A method for treating high-concentration aged nickel electroless plating solution to meet standards

Abstract

The application discloses a treatment method for high-concentration aged plating solution of electroless nickel plating, and is used for waste liquid treatment in the electroless nickel plating industry. The method comprises the following steps: adjusting the pH of the wastewater to be alkaline, and removing part of free nickel and orthophosphate existing in the wastewater; taking the filtrate after precipitation to carry out micro-nano aeration, mainly driving ammonia nitrogen to escape and removing simple organic matters; then, through three-stage advanced oxidation of ozone catalytic oxidation, chloro-oxidation and electrochemical catalytic oxidation, complex is broken, COD is efficiently degraded, and secondary phosphite and ammonia nitrogen are oxidized, so that free nickel ions are released as much as possible; subsequently, alkali is added to carry out precipitation, and nickel hydroxide is recovered; finally, through evaporation crystallization, orthophosphate and residual other pollutants are removed, and the treated water reaches the standard. The treatment method for high-concentration aged plating solution of electroless nickel plating disclosed by the application separates and removes different pollutants through multi-stage treatment, reduces mutual interference between the pollutants. In the treatment process, physical and chemical methods are mainly used, the reagent input and sludge output are reduced, and the treatment method has high application value and resource utilization potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electroplating industrial wastewater treatment, and particularly relates to a method for treating high-concentration aged nickel electroless plating solution to reach a standard. BACKGROUND

[0002] Chemical nickel plating wastewater has the characteristics of variability and strong complexity, and most of the nickel-containing pollutants in the wastewater exist in the form of complexes, which have strong stability and become the biggest resistance in the nickel removal process. Therefore, the key to nickel removal in chemical nickel plating wastewater is to first perform complex breaking treatment, that is, to convert the complex nickel-containing substances into free nickel ions, so as to reduce the difficulty of nickel removal or recovery in the later stage.

[0003] At present, the complex breaking treatment for chemical nickel plating wastewater mainly uses advanced oxidation technology, and common chemical oxidation processes such as Fenton oxidation. Such methods have high complex breaking efficiency, require a large amount of chemical reagents, have high cost, and can produce a large amount of sludge and introduce other pollution factors. The harmless and resourceful treatment of chemical nickel wastewater needs to be further improved. Electrochemical oxidation and ozone catalytic oxidation, etc. advanced oxidation technologies do not require a large amount of chemical input and do not produce a large amount of sludge. In the complex breaking process, different technologies can be combined according to the actual situation of the wastewater to efficiently and lowly consume achieve the standard discharge of chemical nickel plating wastewater.

[0004] It should be noted that in the aging plating solution of electroless nickel plating, in addition to containing high concentration of complex nickel, it also contains high concentration of COD, ammonia nitrogen and phosphorus. Most studies focus on the removal of complex and COD, and some on the oxidation removal or recovery of phosphorus, etc. Few studies focus on ammonia nitrogen as a pollutant, and there are few studies on the coordinated treatment scheme of nickel and carbon, nitrogen and phosphorus pollutants. Ammonia nitrogen can form stable nickel-ammonia complex under certain conditions, as shown in reaction formula (1). With the increase of pH, nickel-ammonia complex gradually accumulates, and after a certain pH, ammonia nitrogen in nickel-ammonia complex can be replaced by OH- to form nickel hydroxide precipitate, etc. Studies by Li Ming et al. (China Water and Wastewater, 2021, 37(23): 101-105.) have shown that when nickel and ammonia nitrogen exist in wastewater at the same time, the removal of nickel lags behind the degradation of ammonia nitrogen and its removal rate and efficiency are related to the content of ammonia nitrogen in wastewater. Therefore, in the process of breaking the complex, the removal of ammonia nitrogen can release more free nickel, reduce the difficulty of nickel removal in the later stage, and reduce the amount of alkali required for precipitated nickel. The removal of phosphorus in electroless nickel waste liquid mainly adopts the method of oxidation and then precipitation, which usually introduces other metal ions such as iron and calcium, increasing the difficulty of treatment. CN113716659A discloses a method for recovering phosphorus from acid electroless nickel plating waste liquid, which uses electrochemistry and chemical oxidation to convert phosphite in waste liquid into orthophosphate and recover it. However, this method only considers phosphorus as a pollutant, and introduces iron ions into the wastewater system, and the method is time-consuming and energy-consuming. CN117800521A discloses a treatment system and method for electroless nickel plating waste liquid, which realizes the separation of nickel salt and phosphate salt through two-stage complex breaking with oxygen and hydrogen peroxide, chemical precipitation and evaporation crystallization. This method does not focus on COD and ammonia nitrogen, and only ensures the standard treatment of nickel and phosphorus. CN216236433U provides a nickel plating waste liquid treatment device, which mainly treats the waste liquid by phosphorus precipitation, nickel precipitation, ammonia nitrogen stripping, and then biochemical treatment to remove phosphorus and ammonia nitrogen, finally making the water quality meet the standard. This method considers various pollutant indicators comprehensively, but does not separate the pollutants in the wastewater, and the method has the problems of high chemical reagent input and sludge output.

