Nanocrystal seed magnetic flocculation precipitation process method for improving removal efficiency of suspended solids and turbidity in wastewater

Abstract

The invention discloses a nanocrystalline seed magnetic flocculation precipitation process method for improving removal efficiency of suspended solids and turbidity in wastewater, which comprises the following steps: (1) preparation of nanocrystalline seed magnetic powder: uniformly mixing iron mud and dysprosium-containing rare earth oxide, heating and roasting for 2-3 hours, cooling, adding sodium citrate dehydrate, and uniformly mixing to obtain the nanocrystalline seed magnetic powder; (2) wastewater pretreatment: firstly, preliminarily filtering the wastewater to remove large-particle impurities and suspended solids; (3) nano-seed magnetic flocculation precipitation: firstly introducing the wastewater into a coagulation tank, adding a coagulant PAC, then introducing the wastewater into a magnetic flocculation tank, adding nano-seed magnetic powder, finally introducing the wastewater into a reaction tank, adding a flocculant PAM, and stirring for reaction for 0.5-0.8 h to form magnetic flocs; (4) clarification: introducing the wastewater into a clarification tank for clarification for 0.6-1 h, wherein the quality of effluent of the clarification tank meets the environmental protection requirement; (5) recovering nano-seed magnetic powder: recovering the nano-seed magnetic powder from the sludge at the bottom of the clarification tank; the method is short in wastewater treatment time, high in treatment efficiency and suitable for popularization.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a nano-crystal seed magnetic flocculation precipitation process method for improving the removal efficiency of suspended matter and turbidity in wastewater; the method of the invention is suitable for rapid solid-liquid separation of wastewater in industries such as metallurgy, mining, and petroleum, has a wide range of applications, and is easy to promote and use. Background Art

[0002] The low removal efficiency of pollutants such as suspended solids (SS) and turbidity in water bodies is the main technical challenge facing the current water treatment field. Traditional sedimentation technologies, such as gravity sedimentation and chemical flocculation sedimentation, have low sedimentation efficiency, resulting in unstable effluent quality and difficulty in meeting increasingly stringent environmental protection standards. In addition, these technologies usually require a large footprint, high construction and operation costs, and high sewage treatment costs, which is a heavy burden on enterprises.

[0003] At present, in order to improve the efficiency of pollutant removal in the sewage treatment process, a large amount of chemical agents are often required, which not only increases the operating cost, but also leads to an increase in sludge production, increasing the difficulty and cost of sludge treatment. In addition, traditional sedimentation technology has poor impact resistance, poor adaptability to water quality fluctuations, unstable effluent quality, and difficulty in coping with complex water environment changes.

[0004] Existing water treatment technologies, such as conventional flocculation sedimentation and membrane filtration technology, can remove suspended matter and turbidity in water to a certain extent, but they have the following shortcomings: 1. Flocculation and sedimentation technology: Traditional flocculation and sedimentation technology mainly relies on chemical flocculants, which form larger flocs with pollutants such as suspended solids and turbidity in the water, and then remove them by gravity sedimentation. This method has the following problems: (1) The amount of flocculant added is large, and the operating cost is high; (2) The floc sedimentation rate is slow and the sedimentation efficiency is low; (3) The flocs are easily broken and the effluent water quality is unstable; (4) The sludge output is large, and the sludge treatment is difficult and costly.

[0005] 2. Membrane filtration technology: Membrane filtration technology removes pollutants such as suspended matter and turbidity from water through the physical interception of the membrane. This method has the following problems: (1) The membrane is easily contaminated, and cleaning and replacement are frequent, resulting in high operating costs; (2) The membrane flux decreases with the extension of operating time, and the membrane needs to be replaced regularly; (3) It has poor adaptability to water quality fluctuations, and the effluent water quality is unstable; (4) The membrane material cost is high, and the equipment investment is large.

