Recycling method of acrylic acid-containing wastewater and composite scale inhibitor

Abstract

The invention discloses a recycling method of acrylic acid-containing wastewater and a composite scale inhibitor, and belongs to the technical field of wastewater recycling. The method specifically comprises the following steps: (1) adding quantitative acrylic acid-containing wastewater into a reaction kettle, stirring, heating to 55-65 DEG C, adding an oxidizing agent, continuously stirring for a period of time, adding a reducing agent, and reacting at 55-65 DEG C for 2-3 hours to obtain a reaction product system; and (2) adjusting the solid content of the reaction product system to 15-20%, adding 20-30wt% of a cellulose dispersant, 1-4wt% of an inorganic salt corrosion inhibitor and 8-15wt% of an auxiliary scale inhibitor based on the total amount of the reaction product system, and uniformly mixing to obtain the composite scale inhibitor. When the method is adopted to treat the acrylic acid-containing wastewater, waste can be turned into wealth while the wastewater treatment cost is reduced, resource utilization of the acrylic acid-containing wastewater is realized, and the obtained composite scale inhibitor is excellent in scale inhibition performance.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater reuse, and in particular relates to a method for reusing acrylic acid-containing wastewater and a composite scale inhibitor. Background Art

[0002] Acrylic acid components will inevitably remain in the wastewater discharged from acrylic acid production equipment and equipment that uses acrylic acid as a reaction monomer to produce acrylic esters. Acrylic acid is very harmful to the human body. High concentration exposure may cause lung changes. It is irritating to the skin and can cause burns. Contact with the eyes can cause burns and permanent damage. It is also mutagenic and can damage DNA.

[0003] At present, there are three main industrial methods for treating acrylic acid wastewater: incineration, catalytic wet oxidation and biological treatment. Incineration is fast in treating acrylic acid wastewater, and the process is simple and effective, but it consumes a lot of fuel and has high operating costs. Catalytic wet oxidation has a fast treatment speed and high removal efficiency, but it consumes a lot of energy during operation and has a large investment cost. Biological methods have low energy consumption and mild reaction conditions, but they are slow in treatment and occupy a large area.

[0004] Patent CN103408175A discloses a method for treating and recycling (meth)acrylic acid production wastewater, which polymerizes organic matter such as acrylic acid and methacrylic acid in the wastewater by stirring and heating, and is used to prepare polymers for boiler scale inhibitors. The wastewater is heated and evaporated, and acetic acid, toluene and unpolymerized aldehydes in the wastewater are also evaporated due to the azeotropic effect, and the oil and water are separated to recover the toluene; the acetic acid is neutralized with alkali, concentrated and crystallized, and the crystalline sodium acetate is recovered; then, the formaldehyde carried out by evaporation is removed by acid catalysis and excess urea precipitation is used to recover methyl urea, and the biodegradability of the wastewater is improved at the same time. After the pH value is adjusted by the limestone filter bed, the COD value drops to below 1000 mg / L, the biodegradability is improved, and the wastewater is discharged into the domestic sewage treatment plant for treatment. The disadvantage is that the process is complicated. Azeotropic evaporation will cause a large amount of formaldehyde to evaporate with the acetic acid. The purity of sodium acetic acid is low and has no utilization value. The urea condensation reaction is unstable and the formaldehyde residue is high, which makes the subsequent biochemical system prone to biological poisoning.

[0005] Patent CN105859037B discloses a combined treatment method for high-concentration acrylic acid and ester wastewater, which uses an oxidant to oxidize and remove formaldehyde, acetaldehyde and acrolein in acidic wastewater, and alkali neutralizes acetic acid and acrylic acid in the oxidized liquid. The neutralized liquid uses a coupling technology of membrane separation and water removal, vacuum concentration, crystallization and drying to prepare acetate to treat the acidic wastewater. The formaldehyde removal rate of the oxidized liquid in this method reaches more than 99.5%, and after the neutralized liquid is separated by RO membrane, its permeate meets the national environmental protection secondary emission standards. However, the membrane is a consumable and has high cost.

