CN211921098U - Processing apparatus of silicon chip processing waste water - Google Patents
Processing apparatus of silicon chip processing waste water Download PDFInfo
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- CN211921098U CN211921098U CN201922125289.0U CN201922125289U CN211921098U CN 211921098 U CN211921098 U CN 211921098U CN 201922125289 U CN201922125289 U CN 201922125289U CN 211921098 U CN211921098 U CN 211921098U
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Abstract
The utility model relates to a processing apparatus of silicon chip processing waste water belongs to water treatment technical field. The solid-liquid separation membrane is used for filtering the silicon wafer processing wastewater; the first nanofiltration membrane is connected to the permeation side of the solid-liquid separation membrane and is used for performing nanofiltration treatment on filtrate of the solid-liquid separation membrane; the second nanofiltration membrane is connected to the interception side of the first nanofiltration membrane and is used for performing nanofiltration treatment on the concentrated solution of the first nanofiltration membrane; the neutralization reaction tank is connected to the interception side of the second nanofiltration membrane and is used for carrying out acid-adding neutralization reaction on the concentrated solution of the second nanofiltration membrane; and the acid liquid adding tank is connected with the neutralization reaction tank and is used for adding acid into the neutralization reaction tank. The utility model has the advantages of good filtering effect, high automation degree, strong adaptability, small occupied area and the like, and is particularly suitable for recovering the silicon wafer alkaline etching solution washing wastewater.
Description
Technical Field
The utility model relates to a recovery unit of silicon chip alkaline etching liquid washing wastewater, more specifically relate to a silicon chip alkaline etching liquid washing wastewater treatment process who contains potassium hydroxide, potassium silicate, silica flour, organic matter, belong to the processing technology field of water, waste water, sewage or mud.
Background
In the production process of monocrystalline and polycrystalline silicon wafers, a crystal bar needs to be cut into required silicon wafers. After the silicon wafer is cut, marking, chamfering and polishing are needed. Before the wafer can be polished, the wafer damage must be removed and then the wafer needs to be etched to remove the damage caused by the lapping. Lapping is the use of abrasive grit to remove material from the wafer surface and damage left over from previous steps. During lapping, both sides of the wafer are ground simultaneously and a certain amount of material is removed from both sides. The main purpose of the lapping is to remove micro-damage of the silicon slice. The grinding disc is mainly arranged on a grinding disc with a gear, the gear is beneficial to the uniform distribution of grinding fluid, the grinding disc is prevented from being submerged, and the silicon wafer is kept to be tightly attached to the surface. The gear can also enable the grinding fluid to flow on the surface of the silicon chip and be uniformly distributed. After lapping, the wafer surface remains a plurality of silicon particles produced during lapping, which are small in size and need to be removed. After the silicon wafer is lapped, a thin damage layer still exists, and damage caused by lapping is removed through other methods. This damage is typically removed by chemically etching the surface of the wafer. There are two methods of etching: alkaline corrosion and acid corrosion. Compared with acid corrosion, the alkali corrosion process has the advantages of low cost, easy treatment of waste liquid, long service life of a corrosion liquid tank and the like. The corroded silicon wafer contains a large amount of alkaline etching liquid which needs to be washed so as to prevent the quality of the silicon wafer from being influenced by additional corrosion of the alkaline liquid to the silicon wafer.
Because the alkali liquor contains a large amount of KOH, the alkali liquor must be specially treated to avoid the damage to the environment. The problem is more serious due to the large production volume. In order to reduce the production cost, reduce the alkali consumption and protect the environment, the alkali recycling is necessary. The recovery treatment of alkaline etching liquid flushing wastewater has been a problem which is difficult to solve. For example, in the production process of silicon wafers, the silicon wafers treated by the alkaline etching solution are washed by pure water, the wastewater has a large water amount and a high alkali concentration, and the wastewater contains a large amount of potassium silicate, silicon powder and organic matters. If the waste water is directly returned to the system, the content of silicate, organic matters and silicon powder in the system is too high, and the quality of the product is influenced.
