CN111039441B

CN111039441B - Method for treating chemical plating wastewater by generating colloid

Info

Publication number: CN111039441B
Application number: CN201811189000.5A
Authority: CN
Inventors: 余江; 徐紫寅; 李泓睿; 施王军
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2021-03-26
Anticipated expiration: 2038-10-12
Also published as: CN111039441A

Abstract

The invention provides a method for treating chemical plating wastewater by generating colloid, which comprises the steps of adjusting ammonia-nickel ratio, pH value and temperature of the chemical plating wastewater, breaking the complex by oxidation and adding alkaline compound for reaction, thereby generating colloid containing nickel hydroxide and further removing nickel; the method provided by the invention has high nickel removal rate, and the generated colloid has low impurity content after replacement drying, so that the recycling of nickel can be realized; the method provided by the invention is simple to operate, green and environment-friendly, and is suitable for industrial application.

Description

Method for treating chemical plating wastewater by generating colloid

Technical Field

The invention relates to the field of treatment of nickel in chemical plating waste liquid, in particular to a method for removing nickel in chemical plating waste liquid by generating colloid.

Background

Electroless nickel plating is an autocatalytic reaction process that utilizes metal ions in a reducing plating solution to deposit on the surface of a metal part. So that a nickel-phosphorus alloy layer is firmly plated on the surface of the metal part. The components of the plating layer are nickel and phosphorus, and the phosphorus accounts for 5-12%.

Electroless baths generally contain metal salts, reducing agents, complexing agents (complexing agents), buffering agents, pH adjusters, stabilizer lubricants, brighteners, and the like.

Nickel, phosphorus and many organic matters contained in the chemical plating wastewater are substances which are prohibited from being directly discharged by the nation and must be treated. Because the components in the chemical plating waste liquid are complex and the treatment of the waste liquid is difficult, no particularly perfect process for treating the chemical plating waste water exists in China at present. The nickel ions belong to heavy metal ions, and the pollution of the heavy metal ions has great influence on human beings, so the nickel ions causing the heavy metal ions to exceed the standard should be treated firstly.

At present, chemical plating waste water treatment methods are various, such as an electrolytic method, a chemical method, an adsorption method, a biological method and the like. Wherein the chemical precipitation method is simple, convenient and practical, and has obvious removal effect.

The proper precipitator is added into the chemical plating wastewater, so that the precipitator can react with harmful substances in the wastewater under the condition of a certain pH value to generate insoluble matters to be precipitated, thereby removing the pollutants in the wastewater. But the energy consumption is high in the treatment process, a large amount of waste residues are generated, proper treatment or comprehensive utilization is needed, or secondary pollution is easily caused.

Disclosure of Invention

In order to solve the above problems, the present inventors have conducted intensive studies and, as a result, have found that: the method for treating chemical plating waste water by generating colloid firstly adopts oxidation to break the complex, then utilizes alkaline compound to make precipitation reaction, and adopts the processes of precipitation and ageing so as to obtain the colloid containing nickel hydroxide.

The object of the present invention is to provide the following:

a method of treating electroless plating wastewater, the method comprising the steps of:

step 1, breaking the complex of the chemical nickel plating wastewater by using an oxidant;

and 2, adding an alkaline compound into the solution after the complex breaking in the step 1.

Wherein, the oxidant comprises one or more of sodium hypochlorite, hydrogen peroxide and calcium oxide, preferably sodium hypochlorite.

In step 2, the alkaline compound is sodium hydroxide or potassium hydroxide, preferably sodium hydroxide, and more preferably sodium hydroxide solution.

Wherein, the method also comprises a step 3 of aging to obtain colloid.

Wherein the aging time is 2-48 h, preferably 4-24 h.

Wherein, the method also comprises a step 01 before the step 1, adding ammonia compounds or nickel compounds into the chemical nickel plating wastewater to adjust the proportion of the amount of ammonia nitrogen substances to the amount of nickel element substances;

the ammonia compound comprises ammonium chloride, ammonia water and ammonium acetate, and preferably the ammonia water;

the nickel compound comprises nickel sulfate, nickel acetate and nickel chloride, and is preferably nickel sulfate.