[0006] Therefore, it is urgent to develop a new process for efficiently removing suspended solids and turbidity in wastewater to solve the above problems. Summary of the invention

[0007] The present invention is aimed at the problem that in the current wastewater treatment field, in order to improve the pollutant removal efficiency, a large amount of chemical agents often need to be added, which not only increases the operating cost, but also leads to an increase in sludge production, increasing the difficulty and cost of sludge treatment; in addition, traditional sedimentation technology has poor impact resistance, poor adaptability to water quality fluctuations, unstable effluent water quality, and difficulty in coping with complex water environment changes. The removal efficiency of pollutants such as suspended solids (SS) and turbidity in the water body is low, resulting in substandard water quality. A nano-seed magnetic flocculation sedimentation process method for improving the removal efficiency of suspended solids and turbidity in wastewater is provided.

[0008] A nano-crystal seed magnetic flocculation precipitation process for improving the removal efficiency of wastewater suspended matter and turbidity of the present invention comprises the following steps: (1) Preparation of nanocrystalline seed magnetic powder: using iron mud with an iron content of ≥65% by mass, adding dysprosium-containing rare earth oxide, fully mixing, and then adding to a seed synthesis device, heating to 1100-1300°C, roasting for 2-3 hours, cooling to room temperature, adding sodium citrate dihydrate to the roasted product, and fully mixing to obtain nanocrystalline seed magnetic powder, wherein the mass fraction of Fe3O4 in the nanocrystalline seed magnetic powder is ≥90%, and the particle size is 100-300 mesh; the mass ratio of the iron mud: rare earth oxide: sodium citrate dihydrate is 100:3-5:3-5; (2) Wastewater pretreatment: Use a 100-200 mesh filter to preliminarily filter the wastewater to remove large particles and suspended matter; (3) Nanocrystalline seed magnetic flocculation precipitation: First, the wastewater is introduced into the coagulation tank, and the coagulant PAC (polyaluminium chloride) is added to the wastewater at a dosage of 0.3-0.7 kg / m 3 Then the wastewater is introduced into the magnetic flocculation tank, and nanocrystalline magnetic powder is added to the wastewater in an amount of 0.001-0.004 kg / m 3 Finally, the wastewater is introduced into the reaction tank and the flocculant PAM (polyacrylamide) is added in an amount of 0.002-0.004kg / m 3 After the reagent is added, react for 0.5-0.8h under stirring to form magnetic flocs; (4) Clarification: The wastewater is introduced into the clarification tank and clarified for 0.6-1h to separate the magnetic flocs and precipitate the remaining fine flocs. The effluent quality of the clarification tank meets environmental protection requirements, with turbidity of ≤5.0NTU, suspended solids ≤10mg / L, COD ≤10mg / L, and total bacteria ≤1000cfu / ml. The sludge from the clarification tank enters the next process; (5) Recovery of nano-crystal seed magnetic powder: The sludge containing nano-crystal seed magnetic powder discharged from the bottom of the clarification tank enters the seed recovery device, and the recovery efficiency reaches more than 85%; the recovered magnetic powder is reused in the preparation of new nano-crystal seed magnetic powder.

[0009] In the present invention, the iron mud having an iron content of ≥65% by mass comprises iron oxide having a mass content of 80% or more, iron powder having a mass content of 18% or more, and the rest being impurities.

[0010] The dysprosium-containing rare earth oxide described in the present invention contains dysprosium oxide in an amount of ≥70% by mass.

[0011] The sodium citrate dihydrate described in the present invention adopts industrial grade purity.

[0012] The wastewater in the present invention has a turbidity of 40-60 NTU, suspended solids of 100-150 mg / L, and COD of 100-300 mg / L.

