Treatment system and method for electroless nickel-plating waste liquid

Abstract

The present application relates to the field of wastewater treatment, and provides a treatment system and method for electroless nickel-plating waste liquid. The treatment system comprises a decomplexing pretreatment system; an oxidation-decomplexing system comprising a redox reactor and a decomplexing reactor which are connected in sequence, wherein an oxidizing agent in the redox reactor is oxygen, and an oxidizing agent in the decomplexing reactor is hydrogen peroxide; a chemical precipitation system comprising a neutralization reaction tank and a sedimentation tank which are connected in sequence, wherein the sedimentation tank is equipped with a filter system; and an evaporation crystallization system comprising an evaporation device, a crystallization device, and a separation device which are arranged in sequence. In the treatment system and method for electroless nickel-plating waste liquid, a two-stage oxidation method is employed to achieve oxidation and decomplexing of the waste liquid; in addition, combining chemical precipitation treatment and evaporation crystallization treatment not only reduces the waste liquid treatment cost but also avoids the introduction of other impurities, and allows for the separation of nickel salts and phosphate salts, so that the operation is easy and convenient, the treatment cost is low, the nickel removal rate is high, and resource utilization of nickel is facilitated.

Description

A treatment system and method for chemical nickel plating waste liquid Technical Field

[0001] The present application relates to the field of wastewater treatment, and more specifically, to a treatment system and method for chemical nickel plating wastewater. Background Art

[0002] There are three main types of reducing agents used in chemical nickel plating: (1) hypophosphites; (2) sodium borohydride-type boron-containing reducing agents; and (3) hydrazine. Among them, acidic chemical nickel plating using sodium hypophosphite as the reducing agent is the most widely used. During the nickel plating process, as the deposition reaction continues, sodium hypophosphite is continuously consumed and phosphite is continuously generated. At present, industrial chemical nickel plating is carried out in an acidic system with sodium hypophosphite as the reducing agent. In order to ensure the stability, service life and coating quality of the plating solution, complexing agents, stabilizers, accelerators, pH buffers and nickel plating brighteners need to be added to the plating solution. These substances are all organic substances, such as citric acid, tartaric acid, malic acid, glycolic acid, succinic acid, succinic acid, acetic acid, etc. The amount of complexing agents added to the chemical plating solution is relatively large. The presence of these substances has a strong complexing property with nickel and easily forms a stable complex with nickel, which brings difficulties to the treatment of the plating solution. Other additives added to the chemical plating solution, such as pH buffer (NaAc), have little effect on waste liquid treatment, and the amount of brightener and stabilizer added is small, which will not cause difficulties in the treatment of waste liquid and wastewater.

[0003] The presence of large amounts of reducing hypophosphites and phosphites, as well as complexing and reducing agents, in the plating bath can cause a sharp increase in COD. Furthermore, the accumulation of sulfates and phosphites generated by these reactions can easily cause the plating bath to age, potentially rendering part or all of the electroless nickel plating solution obsolete. Consequently, the discarded plating bath and rinse water containing the plated parts contain high levels of pollutants and must be treated. Currently, the main methods for treating waste liquids and wastewater include chemical precipitation, electrolysis, ion exchange, and catalytic reduction. In practical applications, a combination of two or more methods may be used. While some treatment methods are effective, they are costly, making them difficult to promote within electroless nickel plating operations. Alternatively, they may introduce impurities during the treatment process, hindering the resource utilization of nickel. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a system and method for treating chemical nickel plating waste liquid. The present application adopts the following technical solutions:

[0005] A treatment system for chemical nickel plating waste liquid includes the following systems connected in sequence: a complex breaking pretreatment system, including a regulating tank for adjusting the pH of the nickel plating waste liquid; an oxidation complex breaking system, including a redox reactor and a complex breaking reactor connected in sequence, wherein the oxidant of the redox reactor is oxygen, and the oxidant of the complex breaking reactor is hydrogen peroxide; a chemical precipitation system, including a neutralization reaction tank and a sedimentation tank connected in sequence, and the sedimentation tank is equipped with a filtration system; an evaporation crystallization system, including an evaporation device, a crystallization device and a separation device arranged in sequence.