In the step 01, the ratio of the amount of the ammonia nitrogen substances to the amount of the nickel elements is (0.2-25) to 1, preferably (1-5): 1.

wherein the method further comprises a step 02 of adjusting the pH value of the electroless plating wastewater with acid and/or alkali II after the step 01 and before the step 1.

Wherein the acid is sulfuric acid or hydrochloric acid, preferably sulfuric acid; the alkali II is sodium hydroxide; the pH value is adjusted to 4-10.5, such as 9.16.

Wherein the chemical plating wastewater is chemical nickel-phosphorus plating wastewater or chemical nickel-boron plating wastewater, and is preferably chemical nickel-phosphorus plating wastewater.

Drawings

FIG. 1 shows SEM scanning electron micrographs of colloids produced in example 1 of the invention;

FIG. 2 shows SEM scanning electron micrographs of the precipitate formed in comparative example 1;

FIG. 3 is a line graph showing the removal rate of nickel at different temperatures in examples 1 to 4;

FIG. 4 is a line graph showing the removal rate of reactive nickel at different temperatures in comparative example 1, example 1 to example 4;

FIG. 5 is a line graph showing the removal rate of nickel at different aging times in example 1 and examples 5 to 7;

FIG. 6 is a line graph showing the nickel removal rate at different reaction times in example 1 and examples 8 to 11;

FIG. 7 is a line graph showing the removal rate of nickel at different ratios of nickel to ammonia in examples 1 and 12 to 15;

fig. 8 is a line graph showing the removal rate of nickel at different pH values in example 1, comparative example 2 to comparative example 7.

Detailed Description

The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.

The present invention is described in detail below.

The chemical plating liquid mainly uses nickel sulfate as main salt, citric acid, lactic acid, malic acid and the like as complexing agents, sodium hypophosphite as a reducing agent, ammonia water and the like as a pH buffering agent, so that the chemical nickel plating wastewater contains nickel salt, phosphate, complexing agents, pH buffering agents and the like. The nickel ions are strongly complexed by the complexing agent, so that the treatment reaches the standard difficultly, and the method is the waste water which is generally recognized to be difficult to treat.

The invention patent of China, CN102329030A, provides a chemical plating wastewater treatment method, which uses (1) strong-base anion exchange resin to treat nickel plating wastewater, so that nickel is complexed and destabilized; (2) adsorbing nickel ions contained in the nickel plating wastewater by using a strong-acid cation exchange resin; (3) adding a strong oxidant into the nickel plating wastewater, and oxidizing hypophosphite, phosphite and a macromolecular organic acid complexing agent contained in the wastewater to form orthophosphate radicals and organic micromolecules; (4) carrying out pulse electrocoagulation on the nickel plating wastewater to ensure that orthophosphate forms ferric phosphate for sedimentation and simultaneously oxidize residual nickel ions to form oxidized scale sediment; (5) and (3) adjusting the wastewater to be alkaline, settling iron ions in the wastewater, and then sequentially adding a deironing agent and a flocculating agent to remove ferrous ions and suspended matters in the wastewater. Although the patent has high nickel removal efficiency, the process operation is complex, and the cost is high due to the use of ion exchange resin.

The inventor takes a chemical precipitation method as a starting point, and generates colloid containing nickel hydroxide by adjusting the amount of ammonia nitrogen substances and the amount ratio of nickel elements, adjusting the pH value of chemical nickel plating wastewater, adjusting the reaction temperature, oxidizing and breaking the complex and adding an alkaline compound.

The inventor surprisingly finds that the nickel in the wastewater is transferred into the colloid, the colloid can be recycled by simple replacement drying, and the content of the nickel in the wastewater is greatly reduced.

According to the invention, the method for treating the electroless plating wastewater to remove the nickel by generating colloid comprises the following steps:

Wherein the content of the first and second substances,

in step 1, the oxidizing agent comprises one or more of sodium hypochlorite, hydrogen peroxide and calcium oxide, preferably sodium hypochlorite.

In one embodiment, the amount of the oxidant added is 10-40 mL, preferably 20mL, per liter of wastewater.

