Industrial wastewater treatment method

Abstract

The invention relates to the technical field of sewage treatment, in particular to a treatment method of industrial wastewater. The industrial wastewater treatment method comprises the following steps: a) under an alkaline condition, adding a sulfur-containing organic compound into the industrial wastewater for reaction to form a solid precipitate containing heavy metals; the industrial wastewater contains a heavy metal-organic amine complex; and b) carrying out solid-liquid separation on the system after the reaction in the step a). According to the method, a sulfur-containing organic compound directly reacts with a heavy metal-organic amine complex in wastewater under an alkaline condition, so that precipitation and separation of heavy metals are realized in one step. The high-energy-consumption and high-cost oxidation complex breaking step does not need to be carried out in advance, so that the treatment flow is remarkably simplified, the treatment time is shortened, and the operation energy consumption and the medicament cost are greatly reduced. According to the method, organic amine complexed with heavy metal can be effectively removed, efficient removal of organic nitrogen is achieved, CODcr in the wastewater is synchronously reduced, and the problem of cooperative treatment of multiple pollutants in the wastewater is solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more particularly to a method for treating industrial wastewater. Background Technology

[0002] Alkaline zinc-nickel alloy electroplating technology has developed rapidly and been widely used in my country in recent years. The coating formed by this process has advantages such as low hydrogen embrittlement, strong corrosion resistance, and high hardness. It exhibits excellent corrosion resistance in harsh industrial atmospheres and marine environments, and is therefore widely used for surface treatment in automotive parts, aerospace components, motorcycle parts, and other fields.

[0003] However, the main components of alkaline zinc-nickel alloy electroplating solutions include zinc salts, nickel salts, organic amine complexing agents, organic brighteners, and other additives. The use of these organic complexing agents and additives makes the wastewater generated during the production process complex in composition and difficult to treat. The concentration of complexed zinc and nickel ions in the production wastewater can reach over 300 mg / L, the concentration of organic nitrogen can reach over 1000 mg / L, and the COD... Cr It can reach concentrations of up to 20,000 mg / L or more, making it a typical example of difficult-to-treat electroplating wastewater.

[0004] Currently, the mainstream methods for treating this type of wastewater typically include: first, breaking the complex structure of heavy metals and organic amines through oxidation to release zinc and nickel ions; then, removing nitrogen pollutants using breakpoint chlorination and other methods; and finally, removing heavy metal ions using precipitants, heavy metal scavengers, or ion exchange resins. However, these traditional processes have significant drawbacks: the complex-breaking reaction is time-consuming, and the overall process is complex and lengthy; the cost of treatment agents is high, reaching hundreds of yuan per ton of water treated; a large amount of sludge is generated, which can easily cause secondary pollution, such as the production of halogenated disinfection byproducts and increased salinity in the effluent; in addition, the heavy metal and total nitrogen levels in the effluent often fail to consistently meet discharge requirements.

[0005] Therefore, developing a simple and efficient alkaline zinc-nickel alloy electroplating wastewater treatment process is of great significance for reducing the operational burden on enterprises and improving environmental benefits, and it is also the focus of current technological research and development in this field. Summary of the Invention

[0006] To solve or partially solve the problems existing in related technologies, the present invention provides a method for treating industrial wastewater.

[0007] This invention provides a method for treating industrial wastewater, comprising: Step a) Under alkaline conditions, a sulfur-containing organic compound is added to the industrial wastewater to react and form a solid precipitate containing heavy metals; the industrial wastewater contains heavy metal-organic amine complexes. Step b) Perform solid-liquid separation on the system after the reaction in step a).

[0008] Furthermore, the sulfur-containing organic compound is one or more of thiourea, thiols, and carbon disulfide.

[0009] Furthermore, in step a), during the reaction process of adding sulfur-containing organic compounds, or after the reaction, the step further includes: adjusting the pH of the reaction system to below 9.

[0010] Furthermore, adjusting the pH of the reaction system to below 9 specifically means adjusting the pH of the reaction system to 7-9.