[0006] Furthermore, the above-mentioned complex breaking reactor has a series-type secondary reaction tank, and the oxidation complex breaking system also includes a circulation storage tank connected to the reaction tank.

[0007] Furthermore, the above-mentioned filtration system includes a primary filtration device and a fine filtration device. The primary filtration device is a plate and frame filter press or a bag filter, and the fine filtration device can use a precision filter of less than 100 microns.

[0008] Furthermore, the above-mentioned network breaking pretreatment system also includes a filtering and impurity removal device connected to the regulating tank.

[0009] A method for treating chemical nickel plating waste liquid, which utilizes the above-mentioned treatment system, comprises: (1) adding acid solution into the regulating tank to obtain acidic nickel plating waste liquid; preferably, adjusting the acidity to pH=0-6 with sulfuric acid or hydrochloric acid solution; (2) passing the acidic nickel plating waste liquid into the redox reactor for a first-stage oxidation, using oxygen to oxidize the hypophosphite and phosphite in the nickel plating waste liquid into hydrogen phosphate or dihydrogen phosphate; passing the nickel plating waste liquid after the first-stage oxidation into the complex breaking reactor for a second-stage oxidation, using hydrogen peroxide to break the organic complex to form a free state ;

[0010] The acidic nickel plating waste liquid is passed into the redox reactor for a first-stage oxidation, and the hypophosphite and phosphite in the nickel plating waste liquid are oxidized into phosphates using oxygen. The first-stage oxidation reaction can be carried out at room temperature. When the temperature is low, the reaction time is longer, and the oxidation reaction takes 12-18 hours to complete. The optimal reaction temperature is 50-90°C, which is conducive to accelerating the reaction speed and improving production efficiency. Under this temperature condition, the complete oxidation reaction time is 2-5 hours; the nickel plating waste liquid after the first-stage oxidation is passed into the decomposition reactor for a second-stage oxidation, and hydrogen peroxide is used to destroy the stable nickel organic complex to form a free state. Since oxygen is used in the first stage of oxidation to oxidize most of the hypophosphite and phosphite into high-valent stable phosphates, the amount of expensive hydrogen peroxide used in the second stage of oxidation is greatly reduced, thereby saving the cost of waste liquid treatment. After the second stage reaction is completed, the solution should be controlled to be weakly acidic, with a pH of 4-6. Nickel exists in the solution in the form of dihydrogen phosphate or hydrogen phosphate. No precipitation will occur;

[0011] (3) The nickel plating waste liquid after the second stage oxidation is transferred to the neutralization reaction tank, and a neutralization precipitant is added to adjust the pH of the system to 9-10, and the free Converted into nickel phosphate or nickel hydroxide for precipitation, filtered to obtain nickel phosphate or nickel hydroxide and secondary wastewater; Since nickel phosphate or sodium hydroxide has extremely low solubility and is a poorly soluble compound, at this time, the solution + ≦1mg / l, the precipitation is complete, solid-liquid separation is achieved after filtration, nickel resources are recovered, and the filtrate is further processed; (4) the supernatant and filtrate wastewater of the sedimentation tank are transferred to the evaporation crystallization system for evaporation crystallization to obtain solid miscellaneous salts and distilled water.

[0012] Furthermore, in the second-stage oxidation process, the reaction time of the decomposition reactor is 0.7-1.3h.

[0013] Furthermore, in the chelation pretreatment system, the acid solution fed into the regulating tank is sulfuric acid or hydrochloric acid solution, and the pH of the nickel plating wastewater after adjustment is 0 to 6. During the oxidation process, the consumed acid solution is replenished to maintain the acidity of the system.

[0014] Furthermore, in the decomposition treatment system, the acid solution fed into the regulating tank is sulfuric acid or hydrochloric acid solution to maintain the pH of the nickel plating waste liquid ≤ 6, with the optimal range being pH = 4 to 6. During the oxidation process, attention should be paid to replenishing the consumed acid solution to maintain the acidity of the system.

[0015] Furthermore, the neutralization precipitant added to the neutralization reaction tank is sodium hydroxide solution.

[0016] Furthermore, the method further includes adding a polymer flocculant into the sedimentation tank.

