Electroplating wastewater zero discharge process based on low-pressure anti-pollution reverse osmosis membrane

Abstract

The invention discloses an electroplating wastewater zero discharge process based on a low-pressure anti-pollution reverse osmosis membrane, and relates to the field of electroplating wastewater discharge, and the electroplating wastewater zero discharge process comprises the following steps: S1, preparing a treatment discharge device; s2, magnetic field pretreatment; s3, performing treatment based on a reverse osmosis membrane; s4, performing electrochemical induction and membrane distillation synergistic concentration crystallization treatment. According to the electroplating wastewater zero-discharge process based on the low-pressure anti-pollution reverse osmosis membrane, no chemical agent is added in the whole process, the secondary pollution risk caused by agent use is eliminated from the source, such as potential hazards of heavy metal residues in chemically precipitated sludge and agent residues to soil and water, and the electroplating wastewater zero-discharge process has the advantages of environmental protection and environmental protection. The zero discharge of electroplating wastewater is realized in a real sense, the surrounding water environment is protected, the ecological problems of water eutrophication, heavy metal pollution and the like caused by wastewater discharge are avoided, and the ecological balance and biological diversity are favorably maintained.

Description

Technical Field

[0001] The present invention relates to the field of electroplating wastewater discharge, and particularly relates to a zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane. Background Art

[0002] Electroplating wastewater refers to various wastewater generated during the electroplating production process. Electroplating is a process that uses an electrochemical method to deposit a layer of metal or alloy on the surface of metal or other materials, and this process will generate various types of wastewater.

[0003] When discharging electroplating wastewater, multiple devices are required, which makes the overall floor area of the devices relatively large. At the same time, a large amount of energy is required during the discharge process. During the discharge process, chemical reagents also need to be added, which will cause secondary pollution and the generation of subsequent sludge. For pollution and sludge, more costs and labor are required to treat them.

[0004] Therefore, it is necessary to propose a zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane to solve the above problems. Summary of the Invention

[0005] The main object of the present invention is to provide a zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane, which can effectively solve the problems in the background art.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane, comprising the following operating steps:

[0008] S1: Prepare the devices for treatment and discharge, including at least one multi-media gradient magnetic field pretreatment device, an adjustment tank, a lift pump, an electrochemical induced crystallization device, a reverse osmosis membrane, a membrane distillation device, and a crystallizer;

[0009] S2: Magnetic field pretreatment. The electroplating wastewater first enters the adjustment tank for equalization of water quality and quantity. The adjusted electroplating wastewater enters the multi-media gradient magnetic field pretreatment device through the lift pump. In the multi-media gradient magnetic field pretreatment device, the electroplating wastewater slowly passes through the media filling bed filled with multi-media at a flow rate of 0.5 - 1.5 m / s. At the inlet, the magnetic field intensity in the strong magnetic field region is 0.5 - 1.0 T, and the metal particles with stronger magnetism are quickly adsorbed in the strong magnetic field region. As the electroplating wastewater flows towards the outlet, the magnetic field intensity gradually decreases to 0.1 - 0.3 T, and the weakly magnetic metal particles and metal ions that react with the surface of the media filling bed are adsorbed and intercepted;

[0010] S3: Treatment is carried out based on the reverse osmosis membrane. The pretreated electroplating wastewater enters the reverse osmosis membrane. Under the low-pressure drive of 0.5 - 1.5 MPa, water molecules pass through the reverse osmosis membrane, while metal ions, soluble salts, and a small amount of residual organic matter are intercepted. The operating pressure of the reverse osmosis membrane is adjusted in real time according to the influent water quality and membrane flux, and automatic control is achieved through pressure sensors, flow sensors, and intelligent control systems. The produced concentrated water enters the electrochemical induction and membrane distillation collaborative concentration and crystallization treatment;

