A method for treating electroless nickel plating waste liquid

Abstract

The application discloses a treatment method of electroless nickel plating waste liquid, which comprises the following steps: waste liquid pretreatment, waste liquid dephosphorization, waste liquid deironing, waste liquid denickelization, nickel-iron purification and biochemical treatment, and the whole process steps are reasonably designed, the resource treatment of nickel and phosphorus in the waste liquid is realized under the premise of not introducing new pollution factors. By adding an oxidizing agent, high ferric acid is used to remove phosphorus ions, then by adjusting the pH value of the waste liquid, most of the iron ions are precipitated, then modified biochar is used to remove most of the nickel ions, then sulfide precipitant and PAM diluent are added to remove the remaining nickel ions and iron ions, finally, hydrolysis acidification and MBR process are used to quickly remove the remaining complex organic matters, the whole process flow is short, the amount of reagent used is small, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a treatment method of chemical nickel plating waste liquid. BACKGROUND

[0002] Chemical plating is a mature surface treatment technology. Compared with electroplating technology, chemical plating is used more widely, and the formed plating layer is uniform, has small pinholes and good weldability. Chemical nickel plating is one of the important plating species, which is widely used in mechanical, chemical, mining, medical and other industries. The plating layer is a nickel-phosphorus alloy. The mainstream nickel plating solution mainly includes nickel salt, phosphorus reducing agent, organic complex, etc. The nickel salt is the main metal component of the plating layer. The phosphorus reducing agent reduces nickel to metallic nickel, and part of the phosphorus also enters the plating layer to improve the chemical properties of the plating layer. The complex mainly improves the stability of the plating solution.

[0003] The chemical nickel plating solution also extends the use time by supplementing various components, but when the accumulation of phosphite, organic matter and the like exceeds a certain limit, the solution cannot be used and needs to be disposed of. At this time, the nickel content in the waste liquid is 2-8 g / L, the phosphorus content is 40-120 g / L, and the organic matter content is 50-200 g / L. The state has strict limits on the discharge concentration of nickel, phosphorus, ammonium and chemical oxygen demand (COD) in wastewater, which must be strictly treated before discharge. From the perspective of resource utilization, nickel is a scarce non-ferrous metal, and phosphorus is the main component of fertilizer. The chemical nickel plating waste liquid with high nickel and phosphorus content undoubtedly has high comprehensive utilization value. However, due to the very complex nature of the chemical nickel plating waste liquid, there are still problems such as high treatment difficulty, high treatment cost, and introduction of new pollution factors by using a large amount of treatment reagents. SUMMARY

[0004] In order to solve the above problems, the present application provides a treatment method of chemical nickel plating waste liquid, comprising the following steps:

[0005] Waste liquid pretreatment: adjust the pH value of the waste liquid to 1.5-2.5;

[0006] Waste liquid phosphorus removal: add an oxidizing agent to the waste liquid with a pH value of 1.5-2.5, and react for 2-5 h;

[0007] Waste liquid iron removal: adjust the pH value of the waste liquid after phosphorus removal to 5.5-6.5, so that the iron ions in the waste liquid form a ferric hydroxide precipitate, and a first filtrate is obtained by filtration to reduce the amount of subsequent nickel-containing sludge;

[0008] Waste liquid nickel removal: add 10-50 g of modified biochar to every 100 ml of the filtrate, and after constant temperature shaking treatment, a second filtrate is obtained by filtration;

[0009] Nickel-iron purification: a sulfide precipitant and PAM concentrated solution are added to the second filtrate, so that the nickel and iron in the solution are all converted into sulfide precipitates, and a third filtrate is obtained by filtration;

[0010] Biochemical treatment: the third filtrate is treated by hydrolysis and acidification combined with MBR process to quickly remove the remaining complex organic matter;

[0011] The modified biochar is prepared according to the following steps: the dry cow dung is crushed and sieved, then pyrolyzed under anoxic conditions to obtain cow dung biochar, the cow dung biochar is impregnated with 0.10 mol / L KMnO4 solution for 1-2 h, then washed with deionized water for 2-4 times, and dried at 100-120℃ for 3-5 h to obtain the modified biochar.