[0017] Furthermore, the polymer flocculant includes polyacrylamide or polyaluminum chloride.

[0018] Furthermore, the reaction temperature of the primary oxidation is 50-90° C., and the reaction time is 2-5 h.

[0019] In summary, the present application has the following beneficial effects: the treatment system and treatment method of the chemical nickel plating waste liquid provided by the present application adopts a two-stage oxidation method to achieve oxidation and decomposition of the waste liquid. The first stage of oxidation is carried out in a redox reactor, using oxygen to oxidize the hypophosphite and phosphite in the nickel plating waste liquid into phosphate; the second stage of oxidation is carried out in a decomposition reactor, using oxygen to oxidize the hypophosphite and phosphite in the nickel plating waste liquid into phosphate; Break down organic complexes and form free Compared with the existing technology Direct oxidation process, this application can save a lot of consumption, industry The concentration is usually around 35%. The large amount of hydrogen peroxide used will introduce a large amount of water into the reaction system, thereby increasing steam consumption for subsequent evaporative desalination and increasing wastewater treatment costs. Compared with the Fenton reaction with the addition of ferrous sulfate for oxidation, this method can avoid the introduction of impurities and the formation of additional precipitated solid waste (ferrous hydroxide), thereby reducing production costs. Chemical precipitation is also used to separate nickel salts from soluble salts, and combined with evaporative crystallization, it reduces the COD, NH3-N, and TN levels of the treated wastewater (evaporation condensate). Depending on the water quality of the evaporation condensate, it can be discharged directly or after biochemical treatment to meet discharge standards.

[0020] The method is easy and simple to operate, has low processing cost, high nickel removal rate, is conducive to realizing nickel resource utilization, and has good economic and ecological and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of a chemical nickel plating waste liquid treatment system according to an embodiment of the present application; FIG2 is a flow chart of a chemical nickel plating waste liquid treatment method according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0023] Industrial chemical nickel plating is carried out in an acidic system with sodium hypophosphite as a reducing agent. The characteristic pollutants of the electroplating wastewater are mainly heavy metal nickel, sodium hypophosphite, ammonia nitrogen, total nitrogen (COD), and organic matter. Specifically, for example, the electroplating wastewater targeted by the embodiments of this application has the following characteristics: pH = 4-6, weak acidity, and the main components are: total phosphorus 30-34g / l, which is hypophosphite; chemical oxygen demand (COD) 60-77.5g / l; ammonia nitrogen 3.3-4.7g / l; total nitrogen 5.1-6.2g / l; nickel 6.8-8.7g / l; specific gravity 1.10-1.20.

[0024] Analysis shows that the main factors causing excessive COD in electroplating wastewater are the following two: first, the chemical oxygen demand consumed by the oxidation of inorganic salts, such as hypophosphite and ammonium salts; second, the chemical oxygen demand consumed when organic complexes are oxidized. Therefore, during the treatment process, this application specifically improves the oxidation and decomposition process to further control treatment costs and achieve the following: first, minimize the amount of solid waste generated during the treatment process; second, minimize the addition of chemical reagents to reduce disposal costs; and third, separate nickel salts from other miscellaneous salts to achieve resource utilization and reduce treatment costs.

[0025] In nickel plating wastewater, the phosphorus in the sodium hypophosphite and phosphite salts has a chemical valence of +1 or +3, both of which are reducing and easily oxidized to orthophosphate with a valence of +5. The following are the redox potentials of phosphorus under different valences: O(0)- (-2)O2+4H++4e- =2H2O1.229O(-1)- (-2)H2O2+2H++2e- =2H2O1.776P(+3)- (+1)H3PO3+2H++2e- =H3PO2+H2O-0.499P(+5)- (+3)H3PO4+2H++2e- =H3PO3+H2O-0.276The chemical reaction equation for oxidation and complex destruction using hydrogen peroxide is as follows: Wherein, [Ni2++mLn-] represents the complex of nickel ions.

