CN100396627C - A clean production method for treating electroplating wastewater by nanofiltration - Google Patents

Abstract

A clean production method for treating electroplating wastewater by a nanofiltration method, belonging to the technical field of electroplating wastewater treatment. The invention comprises pretreatment and nanofiltration concentration processes, the retention rate of divalent ions is more than 99%, feed liquid can be concentrated to 17000mg/L, and the concentrated solution is reused in an electroplating bath. In the concentration process, the concentration of divalent ions in 87.5% of the permeate is less than 1.0mg/L, the concentration of divalent ions in 9.62% of the permeate is less than 2.3mg/L, the two parts of permeate can be directly reused in a rinsing tank, and the concentration of divalent ions in 2.88% of the permeate is less than 15mg/L and can be mixed with feed liquid for feeding. The invention truly realizes the complete reuse of the electroplating wastewater and realizes the clean production process with zero discharge; the novel nanofiltration membrane is adopted to treat the electroplating rinse water, the higher membrane flux is still kept even under the higher concentration ratio, and the method has the characteristics of simple flow, small investment, low operation cost and reasonable material distribution, and is particularly suitable for the industrial application of nickel electroplating.

Description

A clean production method for treating electroplating wastewater by nanofiltration

technical field

The invention discloses a clean production method for treating electroplating wastewater by nanofiltration, belonging to the technical field of electroplating wastewater treatment. The present invention adopts Type nanofiltration membrane, one-step treatment of concentrated electroplating wastewater. The permeate is completely reused in the rinsing tank, and the concentrated solution is directly reused in the electroplating tank, which completely recovers water resources and heavy metal resources, and truly achieves a clean production process with zero emissions in the process.

Background technique

A large amount of nickel-containing waste water will be produced during the rinsing process of the electroplating nickel industry. Ni ²⁺ can complex with various inorganic and organic substances to form water-soluble salts, which are harmful to the human body and have obvious toxic effects on aquatic organisms. At the same time, if the nickel in these nickel-containing wastewater can be effectively enriched, the rinse solution may be recycled and reused. China's comprehensive sewage discharge standard (GB8978-2005) stipulates that the maximum allowable discharge concentration of Ni ²⁺ is 1.0mg/L. At present, the main methods for processing and recovering heavy metals are: chemical reduction precipitation, adsorption, micro-electrolysis, evaporation and ion exchange [[1]Hatfield TL, Kleven TL, Pierce D T. Electrochemical remediation of metal-bearing waste waters.Part 1 : Copperremoval form simulated drainage waters [J]. Journal of Applied Electrochemical, 1996, 26: 567-574. [2] Tu Zhenmi, Li Deyu, Li Ning, Pan Li, Zhang Jingshuang. Status and progress of electroless nickel plating wastewater treatment [J] .Electroplating and Environmental Protection, 2003, 23(2): 1-5. [3] Tang Nana, Ma Shaojian. Recovery of cobalt and nickel from waste materials [J]. Nonferrous Mining and Metallurgy, 2005, 21(7): 113-114 .], there are the following problems in these traditional techniques: (1) large doses of chemical substances are required; (2) the possibility of directly recycling heavy metal ions is eliminated; (3) the sludge to be treated contains a large amount of organic matter and Heavy metals, forming new solid pollutants, are also quite difficult to deal with.