In one embodiment, the time for breaking the complex is 20-120 min, preferably 30 min.

The content of the added sodium hypochlorite (calculated by available chlorine) is more than or equal to 8 percent;

the function of breaking the collaterals by adding an oxidant: in order to improve the quality of the plating layer, the stability of the plating solution and the deposition speed of the metallic nickel, various complexing agents are added into the chemical plating solution. If the waste liquid contains complexing agents such as malic acid, tartaric acid, citric acid and the like, the complexing agents can be complexed with nickel, and the nickel can be removed only by breaking the complexing relationship.

In the present invention, the amount of sodium hypochlorite is not particularly limited as long as it is sufficient to oxidize the nickel-complexing agent.

Step 01Adding an ammonia compound or a nickel compound into the electroless plating wastewater before the step 1;

before the step 1, the method also comprises a step 01 of adding an ammonia compound or a nickel compound into the electroless plating wastewater so as to adjust the ratio of the amount of the substance of ammonia nitrogen to the amount of the substance of nickel element (referred to as ammonia-nickel ratio for short);

The inventor believes that the existence of the ammonia ions can lead the ammonia ions to be complexed with the nickel ions, and the complex is easier to be removed by the sodium hydroxide;

the inventor believes that the concentration of free nickel ions is reduced along with the existence of ammonia water, local supersaturation of a system in the reaction process is avoided, so that relatively proper crystal nucleus generation rate and crystal growth rate in the system are maintained, and the sodium hydroxide is easier to remove after complexing so as to form colloid.

In one embodiment, in the step 01, the ratio of the amount of the substance containing ammonia nitrogen to the amount of the substance containing nickel element is (0.2-25): 1, preferably (1-5): 1.

in the invention, the chemical plating wastewater contains certain ammonium ions and ammonia water, and the quantity of ammonia nitrogen substances in the wastewater (namely ammonia and nitrogen in the ammonium are called ammonia nitrogen) is measured by using a Nashin reagent method;

the inventor finds that the ammonia-nickel ratio is adjusted by adding ammonia compound or nickel compound according to the initial ammonia-nickel ratio, so that the ammonia-nickel ratio is adjusted to reach the optimal ratio, thereby leading the colloid formation and the nickel removal rate to reach the highest.

The method for measuring the concentration of nickel in the chemical nickel plating wastewater is dimethylglyoxime spectrophotometry (GB/T11910-1989).

Step 02After step 01 and before step 1, the pH of the electroless nickel plating wastewater is adjusted with acid and/or alkali II.

In the present invention, the method further comprises a step 02 of adjusting the pH of the electroless plating wastewater with an acid and/or an alkali II after the step 01 is performed and before the step 1 is performed.

The acid is sulfuric acid or hydrochloric acid, preferably sulfuric acid; the alkali II is sodium hydroxide, preferably sodium hydroxide solution; the pH value is adjusted to 4-10.5, such as 9.16.

The acid is preferably 1mol/L sulfuric acid solution;

in the present invention, the reaction temperature is not particularly required when the pH value is adjusted.

The inventor finds that adjusting the ratio of the amount of ammonia nitrogen substances to the amount of nickel elements substances (namely ammonia-nickel ratio) and the pH value of the electroless plating wastewater can generate colloid in the subsequent steps, can stratify, and can improve the removal rate of nickel.

In a preferred embodiment, the basic compound is a 6mol/L sodium hydroxide solution.

In the invention, a sodium hydroxide solution is added as a precipitator to precipitate the complexed ammonia ions and nickel ions and generate colloid containing nickel hydroxide, thereby removing the nickel ions in the wastewater;

in the present invention, the amount of sodium hydroxide solution is such that substantially all of the nickel precipitates to form the nickel hydroxide colloid.

In the invention, before oxidation and complex breaking, the pH value of the chemical plating wastewater is adjusted to be 4-10.5, preferably 5-10, such as 9.16;

in a preferred embodiment, before the oxidation complex breaking, the pH value of the electroless plating wastewater is adjusted to 7-10, and the content of nickel in the colloid generated after the sodium hydroxide solution is added is higher, i.e. the removal rate of nickel is higher, and the removal rate of nickel is more than 99.9% under the pH values of 7.43, 8.03, 8.65, 9.16 and 9.28.