[0011] S4: Electrochemical induction and membrane distillation collaborative concentration and crystallization treatment. The concentrated water enters the electrochemical induction crystallization device. Inside the device, appropriate electrode materials and current densities are selected according to the types of main metal ions in the electroplating wastewater. For nickel-containing wastewater, a nickel cathode is used, and the current density is set at 100 - 300 A / m 2 , and the energization time is 1 - 5 hours. After electrochemical crystallization, the metal ion concentration in the concentrated water is significantly reduced. The remaining concentrated water enters the membrane distillation device. In the membrane distillation device, the temperature on the hot water side is controlled at 60 - 80 °C, and the temperature on the cold water side is maintained at 10 - 20 °C. The generated vapor pressure difference drives water vapor to pass through the hydrophobic membrane pores. The flux of the membrane distillation process is 1 - 5 kg / (m 2 ·h), which is used to further concentrate the concentrated water to a nearly saturated state. The membrane distillation condensate is collected and reused in other water-using links of the electroplating production line and supplemented to the reverse osmosis inlet end. The concentrated liquid after membrane distillation concentration enters the crystallizer. In the crystallizer, the temperature is adjusted to 5 - 10 °C, and the stirring speed is adjusted to 50 - 200 rpm until the remaining salts crystallize out. The crystalline salts are purified and refined through centrifugal separation, washing, and drying. The obtained high-purity metal salts can be re-injected into the electroplating bath as electroplating raw materials.

[0012] Preferably, in the above S1, the multi-media gradient magnetic field pretreatment device is composed of a packed bed layer filled with media with various different magnetic properties and surface modifications. Under the action of the magnetic field generator, a gradient magnetic field with a gradually changing intensity from the inlet to the outlet is formed.

[0013] Preferably, in the above S3, the reverse osmosis membrane uses polyethersulfone as the main polymer matrix material, introduces nano-scale titanium dioxide particles as photocatalytic additives, and dopes zwitterionic polymers, including but not limited to sulfobetaine-type zwitterionic polymers. A thermosensitive polymer segment is introduced into the membrane material. The structure design of the reverse osmosis membrane is as follows: the membrane sheet adopts an asymmetric membrane sheet design. The upper layer of the membrane sheet is an ultra-thin separation layer with a thickness of 0.1 - 0.2 microns, and the lower layer is a porous support layer with a thickness of 100 - 200 microns, which is prepared using materials such as polyethersulfone;

[0014] The flow channel inside the membrane module adopts a spiral flow channel design with a width of 1 - 2 mm and a depth of 0.5 - 1 mm;

[0015] The membrane module uses fluororubber sealing rings. The connection between the membrane sheets is carried out by ultrasonic welding. The inlet and outlet interfaces of the reverse osmosis membrane adopt a standardized design, and pressure monitoring and flow monitoring devices are provided at the interfaces for real-time monitoring of the operating parameters of the membrane module.

[0016] Compared with the prior art, the present invention provides a zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane, which has the following beneficial effects:

[0017] 1. The zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane does not add chemical agents throughout the process, eliminating the risk of secondary pollution caused by the use of agents from the source, such as the potential hazards of heavy metal residues and agent residues in chemical precipitation sludge to soil and water bodies, achieving true zero-discharge of electroplating wastewater, protecting the surrounding water environment, and avoiding ecological problems such as water eutrophication and heavy metal pollution caused by wastewater discharge, which helps to maintain ecological balance and biodiversity.

[0018] 2. The zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane utilizes magnetic force and physicochemical adsorption, with low energy consumption, only 10%-20% of the energy consumption of traditional chemical precipitation pretreatment, and 30%-50% energy saving compared with traditional high-pressure reverse osmosis membrane systems. At the same time, due to the improved anti-pollution performance of the membrane, the cleaning cycle is extended, and the energy consumption and chemical agent consumption during the cleaning process are also significantly reduced. Through the synergistic concentration and crystallization process of electrochemical induction and membrane distillation, by optimizing the electrode materials and process parameters, and the efficient heat utilization of membrane distillation, it can save 40%-60% energy compared with traditional evaporation crystallization processes, effectively reducing the operating costs and energy consumption of enterprises.