[0005]

[0006] Therefore, there is an urgent need for a multi-mechanism complex breaking treatment scheme that can comprehensively consider the coordinated removal of various pollutants, while minimizing chemical reagent input and sludge output, and reasonably avoiding the mutual influence between different pollutants, minimizing the difficulty of pollutant removal and improving the possibility of resource utilization of different pollutants. SUMMARY

[0007] Aiming at the characteristics of high concentration of chemical nickel plating aging plating solution pollutants, complex interaction, and difficult to break the complex, aiming at the mechanism of the current common treatment technology is single, pollutants can not be separated and removed and produce secondary pollution and other problems, the purpose of the present application is to provide a kind of high concentration of chemical nickel plating aging plating solution of standard processing method, realize the step-by-step efficient removal of nickel and other pollutants, while reducing energy consumption and reducing chemical reagent input and sludge output, comprising the following steps:

[0008] (1) wastewater pretreatment: adjust the pH of the waste liquid to 10-12;

[0009] (2) the precipitate obtained in step (1) is filtered;

[0010] (3) the filtrate obtained in step (2) is kept at a temperature of 30-50℃ and subjected to micro-nano aeration for 0.5-3h;

[0011] (4) a certain amount of ozone catalyst is filled into the wastewater after aeration in step (3), and ozone is introduced for 1-4h, and the catalyst can be reused;

[0012] (5) the pH of the wastewater treated in step (4) is adjusted to neutral, and a chlorinating agent is added to continue the oxidation of COD and residual hypophosphorous acid in the wastewater;

[0013] (6) the wastewater treated in step (5) is subjected to electrochemical treatment;

[0014] (7) NaOH is added to the wastewater treated in step (6) to precipitate nickel ions, and the precipitate obtained is separated by filtration;

[0015] (8) the wastewater treated by electrochemical treatment in step (7) is subjected to evaporation crystallization to obtain standard effluent.

[0016] As a preferred embodiment of the method for treating high-concentration chemical nickel plating aging plating solution according to the present application, step (1) adjusts the pH of the waste liquid with flake caustic soda.

[0017] As a preferred embodiment of the method for treating high-concentration chemical nickel plating aging plating solution according to the present application, the ammonia blown off after micro-nano aeration in step (3) can be recovered by an absorption tower.

[0018] As a preferred embodiment of the method for treating high-concentration chemical nickel plating aging plating solution according to the present application, the ozone catalyst in step (4) is an aluminum-based catalyst, and the volume ratio of the catalyst to the wastewater is 1:1-4.

[0019] As a preferred embodiment of the method for treating high-concentration chemical nickel plating aging plating solution according to the present application, the pH adjustment in step (5) is performed with sulfuric acid or hydrochloric acid.

[0020] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the oxychloride agent in step (5) is sodium hypochlorite solution, and the amount of sodium hypochlorite solution added is calculated according to m(COD):m(NaClO)=1:1-4.

[0021] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the anode of the electrochemical system in step (6) is a multi-valent carbon nanometer electro-catalytic electrode, and the cathode is an iron electrode or a stainless steel electrode.