Before the sodium hydroxide solution is added, the ratio of the amount of ammonia nitrogen substances to the amount of nickel elements in the chemical plating wastewater is (0.2-25) to 1, preferably (1-5): 1.

in one embodiment, the reaction temperature when the sodium hydroxide solution is added is 10 to 60 ℃, and more preferably 30 ℃.

In one embodiment, stirring is further performed during the dropping, the stirring speed is 500r/min, and after the dropping is completed, the reaction is continued under stirring, the reaction temperature is 20-70 ℃, preferably 30-60 ℃, such as 30 ℃, and the reaction time is 4-48 hours, preferably 8 hours.

The inventor finds that the control of the reaction temperature after the sodium hydroxide solution is added is more critical, and the colloid can not be formed when the reaction temperature is too low; if the reaction temperature is too high, the colloid becomes more, and the separation of supernatant liquid is disturbed; therefore, the reaction temperature is preferably 30 to 60 ℃, and more preferably 30 ℃.

And 3, performing aging treatment to obtain colloid.

In the invention, the method also comprises a step 3 of carrying out aging treatment to obtain colloid.

The aging time is 2-48 h, preferably 4-24 h.

And (4) aging, wherein the purpose of aging is to separate the colloid from the clear liquid. The water content in the gel was too high to allow separation without aging.

In the invention, after aging, the reaction solution is divided into two layers, namely supernatant and lower layer colloid. After standing and aging, the colloid settled to the bottom.

And taking out the supernatant, and measuring the content of the nickel element in the supernatant and the content of the nickel in the colloid. The concentration of nickel was determined by dimethylglyoxime spectrophotometry (GB/T11910-1989).

By measuring the nickel content of the supernatant and the nickel content in the initial electroless plating wastewater, the removal rate of nickel can be calculated: the removal rate of nickel (nickel content in the initial electroless plating wastewater-nickel content in the supernatant)/nickel content in the initial electroless plating wastewater.

The nickel content of the supernatant liquid treated by the nickel removal method is less than 5ppm, but the supernatant liquid also contains phosphorus impurities. The phosphorus impurities in the supernatant liquid can be purified by a traditional method and used for recycling the supernatant liquid or reaching the discharge standard.

The lower layer colloid can be replaced and dried, namely the colloid is soaked, washed and filtered for many times by using an organic solvent, and the moisture in the colloid is removed as much as possible, so that the agglomeration among particles is avoided in the drying process. The organic solvent is selected from methanol, ethanol, n-butanol, tert-butanol, acetone, hexane, etc. When filtering, the filter paper is a micro-porous filter membrane with the pore diameter of 0.45 micron and the diameter of 50 mm. During displacement drying, the phosphate in the lower layer colloid is dissolved in the water phase and separated out.

After replacement drying, the impurities in the colloid are few, and the nickel in the colloid can be recycled.

The method for treating the chemical plating wastewater by generating the colloid has the following beneficial effects:

(1) the method is simple, easy to realize, mild in operation condition, green and environment-friendly, and suitable for industrial production and application;

(2) according to the invention, the colloid is formed, so that nickel in the chemical plating wastewater is removed, the content of nickel in the solution is very low, and the nickel is separated into the colloid to a great extent;

(3) after the colloid is used for treating the nickel, the upper-layer waste liquid can be further treated and is not influenced by the nickel treatment;

(4) after the generated colloid is replaced and dried, the impurities in the colloid are few, and the nickel can be recycled fully;

(5) the method provided by the invention does not need additional flocculating agent, greatly saves resources and is beneficial to recycling of nickel.

Examples

Preparing simulation liquid of chemical nickel plating wastewater

Adding 20.7g of nickel sulfate hexahydrate into 1L of deionized water under stirring, after dissolving, adding 20.56g of sodium hypophosphite monohydrate, 14.0g of sodium acetate, 30.0g of nickel citrate dihydrate, 45.0g of sodium sulfate, 180.91g of sodium dihydrogen phosphite pentahydrate, 50mg of copper sulfate, 5mg of cerium sulfate and 0.025g of organophosphorus corrosion inhibitor hydroxyethylidene diphosphonic acid (HEDP), and stirring until all the components are dissolved to complete the preparation.