[0019] 3. The zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane has a high water resource recovery rate. Through reverse osmosis and condensate recovery, the reuse rate of electroplating wastewater can reach more than 95%, greatly reducing the enterprise's dependence on fresh water resources and alleviating the pressure of water resource shortage. The metal resource recovery has high purity and good quality. Electrochemical induction crystallization can selectively recover the main metal ions in the wastewater to form high-purity metal crystals. Combined with membrane distillation and crystallization purification processes, the purity of the recovered metal salts can reach more than 95%, which can be directly used as electroplating raw materials or other industrial raw materials, improving the added value of resources and the economic benefits of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1:

[0023] As Figure 1 shown, a zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane includes the following operating steps:

[0024] S1: Prepare the devices for treatment and discharge, including at least one multi-media gradient magnetic field pretreatment device, an adjustment tank, a lift pump, an electrochemically induced crystallization device, a reverse osmosis membrane, a membrane distillation device, and a crystallizer;

[0025] The multi-media gradient magnetic field pretreatment device is composed of a media packed bed filled with various media with different magnetic properties and surface modifications. Under the action of a magnetic field generator, a gradient magnetic field with a gradually changing intensity from the inlet to the outlet is formed. Magnetic and weakly magnetic metal particles in the wastewater are adsorbed and captured by the media packed beds in different regions in turn according to their magnetic strength under the action of magnetic field force, realizing preliminary separation. The surface of the media packed bed is treated with special functionalization and has specific functional groups, including amino groups and carboxyl groups, which are used to complex and ion-exchange with heavy metal ions in electroplating wastewater, fixing the heavy metal ions on the surface of the media packed bed to further reduce the metal ion concentration in the wastewater;

[0026] S2: Magnetic field pretreatment. The electroplating wastewater first enters the adjustment tank for equalization of water quality and quantity. The adjusted electroplating wastewater enters the multi-media gradient magnetic field pretreatment device through a lift pump. In the multi-media gradient magnetic field pretreatment device, the electroplating wastewater slowly passes through the media packed bed filled with multi-media at a flow rate of 0.5 - 1.5 m / s. At the inlet, the magnetic field intensity in the strong magnetic field region is 0.5 - 1.0 T, and metal particles with stronger magnetism are rapidly adsorbed in the strong magnetic field region. As the electroplating wastewater flows towards the outlet, the magnetic field intensity gradually decreases to 0.1 - 0.3 T, and weakly magnetic metal particles and metal ions reacting with the surface of the media packed bed are adsorbed and intercepted. The media is regularly backwashed and regenerated, and the backwash water flows back to the adjustment tank for re-treatment. After magnetic field pretreatment, the removal rate of metal ions in the wastewater can reach 30% - 50%, and the turbidity is reduced by more than 80%, providing good influent water quality for subsequent reverse osmosis membrane treatment;

[0027] S3: Treatment based on the reverse osmosis membrane. The pretreated electroplating wastewater enters the reverse osmosis membrane. Under the low-pressure drive of 0.5 - 1.5 MPa, water molecules pass through the reverse osmosis membrane, while metal ions, soluble salts, and a small amount of residual organic matter are intercepted. The operating pressure of the reverse osmosis membrane is adjusted in real time according to the influent water quality and membrane flux, and automatic control is achieved through a pressure sensor, a flow sensor, and an intelligent control system. The produced concentrated water enters the electrochemically induced and membrane distillation collaborative concentration and crystallization treatment;

[0028] The reverse osmosis membrane uses polyethersulfone as the main polymer matrix material, introduces nanoscale titanium dioxide particles as photocatalytic additives, and dopes zwitterionic polymers, including but not limited to sulfobetaine-type zwitterionic polymers. A thermosensitive polymer segment is introduced into the membrane material. The structure of the reverse osmosis membrane is designed as follows: the membrane sheet adopts an asymmetric membrane sheet design. The upper layer of the membrane sheet is an ultra-thin separation layer with a thickness of 0.1 - 0.2 microns, and the lower layer is a porous support layer with a thickness of 100 - 200 microns, which is prepared using materials such as polyethersulfone;

[0029] The flow channels inside the membrane module adopt a spiral flow channel design, with a width of 1 - 2 mm and a depth of 0.5 - 1 mm;