[0022] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the current density of the electrochemical treatment in step (6) is 5-30 mA / cm 2 .

[0023] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the end point of the alkali precipitation in step (7) is the mutation point after the pH plateau.

[0024] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the precipitate obtained by adding alkali in step (7) is mainly nickel hydroxide with a small amount of nickel phosphate, which has the potential for nickel recovery.

[0025] As a preferred embodiment of the method for treating high-concentration aged plating solution for electroless nickel plating according to the present application, the crystal obtained by evaporation crystallization in step (8) is mainly phosphate.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] Firstly, the present application is suitable for high-concentration aged plating solution for electroless nickel plating with complex pollutants, and has application value for on-site treatment of aged plating solution for electroless nickel plating.

[0028] Secondly, in the present application, a large amount of ammonia nitrogen is first removed by aeration, and carbon, nitrogen and phosphorus pollutants are simultaneously oxidized by three-stage oxidation, so that ammonia nitrogen and COD are efficiently removed in the complex breaking process, part of nickel is obtained by electro-reduction, a large amount of nickel hydroxide is obtained by adding alkali, and finally phosphate and residual carbon and nitrogen pollutants are removed by evaporation crystallization. Different pollutants are separated and removed to obtain standard effluent, and the negative impact of the interaction between different pollutants on the treatment effect is reduced. In this treatment scheme, nitrogen, phosphorus and nickel have the potential for recovery.

[0029] Thirdly, in the present application, a large amount of ammonia nitrogen is first removed in the early stage, and there is no precipitation in the complex breaking process except for a small amount of precipitation generated during the initial pH adjustment process, thereby reducing secondary pollution.

[0030] Fourthly, the present application adopts multi-stage breaking, which is thorough and improves the potential of recovering nickel from the aged plating solution. Meanwhile, the physicochemical method is used in the breaking process, which reduces the cost of reagents.

[0031] Fifthly, the multi-stage breaking and the alkaline precipitation process of the present application do not introduce other metal ions such as calcium and magnesium ions, which can avoid the formation of scale in the evaporation process as much as possible and enhance the stability of system operation. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a process flow diagram of the present application. DETAILED DESCRIPTION

[0033] The present application will be further described in conjunction with examples. It should be pointed out that the following examples are intended to facilitate the understanding of the present application and do not limit the present application in any way.

[0034] Example 1

[0035] The present example provides a standard-reaching treatment method for high-concentration electroless nickel plating aged plating solution. The water quality conditions of the electroless nickel plating aged plating solution adopted are pH 5.06, nickel content 3560 mg / L, COD content 59010 mg / L, ammonia nitrogen content 6590 mg / L, and total phosphorus content 27900 mg / L.

[0036] The standard-reaching treatment method comprises the following steps:

[0037] (1) Take 1 L of electroless nickel plating aged plating solution, and add piece of alkali to adjust the pH to 10.17.

[0038] (2) Air is introduced through a micro-nano aeration plate, the system temperature is maintained at 40℃, the gas-water ratio is 1200:1, and the action time is 2 h.

[0039] (3) The waste liquid after micro-nano aeration is filtered.

[0040] (4) The filtered clear liquid is filled with aluminum-based ozone oxidation catalyst at a volume ratio of 1:1, and ozone is introduced for 2 h.

[0041] (5) Then, the pH of the system is adjusted to about 7, NaClO solution is added at a ratio of m(COD):m(NaClO)=1:2, and stirring reaction is carried out for 2 h.

[0042] (6) Electrochemical oxidation is carried out on the effluent after oxy-chlorination, a multi-valent carbon nanometer electro-catalytic electrode is used as an anode, stainless steel is used as a cathode, the current density is 10 mA / cm 2 , and the action time is 2 h.

[0043] (7) To the wastewater after electrolysis, add sodium hydroxide until the pH no longer changes, stop adding reagent, continue stirring for 2h, and filter.

[0044] (8) Adjust the pH of the filtrate to about neutral, perform low-temperature evaporation, and obtain the effluent.