Example 1

Taking 50mL of waste liquid (simulation liquid), adding 1.13mL of ammonia water, and adjusting the ammonia-nickel ratio to be 3.76:1,

then, 0.4mL of 1mol/L sulfuric acid was added to the solution to adjust the pH to 9.16; then adding 1mL of sodium hypochlorite (the content of the added sodium hypochlorite is more than or equal to 8 percent (calculated by the available chlorine)) for oxidizing and breaking the vein for 30min, wherein a magnetic stirrer is required to continuously stir and properly heat in the oxidizing and breaking process, and the oxidizing and breaking temperature is 30 ℃;

controlling the reaction temperature to be 30 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 48 h;

after aging for 12h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant and the lower layer is colloid; and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Examples 2 to 4

The difference from example 1 is that the reaction temperatures controlled under the water bath conditions in examples 2 to 4 were 40 ℃, 50 ℃ and 60 ℃. And finally, measuring the content of the nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Example 5

controlling the reaction temperature to be 30 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 48 h; after aging for 8h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant and the lower layer is colloid; and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Examples 6 to 7

The difference from the example 5 is that the aging time in the examples 6 to 7 is 4h and 2 h; and finally, measuring the content of the nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Example 8

controlling the reaction temperature to be 30 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 24 h; after aging for 12h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant and the lower layer is colloid; and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Examples 9 to 11

The difference from the example 1 lies in the difference of the reaction time after adding the alkali, the reaction time of the examples 9 to 11 are 16h, 8h and 4h respectively; and finally, measuring the content of the nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Example 12 (where the mock solutions formulated in examples 12-15 were formulated alone, with an initial ammonia to nickel ratio of 3.76:1)

Taking 50mL of waste liquid (simulated liquid), adding 0.095mL of ammonia water, adjusting the ammonia-nickel ratio to 1:1,

controlling the reaction temperature to be 30 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 8 h; after aging for 8h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant and the lower layer is colloid; and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Examples 13 to 15

The difference from the example 12 is that the ammonia-nickel ratio is 2:1, 3:1, 5: 1; and finally, measuring the content of the nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Example 16

(the method for generating colloid provided by the invention is used for removing nickel from the actual chemical plating waste water)

Taking 50mL of wastewater (actual waste liquid), adding 75.34mg of nickel sulfate into the wastewater with the initial ammonia-nickel ratio of 3.76:1, adjusting the ammonia-nickel ratio to 1:1,

then, 4mL of 6mol/L sodium hydroxide solution is added into the solution, and the pH value is adjusted to 9.28; then adding 1mL of sodium hypochlorite (the content of the added sodium hypochlorite is more than or equal to 8 percent (calculated by the available chlorine)) for oxidizing and breaking the vein for 30min, wherein a magnetic stirrer is required to continuously stir and properly heat in the oxidizing and breaking process, and the oxidizing and breaking temperature is 30 ℃;

controlling the reaction temperature to be 30 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 8 h; after aging for 8h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant and the lower layer is colloid; and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel. The concentration of nickel ions in the supernatant is 0.2285 mg/L; the removal rate was 0.9994.

Comparative example

Comparative example 1 (different from example 1 in that the reaction temperature was 15 ℃ C.)

controlling the reaction temperature to be 15 ℃ under the condition of water bath, then adding 6mL of alkaline compound sodium hydroxide solution (6mol/L) under the condition of stirring at 500r/min, and reacting for 48 h;

after aging for 12h, the reaction solution is divided into an upper layer and a lower layer, wherein the upper layer is supernatant, and the lower layer is sediment (not colloid); and taking out the supernatant, measuring the content of nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Comparative example 2

then, 2.0mL of 1mol/L sulfuric acid was added to the solution to adjust the pH to 5.31; then adding 1mL of sodium hypochlorite (the content of the added sodium hypochlorite is more than or equal to 8 percent (calculated by the available chlorine)) for oxidizing and breaking the vein for 30min, wherein a magnetic stirrer is required to continuously stir and properly heat in the oxidizing and breaking process, and the oxidizing and breaking temperature is 30 ℃;

