 97%, indicating that the effect of mercury lamp initiating polymerization is better than that of LED lamp.

[0044] Example 3

[0045] This embodiment is substantially the same as embodiment 1, except that the heating part of the screw extruder is not turned on. The final measurement results show that the appearance of the obtained gel product is similar to that of embodiment 1, the water absorption rate of pure water is 120 times, and the water retention rate is 97%, indicating that the polymerization effect is better after turning on the heating.

[0046] Example 4

[0047] The material of this example was first thermally polymerized in a reactor into a viscous body with a viscosity of about 10000 mPa.s and then stored in a storage tank, and then subjected to the photo-thermal polymerization treatment substantially the same as in Example 2. The final measurement results showed that the appearance of the obtained gel product was similar to that of Example 1, the water absorption rate of pure water was 180 times, and the water retention rate was 97%.

[0048] Comparative Example 1

[0049] This comparative example is substantially the same as Example 1, except that no photoinitiator is added to the solution. The final measurement result is: only viscous material is present at the outlet of the screw extruder, and no gel product is present. About 60 g of the viscous material is stirred with 200 mL of ethanol, and the jelly is separated. After drying, about 10 g of solid is obtained. The water absorption rate to pure water is measured to be about 3 times, and most of the powder is dissolved in water.

[0050] Comparative Example 2

[0051] This embodiment is substantially the same as the embodiment 1, except that the LED light is not turned on. The final measurement results are: the experimental results and the measurement results are similar to those of the comparative embodiment 1.

[0052] In the above embodiments, the soluble and water-soluble starch, photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (abbreviated as 819), and water-soluble thermal initiator azobisisobutylamidine hydrochloride are all commercially available products, the purity of the nitrogen used is 99.995%, and the water absorption rate of the resin is determined according to the method of NY / T886-2016 "Agricultural and Forestry Water Retention Agents". The water retention rate is calculated by the weight change rate of the sample bag that has completed the water absorption test after being hung indoors for 12 hours.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a highly absorbent gel using a screw-type photothermal reactor device and (meth)acrylic acid wastewater, characterized in that: The production method and the photothermal reactor device include a screw extruder, a conveying pipeline and a photoreaction tube. (Meth)acrylic acid wastewater enters the photoreaction tube through the conveying pipeline. The photoreaction tube is used to provide a reaction site for photopolymerization reaction. The material treated by the photoreaction tube enters the screw extruder through the conveying pipeline. The screw extruder is provided with a light source area and a heating area. The light source area is used to perform photopolymerization reaction on the material. The heating area is used to heat the material after the photopolymerization reaction. The heating temperature is 50-110°C. The production method comprises the following steps: S1. Prepare a reaction solution by mixing powder, initiator, water-soluble vinyl monomer and (meth)acrylic acid wastewater; the initiator includes a photoinitiator and a thermal initiator, the photoinitiator is selected from one or more of aromatic ketone, benzoin ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and the amount used is 0.08-2% of the mass of (meth)acrylic acid wastewater; the thermal initiator is selected from one or more of persulfate, hydrogen peroxide and water-soluble azo initiator, and the amount used is 0.08-2% of the mass of (meth)acrylic acid wastewater; the powder is selected from one or more of attapulgite, bentonite and soluble starch, and the amount used is 0-10% of the mass of (meth)acrylic acid wastewater; S2. The reaction liquid enters the photoreaction tube from the conveying pipeline, undergoes photopolymerization reaction in the photoreaction tube, and then is conveyed to the screw extruder through the conveying pipeline to continuously undergo photopolymerization reaction and thermal polymerization reaction. After being extruded by the screw extruder, a highly absorbent gel is obtained, wherein the water absorption rate of the highly absorbent gel is not less than 20 times, and the water retention rate is not less than 90%.

2. The production method according to claim 1, characterized in that The photoreaction tube has at least one layer of transparent tube, and an ultraviolet light source is arranged outside the transparent tube to irradiate the (meth)acrylic acid wastewater in the photoreaction tube to cause photopolymerization reaction.

3. The production method according to claim 1, characterized in that The photoreaction tube has an air inlet, and the air inlet is used to introduce inert gas into the photoreaction tube.

4. An application, characterized in that: The gel material produced by the production method of claim 1 is used as a base material for manufacturing water-retaining and water-absorbing materials, or as a basic material for an improver, water absorbent or water-retaining agent in agriculture, forestry, planting, green space, road engineering, and slope management and maintenance.

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