[0045] Example 2

[0046] The embodiment provides a treatment method for reaching standards of high-concentration aged electroless nickel plating solution, and the water quality conditions of the adopted aged electroless nickel plating solution are as follows: pH 4.96, nickel content 7000 mg / L, COD content 131200 mg / L, ammonia nitrogen content 28750 mg / L, and total phosphorus content 83600 mg / L.

[0047] The treatment method for reaching standards comprises the following steps:

[0048] (1) Take 1L of aged electroless nickel plating solution, and add sodium hydroxide to adjust the pH to 11.28.

[0049] (2) Air is introduced through a micro-nano aeration plate, the system temperature is kept at 40℃, the air-water ratio is 2400:1, and the action time is 2h.

[0050] (3) The wastewater after micro-nano aeration is filtered.

[0051] (4) The filtrate is filled with aluminum-based ozonation catalyst at a volume ratio of 1:1, and ozone is introduced for 2h.

[0052] (5) Then, the pH of the system is adjusted to about 7, NaClO solution is added at a ratio of m(COD):m(NaClO) = 1:2, and stirring reaction is performed for 2h.

[0053] (6) The effluent after oxychlorination is subjected to electrochemical oxidation, a multi-valent carbon nanometer electro-catalytic electrode is used as an anode, stainless steel is used as a cathode, the current density is 30mA / cm 2 , and the action time is 2h.

[0054] (7) Sodium hydroxide is added to the wastewater after electrolysis until the pH no longer changes, the reagent is stopped, stirring reaction is continuously performed for 2h, and filtration is performed.

[0055] (8) The pH of the filtrate is adjusted to about neutral, low-temperature evaporation is performed, and the effluent is obtained.

[0056] Example 3

[0057] The embodiment provides a treatment method for reaching the standard of high-concentration aged electroless nickel plating solution, and the water quality conditions of the adopted aged electroless nickel plating solution are as follows: pH is 5.04, the content of nickel is 3640 mg / L, the content of COD is 75800 mg / L, the content of ammonia nitrogen is 15350 mg / L, and the content of total phosphorus is 42700 mg / L.

[0058] The treatment method for reaching the standard comprises the following steps:

[0059] (1) 1 L of aged electroless nickel plating solution is taken, and flake alkali is added to adjust pH to 11.05.

[0060] (2) Air is introduced through a micro-nano aeration plate, the temperature of the system is kept at 40 DEG C, the air-water ratio is 1800:1, and the action time is 1.5 h.

[0061] (3) The waste liquid after micro-nano aeration is filtered.

[0062] (4) The filtrate is taken, filled with aluminum-based ozone oxidation catalyst at a volume ratio of 1:1, and ozone is introduced for 2 h.

[0063] (5) Then, the pH of the system is adjusted to about 7, NaClO solution is added at a ratio of m (COD) : m (NaClO) = 1:2, and stirring reaction is carried out for 2 h.

[0064] (6) Electrochemical oxidation is carried out on the effluent after oxy-chlorination, a multi-valence carbon nanometer electro-catalytic electrode is used as an anode, stainless steel is used as a cathode, the current density is 15 mA / cm 2 , and the action time is 2 h.

[0065] (7) Flake alkali is added to the wastewater after electrolysis until the pH no longer changes, then the addition of reagent is stopped, stirring reaction is continuously carried out for 2 h, and filtration is carried out.

[0066] (8) The filtrate is taken, the pH is adjusted to about neutral, low-temperature evaporation is carried out, and the effluent is obtained.

[0067] Comparative Example 1

[0068] The only difference between the comparative example and the embodiment 1 is that the treatment method does not comprise a micro-nano aeration stage, and other conditions are the same as those in the embodiment 1.

[0069] Comparative Example 2

[0070] The only difference between the comparative example and the embodiment 1 is that the treatment method does not comprise an electrochemical treatment stage, and other conditions are the same as those in the embodiment 1.

[0071] Comparative Example 3

[0072] The only difference between the comparative example and the embodiment 1 is that the treatment method does not comprise an evaporation stage, and other conditions are the same as those in the embodiment 1.