Comparative example 3

then, 1.0mL of 1mol/L sulfuric acid was added to the solution to adjust the pH to 5.93;

then adding 1mL of sodium hypochlorite (the content of the added sodium hypochlorite is more than or equal to 8 percent (calculated by the available chlorine)) for oxidizing and breaking the vein for 30min, wherein a magnetic stirrer is required to continuously stir and properly heat in the oxidizing and breaking process, and the oxidizing and breaking temperature is 30 ℃;

Comparative examples 4 to 7

Different from the example 1 in that the pH values are adjusted to be 7.43, 8.03, 8.65 and 10.006 in the comparative examples 4 to 7; and finally, measuring the content of the nickel element in the supernatant and the nickel in the colloid, and calculating the removal rate of the nickel.

Examples of the experiments

SEM scanning Electron microscopy analysis of samples of Experimental example 1

Scanning electron microscope analysis was performed on the lower layer colloid obtained in example 1, as shown in fig. 1; scanning electron microscopy analysis was performed on the precipitate obtained in comparative example 1, as shown in fig. 2;

as can be seen from fig. 1 and 2, the colloid obtained by the present invention has no fixed shape and is not granular; whereas the precipitate obtained in comparative example 1 was spherical and not colloidal.

Experimental example 2 characterization of nickel removal rate was performed for each example and/or comparative example

Determination of nickel content: dimethylglyoxime spectrophotometry (GB/T11910-.

1) The results of nickel content and nickel removal rate in the supernatants of examples 1-4 were summarized and plotted, as shown in fig. 3; wherein the broken line with ■ represents the nickel content in the supernatant, and the broken line with a represents the nickel removal rate.

2) The results of nickel content in the supernatant and the removal rate of nickel of comparative example 1, examples 1 to 4 were summarized and plotted, as shown in fig. 4; wherein the broken line with ■ represents the nickel content in the supernatant, and the broken line with a represents the nickel removal rate.

As can be seen from FIGS. 3 and 4, the removal of nickel ions by the colloid-forming method of the present invention was effective at 30 deg.C, 40 deg.C, 50 deg.C, and 60 deg.C, but the removal of nickel ions was slightly decreased with increasing temperature, and the content of nickel ions in the supernatant was the lowest at 30 deg.C, so that the removal was the best at 30 deg.C, whereas in comparative example 1, no colloid was formed and precipitates were formed at 20 deg.C or lower (15 deg.C).

3) The results of nickel content and nickel removal rate in the supernatant of example 1, example 5 to example 7 were summarized and plotted as shown in fig. 5, wherein the broken line with ■ represents the nickel content in the supernatant and the broken line represents the nickel removal rate;

as can be seen from FIG. 5, the removal effect of nickel ions by the colloid generation method of the present invention is improved with the aging time, and the concentration of nickel ions in the supernatant tends to be stable after aging for 8 hours, i.e., the supernatant has reached a state of complete aging after aging for 8 hours, which is necessary to save time and achieve good effect.

4) The results of nickel content and nickel removal rate in the supernatant of example 1, example 8 to example 11 were summarized and plotted, as shown in fig. 6; wherein the broken line with ■ represents the nickel content in the supernatant, and the broken line with a represents the nickel removal rate.

As can be seen from FIG. 6, the method for generating colloid according to the present invention for removing nickel ions at different reaction times does not show a completely stable state with the increase of the reaction time, but the concentration of nickel ions in the supernatant reaches the lowest level when the reaction is carried out for 8 hours, the content of nickel ions in the supernatant rises with the increase of the reaction time, and for analysis reasons, excessive extension of stirring time after the reaction is completed can cause the crushing of precipitate floc particles, incomplete sedimentation, and influence on the quality of effluent.