The waste water can not be directly returned to the system, and the method which is mostly adopted at present is to discharge the waste water into a factory sewage treatment plant after acid-base neutralization. Thus, the problems of great consumption of acid and alkali resources, resource waste, high treatment cost and the like can be caused. If the waste water can be changed into valuable, the pollution problem caused by the waste water can be reasonably solved, and the waste water can be recycled. Therefore, there is an urgent need to find a suitable method for treating such wastewater.
SUMMERY OF THE UTILITY MODEL
The utility model aims at: the method can recover alkali in the waste liquid, remove impurities in the waste liquid, effectively reuse alkali liquor again, ensure that the concentration of the alkali liquor is unchanged after the alkali liquor is treated by the system, ensure that the alkali liquor can be reused, and ensure that K is equal to K2SiO3Less than or equal to 300mg/L, and less than or equal to 5mg/L of clear liquid CODcr; meanwhile, the method can recover the silicon powder in the silicon powder.
The technical scheme is as follows:
a method for treating silicon wafer processing wastewater, which is washing liquid of alkali liquor used for removing damage of silicon wafer grinding plates in a silicon wafer production process, comprises the following steps:
and 3, adding acid into the concentrated solution of the nanofiltration membrane for neutralization treatment.
In one embodiment, the silicon wafer processing wastewater contains 6-7% KOH, 5000-20000mg/L potassium silicate and CODcr50-500 mg/L.
In one embodiment, the nanofiltration treatment in the step 2 refers to two-stage nanofiltration treatment, and the concentrated solution of the nanofiltration membrane in the previous stage is sent to the next stage for filtration treatment.
In one embodiment, the permeate of the nanofiltration membrane is sent to the silicon wafer alkaline etching process for recycling.
In one embodiment, after being filtered by the solid-liquid separation membrane, the silicon wafer processing wastewater is subjected to flocculation treatment.
In one embodiment, the flocculating process employs a flocculating agent that is primarily an organic flocculating agent.
In one embodiment, the organic flocculant is selected from the group consisting of polyacrylamide, sodium polyacrylate, polyoxyethylene, polyvinylamine, polyethylene sulfonate, and the like.
In one embodiment, the flocculant is added in an amount of 50 to 100 ppm.
In one embodiment, a flocculation nucleating agent is also added.
In one embodiment, the flocculation nucleating agent is cationic polystyrene microspheres.
In one embodiment, the amount of the flocculation nucleating agent is 50 to 200 ppm.
In one embodiment, the solid-liquid separation membrane can be an ultrafiltration membrane or a microfiltration membrane, the solid-liquid separation membrane system adopts cross flow filtration, the flow rate of the membrane surface is controlled to be 3-5m/s, the operating pressure is controlled to be 0.1-1MPa, and the temperature is controlled to be 1-80 ℃.
In one embodiment, the solid-liquid separation membrane filtration adopts cross-flow filtration, the membrane element adopts an external pressure type solid-liquid separation membrane, filtrate backwashing and gas scrubbing are arranged, when the transmembrane pressure difference of the membrane is greater than a set value, the system automatically enters a backwashing program, and the filtrate enters a water inlet side through a water production end to take away pollutants, so that the membrane flux is recovered.
In one embodiment, the operating pressure of the nanofiltration membrane element is controlled between 1MPa and 4 MPa.
A silicon wafer processing wastewater treatment device comprises:
the solid-liquid separation membrane is used for filtering the silicon wafer processing wastewater;
the first nanofiltration membrane is connected to the permeation side of the solid-liquid separation membrane and is used for performing nanofiltration treatment on filtrate of the solid-liquid separation membrane;
the second nanofiltration membrane is connected to the interception side of the first nanofiltration membrane and is used for performing nanofiltration treatment on the concentrated solution of the first nanofiltration membrane;
the neutralization reaction tank is connected to the interception side of the second nanofiltration membrane and is used for carrying out acid-adding neutralization reaction on the concentrated solution of the second nanofiltration membrane;
and the acid liquid adding tank is connected with the neutralization reaction tank and is used for adding acid into the neutralization reaction tank.
In one embodiment, further comprising: and the alkali liquor recovery tank is connected to the permeation side of the first nanofiltration membrane and/or the second nanofiltration membrane and is used for storing the recovered alkali liquor.