[0026] Nickel phosphate has a solubility product of 4.5 × 10⁻³⁵ at 25°C, and the phosphate content in the solution is high. Under acidic conditions, the phosphate is primarily monohydrogen phosphate or dihydrogen phosphate, which have high solubility. When the neutralizing precipitant NaOH is added to adjust the pH to 9-10, the hydrogen phosphate and dihydrogen phosphate in the solution are completely converted to phosphate, forming a poorly soluble nickel phosphate precipitate. Calcium hydroxide cannot be used as the neutralizing precipitant because it will react with phosphate ions in the wastewater to form a calcium phosphate precipitate, which will co-precipitate with the nickel phosphate, hindering the subsequent recovery of nickel resources.

[0027] In use During the oxidation process, sodium hypophosphite and sodium phosphite consume a lot of Normally, in nickel plating wastewater, hypophosphite accounts for 40% and phosphite accounts for 60%. It takes 4 molecules of hydrogen peroxide to oxidize one molecule of sodium hypophosphite into orthophosphate, and 2 molecules of hydrogen peroxide to oxidize one molecule of sodium phosphite into orthophosphate. Oxidative decomposition requires a high volume of hydrogen peroxide. The 35% concentration of industrial hydrogen peroxide introduces significant water into the reaction system, increasing steam consumption for subsequent evaporation and desalination, leading to excessive wastewater treatment costs. Using hydrogen peroxide alone to oxidize chemical nickel plating wastewater requires 200-400 kg of 35% industrial hydrogen peroxide per ton of wastewater to remove phosphite. Furthermore, using the Fenton reaction requires the addition of large amounts of ferrous sulfate, resulting in a large amount of ferrous sulfate precipitate. This excessive precipitate increases subsequent solid waste disposal costs, hinders the resource recovery of nickel and phosphorus, and ultimately drives up overall wastewater treatment costs.

[0028] In order to solve the above problems, the present application optimizes the process and provides a treatment system and method for chemical nickel plating waste liquid. Specifically: the treatment system for chemical nickel plating waste liquid, as shown in Figure 1, includes the following systems connected in sequence: 1. A chelation pretreatment system, including a regulating tank for adjusting the pH of the nickel plating waste liquid; wherein the regulating tank is connected to the waste liquid storage tank. The waste liquid tank is a temporary storage tank used by the chemical nickel plating producer to store waste liquid. It is made of fiberglass or steel-lined plastic. The temporary storage process can play a role in pre-precipitation and separation. The regulating tank is used to adjust the pH of the nickel plating waste liquid. Because the pH of the nickel plating wastewater is weakly acidic, an acid (such as H2SO4) must be added to the regulating tank to adjust the wastewater's pH to an acidic pH of 0-6. Since some acid is consumed during the oxidation process and needs to be replenished, the oxidation process also removes most of the organic acid chelating agent. Acidic conditions enhance the oxygen's oxidizing capacity while preventing nickel phosphate precipitation during the oxidation process. To further improve the quality of the resulting nickel phosphate and ensure the proper operation of the subsequent redox and chelation decomposition reactors, the chelation decomposition pretreatment system preferably includes a primary filtration and impurity removal device, including a plate and frame filter press or bag filter, to deoil and remove insoluble impurities before the nickel plating wastewater enters the oxidation and chelation decomposition system. The primary oxygen oxidation reaction can be carried out at room temperature, but the reaction time is relatively long. For example, in winter, when temperatures are low, a complete reaction can take 12-18 hours. The reaction is exothermic, and the oxidation reaction accelerates with increasing temperature. The optimal initial reaction temperature is 60-90°C, at which point the reaction typically completes within 2-4 hours.

[0029] (2) An oxidation and decomposition system, comprising a redox reactor and a decomposition reactor connected in sequence, wherein the oxidant of the redox reactor is oxygen and the oxidant of the decomposition reactor is hydrogen peroxide.

[0030] Among them, the redox reactor has a steel-lined tetrafluoroethylene or steel-lined plastic, and is equipped with a temporary storage tank for storing waste liquid to be further processed after redox. The decomposition reactor has a series-type secondary reaction tank, and the decomposition reaction time is 0.7-1.3h, preferably the decomposition reaction time is 1h. However, after the oxidation decomposition reaction is completed, the solution pH should be maintained at 4-6. Too high an acidity will affect the amount of sodium hydroxide used during neutralization and precipitation, resulting in an increase in processing costs. In order to further ensure the quality of the decomposition reaction, a circulation storage tank connected to the reaction tank is also provided. When the decomposition effect is found to be poor, it is used to return to decomposition again.

