Treatment method for zero discharge of electroplating wastewater

Abstract

The invention provides an electroplating wastewater zero-discharge treatment method which comprises the following steps: S1, electroplating wastewater is subjected to physicochemical treatment, so that metal ions form precipitates, and organic matters are subjected to oxygenolysis; s2, removing slag through a fine filtration system; s3, performing reverse osmosis treatment in a membrane treatment device, and recovering clear liquid; s4, concentrated liquor obtained after reverse osmosis treatment enters an electrodialysis system to be concentrated; and S5, carrying out evaporation curing treatment on the concentrated solution to realize zero discharge of wastewater. According to the zero-discharge treatment method for the electroplating wastewater, the discharged soil, filter residues and solid waste are all in a solid state, the treated clear liquid and condensate water can be recycled, and zero discharge of the electroplating oil removal wastewater is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a treatment method for zero discharge of electroplating wastewater. Background Art

[0002] In the electroplating process, in order to enhance the adhesion between the electroplated part and the metal coating, the surface of the electroplated part needs to be kept clean. During the manufacturing, transportation, and storage of electroplated parts, external dirt such as grease, rust products of oxides, hydroxides, and dust is easily attached to their surfaces. If these dirt are not removed, the electroplated parts will not obtain a good coating, thus affecting the quality of the electroplated parts. Therefore, before electroplating, it is necessary to use a degreasing solution to clean them. Since the degreasing solution generally contains components of organic solvents, such as surfactants, corrosion inhibitors, and various organic additives, plus the oil and wax substances that fall off from the electroplated parts during the treatment process, the wastewater contains a large amount of oil, the COD concentration is very high, the pH value is mostly strongly alkaline, and it contains a large amount of inorganic salt components. If directly discharged, it will cause serious harm to the environment.

[0003] At present, the general electroplating degreasing wastewater is usually preliminarily treated to reduce harmful substances to the dischargeable level and then discharged into the environment. The treated electroplating wastewater cannot be recycled, resulting in waste of resources. Moreover, with the increasingly strict national environmental protection policies, regions with fragile ecology and dense population require "zero discharge", and the current technology can no longer meet the requirements. Summary of the Invention

[0004] The purpose of the present invention is to fill the gaps in the above fields and provide a treatment method for zero discharge of electroplating wastewater that can realize the recycling of wastewater and all discharge substances are solids.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A treatment method for zero discharge of electroplating wastewater, comprising the following steps:

[0007] S1: The electroplating wastewater is subjected to physical and chemical treatment to form precipitates of metal ions and oxidize and decompose organic substances;

[0008] S2: Remove slag through a fine filtration system to remove large-particle-size soil and sediment particles;

[0009] S3: Enter a membrane treatment system for reverse osmosis treatment, the clear liquid is recovered for reuse, and the salt ions in the wastewater enter the concentrated liquid;

[0010] S4: The concentrated liquid after reverse osmosis treatment enters an electrodialysis system, and under the action of an electric field, the concentrated liquid is further concentrated to separate water;

[0011] S5: The concentrated liquid after the concentration treatment of the electrodialysis system is subjected to evaporation and solidification treatment to achieve zero discharge of wastewater.

[0012] As a preferred embodiment of the present invention, the method for forming a precipitate of metal ions in the S1 step is as follows: the electroplating wastewater first enters the demulsification reaction tank, the pH is adjusted to 6-8 by adding alkali, then it enters the alkalization tank to adjust the pH to 8-11 by adding alkali, then it enters the oxidation tank to add an oxidant to oxidize and break the complex, and then it enters the flocculation reaction tank to add a PAC flocculant to form a precipitate of metal ions.

[0013] Further, the residence time of the electroplating wastewater in the flocculation reaction tank in the S1 step is 3 to 5 hours.

[0014] As another preferred embodiment of the present invention, the method for oxidizing and decomposing organic matter in the S1 step is: the electroplating wastewater enters the aeration reaction tank to oxidize and decompose the organic matter.