In one embodiment, further comprising: and the plate-frame filter is connected to the interception side of the solid-liquid separation membrane and is used for carrying out solid-liquid separation treatment on the concentrated solution obtained by the solid-liquid separation membrane.
In one embodiment, further comprising: and the flocculation reaction tank is connected to the inlet of the solid-liquid separation membrane and is used for carrying out flocculation treatment on the silicon wafer processing wastewater.
In one embodiment, further comprising: and the flocculating agent feeding tank is connected with the flocculation reaction tank and used for feeding flocculating agent into the flocculation reaction tank.
In one embodiment, further comprising: and the flocculation nucleating agent feeding tank is connected with the flocculation reaction tank and is used for feeding the flocculation nucleating agent into the flocculation reaction tank.
In one embodiment, the rejection rate of the first nanofiltration membrane and/or the second nanofiltration membrane for magnesium sulfate is not less than 95%.
In one embodiment, the configuration of the solid-liquid separation membrane is a tubular type, a plate type, a disc type or a capillary type, and the average pore size of the solid-liquid separation membrane is in the range of 0.002 to 0.2 μm.
Advantageous effects
The utility model discloses a processing method of waste water of course of working that technological method can handle silicon chip alkaline etching effectively, this method can retrieve the alkali in the waste liquid to get rid of impurity wherein, can be effectively with alkali lye retrieval and utilization once more, alkali lye handles the back through this system, alkali lye concentration is unchangeable, alkali lye can satisfy the retrieval and utilization, K2SiO3Less than or equal to 300mg/L, and clear liquid CODcr less than or equal to 5 mg/L.
Meanwhile, the method can recover the silicon powder in the wastewater, and the potassium silicate and the silicon powder in the wastewater can be more efficiently flocculated and settled by using the electrostatic action through the flocculating agent and the cationic flocculating aid, so that the load of a subsequent solid-liquid separation membrane is reduced.
Drawings
Fig. 1 is a flow chart of the present invention.
Fig. 2 is a flow chart of the present invention.
Fig. 3 is a diagram of the device of the present invention.
Fig. 4 is a diagram of the apparatus of the present invention. FIG. 5 is a graph showing flux decay curves during the operation of the microfiltration membrane.
Wherein, 1, a solid-liquid separation membrane; 2. a first nanofiltration membrane; 3. a second nanofiltration membrane; 4. a neutralization reaction tank; 5. an acid liquor feeding tank; 6. a plate frame filter; 7. a flocculation reaction tank; 8. a flocculating agent feeding tank; 9. adding a flocculation nucleating agent into the tank; 10. an alkali liquor recovery tank.
Detailed Description
The utility model discloses the waste water that will handle indicates the flush fluid that is used for cleaing away the alkali lye of the damage of silicon chip abrasive disc in the course of working of silicon chip, in the middle of the waste water that obtains after the surface alkaline etching treatment, mainly can contain silica flour, some organic matters, KOH, K2SiO3And the like. The utility model discloses can effectively handle this kind of waste water to retrieve alkali lye wherein.