[0006] Patent CN114804422A discloses a pretreatment method and pretreatment system for acrylic acid wastewater, which comprises: (1) adding calcium solution to wastewater to obtain wastewater containing calcium ions; (2) adding alkali solution to the wastewater to adjust the pH value to 10.5-11.5; (3) subjecting the wastewater to steam heating treatment; (4) subjecting the obtained wastewater to decalcification treatment to obtain wastewater and calcium mud. Although this method can remove acrylic acid, the treatment process is time-consuming and labor-intensive, and requires a large amount of raw materials or equipment investment, which is not conducive to energy saving and consumption reduction, and does not meet the requirements of green environmental protection and sustainable development. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for recycling acrylic acid-containing wastewater and a composite scale inhibitor. By using this method to treat acrylic acid-containing wastewater, waste can be turned into treasure while reducing wastewater treatment costs, thereby realizing resource utilization of acrylic acid-containing wastewater. The obtained composite scale inhibitor has excellent scale inhibition performance.

[0008] In order to achieve the above object, according to one aspect of the present invention, a method for recycling acrylic acid-containing wastewater is provided, comprising the following steps: (1) Add a certain amount of acrylic acid-containing wastewater into a reactor, stir and heat to 55-65°C, add an oxidant, continue stirring for a period of time, then add a reducing agent, maintain the temperature at 55-65°C for 2-3 hours, and obtain a reaction product system; (2) The solid content of the reaction product system is adjusted to 15-20%. Based on the total amount of the reaction product system, 20-30 wt% of a cellulose dispersant, 1-4 wt% of an inorganic salt corrosion inhibitor, and 8-15 wt% of an auxiliary scale inhibitor are added and mixed evenly to obtain a composite scale inhibitor.

[0009] In some embodiments, in step (1), the oxidant is persulfate, and the concentration of the oxidant in the wastewater is 0.5-5.0 g / L.

[0010] In some embodiments, the oxidant includes one or both of potassium persulfate and sodium persulfate.

[0011] In some embodiments, in step (1), the reducing agent is dodecanethiol, and the concentration of the reducing agent in the wastewater is 0.5-3.0 g / L.

[0012] In some embodiments, the reducing agent includes one or both of primary dodecanethiol and tert-dodecanethiol.

[0013] In some embodiments, in step (1), the stirring time is 5-10 min.

[0014] In some embodiments, in step (2), the cellulose dispersant includes one or both of hydroxymethyl cellulose and hydroxypropyl methyl cellulose.

[0015] In some embodiments, in step (2), the inorganic salt corrosion inhibitor includes one or both of zinc sulfate and zinc chloride.

[0016] In some embodiments, in step (2), the auxiliary antiscalant is an amino acid auxiliary antiscalant.

[0017] According to another aspect of the present invention, a composite scale inhibitor prepared according to the above-mentioned method for recycling acrylic acid-containing wastewater is also provided, and the composite scale inhibitor is used for scale inhibition of circulating cooling water.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for recycling acrylic acid-containing wastewater, wherein acrylic acid in the wastewater is reacted to generate a polymer through a specific initiation system, and a dispersant, a corrosion inhibitor and an auxiliary scale inhibitor are added at the same time to prepare a composite scale inhibitor that can be used for anti-scaling of circulating cooling water. The method can reduce the cost of wastewater treatment while turning waste into treasure, and realize resource utilization of acrylic acid-containing wastewater. The obtained scale inhibitor has excellent scale inhibition performance.