[0073] The pollutant concentrations of the raw water and the effluent before and after the treatment of Examples 1-3 and Comparative Examples 1-3 are shown in the following table:

[0074] Table 1 Comparison of pollutant concentrations of raw water and effluent in different examples and comparative examples

[0075]

[0076] As shown in the data in Table 1, in Examples 1-3, the treatment process route provided by the present application is used to treat high-concentration aged plating solution of electroless nickel plating in different ranges, and the specific parameters are adjusted according to the pollutant concentration range of the waste liquid, and the treatment effect reaches the Discharge Standard of Electroplating Pollutants (GB 21900-2008). In Comparative Example 1, micro-nano aeration is not performed in the initial stage of treatment, resulting in a high concentration of ammonia nitrogen in the effluent; the treatment process in Comparative Example 2 does not include electrochemical treatment, resulting in poor degradation of COD in the wastewater; and in Comparative Example 3, the wastewater is not evaporated, resulting in that the phosphorus in the wastewater is not effectively removed, and there is still low-concentration nickel in the wastewater. The above data show that the treatment method for high-concentration aged plating solution of electroless nickel plating provided by the present application can effectively separate various pollutants in high-concentration aged plating solution in different treatment stages, and can also cooperatively remove various pollutants to meet the discharge standard.

[0077] The above disclosed examples and comparative examples are only illustrative and are used to explain the relevant features of the method described in the present application, and cannot limit the scope of protection of the present application. Therefore, equivalent changes made in accordance with the scope of the patent application of the present application still fall within the scope of protection covered by the present application.

Claims

1. A method for treating an aged plating solution of high concentration electroless nickel plating to meet the standard, characterized by, It comprises the following steps: (1) wastewater pretreatment: adjust the pH of the aged plating solution of electroless nickel plating to alkaline; (2) filter the precipitate obtained in step (1); (3) under heating conditions, carry out micro-nano aeration on the filtrate obtained in step (2) to remove simple organic matter and drive ammonia gas to escape; In the aeration process of step (3), a micro-nano aeration plate is used, the wastewater temperature is set to 30-50℃ according to the ammonia nitrogen concentration in the wastewater, and the aeration time is set to 0.5-3h; (4) fill a certain amount of ozone catalyst into the wastewater after aeration in step (3), and oxidize with ozone for 1-4h; (5) adjust the pH of the wastewater treated in step (4) to neutral, add a chloro-oxidizing agent, and continue to oxidize the ammonia nitrogen, hypophosphite and COD in the wastewater; (6) electrochemically treat the wastewater treated in step (5) to mainly oxidize refractory organic matter and remove residual ammonia nitrogen; (7) add NaOH to the wastewater treated in step (6) to precipitate nickel ions, and filter and separate the obtained precipitate; (8) evaporate and crystallize the wastewater treated in step (7) by electrochemical treatment to obtain standard effluent.

2. The method according to claim 1, wherein the method is characterized by, The nickel content of the aged plating solution of electroless nickel plating in step (1) is more than 2000 mg / L, the COD content is more than 50000 mg / L, the ammonia nitrogen content is more than 5000 mg / L, and the phosphorus content is more than 20000 mg / L.

3. The method according to claim 1, wherein the method is characterized by: In step (1), the pH of the waste solution is adjusted to 10-12 with sheet alkali.

4. The method for treating aged plating solution of high concentration electroless nickel plating according to claim 1, characterized in that, The ozone catalyst in step (4) is an aluminum-based catalyst, and the volume ratio of the catalyst to wastewater is 1:1-4. The catalyst can be reused.

5. The method of claim 1, wherein the method is characterized by: The pH adjustment in step (5) is carried out with sulfuric acid or hydrochloric acid.

6. The method of claim 1, wherein the method is characterized by: The chloro-oxidizing agent in step (5) is sodium hypochlorite solution, and the amount of addition is calculated according to m(COD):m(NaClO)=1:1-4.

7. The method according to claim 1, wherein the method is characterized by: The anode of the electrochemical system in step (6) is a multi-valent carbon nanometer electro-catalytic electrode, and the cathode is an iron electrode or a stainless steel electrode.

8. The method for treating aged plating solution of high concentration electroless nickel plating according to claim 1, characterized in that, The current density range for the electrochemical treatment described in step (6) is 5-30 mA / cm 2 .

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