[0011] Further, following step b) includes: Step c) Adjust the pH of the solid-liquid separation solution to less than 7, and precipitate will gradually form in the solution. Step d) Perform solid-liquid separation on the mixed system obtained in step c).

[0012] Furthermore, adjusting the pH of the reaction system to below 9 specifically means adjusting the pH of the reaction system to less than 7.

[0013] Furthermore, the pH of the reaction system is adjusted using an inorganic acid solution; the inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid; and / or, the solid-liquid separation is achieved by sedimentation, filtration, or centrifugation.

[0014] Furthermore, in step a), the mass concentration ratio of the sulfur-containing organic compound to the organic nitrogen in the reaction system is 0.5-5:1.

[0015] The present invention also provides a treatment agent for treating industrial wastewater, the effective component of which is a sulfur-containing organic compound.

[0016] This invention also provides an application of sulfur-containing organic compounds in the treatment of industrial wastewater.

[0017] The industrial wastewater treatment method provided by this invention can include the following beneficial effects: 1. This method directly reacts sulfur-containing organic compounds with heavy metal-organic amine complexes in wastewater under alkaline conditions, achieving precipitation and separation of heavy metals in one step. It eliminates the need for energy-intensive and costly pre-treatment oxidation and complex-breaking steps, significantly simplifying the treatment process, shortening treatment time, and substantially reducing operating energy consumption and reagent costs.

[0018] 2. This method can not only deeply remove complexed heavy metal ions, making their effluent concentration consistently below 0.1 mg / L; at the same time, it can also effectively remove organic amines complexed with heavy metals, achieve efficient removal of organic nitrogen, and simultaneously reduce CODcr in wastewater, thus solving the problem of synergistic treatment of multiple pollutants in this type of wastewater.

[0019] 3. The core steps of this method are simple, requiring only the addition of reagents, reaction, and separation. It is well adaptable to fluctuations in wastewater quality, and the main reaction conditions are mild, which can be carried out at room temperature. It is easy to achieve stable operation and automated control in actual engineering, reducing the difficulty of operation and management for enterprises.

[0020] 4. The treated liquid obtained by this method contains components that can capture heavy metal ions and precipitate them out in the form of precipitates. Therefore, this treated liquid can also be used as a treatment agent to treat other types of wastewater containing heavy metal ions, thereby achieving the synergistic treatment of different heavy metal wastewaters and treating waste with waste.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0022] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0023] Figure 1 This is a physical diagram of the wastewater system before solid-liquid separation in Embodiment 1 of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0026] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] This invention provides a method for treating industrial wastewater, comprising the following steps: Step a) Under alkaline conditions, a sulfur-containing organic compound is added to the industrial wastewater to react and form a solid precipitate containing heavy metals; the industrial wastewater contains heavy metal-organic amine complexes. Step b) Perform solid-liquid separation on the system after the reaction in step a).

[0028] The inventors of this application have discovered through research that, under alkaline conditions, sulfur-containing organic compounds can react with heavy metals—organic amines—in wastewater, converting the heavy metals into easily separable forms without disrupting their complexation. Therefore, this application performs step a) above.

[0029] The alkaline conditions described in step a) above are preferably conditions with a pH greater than 10. For different industrial wastewaters, those skilled in the art can first determine their pH. For wastewater with a pH less than 10, the pH can be increased to greater than 10 by adding alkali. The reaction temperature in step a) can be room temperature, and the reaction time is preferably 0.5-2 hours. To improve reaction efficiency, the reaction is preferably carried out under stirring.

[0030] The sulfur-containing organic compounds mentioned above are preferably one or more of thiourea, thiols, and carbon disulfide. Specifically, one can be used, two can be used in combination, or all three compounds can be used in combination. More preferably, carbon disulfide or a combination of other components with carbon disulfide is used. In addition, in the reaction system in which the sulfur-containing organic compounds are added, the mass concentration ratio of the sulfur-containing organic compounds to the organic nitrogen is 0.5-5:1.

[0031] After adding sulfur-containing organic compounds, heavy metals in the wastewater precipitate out as sediment, along with their complexes—organic amines. Then, following step b), solid-liquid separation, the heavy metals are removed from the wastewater, and most of the organic amines are also removed. Solid-liquid separation can be achieved through sedimentation, filtration, or centrifugation. During sedimentation, coagulants can be added to improve the sedimentation effect.