[0013] The principle of the present invention is: using nano-crystal seed magnetic flocculation + high-efficiency sedimentation process, adding nano-crystal seed magnetic powder in the conventional sewage treatment process, and using fine crystal seed magnetic powder particles as precipitation nuclei, so that colloidal particles in water and crystal seed particles are more likely to collide and destabilize to form flocs, thereby greatly improving the removal efficiency of suspended matter (since the nano-crystal seed magnetic powder in the present invention can adsorb micron and nanometer-level particle flocs, the magnetic powder in the present invention is named nano-crystal seed magnetic powder); at the same time, due to the ultra-high specific gravity of the crystal seeds, the floc density is much greater than that of conventional coagulation flocs, thereby greatly improving the sedimentation speed, and greatly improving the flocculation and sedimentation efficiency.

[0014] The surface of nano-crystal seeds is porous, with huge specific surface area and surface free radicals, and high surface activity. It has a good micro-electrolysis effect, not only has a good adsorption and removal effect on impurities in water, but also can penetrate into all flocs and strengthen the network structure of flocs, effectively increase the specific surface area of ​​flocs, make them firm and not easy to break, which is conducive to rapid solid-liquid separation and improve the drying degree of sludge. At the same time, because nano-crystal seeds have rich active sites and surface hydroxyl adsorption capacity and large specific surface area, they can effectively remove pollutants such as SS, turbidity, COD, and have a significant removal effect on viruses and bacteria.

[0015] The beneficial effects of the present invention are: 1. Improve removal efficiency: By optimizing the preparation process of active sites on the surface of the seed crystals, the adsorption effect of pollutants such as SS and turbidity is enhanced, and the removal efficiency of suspended solids and turbidity in the water body is significantly improved, so that the water quality meets the standards.

[0016] 2. Reduce floor space: Since this method greatly improves the water purification efficiency, it can greatly reduce the floor space required by traditional sedimentation technology and save space resources.

[0017] 3. Reduce operating costs: With the improvement of treatment efficiency, energy consumption and operating costs can be greatly reduced, while reducing the amount of reagents added, further reducing water treatment costs.

[0018] 4. Reduce resource consumption and environmental pollution: Improve the regeneration and recovery technology of crystal seeds, realize the recycling of crystal seeds, reduce resource consumption and environmental pollution, and promote green and sustainable development.

[0019] 5. Improve impact resistance: Optimize magnetic flocculation + high-efficiency sedimentation process to improve the impact resistance of traditional sedimentation technology, enhance adaptability to water quality fluctuations, and make the effluent water quality more stable.

[0020] 6. The method of the present invention is suitable for rapid solid-liquid separation of wastewater in industries such as metallurgy, mining, and petroleum, and has broad market demand and good application prospects. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention. Example

[0022] This embodiment takes the wastewater treatment of a smelter as an example to illustrate the process method of the present invention. In this embodiment, the turbidity of the wastewater is 50.5 NTU, the suspended solids are 125 mg / L, and the COD is 220 mg / L.

[0023] A nano-crystal seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater comprises the following steps: (1) Preparation of nanocrystalline seed magnetic powder: 1000 g of iron mud with an iron content of 67.2% by mass was added with 4 g of rare earth oxide containing dysprosium, mixed thoroughly and added to a seed synthesis device, heated to 1200-1250°C, roasted for 2.5 h, cooled to room temperature, and then 4 g of sodium citrate dihydrate was added to the roasted product and mixed thoroughly to obtain nanocrystalline seed magnetic powder. The mass fraction of Fe3O4 in the nanocrystalline seed magnetic powder was 92.5%, and the particle size was 200-300 mesh. (2) Wastewater pretreatment: Use a 100-mesh filter to preliminarily filter the wastewater to remove large particles and suspended matter; (3) Nanocrystalline seed magnetic flocculation precipitation: First, the wastewater is introduced into the coagulation tank, and the coagulant PAC is added to the wastewater at a dosage of 0.5 kg / m 3 Then the wastewater is introduced into the magnetic flocculation tank, and nanocrystalline magnetic powder is added to the wastewater at a dosage of 0.0032 kg / m 3 Finally, the wastewater was introduced into the reaction tank and the flocculant PAM was added at a dosage of 0.0033 kg / m 3 After the reagent is added, the reaction is stirred for 0.65 hours to form magnetic flocs; (4) Clarification: The wastewater is introduced into the clarification tank and clarified for 0.8 hours to separate the magnetic flocs and precipitate the remaining fine flocs. The effluent quality of the clarification tank meets environmental protection requirements. The turbidity of the effluent is 4.3NTU, the suspended solids are 5.2mg / L, the COD is 6.5mg / L, and the total number of bacteria is ≤1000cfu / ml. The sludge in the clarification tank enters the next process. (5) Recovery of nano-crystal seed magnetic powder: The sludge containing nano-crystal seed magnetic powder discharged from the bottom of the clarification tank enters the seed recovery device, and the recovery efficiency reaches more than 85%; the recovered magnetic powder is reused in the preparation of new nano-crystal seed magnetic powder.