[0012] Further, in the preparation step of the modified biochar, the pyrolysis temperature is 400-600℃, and the pyrolysis time is 3-5 h. Controlling the pyrolysis temperature and time can significantly improve the pore structure, specific surface area and surface functional groups of the biochar. As the temperature rises and the time increases, the pore channels of the cow dung biochar collapse and the pore size becomes smaller, forming a large number of micropores.

[0013] Further, in the preparation step of the modified biochar, the ratio of cow dung biochar to KMnO4 solution is 1g:(3-6)ml.

[0014] Further, in the waste liquid pretreatment step, 40%-50% sulfuric acid and 20%-30% sodium hydroxide are used to adjust the pH value of the waste liquid, which can improve the subsequent phosphorus oxidation effect.

[0015] Further, in the waste liquid phosphorus removal step, the oxidizing agent is high ferric salt.

[0016] Further, the oxidizing agent is sodium ferrate or potassium ferrate.

[0017] Further, in the waste liquid phosphorus removal step, the amount of oxidizing agent added is 1.1-1.4 times the total phosphorus molar number, which can oxidize all phosphorus-containing groups to orthophosphate, and also oxidize a small amount of organic complexes to improve the subsequent nickel precipitation effect. The generated orthophosphate reacts with ferric ions to form iron phosphate precipitate, achieving phosphorus recovery.

[0018] Further, in the waste liquid phosphorus removal step, the oxidizing agent is added in batches within 1-2 h, and stirring is performed while adding, with a stirring speed of 400-700 rpm.

[0019] Further, in the nickel-iron purification step, the sulfide precipitant is any one of sodium sulfide, sodium hydrosulfide and hydrogen sulfide, and the amount of sulfide precipitant added is 2-3 times the theoretical precipitation molar amount, and the reaction time is 1-3 h, further removing nickel and iron in the waste liquid.

[0020] Further, in the nickel-iron purification step, the PAM concentrated solution has a concentration of 10% to 20%, the adding amount is 0.5‰ to 1.5‰ of the total mass of the solution, and the reaction time is 0.5 to 1.5 hours. Through flocculation precipitation, standing and filtration, the nickel and iron in the waste liquid can be further removed.

[0021] The beneficial effects are:

[0022] 1. The whole process is reasonably designed, and the nickel and phosphorus in the waste liquid are recycled under the premise of not introducing new pollution factors. By adding an oxidizing agent, ferric salt, to remove phosphorus ions, then adjusting the pH value of the waste liquid to make most of the iron ions precipitate, then using modified biochar to remove most of the nickel ions, then adding sulfide precipitants and PAM diluent to remove the remaining nickel ions and iron ions, and finally using hydrolysis acidification combined with MBR process to quickly remove the remaining complex organic matter, the whole process is short, the amount of reagent used is small, and the cost is low.

[0023] 2. In the waste liquid nickel removal step, the modified biochar is modified by 0.10 to 0.14 mol / L KMnO4. The KMnO4 in this concentration range can significantly improve the adsorption capacity of the biochar for complex nickel ions. The adsorption capacity of the modified biochar for nickel ions reaches the maximum. This is because KMnO4 has strong oxidizing properties and can undergo redox reactions with biochar, increasing the number of oxygen-containing functional groups on the surface of biochar. When KMnO4 is reduced to insoluble MnO2 and adsorbed on the surface of biochar, it has strong adsorption capacity for nickel ions. If the concentration of KMnO4 is too high, the number of micropores in the biochar will decrease, the specific surface area will decrease, and the adsorption capacity of the biochar for nickel ions will decrease.

[0024] 3. In the waste liquid phosphorus removal step, the oxidizing agent used is ferric salt. Ferric salt is a strong oxidizing agent with a high oxidation-reduction potential of 2.2V, higher than ozone (2.076V). Although it is lower than hydroxyl radical (2.85V), the commonly used Fenton oxidation method has high requirements for conditions, and the effect of ferrous iron catalytic hydrogen peroxide to produce hydroxyl radical is unstable. Hydrogen peroxide is easily catalyzed and decomposed by various substances, resulting in poor actual oxidation effect. The strong oxidizing property of ferric salt due to the high valence state of iron is stable, and the oxidation process is simple. The strong oxidizing property of ferric salt can quickly convert two kinds of ions into orthophosphate, and then react with the trivalent iron produced by the reduction of the oxidizing agent to produce iron phosphate, realizing the recovery of phosphoric acid.