[0015] As another preferred embodiment of the present invention, the slag removal method in the S2 step is as follows: first, the mud and water are separated by a sludge removal machine, and after the sludge is discharged, the clear liquid enters the fine filter for filtration and slag removal, which improves the slag removal efficiency and reduces the probability of clogging of the fine filter.

[0016] As another preferred embodiment of the present invention, before the S3 step, the clear liquid after slag removal by the fine filtration system needs to be adjusted to pH 6-8.

[0017] As another preferred embodiment of the present invention, the conductivity of the clear liquid after the reverse osmosis treatment by the membrane treatment system in the S3 step is ≤1 us / cm, and the total organic carbon TOC is ≤0.1 mg / L, meeting the standard for recycling.

[0018] As another preferred embodiment of the present invention, the salt concentration of the concentrated liquid after the concentration treatment of the electrodialysis system in the S4 step is ≥15%.

[0019] As another preferred embodiment of the present invention, the clear liquid after the concentration treatment of the electrodialysis system in the S4 step re-enters the membrane treatment system for reverse osmosis treatment to further purify the water in the clear liquid.

[0020] As another preferred embodiment of the present invention, the evaporation and solidification treatment in the S5 step is as follows: first, the salts are precipitated by a low-temperature evaporation system, the condensed water is recycled, and the salts are then formed into solid waste through a solidification system.

[0021] Advantages of the present invention:

[0022] Compared with the prior art, the treatment method for zero discharge of electroplating wastewater provided by the present invention sequentially performs physical and chemical treatment, fine filtration to remove slag, desalination and impurity removal, and evaporation and solidification on the wastewater. The discharged soil, residue, and solid waste are all in solid form, and the clarified liquid after treatment by the membrane treatment system and the condensed water after treatment by the low-temperature evaporation system can be recycled, achieving "zero discharge" of electroplating degreasing wastewater, which is of great significance for environmental protection and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of the treatment process of the present invention;

[0024] Figure 2 is a schematic structural diagram of an embodiment of the present invention, wherein: 1 - wastewater fractionation and diversion equipment; 2 - demulsification reaction tank; 3 - alkalization tank; 4 - oxidation tank; 5 - flocculation reaction tank; 6 - aeration reaction tank; 7 - sludge removal machine; 8 - fine filter; 9 - neutralization tank; 10 - membrane treatment system; 11 - electrodialysis system; 12 - low-temperature evaporation system; 13 - solidification system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to better understand the present invention, the following further describes the specific embodiments of the present invention in detail with reference to the accompanying drawings.

[0026] See the attached Figure 1-2 , a treatment method for zero discharge of electroplating wastewater provided by the present invention includes:

[0027] S1: The electroplating wastewater undergoes physical and chemical treatment to form precipitates of metal ions and oxidize and decompose organic substances. The electroplating degreasing wastewater collected by the wastewater fractionation and diversion system 1 enters the demulsification reaction tank 2 through a pipeline, and alkali is added to adjust the pH to 6 - 8 for demulsification; then it enters the alkalization tank 3, where alkali is added to adjust the pH to 8 - 11, an oxidant is added to the oxidation tank 4 for oxidative breaking of complexing, and then PAC flocculant is added to the flocculation reaction tank 5, with a residence time of 5 hours, to form precipitates of metal ions; then it enters the aeration reaction tank 6 to oxidize and decompose the organic substances in the wastewater;

[0028] S2: Remove slag through the fine filtration system. The wastewater after physical and chemical treatment enters the sludge removal machine 7 for separation of mud and water, the soil particles are discharged, the clarified liquid enters the fine filter 8 for filtration to remove slag, and then the pH is adjusted to 6 - 8 through the neutralization tank 9;

[0029] S3: The clarified liquid after neutralization treatment enters the membrane treatment system 10 for reverse osmosis treatment. The conductivity of the clarified liquid ≤ 1 us / cm, and the total organic carbon TOC ≤ 0.1 mg / L. The clarified liquid is recycled for reuse, and the salt ions in the wastewater enter the concentrated liquid;