[0024] The iron mud containing 67.2% iron by mass in this embodiment has a mass fraction of iron oxide of more than 80.1%, a mass fraction of iron powder of more than 18.1%, and the rest being impurities.

[0025] The dysprosium-containing rare earth oxide described in this embodiment has a mass fraction of dysprosium oxide ≥ 70%, the same below.

[0026] The sodium citrate dihydrate described in this embodiment adopts industrial grade purity, the same below. Example

[0027] This embodiment takes the wastewater treatment of a mining plant as an example to illustrate the process method of the present invention. In this embodiment, the turbidity of the wastewater is: 58.2NTU, the suspended solids are: 142mg / L, and the COD is: 186mg / L.

[0028] A nano-crystal seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater comprises the following steps: (1) Preparation of nanocrystalline seed magnetic powder: 1000 g of iron mud with an iron content of 66.5% by mass was added with 5 g of rare earth oxide containing dysprosium, mixed thoroughly and added to a seed synthesis device, heated to 1120-1180°C, roasted for 3 h, cooled to room temperature, and then 5 g of sodium citrate dihydrate was added to the roasted product and mixed thoroughly to obtain nanocrystalline seed magnetic powder. The mass fraction of Fe3O4 in the nanocrystalline seed magnetic powder was 91.2%, and the particle size was 100-200 mesh. (2) Wastewater pretreatment: Use a 150-mesh filter to preliminarily filter the wastewater to remove large particles and suspended matter; (3) Nanocrystalline seed magnetic flocculation precipitation: First, the wastewater is introduced into the coagulation tank, and the coagulant PAC is added to the wastewater at a dosage of 0.7 kg / m 3 Then the wastewater is introduced into the magnetic flocculation tank, and nanocrystalline magnetic powder is added to the wastewater at a dosage of 0.004 kg / m 3 Finally, the wastewater was introduced into the reaction tank and the flocculant PAM was added at a dosage of 0.004 kg / m 3After the reagent is added, the mixture is stirred for 0.8 hours to form magnetic flocs; (4) Clarification: The wastewater is introduced into the clarification tank and clarified for 1 hour to separate the magnetic flocs and precipitate the remaining fine flocs. The effluent quality of the clarification tank meets environmental protection requirements. The turbidity of the effluent is 4.4 NTU, the suspended solids are 8.6 mg / L, the COD is 7.5 mg / L, and the total bacterial count is ≤1000 cfu / ml. The sludge in the clarification tank enters the next process. (5) Recovery of nano-crystal seed magnetic powder: The sludge containing nano-crystal seed magnetic powder discharged from the bottom of the clarification tank enters the seed recovery device, and the recovery efficiency reaches more than 85%; the recovered magnetic powder is reused in the preparation of new nano-crystal seed magnetic powder.

[0029] The iron mud containing 66.5% iron by mass in this embodiment has a mass fraction of iron oxide of more than 80.2%, a mass fraction of iron powder of more than 18.3%, and the rest being impurities. Example

[0030] This embodiment takes the wastewater treatment of a chemical plant as an example to illustrate the process method of the present invention. In this embodiment, the turbidity of the wastewater is: 42.5NTU, the suspended solids are: 136mg / L, and the COD is: 205mg / L.