[0032] During solid-liquid separation, the inventors of this application discovered that the pH of the system affects the morphology of the precipitate. When the pH of the system is greater than 9, the precipitate is mainly in the form of fine powder; when the pH of the system is less than 9, the precipitate is mainly in the form of flocculent particles. Based on this discovery, in order to reduce the difficulty of solid-liquid separation operations, step a) above, during or after the addition of sulfur-containing organic compounds for the reaction, further includes a step of adjusting the pH of the reaction system to below 9. Specifically, this can be achieved by adjusting the pH of the reaction system to 7-9.

[0033] The inventors of this application further discovered that the pH of the reaction system also affects the composition of the precipitates. When the pH of the reaction system drops below 7, the precipitates include not only the precipitates corresponding to heavy metal-organic amine complexes, but also the precipitates corresponding to excess organic amines (i.e., organic amines that have not chelated with heavy metal ions) in industrial wastewater. Therefore, the pH of the reaction system after adding the sulfur-containing organic compound can be lowered to below 9 first, and then further reduced to below 7, or the pH can be directly lowered to below 7 after adding the sulfur-containing organic compound. Specifically: The process can begin during the reaction with sulfur-containing organic compounds, or after the reaction, and may also include adjusting the pH of the reaction system to below 9. Then proceed with step b); followed by the following steps: Step c) Adjust the pH of the solid-liquid separation solution to less than 7, and precipitate will gradually form in the solution; more preferably, adjust the pH to 2-3. Step d) Perform solid-liquid separation on the mixed system obtained in step c).

[0034] or, During or after the reaction, the reaction may involve: adjusting the pH of the reaction system to less than 7; adjusting the pH to 2-3; and then proceeding according to step b).

[0035] Those skilled in the art can make the selection based on actual needs and working conditions.

[0036] In the aforementioned operation of adjusting the pH of the reaction system to below 9, it is preferable to use an inorganic acid solution to adjust the pH of the reaction system; specifically, the inorganic acid can be one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0037] For the treated liquid (the liquid obtained after solid-liquid separation, pH greater than 7) where the reaction system was not adjusted to acidity, the inventors of this application discovered that its components can capture heavy metal ions and precipitate them out in the form of precipitates. Therefore, in this case, the treated liquid obtained after step b) can be used as a treatment agent to treat other types of wastewater containing heavy metal ions, thereby achieving the synergistic treatment of different heavy metal wastewaters and treating waste with waste. The specific operation can be as follows: The treatment liquid with a pH greater than 7 obtained after solid-liquid separation in step b) is mixed with other wastewater containing heavy metals to form a solid precipitate containing heavy metals; then solid-liquid separation is performed.

[0038] The industrial wastewater described in this application can be electroplating wastewater, electroless plating wastewater, or metallurgical wastewater. More preferably, the electroplating wastewater is alkaline zinc-nickel alloy electroplating wastewater. The aforementioned other wastewater containing heavy metals is wastewater containing heavy metals that is different from the industrial wastewater described herein.

[0039] Another embodiment of the present invention provides a treatment agent for treating industrial wastewater, the effective component of which is a sulfur-containing organic compound, specifically a combination of one or more of thiourea, thiols, and carbon disulfide. Further, the treatment agent may also include an acid-base regulator component, specifically an alkaline component and / or an acidic component. The alkaline component specifically includes sodium hydroxide, potassium hydroxide, etc., and the acidic component includes inorganic acids, preferably one or more of hydrochloric acid, sulfuric acid, and nitric acid. The industrial wastewater contains heavy metal-organic amine complexes. Specifically, it can be electroplating wastewater, chemical plating wastewater, or metallurgical wastewater. More preferably, the electroplating wastewater is alkaline zinc-nickel alloy electroplating wastewater.