The method of the utility model is shown in figure 1 and mainly comprises:
since the wastewater contains silicon particle powder, the particles can be filtered out through a solid-liquid separation membrane and can be recycled. In some embodiments, the solid-liquid separation membrane system adopts cross-flow filtration, the flow rate of the membrane surface is controlled to be 3-5m/s, the operation pressure is controlled to be 0.1-1MPa, and the temperature is controlled to be 1-80 ℃. The microfiltration membrane or ultrafiltration membrane used for the utility model is a membrane with the average pore diameter of 0.01 mu m-5 mm, such as a microfiltration membrane, an MF membrane and the like for short. The material of the microfiltration membrane or ultrafiltration membrane is not particularly limited as long as the object of the present invention can be achieved by removing the water-soluble polymer and the colloidal component, and examples thereof include: cellulose, cellulose ester, polysulfone, polyethersulfone, polyvinyl chloride, chloropropylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, or other organic materials, or stainless steel or other metals, or ceramics or other inorganic materials. The material of the microfiltration membrane or ultrafiltration membrane may be appropriately selected in consideration of the properties of the hydrolysate or the running cost, and is preferably an organic material, preferably polyvinyl chloride, polypropylene, polyvinylidene fluoride, polysulfone, or polyether sulfone, in view of ease of handling. The material of the porous membrane constituting the ceramic separation membrane can be appropriately selected from conventionally known ceramic materials. For example, oxide-based materials such as alumina, zirconia, magnesia, silica, titania, ceria, yttria, and barium titanate; composite oxide materials such as cordierite, mullite, forsterite, steatite, sialon, zircon, ferrite and the like; nitride materials such as silicon nitride and aluminum nitride; carbide-based materials such as silicon carbide; hydroxide materials such as hydroxyapatite; elemental materials such as carbon and silicon; or an inorganic composite material containing two or more of them. Natural minerals (clay, clay minerals, earthenware slag, silica sand, pottery stone, feldspar, white sand) or blast furnace slag, fly ash, etc. may also be used. Among these, 1 or 2 or more kinds selected from alumina, zirconia, titania, magnesia and silica are preferable, and ceramic powder mainly composed of alumina, zirconia or titania is more preferable. The term "mainly" as used herein means that 50 mass% or more (preferably 75 mass% or more, and more preferably 80 to 100 mass%) of the entire ceramic powder is alumina or silica. For example, among porous materials, alumina is inexpensive and excellent in handling properties. Further, since a porous structure having pore diameters suitable for liquid separation can be easily formed, a ceramic separation membrane having excellent liquid permeability can be easily produced. Among the above aluminas, alpha-alumina is particularly preferably used. Alpha-alumina has the characteristics of being chemically stable and having high melting point and mechanical strength. Therefore, by using α -alumina, a ceramic separation membrane that can be utilized in a wide range of applications (e.g., industrial fields) can be manufactured. The membrane element adopts a tubular type, a plate type, a disc type or a capillary type. The microfiltration membrane filtration adopts cross flow filtration, the membrane element adopts an external pressure type microfiltration membrane, filtrate backwashing and gas scrubbing are arranged, and when the transmembrane pressure difference of the membrane is greater than a set value, the system automatically enters a backwashing program. The filtrate enters the water inlet side through the water production end to take away the pollutants, so that the membrane flux is recovered. The micro-filtration membrane or the ultrafiltration membrane is cleaned chemically, and the chemicals are mainly acid, alkali and sodium hypochlorite.
Before solid-liquid separation, it is best to use flocculation treatment to coat the organic matter with flocculate and to coagulate the fine silica powder, so as to effectively reduce the pollutant in waste water and reduce the pollution of solid-liquid separation membrane. Since the wastewater to be treated in the present invention is alkaline wastewater, it is preferable to use an organic flocculant which is less affected by pH, such as polyacrylamide, sodium polyacrylate, polyoxyethylene, polyvinylamine, polyethylene sulfonate, etc. In addition, in order to generate flocculating constituent more quickly in the flocculation process, the flocculation nucleating agent can be added in the flocculation process, because the potassium silicate can be adsorbed on the surface of the silicon powder and the zeta potential of the potassium silicate is electronegative under the alkaline condition, the cationic polystyrene microsphere can be adopted as the nucleating agent, and the surface of the microsphere has positive charges, the potassium silicate can be adsorbed on the surface and nucleated more quickly, so that the flocculation effect is better; the cationic polystyrene microspheres used herein can be prepared by methods known in the art, and cationic monomers (such as methacryloyloxyethyl trimethyl ammonium chloride) are added during the polymerization of styrene monomers.