In recent years, the use of membrane separation technology to treat electroplating wastewater has been extensively studied, especially nanofiltration (NF) technology, which has received great attention since its inception and has been widely used [[4]Petersen R J. Composite reverse osmosis and nanofiltration membrane [J]. J MembrSci, 1993, 83: 81. [5] Rautenbach R, Groschl A. Separation potential of nanofiltration membranes [J]. Desalination, 1990, 77: 73-84.]. Nanofiltration membranes have the following notable characteristics in application: (1) physical retention or retention sieving effect, which can effectively retain smaller dissolved components; (2) chargeability [[6] Wang X L, Tsuru T, Nakao S, et al. Electrolytetransport through nanofiltration membranes by the Space-charge model and the comparison with Teorell-Meyer-Sievers model [J]. J Membr Sci, 1995, 103: 117-133.], that is, selective interception, for unit price The interception rate of ions is low (40%～80%)[[7] Ding Huanru, Du Fangzheng, Wang Lihai. Application status and prospect of membrane technology in power plant water treatment in China [J]. Journal of Shanghai Electric Power Institute, 2002, 18( 3): 271.], the rejection rate of divalent and multivalent ions is relatively high, so it can retain most of the heavy metal ions, realize the enrichment of heavy metal ions, and can replace multiple steps such as desalination and concentration in traditional engineering , so it is more economical; (3) Compared with reverse osmosis, the operating pressure is low and the permeation flow rate is large[[8]Xu Y Z, Lebrun R E.Comparison of nanofiltration properties of twomembranes using electrolyte and non-electrolyte solutes[J] . Desalination, 1999, 122:95-106.]. (4) Compared with the evaporation method or other treatment methods with "phase" change, the membrane method has no "phase" change in the treatment process of electroplating wastewater, so the energy consumption is low; (5) The area occupied by the nanofiltration treatment equipment Small, compact equipment, easy self-control, continuous operation.

At present, the method of using membrane separation method to treat electroplating production wastewater, such as the Chinese patent application number 03157655.9 "Membrane Separation Method for Zero Discharge of Electroplating Wastewater Treatment", discloses a method for electroplating wastewater treatment, which uses pretreated electroplating wastewater After the first stage of nanofiltration, the concentrated water obtained after nanofiltration is further concentrated through the second stage of brackish water reverse osmosis membrane, and finally the concentrated water is separated and concentrated through the third stage of seawater reverse osmosis membrane, and an example of electroplating nickel wastewater treatment is provided. The whole system operates at normal temperature and concentrates the electroplating nickel wastewater by about 100 times. This technology overcomes the shortcomings of traditional methods, but for industrial applications, the operation is complicated, the production cost is high, and the process is cumbersome.

Therefore, the present invention uses a one-step nanofiltration membrane method to treat concentrated electroplating wastewater, which has the advantages of simple process, small investment, low production cost, complete recovery of water and heavy metal ion resources, and a clean production process with zero discharge in the process.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for treating concentrated electroplating wastewater using a new one-step nanofiltration method, which can not only save water resources in the electroplating industry, but also make full use of heavy metals to eliminate pollution and pollution to the environment. Reduce the production cost of the electroplating industry and realize the clean production of the electroplating industry.

The present invention is based on the application of nanofiltration technology, and its theoretical basis is: (1) physical interception or interception sieving effect can effectively intercept smaller dissolved components; The interception rate of ions is low (40%-80%), and the interception rate of divalent and multivalent ions is relatively high (above 90%), so most of the metal ions can be retained and the enrichment of metal ions can be realized.

Technical scheme of the present invention, this method is:

1) Pretreatment of electroplating wastewater

First use filters (including bag filter, fiber filter, microfiltration, sand filter, etc.) to filter out anode slime and debris particles impurities; then use activated carbon to adsorb and filter organic matter in wastewater; then use ultrafiltration membrane to filter out wastewater of suspended matter.

2) Concentration and separation by nanofiltration membrane

-S型纳滤膜进行浓缩分离，操作压力为1.4MPa～2.6MPa(最佳为1.8MPa～2.2MPa)，对于二价离子的浓度小于或等于30mg/L的料液，达到浓缩600倍，至二价离子的浓度为17700mg/L，浓缩液回到电镀槽使用；对二价离子的截留率大于99％，87.5％质量的透过液中二价离子浓度小于1.0mg/L，9.62％质量的透过液中二价离子浓度小于2.3mg/L，透过液可以作为漂洗水回用，2.88％质量的透过液中二价离子浓度小于15mg/L，与料液混合进入纳滤处理。所处理的电镀废水为电镀金属离子价键为2或3的废水，如电镀Ni²⁺、Zn²⁺、Cu²⁺或Cr³⁺的废水。The pretreated wastewater is treated with TFC with a molecular weight cut-off of 80Da to 120Da