[0025] 4. In the nickel-iron purification step, the dual action of sulfide precipitants and PAM diluent can remove the residual metals in the electroless nickel plating waste liquid, greatly improving the biodegradability of the waste liquid. Biodegradability refers to the ease of degradation of pollutants in wastewater by microorganisms. DETAILED DESCRIPTION

[0026] The application will be described in further detail below with reference to specific examples, so that those skilled in the art can more clearly understand the application.

[0027] The following examples are used to illustrate the application but not to limit the scope of the application. Based on the specific examples in the application, all other examples obtained by those skilled in the art without creative labor are within the scope of the application.

[0028] In the embodiments of the application, all raw material components are commercially available products well known to those skilled in the art, unless otherwise specified. In the embodiments of the application, the technical means used are conventional means well known to those skilled in the art, unless otherwise specified.

[0029] Source of raw materials:

[0030] Dry cow dung, purchased from Shijiazhuang Baifeng Biotechnology Co., Ltd.;

[0031] KMnO4, sodium hydroxide and concentrated sulfuric acid, all purchased from Guangdong Qiming Chemical Technology Co., Ltd.;

[0032] Sodium ferrite, purchased from Jiangsu Bosite Chemical Technology Co., Ltd.;

[0033] Potassium ferrite, purchased from Shandong Chuangyi Chemical Co., Ltd.;

[0034] Sodium sulfide, purchased from Shandong Puli Chemical Co., Ltd.;

[0035] Sodium hydrosulfide, purchased from Jiujiang Hengtong Chemical Co., Ltd.;

[0036] Hydrogen sulfide, purchased from Chengdu Yuanhejiye Chemical Co., Ltd.;

[0037] PAM, purchased from Henan Sendeng Environmental Protection Technology Co., Ltd.;

[0038] The remaining reagents are all conventional commercially available.

[0039] Example 1

[0040] Take a factory electroless nickel plating waste liquid 3.5L, wherein the nickel content is 3.7g / L, total phosphorus (TP) is 69g / L, COD content is 52g / L, and pH is 3.2. The waste liquid is transferred to a 5L beaker, 40% sulfuric acid and 20% sodium hydroxide are added to adjust the solution pH to 1.5, and 1377.2g of sodium ferrate is weighed according to the molar number TP:sodium ferrate = 1:1.1, 200g of sodium ferrate is added every 10 minutes, the stirring speed is 400rpm, the reaction is 5h, the iron phosphate is recovered by filtration, and 1147g of solid is obtained by drying at 50℃ for 24h, the iron content in the solid is 36.41%, the phosphorus content is 19.08%, and the phosphorus recovery rate reaches 90.7%.

[0041] The filtrate is adjusted to pH 5.5 with 20% sodium hydroxide solution to make the iron ions in the waste liquid form iron hydroxide precipitate, and the first filtrate is obtained by filtration; 10-50g of modified biochar is added to each 100ml of the above filtrate, and the second filtrate is obtained by filtration after constant temperature oscillation treatment;

[0042] According to the content of residual nickel and iron in the second filtrate, 34.5g of sodium sulfide (the amount of sulfide precipitant added is 2 times the theoretical precipitation molar amount) is added, the pH is controlled at 5.5, and the stirring reaction is 1h, then 0.5‰ mass concentration of 10% PAM solution is added, and the stirring reaction is continued for 0.5h, so that the nickel and iron in the solution are completely converted into sulfide precipitate, and the third filtrate is obtained by standing and filtering. The COD content in the third filtrate is 36mg / L, the nickel content is 0.27mg / L, the iron content is 0.12mg / L, and the phosphorus content is 0.07mg / L;

[0043] The third filtrate is treated by hydrolysis and acidification combined with MBR process to quickly remove the remaining complex organic matter;

[0044] The modified biochar is prepared according to the following steps: 1kg of dry cow dung is crushed and sieved, then pyrolyzed under anaerobic conditions for 3h, the pyrolysis temperature is 400℃, and the cow dung biochar is obtained. The cow dung biochar is immersed in 0.10mol / L KMnO4 solution for 1h, the material liquid ratio of cow dung biochar to KMnO4 solution is 1g:3ml, then washed with deionized water for 2 times, and dried at 100℃ for 3h to obtain the modified biochar.