because the waste water contains a large amount of potassium silicate generated by reaction, potassium silicate/organic matters can be separated from KOH by designing a multi-stage nanofiltration system, and permeation liquid of nanofiltration mainly contains KOH, so that the potassium silicate/organic matters can be recycled. Nanofiltration membranes are herein defined as "pressure driven membranes that block particles smaller than 2nm and dissolved macromolecules". Suitable for the utility model discloses an effective nanofiltration membrane is preferred to be such membrane: there is an electric charge on the membrane surface, and thus improved separation efficiency is exhibited by a combination of fine pore separation (particle size separation) and electrostatic separation benefiting from the electric charge on the membrane surface. Therefore, it is necessary to use a nanofiltration membrane capable of removing a high molecular substance by particle size separation while separating an alkali metal ion to be recovered from another ion having a different charge characteristic by means of charge. As the material of the nanofiltration membrane used in the utility model, high polymer materials such as cellulose acetate polymer, polyamide, sulfonated polysulfone, polyacrylonitrile, polyester, polyimide, vinyl polymer and the like can be used. The film is not limited to one composed of only one material, and may be a film containing a plurality of the materials. With respect to the membrane structure, the membrane may be an asymmetric membrane having a dense layer on at least one side of the membrane and having micropores with pore diameters gradually increasing from the dense layer toward the inside of the membrane or the other side; or a composite membrane having a very thin functional layer of another material on the dense layer of the asymmetric membrane. The nanofiltration membrane used here adopts an alkali-resistant nanofiltration membrane element, the modified membrane element includes but is not limited to a Coriolis alkali-resistant membrane, a Mennade alkali-resistant membrane and an AMS alkali-resistant membrane, and the rejection rate of the membrane element to magnesium sulfate is not less than 95%. The nanofiltration membrane system comprises a nanofiltration membrane water inlet pump, a cartridge filter, a booster pump and a nanofiltration membrane component, and all the devices are connected through pipelines. Wastewater from the cartridge filter sequentially enters the nanofiltration membrane unit through various pumps, and concentrated water enters the second-stage special nanofiltration membrane system for concentration after being treated by the special nanofiltration membrane. The nanofiltration membrane system comprises a multi-stage nanofiltration membrane device, wastewater from the cartridge filter firstly enters a first-stage special nanofiltration membrane device, and concentrated solution of the first-stage special nanofiltration membrane device enters a second-stage special nanofiltration membrane device for further filtration. And the two-stage nanofiltration membrane permeate is recycled, and the second-stage reverse osmosis membrane concentrate enters the membrane concentrate tank. A transfer tank is arranged between the nanofiltration membrane systems. The first-stage special nanofiltration membrane system is provided with a first-stage special nanofiltration membrane water inlet tank and a first-stage special nanofiltration membrane concentrated water tank. The second-stage special nanofiltration membrane system is provided with a nanofiltration membrane system water production tank, and the second-stage special nanofiltration membrane concentrated water directly enters a membrane concentrated liquid tank. The two-stage special nanofiltration membrane system shares a nanofiltration membrane water production tank, and the operating pressure of the nanofiltration membrane system is controlled to be 1-4 MPa.
And 3, adding acid into the concentrated solution of the nanofiltration membrane for neutralization treatment.
The nanofiltration concentrated solution mainly contains organic matters, alkali and potassium silicate, and after neutralization reaction is carried out by adding acid, the waste liquid can be sent to a biochemical treatment process for biological treatment.
After the wastewater is treated by the nanofiltration membrane system, the concentration of the alkali liquor is unchanged, the alkali liquor can meet the requirement of recycling, and K is2SiO3Less than or equal to 300mg/L, and clear liquid CODcr less than or equal to 5 mg/L.
Based on the above process, the device diagram provided by the present invention can be as shown in fig. 3 or fig. 4.
A silicon wafer processing wastewater treatment device comprises:
the solid-liquid separation membrane 1 is used for filtering the silicon wafer processing wastewater;
the first nanofiltration membrane 2 is connected to the permeation side of the solid-liquid separation membrane 1 and is used for performing nanofiltration treatment on the filtrate of the solid-liquid separation membrane 1;
the second nanofiltration membrane 3 is connected to the interception side of the first nanofiltration membrane 2 and is used for performing nanofiltration treatment on the concentrated solution of the first nanofiltration membrane 2;
the neutralization reaction tank 4 is connected to the interception side of the second nanofiltration membrane 3 and is used for carrying out acid-adding neutralization reaction on the concentrated solution of the second nanofiltration membrane 3;
and the acid liquid adding tank 5 is connected to the neutralization reaction tank 4 and is used for adding acid into the neutralization reaction tank 4.
In one embodiment, further comprising: and the alkali liquor recovery tank 10 is connected to the permeation side of the first nanofiltration membrane 2 and/or the second nanofiltration membrane 3 and is used for storing the recovered alkali liquor.