- S-type nanofiltration membrane for concentration and separation, the operating pressure is 1.4MPa ~ 2.6MPa (optimally 1.8MPa ~ 2.2MPa), for the feed liquid with the concentration of divalent ions less than or equal to 30mg/L, it can be concentrated 600 times, When the concentration of divalent ions is 17700mg/L, the concentrated solution is returned to the electroplating tank for use; the rejection rate of divalent ions is greater than 99%, and the concentration of divalent ions in the permeate of 87.5% of the mass is less than 1.0mg/L, 9.62% The concentration of divalent ions in the quality permeate is less than 2.3mg/L, and the permeate can be reused as rinse water, and the concentration of divalent ions in the 2.88% quality permeate is less than 15mg/L, which is mixed with the feed liquid and enters nanofiltration deal with. The electroplating wastewater to be treated is wastewater with electroplating metal ion valence bond of 2 or 3, such as electroplating wastewater of Ni ²⁺ , Zn ²⁺ , Cu ²⁺ or Cr ³⁺ .

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. Since the relative molecular weight of the nanofiltration membrane reaches 120Da, it can basically intercept all organic matter, and it has been verified that it can intercept more than 99% of divalent ions; during the operation, there is no need to add chemical substances, and there is no phase change; The permeate can be completely reused without causing secondary pollution; the process is simple, the investment is small, the equipment occupies a small area, and the operating cost is low.

2. The system adopts the method of nanofiltration, which can concentrate electroplating nickel wastewater by 600 times, and the concentrated solution is directly returned to the electroplating tank, and the permeate is reused as rinsing water, which provides a recycling of waste chemicals for the electroplating industry and recycling of production wastewater The clean production process used reduces the pollution of production to the environment and realizes zero discharge of electroplating wastewater.

3. After being treated by the method of the present invention, the total reuse rate of water in the electroplating nickel wastewater is greater than 99%, and the recovery rate of heavy metal resources is greater than 99%.

Description of drawings

Figure 1 Process flow diagram.

Figure 2 Schematic diagram of the process device.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Figure 1 shows the process flow of the embodiment of the present invention, as shown in Figure 1, including pretreatment, nanofiltration membrane separation, concentrate and permeate reuse.

Example 1 Treatment of electroplating Ni ²⁺ wastewater

1. Pretreatment

First, the electroplating nickel wastewater with a Ni ²⁺ concentration of 30mg/L is passed through a 5μm bag filter to filter out large suspended impurities such as anode slime and debris in the wastewater; then the activated carbon adsorption method is used to absorb most of the organic matter in the wastewater , to reduce the pollution of organic matter to the membrane module; and then through the ultrafiltration device, the wastewater is further separated at 0.1MPa to remove the fine suspended matter in the wastewater, thereby protecting the membrane element and prolonging its service life.

2. Nanofiltration membrane separation

The pretreated wastewater enters the nanofiltration membrane concentration device under the pressure of 2.0MPa by the booster pump and multi-stage pump for separation. The nanofiltration membrane is TFC produced by KOCH Company of the United States. -S-type nanofiltration membrane, the pore size is nanoscale, and its relative molecular mass cut-off range is 80 (Dalton), the surface of the nanofiltration membrane is positively charged, and has different Donnan potentials for ions with different charges and different valence states. The unique surface characteristics and pore size of the filter membrane determine its unique performance. It has a lower rejection rate for monovalent ions, but a higher rejection rate for divalent ions, that is, it has selective retention for metal ions of different valence states. The nanofiltration membrane used in this system has a low rejection rate of sodium chloride at a pressure of 2.0 MPa, only about 20%, while the rejection rate of divalent ions can be as high as 99%. Most of the sodium chloride passes through the membrane element, while Ni ²⁺ is trapped and concentrated, so the concentrated solution can be directly returned to the electroplating tank for production. Heavy metal salts can also be recovered by evaporation, or heavy metals can be recovered by electrolysis. Compared with reverse osmosis membrane, nanofiltration membrane has lower pressure, higher flux and less investment. In order to reduce the pollution of the membrane surface and prolong the service life of the membrane, the device is cleaned regularly, and the flux recovery is in good condition. After passing through the nanofiltration system, the wastewater is concentrated about 600 times, the Ni ²⁺ concentration reaches 17700mg/L, the rejection rate of Ni ²⁺ is greater than 99%, and the Ni ²⁺ concentration in the permeate of 87.5% of the mass is less than 1.0mg/L , the Ni ²⁺ concentration in the 9.62% mass permeate is less than 2.3 mg/L, and these two parts of the permeate can all be reused as electroplating rinse water. The Ni ²⁺ concentration in the 2.88% mass permeate is less than 15 mg/L, which can be mixed with the feed liquid.