[0030] S4: The concentrated solution after reverse osmosis treatment enters the electrodialysis system 11. Under the action of an electric field, the concentrated solution is further concentrated to a salt content concentration ≥ 15%, and the clear solution enters the membrane treatment system 10 for further purification;

[0031] S5: The concentrated solution concentrated by the electrodialysis system 11 enters the low-temperature evaporation system 12 to separate inorganic salts and condensed water. The condensed water can be recycled, and the inorganic salts enter the solidification system 13 to form solid waste, realizing zero discharge of wastewater.

[0032] In the treatment method for zero discharge of electroplating wastewater provided by the present invention, the soil treated by the sludge remover 7, the residue treated by the fine filter 8, and the soil, filter residue, and solid waste treated by the solidification system 13 are all solids. The clear solution treated by the membrane treatment system 10 and the condensed water treated by the low-temperature evaporation system 12 can be recycled, realizing "zero discharge" of electroplating degreasing wastewater.

[0033] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A treatment method for zero discharge of electroplating wastewater, characterized in that, It includes the following steps: S1: The electroplating wastewater is subjected to physicochemical treatment to form metal ion precipitates and oxidize and decompose organic substances; S2: Remove residues through a fine filtration system; S3: Enter the membrane treatment system for reverse osmosis treatment, and recycle the clear liquid; S4: The concentrated liquid after reverse osmosis treatment enters the electrodialysis system for concentration; S5: The concentrated liquid after concentration is subjected to evaporation and solidification treatment to achieve zero discharge of wastewater.

2. The treatment method for zero discharge of electroplating wastewater according to claim 1, wherein, The method for forming metal ion precipitates in step S1 is as follows: The electroplating wastewater first enters the demulsification reaction tank, the pH is adjusted to 6-8 by adding alkali, then enters the alkalization tank to adjust the pH to 8-11 by adding alkali, then enters the oxidation tank to add an oxidant to oxidize and break the complex, and then enters the flocculation reaction tank to add PAC flocculant to form metal ion precipitates.

3. The treatment method for zero discharge of electroplating wastewater according to claim 2, characterized in that, In step S1, the residence time of the electroplating wastewater in the flocculation reaction tank is 3 to 5 hours.

4. The treatment method for zero discharge of electroplating wastewater according to claim 1, characterized in that, The method for oxidizing and decomposing organic substances in step S1 is as follows: The electroplating wastewater enters the aeration reaction tank to oxidize and decompose organic substances.

5. The treatment method for zero discharge of electroplating wastewater according to claim 1, characterized in that, The method for removing residues in step S2 is as follows: First, perform mud-water separation through a sludge removal machine, and after the sludge is discharged, the clear liquid enters the fine filter for filtration and residue removal.

6. The treatment method for zero discharge of electroplating wastewater according to claim 1, characterized in that, Before step S3, the pH of the clear liquid after residue removal by the fine filtration system needs to be adjusted to 6-8.

7. The zero-discharge treatment process for electroplating nickel wastewater according to claim 1, characterized in that, In step S3, the conductivity of the clear liquid after reverse osmosis treatment by the membrane treatment system is ≤1 us / cm, and the total organic carbon TOC is ≤0.1 mg / L.

8. The zero-discharge treatment process for electroplating nickel wastewater according to claim 1, wherein, In step S4, the salt concentration of the concentrated liquid after concentration treatment by the electrodialysis system is ≥15%.

9. The treatment method for zero discharge of electroplating wastewater according to claim 1, characterized in that, In step S4, the clear liquid after concentration treatment by the electrodialysis system enters the membrane treatment system again for reverse osmosis treatment.

10. The treatment method for zero discharge of electroplating wastewater according to claim 1, characterized in that, In step S5, the evaporation and solidification treatment is to first precipitate salts through a low-temperature evaporation system, recycle the condensed water, and then form solid waste through the solidification system.

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