In one embodiment, further comprising: and the plate-frame filter 6 is connected to the interception side of the solid-liquid separation membrane 1 and is used for performing solid-liquid separation treatment on the concentrated solution obtained by the solid-liquid separation membrane 1.
In one embodiment, further comprising: and the flocculation reaction tank 7 is connected to the inlet of the solid-liquid separation membrane 1 and is used for carrying out flocculation treatment on the silicon wafer processing wastewater.
In one embodiment, further comprising: and the flocculating agent feeding tank 8 is connected to the flocculation reaction tank 7 and is used for feeding flocculating agent into the flocculation reaction tank 7.
In one embodiment, further comprising: and the flocculation nucleating agent adding tank 9 is connected to the flocculation reaction tank 7 and is used for adding the flocculation nucleating agent into the flocculation reaction tank 7.
In one embodiment, the rejection rate of the first nanofiltration membrane 2 and/or the second nanofiltration membrane 3 for magnesium sulfate is not less than 95%.
In one embodiment, the configuration of the solid-liquid separation membrane 1 is a tubular type, a plate type, a disc type, or a capillary type, and the average pore diameter of the solid-liquid separation membrane 1 is in the range of 0.002 to 0.2 μm.
Example 1
And (3) carrying out 100m ethanol planting on the silicon wafer alkaline etching solution washing wastewater, wherein the concentration of KOH in the fed material is 6-7%, and the concentration of potassium silicate is 13000 mg/L. Entering a microfiltration membrane system at the temperature of 30 ℃, adopting cross flow filtration, controlling the flow rate of the membrane surface at 3-5m/s, controlling the aperture of the microfiltration membrane at 200nm, and controlling the operating pressure at 0.2 Mpa. The recovery rate is 95%, the clear solution of the microfiltration membrane enters a primary nanofiltration membrane system, the operating pressure is 2MPa, and the temperature is 30-40 ℃. When the concentration of the potassium silicate is more than 30000mg/L, the concentrated solution enters a secondary nanofiltration membrane system for continuous separation and concentration, the operating pressure of the secondary nanofiltration membrane is 3MPa, and the temperature is 35-40 ℃. The membrane filtrate of the first-stage membrane separation system and the second-stage membrane separation system is placed in a clear liquid tank for later use. When the clear liquid amount is 84m, the nanofiltration membrane concentrated solution enters a sewage treatment station after the pH is adjusted to 6-9. And further recovering the silicon powder from the concentrated solution of the microfiltration membrane in a plate-and-frame filtration mode.
Example 2
And (3) carrying out 100m ethanol harvest on the silicon wafer alkaline etching solution washing wastewater, wherein the concentration of KOH in the feeding material is 6-7%, and the concentration of potassium silicate is 13500 mg/L. Entering a microfiltration membrane system at the temperature of 35 ℃, adopting cross flow filtration, controlling the flow rate of the membrane surface to be 3-5m/s, controlling the aperture of the microfiltration membrane to be 50nm, and controlling the operating pressure to be 0.3 Mpa. The recovery rate is 92%, the clear solution of the micro-filtration membrane enters a first-stage nanofiltration membrane system, the operating pressure is 2MPa, and the temperature is 30-40 ℃. When the concentration of the potassium silicate is more than 30000mg/L, the concentrated solution enters a secondary nanofiltration membrane system for continuous separation and concentration, the operating pressure of the secondary nanofiltration membrane is 3MPa, and the temperature is 35-40 ℃. The membrane filtrate of the first-stage membrane separation system and the second-stage membrane separation system is placed in a clear liquid tank for later use. When the clear liquid amount is 80m, the nanofiltration membrane concentrated solution enters a sewage treatment station after the pH is adjusted to 6-9. And further recovering the silicon powder from the concentrated solution of the microfiltration membrane in a plate-and-frame filtration mode.