The method in the embodiment of the present invention has certain reference. For example, it is directly applicable to electroplating wastewater of other divalent or trivalent metal ions, such as electroplating wastewater of Zn ²⁺ , Cu ²⁺ or Cr ³⁺ .

Embodiment 2 processes electroplating Cr ³⁺ waste water

1. Pretreatment

First, the concentration of Cr ³⁺ is 70 mg/L of electroplating chromium wastewater for pretreatment, and the operation is the same as in Example 1.

2. Nanofiltration membrane separation

-S型纳滤膜进行纳滤浓缩，经过处理后，浓缩液中Cr³⁺浓度达到18000mg/L，对Cr³⁺的截留率大于99％，90％以上的透过液可以回用于电镀漂洗水，其余的透过液中的Cr³⁺浓度在5～15mg/L，可与料液混合处理。The pretreated wastewater enters the nanofiltration membrane concentration device under the pressure of 1.6MPa by the booster pump and the multi-stage pump for separation, and is separated by TFC

-S-type nanofiltration membrane for nanofiltration concentration, after treatment, the concentration of Cr ³⁺ in the concentrated solution reaches 18000mg/L, the rejection rate of Cr ³⁺ is greater than 99%, and more than 90% of the permeate can be reused for electroplating The concentration of Cr ³⁺ in the rinse water and the rest of the permeate is 5-15 mg/L, which can be mixed with the feed liquid for treatment.

Claims (4)

1. A clean production method for treating electroplating wastewater by nanofiltration, characterized in that: 1) Pretreatment of electroplating wastewater First use a filter to filter out anode slime and debris particles; then use activated carbon to adsorb and filter organic matter in the wastewater; then use an ultrafiltration membrane to filter out suspended solids in the wastewater; 2) Concentration and separation by nanofiltration membrane Concentrate and separate the pretreated wastewater with a nanofiltration membrane with a molecular weight cut-off of 80Da to 120Da. The operating pressure is 1.4MPa to 2.6MPa. For the feed liquid with a concentration of divalent ions less than or equal to 30mg/L, it can be concentrated to 600 times, until the concentration of divalent ions is 17700mg/L, the concentrated solution is returned to the electroplating tank for use; the rejection rate of divalent ions is greater than 99%, and the concentration of divalent ions in the permeate of 87.5% of the mass is less than 1.0mg/L. The concentration of divalent ions in the permeate of 9.62% mass is less than 2.3mg/L, and the permeate is reused as rinse water, and the concentration of divalent ions in the permeate of 2.88% mass is less than 15mg/L, mixed with the feed liquid into the sodium filter. 2. The method according to claim 1, characterized in that the operating pressure of nanofiltration membrane concentration and separation is 1.8MPa～2.2MPa. 3. The method according to claim 1, characterized in that the treated electroplating wastewater is wastewater whose valence state of electroplating metal ions is 2 or 3. 4. The method according to claim 3, characterized in that the treated electroplating wastewater is electroplating Ni ²⁺ , Zn ²⁺ , Cu ²⁺ or Cr ³⁺ wastewater.

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