[0030] The membrane module uses fluororubber sealing rings. The connection between membrane sheets is carried out by ultrasonic welding. The water inlet and outlet interfaces of the reverse osmosis membrane adopt a standardized design, and pressure monitoring and flow monitoring devices are provided at the interfaces to monitor the operating parameters of the membrane module in real time;

[0031] S4: Electrochemical induction and membrane distillation are used for co - concentration and crystallization treatment. The concentrated water enters the electrochemical induction crystallization device. Inside the device, appropriate electrode materials and current densities are selected according to the types of main metal ions in the electroplating wastewater. For nickel - containing wastewater, a nickel cathode is used, and the current density is set at 100 - 300 A / m 2 , and the power - on time is 1 - 5 hours. After electrochemical crystallization, the metal ion concentration in the concentrated water is significantly reduced. The remaining concentrated water enters the membrane distillation device. In the membrane distillation device, the temperature on the hot water side is controlled at 60 - 80 °C, and the temperature on the cold water side is maintained at 10 - 20 °C. The generated vapor pressure difference drives water vapor to permeate through the hydrophobic membrane pores. The flux of the membrane distillation process is 1 - 5 kg / (m 2 ·h), which is used to further concentrate the concentrated water to a near - saturated state. The membrane distillation condensed water is collected and reused in other water - using links of the electroplating production line and supplemented to the reverse osmosis inlet end. The concentrated liquid after membrane distillation concentration enters the crystallizer. In the crystallizer, the temperature is adjusted to 5 - 10 °C, and the stirring speed is adjusted to 50 - 200 rpm until the remaining salts crystallize out. The crystalline salts are purified and refined through centrifugal separation, washing, and drying. The obtained high - purity metal salts can be re - input into the electroplating bath as electroplating raw materials.

[0032] The performance of this process is compared with the existing technology. This process is recorded as the example, and the existing technology is recorded as Comparative Examples 1 - 2. The following is the comparison table:

[0033]

[0034] It can be seen from this that the process performance of the present invention is relatively excellent.

[0035] There is no addition of chemical agents throughout the process, eliminating the risk of secondary pollution caused by the use of agents from the source, such as the potential hazards of heavy metal residues and agent residues in chemical precipitation sludge to soil and water bodies, achieving true zero discharge of electroplating wastewater, protecting the surrounding water environment, and avoiding ecological problems such as water eutrophication and heavy metal pollution caused by wastewater discharge, which helps to maintain ecological balance and biodiversity. By utilizing magnetic force and physicochemical adsorption, the energy consumption is low, only 10%-20% of the energy consumption of traditional chemical precipitation pretreatment, and it is 30%-50% more energy-efficient than the traditional high-pressure reverse osmosis membrane system. At the same time, due to the improved anti-fouling performance of the membrane, the cleaning cycle is extended, and the energy consumption and chemical agent consumption during the cleaning process are also significantly reduced. Through the synergistic concentration and crystallization process of electrochemical induction and membrane distillation, by optimizing the electrode materials and process parameters, as well as the efficient heat utilization of membrane distillation, it is 40%-60% more energy-efficient than the traditional evaporation crystallization process, effectively reducing the operating costs and energy consumption of enterprises. The water resource recovery rate is high. Through reverse osmosis and condensate recovery, the reuse rate of electroplating wastewater can reach over 95%, greatly reducing the dependence of enterprises on fresh water resources and alleviating the pressure of water resource shortage. The purity and quality of metal resource recovery are high. Electrochemical induction crystallization can selectively recover the main metal ions in wastewater to form high-purity metal crystals. Combining with membrane distillation and crystallization purification processes, the purity of the recovered metal salts can reach over 95%, which can be directly used as electroplating raw materials or other industrial raw materials, improving the added value of resources and the economic benefits of enterprises.