[0019] (2) The recycling method of the present invention will not cause an increase in TOC and COD of wastewater, and at the same time avoids the presence of ions that cause color changes in wastewater in the system. Therefore, when used for scale prevention of circulating cooling water, it will not affect the color change of circulating cooling water. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0022] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0023] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0024] The acrylic acid-containing wastewater described in the present invention refers to wastewater whose main component is acrylic acid and whose other components will not affect subsequent applications, specifically including industrial wastewater generated by acrylic acid production equipment and industries using acrylic acid.

[0025] The present invention provides a method for recycling acrylic acid-containing wastewater, comprising the following steps: (1) Add a certain amount of acrylic acid-containing wastewater into a reactor, stir and heat to 55-65°C, add an oxidant, continue stirring for a period of time, then add a reducing agent, maintain the temperature at 55-65°C for 2-3 hours, and obtain a reaction product system; (2) The solid content of the reaction product system is adjusted to 15-20%. Based on the total amount of the reaction product system, 20-30 wt% of a cellulose dispersant, 1-4 wt% of an inorganic salt corrosion inhibitor, and 8-15 wt% of an auxiliary scale inhibitor are added and mixed evenly to obtain a composite scale inhibitor.

[0026] According to the treatment process of the present invention, in some embodiments, a quantitative amount of acrylic acid-containing wastewater is first added to a reactor, stirred and heated to 55-65°C. It can be understood that the temperature can be any specific value of 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C or any value within the range of 55-65°C. The present invention can provide necessary conditions for subsequent reactions by stirring and heating the wastewater to the temperature, and can control the energy consumption required for the reaction within a lower range on the other hand. If the temperature is too low, the reaction is incomplete, affecting the treatment effect, especially resulting in poor application effect of the obtained composite scale inhibitor; if the temperature is too high, the reaction is uncontrollable, and at the same time, it will lead to excessive energy consumption, which does not meet the requirements of green chemistry.

[0027] According to the treatment process of the present invention, in some embodiments, in step (1), the oxidant is a persulfate, preferably, the oxidant includes one or both of potassium persulfate and sodium persulfate. Further, the concentration of the oxidant in the wastewater is 0.5-5.0 g / L. It can be understood that the concentration of the oxidant in the wastewater can be any specific value of 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L, 5.0 g / L or any value within the range of 0.5-5.0 g / L.

[0028] Preferably, the concentration of the oxidant in the wastewater is 1.0-3.0 g / L.

[0029] According to the treatment process of the present invention, in some embodiments, in step (1), the reducing agent is dodecanethiol, preferably, the reducing agent includes one or two of primary dodecanethiol and tert-dodecanethiol. Further, the concentration of the reducing agent in the wastewater is 0.5-3.0 g / L. It can be understood that the concentration of the reducing agent in the wastewater can be any specific value of 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.0 g / L or any value within the range of 0.5-3.0 g / L.

[0030] Preferably, the concentration of the reducing agent in the wastewater is 0.5-2.0 g / L.

[0031] The inventors of the present invention have found that by adding specific types and amounts of oxidants and reductants to the wastewater containing acrylic acid, it is possible to ensure that the residual acrylic acid in the wastewater is fully reacted at a relatively low temperature, and the resulting composite scale inhibitor has better scale inhibition performance; at the same time, it will not cause an increase in TOC and COD of the wastewater, and avoid the presence of ions that cause changes in the color of the wastewater in the system. Therefore, when used for scale inhibition of circulating cooling water, it will not affect the color change of the circulating cooling water.

[0032] According to the treatment process of the present invention, in some embodiments, in step (1), the stirring time is 5-10 minutes. In the present invention, stirring is continued for a period of time after adding the oxidant and then adding the reducing agent, so that the oxidant can be fully and evenly dissolved in the wastewater, and the subsequent addition of the reducing agent can more fully induce the acrylic acid polymerization reaction.