[0031] (3) A chemical precipitation system, comprising a neutralization reaction tank and a sedimentation tank connected in sequence, wherein the sedimentation tank is equipped with a filtration system; the neutralization reaction tank can be a series-type secondary reaction tank, made of fiberglass, PP or carbon steel with anti-corrosion treatment.

[0032] The sedimentation tank is used to rapidly precipitate and separate the solids and liquids produced by the neutralization reaction, producing a nickel phosphate or hydroxide precipitate. The sedimentation tank is equipped with a filtration system, using either a plate and frame filter press or a centrifugal filter. Preferably, the plate and frame filter press is a diaphragm filter press, which filters the nickel phosphate or nickel hydroxide precipitate daily, with the filtrate temporarily stored in a storage tank.

[0033] (4) An evaporation crystallization system, comprising an evaporation device, a crystallization device, and a separation device arranged in sequence.

[0034] Since the filtered mother liquor after the neutralization and precipitation of nickel contains a large amount of sodium phosphate, sodium sulfate, sodium chloride, sodium nitrate, ammonium salts and a small amount of organic matter that has not been oxidized and removed, the COD and salt content of this waste liquid are very high, and it is impossible to use biochemical methods to treat this wastewater. Evaporation and desalination treatment must be carried out. Depending on the COD of the evaporation condensate, it is chosen to be discharged directly or to undergo biochemical treatment before meeting the discharge standards.

[0035] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] Example 1

[0037] This embodiment provides a method for treating chemical nickel plating waste liquid, which utilizes the treatment system described above. The treatment process is shown in Figure 2 and specifically includes: (1) passing the waste liquid to be treated into a regulating tank, adding acid solution to the regulating tank, adjusting the pH to 0-1.0 with sulfuric acid or hydrochloric acid, and filtering to remove most of the insoluble impurities.

[0038] (2) The acidic nickel plating waste liquid is passed into the redox reactor for a first stage oxidation, which can be carried out at room temperature and the reaction is completed in 12 hours. The hypophosphite and phosphite in the nickel plating waste liquid are oxidized into phosphates by oxygen. During the oxidation process, part of the acid solution is added to keep the pH of the reaction system less than 6. The more thorough the first stage oxidation reaction is, the more effective the second stage oxidation process is. The less the consumption, the more oxygen is consumed. One oxidation reaction consumes 25.3 kg of oxygen to treat 1 ton of waste liquid.

[0039] (3) Subsequently, the nickel plating waste liquid after the first stage oxidation is passed into the decomposition reactor for the second stage oxidation. The reaction time is 1 hour. The organic complex is broken by hydrogen peroxide to form free Ni2+. The pH of the reaction system is kept below 6. The oxidation and decomposition consumption of 1 ton of waste liquid is 200 ppm. The dosage is about 30kg.

[0040] (4) The nickel plating wastewater after the second stage oxidation is then transferred to a neutralization reaction tank, sodium hydroxide is added as a neutralizing precipitant, and the pH of the wastewater system is adjusted to 9.5. The free Ni2+ is converted into nickel phosphate or nickel hydroxide precipitate. Subsequently, it is passed into a sedimentation tank, and a high molecular weight flocculant polyacrylamide (PAM) is added to quickly precipitate the nickel phosphate or nickel hydroxide in the system. The nickel phosphate or nickel hydroxide is obtained by filtration. The amount of sodium hydroxide used per ton of wastewater is 10 kg, and the amount of PAM used is 0.1 kg. 9.2 kg of nickel phosphate or 7 kg of nickel hydroxide can be recovered.

[0041] (5) The supernatant or filtrate of the separated nickel resources is transferred to the evaporation crystallization system for direct evaporation crystallization desalination. After centrifugation, solid miscellaneous salts are obtained. The main components of the solid miscellaneous salts are: Na3PO4, Na2SO4, NaCl, and NaNO3. The treated evaporation condensate sample is then analyzed. Based on the COD, NH3-N and TN analysis report of the distilled water, it is determined whether further biochemical treatment or direct discharge is required.