[0040] Another embodiment of the present invention provides the application of a sulfur-containing organic compound in the treatment of industrial wastewater. The sulfur-containing organic compound is preferably a combination of one or more of thiourea, thiols, and carbon disulfide. The industrial wastewater contains heavy metal-organic amine complexes, specifically electroplating wastewater, electroless plating wastewater, or metallurgical wastewater. More preferably, the electroplating wastewater is alkaline zinc-nickel alloy electroplating wastewater. The remaining preferred embodiments are the same as in the previous embodiment and will not be repeated here.

[0041] Another embodiment of the present invention provides an application of the above-mentioned treatment agent in the treatment of industrial wastewater. The industrial wastewater contains heavy metal-organic amine complexes, specifically electroplating wastewater, electroless plating wastewater, or metallurgical wastewater. More preferably, the electroplating wastewater is alkaline zinc-nickel alloy electroplating wastewater. The remaining preferred embodiments are the same as in the previous embodiment and will not be repeated here.

[0042] The industrial wastewater treatment method provided in this embodiment of the invention has the following advantages: 1. This method directly reacts sulfur-containing organic compounds with heavy metal-organic amine complexes in wastewater under alkaline conditions, achieving precipitation and separation of heavy metals in one step. It eliminates the need for energy-intensive and costly pre-treatment oxidation and complex-breaking steps, significantly simplifying the treatment process, shortening treatment time, and substantially reducing operating energy consumption and reagent costs.

[0043] 2. This method can not only deeply remove complexed heavy metal ions, making their effluent concentration consistently below 0.1 mg / L; at the same time, it can also effectively remove organic amines complexed with heavy metals, achieve efficient removal of organic nitrogen, and simultaneously reduce CODcr in wastewater, thus solving the problem of synergistic treatment of multiple pollutants in this type of wastewater.

[0044] 3. The core steps of this method are simple, requiring only the addition of reagents, reaction, and separation. It is well adaptable to fluctuations in wastewater quality, and the main reaction conditions are mild, which can be carried out at room temperature. It is easy to achieve stable operation and automated control in actual engineering, reducing the difficulty of operation and management for enterprises.

[0045] 4. The treated liquid obtained by this method contains components that can capture heavy metal ions and precipitate them out. Therefore, this treated liquid can also be used as a treatment agent to treat other types of wastewater containing heavy metal ions, thereby achieving synergistic treatment of different heavy metal wastewaters and treating waste with waste.

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments: Example 1 Wastewater to be treated: 1L of alkaline zinc-nickel alloy wastewater from an electroplating workshop was taken, and its indicators were measured as follows: pH=11, COD Cr The wastewater concentration was 19670 mg / L, organic nitrogen content was 890 mg / L, nickel content was 349 mg / L, and zinc content was 1366 mg / L. The wastewater was treated as follows: The wastewater to be treated was placed in a reactor, and thiourea at twice the organic nitrogen concentration was added (i.e., after adding thiourea to the reactor, the mass concentration of thiourea was twice the mass concentration of organic nitrogen, the same below). The reaction was stirred at room temperature for 0.5 hours. Then, sulfuric acid solution was added to the wastewater to adjust the pH to 7.0. As the pH decreased, a large amount of solid insoluble matter precipitated. Please refer to [link to physical sample]. Figure 1 The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment process.

[0047] Example 2 Wastewater to be treated: Same as in Example 1.

[0048] The wastewater to be treated is placed in a reactor, and thiourea with an organic nitrogen concentration three times that of the reactor is added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 6.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solid is separated by filtration, and the resulting wastewater is the final effluent from the treatment process.

[0049] Example 3 Wastewater to be treated: Same as in Example 1.

[0050] The wastewater to be treated is placed in a reactor, and thiols with an organic nitrogen mass concentration equal to that of the reactor are added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 9.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment process.

[0051] Example 4 Wastewater to be treated: Same as in Example 1.

[0052] The wastewater to be treated is placed in a reactor, and carbon disulfide with an organic nitrogen concentration three times that of the reactor is added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 3.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment process.

[0053] Example 5 Wastewater to be treated: Same as in Example 1.

[0054] The wastewater to be treated is placed in a reactor, and carbon disulfide with an organic nitrogen concentration equal to that of the reactor is added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 2.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment process.