[0033] According to the treatment process of the present invention, in some embodiments, after the reaction is complete, the solid content of the reaction product system is adjusted to 15-20%. It can be understood that the solid content of the reaction product system can be any specific value of 15%, 16%, 17%, 18%, 19%, 20%, or any value within the range of 15-20%. Specifically, the present invention can adjust the solid content by evaporation concentration or dilution. For example, if the solid content of the reaction product system is lower than the range, the solid content can be increased to the range by evaporation concentration; if the solid content of the reaction product system is higher than the range, the solid content can be increased to the range by adding water dilution. The inventors of the present invention have found that by adjusting the solid content of the reaction product system within a suitable range, the comprehensive performance of the obtained composite scale inhibitor is better, especially the scale inhibition performance is better.

[0034] According to the treatment process of the present invention, in some embodiments, in step (2), the cellulose dispersant includes one or more of hydroxymethyl cellulose and hydroxypropyl methyl cellulose. Preferably, based on the total amount of the reaction product system, the amount of the cellulose dispersant added is 20-30wt%. It is understandable that the amount of the cellulose dispersant added can be any specific value of 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt% or any value within the range of 20-30wt%.

[0035] According to the treatment process of the present invention, in some embodiments, in step (2), the inorganic salt corrosion inhibitor includes one or both of zinc sulfate and zinc chloride. Preferably, the amount of the inorganic salt corrosion inhibitor added is 1-4wt% based on the total amount of the reaction product system. It can be understood that the amount of the inorganic salt corrosion inhibitor added can be any specific value of 1wt%, 2wt%, 3wt%, 4wt% or any value within the range of 1-4wt%.

[0036] According to the treatment process of the present invention, in some embodiments, in step (2), the auxiliary scale inhibitor is an amino acid auxiliary scale inhibitor, preferably polyaspartic acid. More preferably, based on the total amount of the reaction product system, the amount of the auxiliary scale inhibitor added is 8-15wt%. It can be understood that the amount of the auxiliary scale inhibitor added can be any specific value of 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt% or any value within the range of 8-15wt%.

[0037] According to another aspect of the present invention, a composite scale inhibitor prepared according to the above-mentioned method for recycling acrylic acid-containing wastewater is also provided, and the composite scale inhibitor is used for scale inhibition of circulating cooling water.

[0038] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0039] In the present invention, the testing methods of various performance parameters in the embodiments and comparative examples are as follows: Chemical oxygen demand CODcr: determined according to the method of JJG1012-2019; Total organic carbon TOC: tested according to HJ501-2009 standard; The change in color is judged by visual observation; Application effect of composite scale inhibitor: evaluated in accordance with GB / T16632-2019.

[0040] In the following examples and comparative examples, unless otherwise specified, the acrylic acid-containing wastewater is wastewater generated by an acrylic acid device, and its water quality analysis is: pH=3.1, CODcr is 1830 mg / L, and TOC is 419 mg / L.

[0041] Example 1 The method for recycling acrylic acid-containing wastewater described in this embodiment specifically comprises the following steps: (1) 1L of the above wastewater was placed in a normal pressure reactor. After stirring, the temperature was gradually raised to 55°C. Then, 20ml of a pre-prepared 10% potassium persulfate solution (dry weight: 2.0g) was added. After stirring for 5min, 1.5g of tert-dodecyl mercaptan was added. The reaction was continued for 2h and then discharged to obtain a reaction product system.

[0042] (2) The solid content of the obtained reaction product system was adjusted to 17.5%, and then 25 wt % of hydroxypropyl methylcellulose, 2.5 wt % of zinc sulfate and 12 wt % of polyaspartic acid (PASP) were added and mixed evenly to obtain a composite scale inhibitor.

[0043] The comparison of water quality before and after the wastewater treatment described in this example, as well as the performance evaluation results of the obtained composite scale inhibitor are shown in Table 1.