[0042] Example 2

[0043] This embodiment provides a method for treating chemical nickel plating waste liquid, which specifically includes: (1) passing the waste liquid to be treated into a regulating tank, adding acid solution into the regulating tank, adjusting the pH to 1-2 with sulfuric acid, filtering, and removing most of the suspended matter and impurities.

[0044] (2) The acidic nickel plating wastewater is passed into a redox reactor for a first oxidation step. The reaction starts at a temperature of 50-60°C and the reaction lasts for 4 hours. Oxygen is used to oxidize the hypophosphite and phosphite in the nickel plating wastewater into phosphates. The reaction replenishes some of the consumed acid to reduce the H2O2 consumption in the subsequent oxidation process. 26 kg of oxygen is consumed to treat 1 ton of wastewater.

[0045] (3) Subsequently, the nickel plating waste liquid after the first stage oxidation is passed into the decomposition reactor for the second stage oxidation. The reaction time is 0.7h. Hydrogen peroxide is used to break the organic complex to form free Ni2+. The amount of H2O2 consumed for oxidation and decomposition of each ton of waste liquid is about 30kg.

[0046] (4) The nickel plating wastewater after the secondary oxidation is then passed into a neutralization reaction tank, sodium hydroxide is added as a neutralizing precipitant, and the pH of the wastewater system is adjusted to 9. The free Ni2+ is converted into nickel phosphate or nickel hydroxide and precipitated and separated. Subsequently, the wastewater is passed into a sedimentation tank to precipitate and separate the nickel phosphate or nickel hydroxide in the system, and filtered to obtain nickel phosphate or nickel hydroxide and a filtrate. The amount of sodium hydroxide used in 1 ton of wastewater is 10 kg, and 9.2 kg of nickel phosphate or 7 kg of nickel hydroxide can be recovered.

[0047] (5) The supernatant and filtrate from the sedimentation tank are passed through the evaporation and crystallization system for direct evaporation and crystallization desalination. After centrifugation, solid miscellaneous salts are obtained. The main components of the solid miscellaneous salts are: Na3PO4, Na2SO4, NaCl, and NaNO3. The treated water samples are then analyzed. Based on the COD, NH3-N, and TN analysis reports of the evaporated condensate, it is determined whether further biochemical treatment or direct discharge is required.

[0048] Example 3

[0049] This embodiment provides a method for treating chemical nickel plating waste liquid, which specifically includes:

[0050] (1) The waste liquid to be treated is passed into a regulating tank, hydrochloric acid is added to the regulating tank, the pH is adjusted to 2-4, and filtered to remove most of the organic acid complexing agent.

[0051] (2) The acidic nickel plating waste liquid is passed into the redox reactor for a stage of oxidation, and the hypophosphite and phosphite in the nickel plating waste liquid are oxidized into phosphates using oxygen. The reaction starting temperature is about 60 ° C and the reaction is carried out for 3 hours to reduce the subsequent oxidation process. Consumption: 26Kg of oxygen is required to treat 1 ton of waste liquid.

[0052] (3) The nickel plating waste liquid after the first stage oxidation is passed into the complex breaking reactor for the second stage oxidation. The reaction time is 1.3 hours. Hydrogen peroxide is used to break the organic complex to form free Ni2+.

[0053] (4) The nickel plating wastewater after the secondary oxidation is then passed into a neutralization reaction tank, where sodium hydroxide is added as a neutralizing precipitant to adjust the pH of the wastewater system to 10. Free Ni2+ is converted into nickel phosphate or nickel hydroxide. The wastewater is then passed into a sedimentation tank where a polymer flocculant, polyacrylamide (PAM), is added to precipitate the nickel phosphate or nickel hydroxide in the system. The nickel phosphate or nickel hydroxide is then filtered to obtain the nickel phosphate or nickel hydroxide.

[0054] (5) The supernatant and filtrate wastewater from the secondary precipitation treatment are passed through an evaporation and crystallization system for direct evaporation and crystallization desalination. After centrifugation, solid miscellaneous salts are obtained. The main components of the solid miscellaneous salts are: Na3PO4, Na2SO4, NaCl, and NaNO3. The treated evaporation condensate water sample is then analyzed. Based on the COD, NH3-N, and TN analysis report of the distilled water, it is determined whether further biochemical treatment or direct discharge is required.