[0045] Example two

[0046] Take a factory electroless nickel plating waste liquid 3.5L, wherein the nickel content is 3.7g / L, total phosphorus (TP) 69g / L, COD content 52g / L, pH is 3.2. The waste liquid is transferred to a 5L beaker, 45% sulfuric acid and 25% sodium hydroxide are added to adjust the solution pH to 2.0, according to the molar number TP: sodium ferrate = 1:1.2, 1502.4g sodium ferrate is weighed, 200g sodium ferrate is added every 10 minutes, the stirring speed is 550rpm, the reaction is 3.5h, the iron phosphate is recovered by filtration, and 1163g solid is obtained by drying at 50℃ for 24h, the iron content in the solid is 36.78%, the phosphorus content is 20.02%, and the phosphorus recovery rate reaches 96.4%.

[0047] The filtrate is adjusted to pH 6.0 with 25% sodium hydroxide to make the iron ions in the waste liquid form iron hydroxide precipitate, and the first filtrate is obtained by filtration; 10-50g of modified biochar is added to every 100ml of the above filtrate, and the second filtrate is obtained by filtration after constant temperature oscillation treatment;

[0048] According to the content of residual nickel and iron in the second filtrate, 40.0g of sodium hydrosulfide (the amount of sulfide precipitant added is 2.5 times the theoretical precipitation molar amount) is added, the pH is controlled at 6.0, and the stirring reaction is carried out for 2h, then 1.0‰ mass concentration 15% PAM solution is added, and the stirring reaction is continued for 1h, so that the nickel and iron in the solution are completely converted into sulfide precipitate, and the third filtrate is obtained by standing and filtering. The COD content in the third filtrate is 22mg / L, the nickel content is 0.13mg / L, the iron content is 0.06mg / L, and the phosphorus content is 0.03mg / L;

[0049] The third filtrate is treated by hydrolysis and acidification combined with MBR process to quickly remove the remaining complex organic matter;

[0050] The modified biochar is prepared according to the following steps: 1kg of dry cow dung is crushed and sieved, then pyrolyzed under anaerobic conditions for 4h, and the pyrolysis temperature is 500℃, to obtain cow dung biochar. The cow dung biochar is immersed in 0.12mol / L KMnO4 solution for 1.5h, the cow dung biochar to KMnO4 solution ratio is 1g:4.5ml, then washed with deionized water for 2 times, and dried at 100℃ for 4h to obtain the modified biochar.

[0051] Example three

[0052] Take a factory electroless nickel plating waste liquid 3.5L, wherein the nickel content is 3.7g / L, total phosphorus (TP) 69g / L, COD content 52g / L, pH is 3.2. The waste liquid is transferred to a 5L beaker, 50% sulfuric acid and 30% sodium hydroxide are added to adjust the solution pH to 2.5, according to the molar number TP: potassium ferrite = 1:1.4, 1627.6g of sodium ferrite is weighed, 200g of potassium ferrite is added every 10 minutes, the stirring speed is 700rpm, the reaction is 5h, the iron phosphate is recovered by filtration, and 1178g of solid is obtained by drying at 50℃ for 24h, the iron content in the solid is 37.35%, the phosphorus content is 19.57%, and the phosphorus recovery rate reaches 95.46%.

[0053] The filtrate is adjusted to pH 6.5 with 30% sodium hydroxide solution, so that the iron ions in the waste liquid form iron hydroxide precipitate, and the first filtrate is obtained by filtration; 10-50g of modified biochar is added to each 100ml of the above filtrate, and the second filtrate is obtained by filtration after constant temperature oscillation treatment;

[0054] According to the content of residual nickel and iron in the second filtrate, 45.0g of hydrogen sulfide (the amount of sulfide precipitant added is 3 times the theoretical precipitation molar amount) is added, the pH is controlled at 6.5, and the stirring reaction is carried out for 3h, then 1.5‰ of PAM solution with a mass concentration of 20% is added, and the stirring reaction is continued for 1.5h, so that the nickel and iron in the solution are completely converted into sulfide precipitate, and the third filtrate is obtained by standing and filtering; the COD content in the third filtrate is 30mg / L, the nickel content is 0.22mg / L, the iron content is 0.09mg / L, and the phosphorus content is 0.13mg / L;