[0044] Example 2 The method for recycling acrylic acid-containing wastewater described in this embodiment specifically comprises the following steps: (1) 1L of the above wastewater was placed in a normal pressure reactor. After stirring, the temperature was gradually raised to 60°C. Then, 30ml of a pre-prepared 10% potassium persulfate solution (dry weight: 3.0g) was added. After stirring for 5min, 2.0g of primary dodecanethiol was added. The reaction was continued for 2.5h and then the reaction was discharged to obtain a reaction product system.

[0045] (2) The solid content of the obtained reaction product system is adjusted to 20%, and then 30 wt % of hydroxypropyl methylcellulose, 4 wt % of zinc sulfate and 15 wt % of polyaspartic acid (PASP) are added and mixed evenly to obtain a composite scale inhibitor.

[0046] The comparison of water quality before and after the wastewater treatment described in this example, as well as the performance evaluation results of the obtained composite scale inhibitor are shown in Table 1.

[0047] Example 3 The method for recycling acrylic acid-containing wastewater described in this embodiment specifically comprises the following steps: (1) 1L of the above wastewater was placed in a normal pressure reactor. After stirring, the temperature was gradually raised to 65°C. Then, 18ml of a pre-prepared 10% potassium persulfate solution (dry weight: 1.8g) was added. After stirring for 5min, 1.3g of tert-dodecyl mercaptan was added. The reaction was continued for 2.3h and then the reaction product system was obtained.

[0048] (2) The solid content of the obtained reaction product system was adjusted to 15%, and then 20 wt % of hydroxypropyl methylcellulose, 1 wt % of zinc sulfate and 8 wt % of polyaspartic acid (PASP) were added and mixed evenly to obtain a composite scale inhibitor.

[0049] The comparison of water quality before and after the wastewater treatment described in this example, as well as the performance evaluation results of the obtained composite scale inhibitor are shown in Table 1.

[0050] Example 4 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution was replaced with 50 ml of sodium persulfate solution (dry weight 5.0 g), tert-dodecyl mercaptan was replaced with 3.0 g of primary dodecyl mercaptan, the reaction temperature was adjusted to 60° C., the reaction time was adjusted to 2.3 h, and the rest was the same as in Example 1. The comparison of water quality before and after treatment and the performance evaluation results of the composite scale inhibitor are shown in Table 1.

[0051] Example 5 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution was replaced with 5 ml of sodium persulfate solution (dry weight 0.5 g), the amount of tert-dodecyl mercaptan was changed to 0.5 g, the reaction temperature was adjusted to 55° C., the reaction time was adjusted to 2.5 h, and the rest was the same as in Example 1. The comparison of water quality before and after treatment and the performance evaluation results of the composite scale inhibitor are shown in Table 1.

[0052] Example 6 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution was replaced with 18 ml of sodium persulfate solution (dry weight 1.8 g), tert-dodecyl mercaptan was replaced with an equal amount of primary dodecyl mercaptan, the reaction temperature was adjusted to 65° C., the reaction time was adjusted to 2.0 h, and the rest was the same as in Example 1. The comparison of water quality before and after treatment and the performance evaluation results of the composite scale inhibitor are shown in Table 1.

[0053] Comparative Example 1 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution was replaced with an equal amount of ammonium persulfate solution (dry weight 2.0 g), and tert-dodecyl mercaptan was replaced with sodium bisulfite. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0054] Comparative Example 2 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution was replaced with 1.8 g of cumene hydroperoxide, and tert-dodecyl mercaptan was replaced with 1.3 g of ferrous sulfate. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0055] Comparative Example 3 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution and 1.5 g of tert-dodecyl mercaptan were replaced with 3.0 g of benzoyl peroxide, and the reaction temperature was adjusted to 75° C. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0056] Comparative Example 4 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution and 1.5 g of tert-dodecyl mercaptan were replaced with 3.0 g of azobisisobutyronitrile, and the reaction temperature was adjusted to 80° C. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0057] Comparative Example 5 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution (dry weight 2.0 g) was replaced with 4 ml of 10% potassium persulfate solution (dry weight 0.4 g), and 1.5 g of tert-dodecyl mercaptan was replaced with 0.3 g of tert-dodecyl mercaptan. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0058] Comparative Example 6 The same amount of sewage and treatment process as in Example 1 were used, except that 20 ml of 10% potassium persulfate solution (dry weight 2.0 g) was replaced with 60 ml of 10% potassium persulfate solution (dry weight 6.0 g), and 1.5 g of tert-dodecyl mercaptan was replaced with 6 g of tert-dodecyl mercaptan. The comparison of water quality before and after treatment and the evaluation results of the composite scale inhibitor performance are shown in Table 1.