5) The results of nickel content and nickel removal rate in the supernatant of example 1, example 12 to example 15 were summarized and plotted, as shown in fig. 7; wherein the broken line with ■ represents the nickel content in the supernatant, and the broken line with a represents the nickel removal rate.

As can be seen from FIG. 7, the presence of the ammonia ions allows the ammonia ions to complex with the nickel ions, which are more easily removed by sodium hydroxide. The inventor believes that the concentration of free nickel ions is reduced along with the existence of ammonia water, the local supersaturation of a system in the reaction process is avoided, so that the relatively proper crystal nucleus generation rate and crystal growth rate in the system are maintained, and the complexed nickel ions are more easily removed by sodium hydroxide to form colloid, which has positive influence on the removal of nickel ions in the supernatant. And the ammonia-nickel ratio is 1: the highest removal rate was obtained at 1.

6) The results of nickel content and nickel removal rate in the supernatant of example 1, comparative example 2 to comparative example 7 were summarized and plotted as shown in fig. 8, in which the broken line with ■ represents the nickel element content in the supernatant and the broken line with a-solidup represents the nickel removal rate.

As can be seen from fig. 8, the concentration of nickel ions in the supernatant is obviously different with the change of pH in acid and base, the supernatant obtained under acidic condition is obviously seen to be a light green transparent liquid without being colorless and transparent, and a large amount of residual nickel ions can be obviously observed, when the pH is adjusted to be neutral, the green is not observed to be colorless and transparent, and after measurement, a sharp drop process of nickel ions can be found, and the removal rate under alkaline condition is not changed much, and when the pH is respectively 7.43, 8.03, 8.65, 9.16, and 10.006, the removal rate of nickel can be up to 99.9% or more.

7) The method for generating colloid is used for nickel removal treatment of the actual plating wastewater. The concentration of nickel ions in the supernatant is 0.2285 mg/L; the removal rate of nickel was 0.9994. Therefore, the colloid generating method provided by the invention has high nickel removal efficiency on actual chemical nickel plating wastewater, and obtains excellent effect.

The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims

1. A method for treating electroless plating wastewater, characterized in that the method comprises the following steps:

step 1, breaking the complex of the chemical plating wastewater by using an oxidant;

step 2, adding a sodium hydroxide solution into the solution after the complex breaking in the step 1;

the reaction temperature when the sodium hydroxide solution is added is 10-60 ℃, stirring is carried out during dripping, the stirring speed is 500r/min, and the reaction is carried out under continuous stirring after the dripping is finished, wherein the reaction temperature is 20-70 ℃;

the method also comprises a step 3 of carrying out aging treatment to obtain colloid;

the aging time is 4-24 h;

the method also comprises a step 01 before the step 1, wherein an ammonia compound or a nickel compound is added into the chemical plating wastewater to adjust the ratio of the amount of ammonia nitrogen to the amount of nickel element to be (0.2-25): 1;

the ammonia compound comprises ammonium chloride, ammonia water and ammonium acetate;

the nickel compound comprises nickel sulfate, nickel acetate and nickel chloride;

the method further comprises, after step 01 and before step 1, a step 02 of treating the mixture with an acid and/or a base

And adjusting the pH value of the chemical plating wastewater to 5-10.

2. The method of claim 1, wherein the oxidizing agent comprises one or more of sodium hypochlorite, hydrogen peroxide.

3. The method of claim 2, wherein the oxidizing agent is sodium hypochlorite;

the ammonia compound is ammonia water;

the nickel compound is nickel sulfate.

4. The method according to claim 1, wherein in the step 01, the ratio of the amount of the substance containing ammonia nitrogen to the amount of the substance containing nickel element is adjusted to (1-5): 1.

5. the method of claim 1, wherein the acid is sulfuric acid; the base is

Is sodium hydroxide.

6. The method of claim 5, wherein the pH is adjusted to 9.16.

7. The method according to any one of claims 1 to 6, wherein the electroless plating wastewater is an electroless nickel-phosphorus plating wastewater or an electroless nickel-boron plating wastewater.

8. The method of claim 7, wherein the electroless plating wastewater is an electroless nickel-phosphorus plating wastewater.