[0055] The third filtrate is treated by hydrolysis and acidification combined with MBR process to quickly remove the remaining complex organic matter;

[0056] The modified biochar is prepared according to the following steps: 1kg of dry cow dung is crushed and sieved, then pyrolyzed under anaerobic conditions for 5h, the pyrolysis temperature is 600℃, and the cow dung biochar is obtained; the cow dung biochar is immersed in 0.14mol / L KMnO4 solution for 2h, the material liquid ratio of cow dung biochar to KMnO4 solution is 1g:6ml, then washed with deionized water for 4 times, and dried at 100℃ for 5h to obtain the modified biochar.

[0057] Comparative Example One

[0058] Different from Example Two, the modified biochar of the present comparative example is prepared from dry chicken manure, and after the same operation steps as Example Two, the COD content in the third filtrate is 46mg / L, the nickel content is 0.37mg / L, the iron content is 0.26mg / L, and the phosphorus content is 0.43mg / L.

[0059] Comparative Example Two

[0060] Different from Example 2, the modified biochar of the present comparative example is prepared from dry corn stalks. After the same operation steps as in Example 2, the COD content in the third filtrate is 71 mg / L, the nickel content is 0.76 mg / L, the iron content is 0.42 mg / L, and the phosphorus content is 0.51 mg / L.

[0061] The above merely illustrates the embodiments of the present application, and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. A method for treating a waste solution of electroless nickel plating, characterized by, The method comprises the following steps: waste liquid pretreatment: adjusting the pH value of the waste liquid to 1.5-2.5; waste liquid phosphorus removal: adding a high ferric salt to the waste liquid with a pH value of 1.5-2.5, and reacting for 2-5 h; waste liquid iron removal: adjusting the pH value of the waste liquid after phosphorus removal to 5.5-6.5, so that the iron ions in the waste liquid form a ferric hydroxide precipitate, and a first filtrate is obtained by filtration; waste liquid nickel removal: adding 10-50 g of modified biochar to every 100 ml of the first filtrate, and after constant temperature oscillation treatment, a second filtrate is obtained by filtration; nickel and iron purification: adding a sulfide precipitant and a PAM solution to the second filtrate, so that the nickel and iron in the solution are all converted into sulfide precipitates, and a third filtrate is obtained by filtration; biochemical treatment: using a hydrolysis acidification combined with MBR process to quickly remove the remaining complex organic matter from the third filtrate; The modified biochar is prepared according to the following steps: after the dry cow dung is crushed and sieved, it is pyrolyzed under anoxic conditions to obtain cow dung biochar, wherein the pyrolysis temperature is 400-600 DEG C, and the pyrolysis time is 3-5 h; then 0.10-0.14 mol / L KMnO4 solution is added to the cow dung biochar at a solid-liquid ratio of 1 g:(3-6) ml, and the impregnation time is 1-2 h; then the modified biochar is washed with deionized water for 2-4 times, and dried at 100-120 DEG C for 3-5 h.

2. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, In the waste liquid pretreatment step, 40%-50% sulfuric acid and 20%-30% sodium hydroxide are used to adjust the pH value of the waste liquid.

3. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, The high ferric salt is sodium ferrate or potassium ferrate.

4. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, In the waste liquid phosphorus removal step, the amount of oxidant added is 1.1-1.4 times the total phosphorus molar number.

5. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, In the waste liquid phosphorus removal step, the oxidant is added in batches within 1-2 h, and stirring is performed while adding, with a stirring speed of 400-700 rpm.

6. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, In the nickel and iron purification step, the sulfide precipitant is any one of sodium sulfide, sodium hydrosulfide and hydrogen sulfide, and the amount of the sulfide precipitant added is 2-3 times the theoretical precipitate molar amount, and the reaction time is 1-3 h.

7. The treatment method of the electroless nickel plating waste solution according to claim 1, characterized by, In the nickel and iron purification step, the PAM solution has a concentration of 10%-20%, and the amount added is 0.5‰-1.5‰ of the total mass of the solution, and the reaction time is 0.5-1.5 h.