[0055] Application Example: In this application example, the nickel plating waste liquid treatment method and treatment system provided in Example 1 are used to treat the waste liquid:

[0056] After homogenization in the regulating tank, the nickel plating wastewater has a pH of 4-6, indicating a weak acidity; total phosphorus of 30-34 g / L, primarily hypophosphite and hypophosphite; COD of 60-77.5 g / L; ammonia nitrogen of 3.3-4.7 g / L; total nitrogen of 5.1-6.2 g / L; nickel of 6.8-8.7 g / L; and a specific gravity of 1.10-1.20. Pollutant emission standards are implemented in accordance with the "Electroplating Pollutant Emission Standard" (GB2I900-2008), as shown in Table 1. The maximum nickel emission concentration is 0.5 mg / L, and the maximum phosphorus emission concentration is 1.0 mg / L.

[0057] Table 1. Water pollution emission concentration limits for newly built enterprises

[0058]

[0059]

[0060] In the wastewater treated in this application, the concentration of nickel is 0.2 mg / L and the concentration of phosphorus is 0.6 mg / L, which is in compliance with

[0061] The emission concentration of electroplating pollutants complies with the "Electroplating Pollutant Emission Standard" and is far lower than the maximum emission concentration specified in the standard.

[0062] Assuming that 30 tons of nickel plating waste liquid is processed daily, the conditions of the materials before and after daily processing are shown in Table 2 and Table 3:

[0063] Table 2. Daily consumption of materials for sewage treatment

[0064]

[0065] Table 3. Materials recovered from daily sewage treatment

[0066]

[0067] As can be seen from Tables 2 and 3, processing 30 tons of nickel plating waste liquid daily requires consuming 300 kg of sodium hydroxide, 800 kg of oxygen, 1000 kg of 35% hydrogen peroxide, and evaporating 20,000 kg of water. After treatment, 828 kg of 60% aqueous nickel hydroxide is recovered, and approximately 13,000 kg of crystalline salts are produced. This shows that the treatment method provided in Example 1 can significantly save the use of 35% hydrogen peroxide, reduce the amount of evaporated water, and simultaneously produce a higher content of nickel hydroxide and crystalline salts.

[0068] At the same time, from the perspective of economic benefits, the raw material cost of treating one ton of chemical nickel plating waste liquid using the method provided in Example 1 is shown in Table 4:

[0069] Table 4. Raw material cost per ton of chemical nickel plating wastewater

[0070] Reagent Name Unit Price (Yuan) Consumption Recovery (kg / mJ) Cost (Yuan / H20233399NaOH3.51035PAM6.50.10.65Miscible Salt Treatment 2443886Sulfuric Acid 0.521O21.22732.4Cost 1044.05YuanNi Recovery 190*0.67798Income ---798Yuan

[0071] As can be seen from Table 4, the nickel recovery value is calculated based on 60% of the market price of nickel plates. The price of nickel plates is 190,000 yuan / ton. The material income of treating each ton of chemical nickel plating waste liquid is: income - cost = 798-1044.05 = -246.05, that is, 246.05 yuan / ton needs to be invested at the material level.

[0072] Steam consumption: Using single-effect evaporation equipment, 900kg of steam is required per ton, and the cost of steam is 300 yuan per ton, which is equivalent to 270 yuan. Using double-effect evaporation equipment, 700kg of steam is required per ton, which is equivalent to 210 yuan.

[0073] Electricity cost: Assuming a power of 60kw and an average working time of 16 hours, 960 kWh of electricity per day, 20 kWh per ton, at 0.80 yuan / kWh, the cost is 25.6 yuan / ton.

[0074] Comprehensive operating cost = material input + steam consumption + electricity cost = 246.05 + 270 (based on single-effect evaporation) + 25.6 = 541.65 yuan / ton.