[0059] Table 1 Water quality analysis and scale inhibition performance evaluation before and after treatment of the embodiments and comparative examples It can be seen from Example 1 and Comparative Examples 1-4 that after using the oxidant and reductant types in the examples of the present invention to treat acrylic acid-containing wastewater, the color of the wastewater is better than that of the comparative examples. At the same time, the scale inhibition performance of the composite scale inhibitor obtained in the examples is significantly better than that of the comparative examples, indicating that the types of oxidant and reductant in the present application are very critical to the treatment effect of wastewater. It can be seen from Example 1 and Comparative Examples 5-6 that the dosage of the oxidant and reductant in the examples of the present invention is also very critical to the treatment effect. The scale inhibition performance of the composite scale inhibitor obtained in the examples is significantly better than that of the comparative examples. It can be seen that the present invention selects a specific initiation system to react acrylic acid in wastewater to generate a polymer, thereby preparing a composite scale inhibitor that can be used for scale inhibition of circulating cooling water, which can reduce the cost of wastewater treatment while turning waste into treasure and realizing the resource utilization of acrylic acid-containing wastewater. At the same time, the scale inhibition effect of the composite scale inhibitor obtained by the treatment method of the present invention is more excellent, will not cause the increase of TOC and COD of wastewater, and the color of wastewater is better.

[0060] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for recycling acrylic acid-containing wastewater, characterized in that: The steps include: (1) Add a certain amount of acrylic acid-containing wastewater into a reactor, stir and heat to 55-65°C, add an oxidant, continue stirring for a period of time, then add a reducing agent, maintain the temperature at 55-65°C for 2-3 hours, and obtain a reaction product system; (2) The solid content of the reaction product system is adjusted to 15-20%. Based on the total amount of the reaction product system, 20-30 wt% of a cellulose dispersant, 1-4 wt% of an inorganic salt corrosion inhibitor, and 8-15 wt% of an auxiliary scale inhibitor are added and mixed evenly to obtain a composite scale inhibitor.

2. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (1), the oxidant is persulfate, and the concentration of the oxidant in the wastewater is 0.5-5.0 g / L.

3. The method for recycling acrylic acid-containing wastewater according to claim 2, characterized in that: The oxidant includes one or both of potassium persulfate and sodium persulfate.

4. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (1), the reducing agent is dodecanethiol, and the concentration of the reducing agent in the wastewater is 0.5-3.0 g / L.

5. The method for recycling acrylic acid-containing wastewater according to claim 4, characterized in that: The reducing agent includes one or both of primary dodecanethiol and tert-dodecanethiol.

6. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (1), the stirring time is 5-10 min.

7. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (2), the cellulose dispersant includes one or both of hydroxymethyl cellulose and hydroxypropyl methyl cellulose.

8. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (2), the inorganic salt corrosion inhibitor includes one or both of zinc sulfate and zinc chloride.

9. The method for recycling acrylic acid-containing wastewater according to claim 1, characterized in that: In step (2), the auxiliary scale inhibitor is an amino acid auxiliary scale inhibitor.

10. A composite scale inhibitor prepared according to the method for recycling acrylic acid-containing wastewater according to any one of claims 1 to 9, wherein the composite scale inhibitor is used for scale inhibition of circulating cooling water.

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