[0055] Example 6 Wastewater to be treated: Same as in Example 1.

[0056] The wastewater to be treated is placed in a reactor, and thiourea and carbon disulfide (1:1 mass ratio) with an organic nitrogen concentration of 4 times are added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 2.5. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment.

[0057] Example 7 Wastewater to be treated: Same as in Example 1.

[0058] The wastewater to be treated is placed in a reactor, and thiols and carbon disulfide (1:2 mass ratio) with an organic nitrogen concentration of 4 times are added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 5.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment.

[0059] Example 8 Wastewater to be treated: Same as in Example 1.

[0060] The wastewater to be treated is placed in a reactor, and a mixture of thiourea, thiol and carbon disulfide (1:1:1 mass ratio) with an organic nitrogen concentration of 5 times is added. The mixture is stirred and reacted at room temperature for 0.5 hours. Then, sulfuric acid solution is added to the wastewater to adjust the pH to 8.0. As the pH decreases, a large amount of solid insoluble matter is precipitated. The solids are separated by filtration, and the resulting wastewater is the final effluent from the treatment.

[0061] Example 9 Wastewater to be treated: 1L of high-concentration alkaline zinc-nickel alloy wastewater from an electroplating workshop was taken, and its indicators were measured as follows: pH=12, COD Cr The concentration was 23580 mg / L, the organic nitrogen content was 1200 mg / L, the nickel content was 580 mg / L, and the zinc content was 1500 mg / L.

[0062] The wastewater was treated in the same way as in Example 6.

[0063] Example 10 Wastewater to be treated: 1L of high-concentration alkaline zinc-nickel alloy wastewater from an electroplating workshop was taken, and its indicators were measured as follows: pH=10, COD Cr The concentration was 9570 mg / L, the organic nitrogen content was 500 mg / L, the nickel content was 310 mg / L, and the zinc content was 800 mg / L.

[0064] The wastewater was treated in the same way as in Example 7.

[0065] The wastewater from solid-liquid separation in Examples 1-10 was tested to determine its nickel and zinc ion concentrations, organic nitrogen and CODcr removal rates. The test results are listed in Table 1. Table 1. Detection results of wastewater from solid-liquid separation

[0066] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for treating industrial wastewater, characterized by, The method comprises: Step a), adding a sulfur-containing organic compound to the industrial wastewater under alkaline conditions to form a solid precipitate containing heavy metals; the industrial wastewater contains heavy metal-organic amine complexes; Step b), solid-liquid separation of the system after step a).

2. The treatment method according to claim 1, characterized in that, The sulfur-containing organic compound is a combination of one or more of thiourea, mercaptan and carbon disulfide.

3. The treatment method of claim 1, wherein, In step a), during the reaction of adding the sulfur-containing organic compound, or after the reaction, the method further comprises the step of adjusting the pH of the reaction system to below 9.

4. The treatment method according to claim 3, characterized in that, The adjustment of the pH of the reaction system to below 9 specifically refers to adjusting the pH of the reaction system to 7-9.

5. The treatment method according to claim 4, characterized in that, After step b), the method comprises: Step c), adjusting the pH of the treated liquid after solid-liquid separation to less than 7, and gradually forming a precipitate in the treated liquid; Step d), solid-liquid separation of the mixed system obtained in step c).

6. The treatment method of claim 3, wherein The adjustment of the pH of the reaction system to below 9 specifically refers to adjusting the pH of the reaction system to less than 7.

7. The treatment method according to any one of claims 3 to 6, characterized in that, An inorganic acid solution is used to adjust the pH of the reaction system; the inorganic acid is one or more of hydrochloric acid, sulfuric acid and nitric acid; and / or, the solid-liquid separation is achieved by sedimentation, filtration or centrifugation.

8. The treatment method of claim 1, wherein In step a), the mass concentration ratio of the sulfur-containing organic compound to the organic nitrogen in the reaction system of adding the sulfur-containing organic compound is 0.5-5:

1.

9. A treatment agent for treating industrial wastewater, characterized by, The effective component is a sulfur-containing organic compound.

10. Application of a sulfur-containing organic compound in treating industrial wastewater.

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