[0075] Using direct The oxidation method requires 400 kg of hydrogen peroxide to treat one ton of the aforementioned chemical nickel plating wastewater. Treating 30 tons of wastewater requires 12 tons of 35% hydrogen peroxide. Other chemical consumables are similar, costing 1,200 yuan per ton. Evaporation using a single-effect evaporator requires 1,400 kg of steam per ton, costing 300 yuan per ton, or 420 yuan. Using a double-effect evaporator, steam consumption is 1,100 kg per ton, costing 330 yuan. The miscellaneous salt treatment fee is 886 yuan. Therefore, the total cost of treating one ton of wastewater is over 2,400 yuan.

[0076] In summary, the nickel plating wastewater treatment system and treatment method provided by this application only costs 541.65 yuan per ton of nickel plating wastewater. This shows that through this treatment system and treatment method, the wastewater can not only meet the emission standards, but also further reduce the treatment cost, recover nickel and solid salts, and realize the resource utilization of nickel, with good economic and ecological benefits.

[0077] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A treatment system for electroless nickel plating waste liquid, characterized in that It includes the following systems connected in sequence: a breaking-network pretreatment system, including a regulating tank for adjusting the pH of nickel-plating waste liquid; an oxidation and breaking-network system, including a redox reactor and a breaking-network reactor connected in sequence, wherein the oxidant of the redox reactor is oxygen, and the oxidant of the breaking-network reactor is hydrogen peroxide; a chemical precipitation system, including a neutralization reaction tank and a sedimentation tank connected in sequence, and the sedimentation tank is equipped with a filtration system; an evaporation and crystallization system, including an evaporation device, a crystallization device and a separation device arranged in sequence.

2. The treatment system for electroless nickel plating waste liquid according to claim 1, wherein The breaking-network reactor has a series-connected two-stage reaction tank, and the oxidation and breaking-network system further includes a circulation storage tank communicated with the reaction tank.

3. The treatment system for electroless nickel plating waste liquid according to claim 1, wherein The filtration system includes a primary filtration device and a fine filtration device, and the primary filtration device is a plate-and-frame filter press or a bag filter.

4. The treatment system for electroless nickel plating waste liquid according to claim 1, wherein The breaking-network pretreatment system further includes a filtration and impurity removal device connected to the regulating tank.

5. A method for treating electroless nickel plating waste liquid, characterized in that, Using the treatment system for electroless nickel-plating waste liquid according to any one of claims 1-4, the treatment method includes: adding an acid solution into the regulating tank to obtain acidic nickel-plating waste liquid; The acidic nickel plating waste liquid is introduced into the redox reactor for primary oxidation, and oxygen is used to oxidize hypophosphite and phosphite in the nickel plating waste liquid into hydrogen phosphate or dihydrogen phosphate; the nickel plating waste liquid after primary oxidation is introduced into the complex-breaking reactor for secondary oxidation, and hydrogen peroxide is used to break the organic complex to form free ； Then, the nickel-plating waste liquid after secondary oxidation is introduced into the neutralization reaction tank, and a neutralization precipitant is added to adjust the pH of the system to 9-10, and the free Converting it into nickel phosphate or nickel hydroxide for precipitation, and filtering to obtain nickel phosphate or nickel hydroxide and secondary wastewater; introducing the secondary wastewater into the evaporation and crystallization system for evaporation and crystallization to obtain solid miscellaneous salts.

6. The method for treating electroless nickel plating waste liquid according to claim 5, wherein In the two-stage oxidation process, the reaction time is 0.7-1.3 h.

7. The treatment method of electroless nickel plating waste liquid according to claim 5, wherein, In the breaking-network pretreatment system, the acid solution input into the regulating tank is sulfuric acid or hydrochloric acid solution, and the pH of the nickel-plating waste liquid after adjustment is 0-6.

8. The method for treating electroless nickel plating waste liquid according to claim 5, wherein The neutralization precipitant added into the neutralization reaction tank is sodium hydroxide solution.

9. The method for treating electroless nickel plating waste liquid according to claim 8, characterized in that, It also includes adding a polymer flocculant into the sedimentation tank.

10. The method for treating electroless nickel plating waste liquid according to claim 9, wherein, The reaction temperature of the first-stage oxidation is 50-90 °C, and the reaction time is 2-5 h.

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