Example 3
And (3) carrying out 100m ethanol planting on the silicon wafer alkaline etching solution washing wastewater, wherein the concentration of KOH in the fed material is 6-7%, and the concentration of potassium silicate is 13000 mg/L. Firstly, adding 75mg/L of polyacrylamide serving as a flocculating agent for flocculation reaction, naturally settling after reaction, introducing settled clear liquid into a microfiltration membrane system at the temperature of 30 ℃, adopting cross flow filtration, controlling the flow rate of the membrane surface to be 3-5m/s, controlling the aperture of the microfiltration membrane to be 200nm, and controlling the operating pressure to be 0.2 Mpa. The recovery rate is 95%, the clear solution of the microfiltration membrane enters a primary nanofiltration membrane system, the operating pressure is 2MPa, and the temperature is 30-40 ℃. When the concentration of the potassium silicate is more than 30000mg/L, the concentrated solution enters a secondary nanofiltration membrane system for continuous separation and concentration, the operating pressure of the secondary nanofiltration membrane is 3MPa, and the temperature is 35-40 ℃. The membrane filtrate of the first-stage membrane separation system and the second-stage membrane separation system is placed in a clear liquid tank for later use. When the clear liquid amount is 84m, the nanofiltration membrane concentrated solution enters a sewage treatment station after the pH is adjusted to 6-9. And further recovering the silicon powder from the concentrated solution of the microfiltration membrane in a plate-and-frame filtration mode.
Example 4
And (3) carrying out 100m ethanol planting on the silicon wafer alkaline etching solution washing wastewater, wherein the concentration of KOH in the fed material is 6-7%, and the concentration of potassium silicate is 13000 mg/L. Firstly, adding 75mg/L polyacrylamide and 100mg/L polystyrene microspheres serving as flocculating agents for flocculation reaction, naturally settling after reaction, then feeding settled clear liquid into a microfiltration membrane system at the temperature of 30 ℃, adopting cross flow filtration, controlling the flow rate of the membrane surface to be 3-5m/s, controlling the aperture of the microfiltration membrane to be 200nm, and controlling the operating pressure to be 0.2 Mpa. The recovery rate is 95%, the clear solution of the microfiltration membrane enters a primary nanofiltration membrane system, the operating pressure is 2MPa, and the temperature is 30-40 ℃. When the concentration of the potassium silicate is more than 30000mg/L, the concentrated solution enters a secondary nanofiltration membrane system for continuous separation and concentration, the operating pressure of the secondary nanofiltration membrane is 3MPa, and the temperature is 35-40 ℃. The membrane filtrate of the first-stage membrane separation system and the second-stage membrane separation system is placed in a clear liquid tank for later use. When the clear liquid amount is 84m, the nanofiltration membrane concentrated solution enters a sewage treatment station after the pH is adjusted to 6-9. And further recovering the silicon powder from the concentrated solution of the microfiltration membrane in a plate-and-frame filtration mode.
Example 5
And (3) carrying out 100m ethanol planting on the silicon wafer alkaline etching solution washing wastewater, wherein the concentration of KOH in the fed material is 6-7%, and the concentration of potassium silicate is 13000 mg/L. Firstly, adding 75mg/L and 100mg/L of polyacrylamide as flocculating agents to carry out flocculation reaction, naturally settling after reaction, then feeding the settled clear liquid into a microfiltration membrane system at the temperature of 30 ℃, adopting cross flow filtration, controlling the flow rate of the membrane surface at 3-5m/s, controlling the aperture of the microfiltration membrane at 200nm, and controlling the operating pressure at 0.2 Mpa. The recovery rate is 95%, the clear solution of the microfiltration membrane enters a primary nanofiltration membrane system, the operating pressure is 2MPa, and the temperature is 30-40 ℃. When the concentration of the potassium silicate is more than 30000mg/L, the concentrated solution enters a secondary nanofiltration membrane system for continuous separation and concentration, the operating pressure of the secondary nanofiltration membrane is 3MPa, and the temperature is 35-40 ℃. The membrane filtrate of the first-stage membrane separation system and the second-stage membrane separation system is placed in a clear liquid tank for later use. When the clear liquid amount is 84m, the nanofiltration membrane concentrated solution enters a sewage treatment station after the pH is adjusted to 6-9. And further recovering the silicon powder from the concentrated solution of the microfiltration membrane in a plate-and-frame filtration mode.