[0036] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane, characterized in that: The steps include: S1: Prepare a device for treating discharge, including at least one multi-media gradient magnetic field pretreatment device, a regulating tank, a lift pump, an electrochemical induced crystallization device, a reverse osmosis membrane, a membrane distillation device, and a crystallizer; S2: Magnetic field pretreatment. The electroplating wastewater first enters the regulating tank to balance the water quality and water quantity. The regulated electroplating wastewater enters the multi-medium gradient magnetic field pretreatment device through the lifting pump. In the multi-medium gradient magnetic field pretreatment device, the electroplating wastewater slowly passes through the medium-filled bed filled with multi-medium at a flow rate of 0.5-1.5m / s. At the inlet, the magnetic field strength of the strong magnetic field area is 0.5-1.0T. The strong magnetic field area quickly adsorbs metal particles with strong magnetism. As the electroplating wastewater flows to the outlet, the magnetic field strength gradually decreases to 0.1-0.3T, and weakly magnetic metal particles and metal ions reacting with the surface of the medium-filled bed are adsorbed and retained; S3: Treatment based on reverse osmosis membrane. The pretreated electroplating wastewater enters the reverse osmosis membrane. Driven by a low pressure of 0.5-1.5MPa, water molecules pass through the reverse osmosis membrane, while metal ions, soluble salts and a small amount of residual organic matter are retained. The operating pressure of the reverse osmosis membrane is adjusted in real time according to the influent water quality and membrane flux. Automatic control is achieved through pressure sensors, flow sensors and intelligent control systems. The concentrated water produced enters electrochemical induction and membrane distillation synergistic concentration and crystallization treatment; S4: Electrochemical induction and membrane distillation synergistic concentration and crystallization treatment. The concentrated water enters the electrochemical induction crystallization device. In the device, the appropriate electrode material and current density are selected according to the main metal ion types in the electroplating wastewater. For nickel-containing wastewater, a nickel cathode is used and the current density is set at 100-300A / m 2 The power-on time is 1-5 hours. After electrochemical crystallization, the metal ion concentration in the concentrated water is significantly reduced, and the remaining concentrated water enters the membrane distillation device. In the membrane distillation device, the temperature of the hot water side is controlled at 60-80℃, and the temperature of the cold water side is maintained at 10-20℃. The generated vapor pressure difference drives the water vapor to pass through the hydrophobic membrane pores. The flux of the membrane distillation process is 1-5kg / (m 2 h), used to further concentrate the concentrated water to a state close to saturation. The condensed water from membrane distillation is collected and reused in other water-using links of the electroplating production line and supplemented to the water inlet of reverse osmosis. The concentrated solution from membrane distillation enters the crystallizer. In the crystallizer, the temperature is adjusted to 5-10°C and the stirring speed is adjusted to 50-200rpm until the remaining salt crystallizes out. The crystallized salt is purified and refined by centrifugal separation, washing and drying. The obtained high-purity metal salt can be used as an electroplating raw material and put back into the electroplating tank.

2. The zero-discharge process for electroplating wastewater based on a low-pressure anti-pollution reverse osmosis membrane according to claim 1 is characterized in that: In S1, the multi-medium gradient magnetic field pretreatment device is composed of a bed layer filled with media with various magnetic properties and surface modifications, and under the action of a magnetic field generator, a gradient magnetic field with a strength that gradually changes from the inlet to the outlet is formed.

3. The zero discharge process for electroplating wastewater based on low-pressure anti-pollution reverse osmosis membrane according to claim 1 is characterized in that: In S3, the reverse osmosis membrane uses polyethersulfone as the main polymer matrix material, introduces nano-scale titanium dioxide particles as a photocatalytic additive, doped with zwitterionic polymers, including but not limited to sulfobetaine zwitterionic polymers, and introduces temperature-sensitive polymer segments into the membrane material. The structure of the reverse osmosis membrane is designed as follows: the membrane adopts an asymmetric membrane design, the upper layer of the membrane is an ultra-thin separation layer with a thickness of 0.1-0.2 microns, and the lower layer is a porous support layer with a thickness of 100-200 microns, which is made of materials such as polyethersulfone; The flow channel inside the membrane module adopts a spiral flow channel design with a width of 1-2 mm and a depth of 0.5-1 mm; The membrane assembly adopts fluororubber sealing ring, and the connection between the diaphragms is made by ultrasonic welding. The inlet and outlet water interfaces of the reverse osmosis membrane adopt standardized design. The interfaces are equipped with pressure monitoring and flow monitoring devices for real-time monitoring of the operating parameters of the membrane assembly.

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