The main results of the operation process in the above embodiments are as follows:
as can be seen from the above table, the treated clear liquid of the nanofiltration membrane of the utility model basically keeps higher KOH concentration, and basically removes most potassium silicate and COD substances, so that the clear liquid obtained by nanofiltration recovery can be applied to the corrosion treatment of the silicon wafer again; meanwhile, as can be seen from the comparison between the embodiment 3 and the embodiment 1, after the flocculation treatment is carried out on the wastewater, silicon powder and some organic matters in the wastewater can be effectively removed, and the flux of the microfiltration membrane in the operation process can be effectively improved; the comparison between examples 4 and 5 and example 3 shows that the flocculation effect can be improved by adding the microspheres capable of promoting the flocculation nucleation in the flocculation process, and the solid content in the microfiltration membrane is obviously reduced by measuring the solid content of the inlet water; after the polymer microspheres with cationized surfaces are adopted in the embodiment 5, the positive charges on the surfaces can act on silicate ions with negative zeta potential under alkaline conditions, so that the generation of floccules in the flocculation process can be promoted, and the microfiltration flux is improved. The flux decay curve of the microfiltration membrane in the operation process is shown in fig. 5, and it can be seen that the flux decays more slowly when the wastewater after the flocculation and nucleation treatment processes is subjected to microfiltration.
Claims (9)
1. A treatment device for silicon wafer processing wastewater is characterized by comprising:
the solid-liquid separation membrane (1) is used for filtering the silicon wafer processing wastewater;
the first nanofiltration membrane (2) is connected to the permeation side of the solid-liquid separation membrane (1) and is used for performing nanofiltration treatment on the filtrate of the solid-liquid separation membrane (1);
the second nanofiltration membrane (3) is connected to the interception side of the first nanofiltration membrane (2) and is used for performing nanofiltration treatment on the concentrated solution of the first nanofiltration membrane (2);
the neutralization reaction tank (4) is connected to the interception side of the second nanofiltration membrane (3) and is used for carrying out acid-adding neutralization reaction on the concentrated solution of the second nanofiltration membrane (3);
and the acid liquid adding tank (5) is connected to the neutralization reaction tank (4) and is used for adding acid into the neutralization reaction tank (4).
2. The apparatus for treating silicon wafer processing wastewater according to claim 1, further comprising: and the alkali liquor recovery tank (10) is connected to the permeation side of the first nanofiltration membrane (2) and/or the second nanofiltration membrane (3) and is used for storing the recovered alkali liquor.
3. The apparatus for treating silicon wafer processing wastewater according to claim 1, further comprising: and the plate-frame filter (6) is connected to the interception side of the solid-liquid separation membrane (1) and is used for carrying out solid-liquid separation treatment on the concentrated solution obtained by the solid-liquid separation membrane (1).
4. The apparatus for treating silicon wafer processing wastewater according to claim 1, further comprising: and the flocculation reaction tank (7) is connected to the inlet of the solid-liquid separation membrane (1) and is used for carrying out flocculation treatment on the silicon wafer processing wastewater.
5. The apparatus for treating silicon wafer processing wastewater according to claim 1, further comprising: and the flocculating agent feeding tank (8) is connected to the flocculation reaction tank (7) and is used for feeding flocculating agent into the flocculation reaction tank (7).
6. The apparatus for treating silicon wafer processing wastewater according to claim 5, further comprising: and the flocculation nucleating agent feeding groove (9) is connected to the flocculation reaction groove (7) and is used for feeding the flocculation nucleating agent into the flocculation reaction groove (7).
7. The silicon wafer processing wastewater treatment device according to claim 1, wherein the rejection rate of the first nanofiltration membrane (2) and/or the second nanofiltration membrane (3) on magnesium sulfate is not lower than 95%.
8. The apparatus for treating silicon wafer processing wastewater according to claim 1, wherein the solid-liquid separation membrane (1) has a tubular, plate, disc, or capillary configuration.
9. The apparatus for treating silicon wafer processing wastewater according to claim 1, wherein the solid-liquid separation membrane (1) is an ultrafiltration membrane or a microfiltration membrane, and the average pore diameter of the solid-liquid separation membrane (1) is in the range of 0.002 to 0.2 μm.
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