[0031] A nano-crystal seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater comprises the following steps: (1) Preparation of nanocrystalline seed magnetic powder: 1000 g of iron mud with an iron content of 66.8% by mass was added with 3 g of rare earth oxide containing dysprosium, mixed thoroughly and added to a seed synthesis device, heated to 1250-1300°C, roasted for 2 h, cooled to room temperature, and then 3 g of sodium citrate dihydrate was added to the roasted product and mixed thoroughly to obtain nanocrystalline seed magnetic powder. The mass fraction of Fe3O4 in the nanocrystalline seed magnetic powder was 91.7%, and the particle size was 100-200 mesh. (2) Wastewater pretreatment: Use a 200-mesh filter to preliminarily filter the wastewater to remove large particles and suspended matter; (3) Nanocrystalline seed magnetic flocculation precipitation: First, the wastewater is introduced into the coagulation tank, and the coagulant PAC is added to the wastewater at a dosage of 0.2 kg / m 3 Then the wastewater is introduced into the magnetic flocculation tank, and nanocrystalline magnetic powder is added to the wastewater at a dosage of 0.002 kg / m 3 Finally, the wastewater was introduced into the reaction tank and the flocculant PAM was added at a dosage of 0.002 kg / m 3 After the reagent is added, the mixture is stirred for 0.5 h to form magnetic flocs; (4) Clarification: The wastewater is introduced into the clarification tank and clarified for 0.6 hours to separate the magnetic flocs and precipitate the remaining fine flocs. The effluent quality of the clarification tank meets environmental protection requirements. The turbidity of the effluent is 4.8 NTU, suspended solids: 8.7 mg / L, COD: 8.9 mg / L, and the total number of bacteria is ≤1000 cfu / ml. The sludge in the clarification tank enters the next process. (5) Recovery of nano-crystal seed magnetic powder: The sludge containing nano-crystal seed magnetic powder discharged from the bottom of the clarification tank enters the seed recovery device, and the recovery efficiency reaches more than 85%; the recovered magnetic powder is reused in the preparation of new nano-crystal seed magnetic powder.

[0032] The iron mud containing 66.8% iron by mass in this embodiment has a mass fraction of iron oxide of more than 81.6%, a mass fraction of iron powder of more than 18.3%, and the rest being impurities.

[0033] It can be seen from the above three embodiments that after being treated by the method of the present invention, the effluent water quality of the wastewater meets the environmental protection requirements, which shows that the method of the present invention is practicable.

[0034] The above embodiments of the present invention are only examples for further illustrating the specific implementation of the present invention, and are not intended to limit the implementation of the present invention. Any replacement or modification made by a person skilled in the art within the technical scope disclosed by the present invention and in accordance with the content and spirit of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nano-crystal magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater, characterized in that The steps include: (1) Preparation of nanocrystalline seed magnetic powder: using iron mud with an iron content of ≥65% by mass, adding dysprosium-containing rare earth oxide, fully mixing, and then adding to a seed synthesis device, heating to 1100-1300°C, roasting for 2-3 hours, cooling to room temperature, adding sodium citrate dihydrate to the roasted product, and fully mixing to obtain nanocrystalline seed magnetic powder, wherein the mass fraction of Fe3O4 in the nanocrystalline seed magnetic powder is ≥90%, and the particle size is 100-300 mesh; the mass ratio of the iron mud: rare earth oxide: sodium citrate dihydrate is 100:3-5:3-5; (2) Wastewater pretreatment: Use a 100-200 mesh filter to preliminarily filter the wastewater to remove large particles and suspended matter; (3) Nanocrystalline seed magnetic flocculation precipitation: First, the wastewater is introduced into the coagulation tank, and the coagulant PAC is added to the wastewater at a dosage of 0.3-0.7 kg / m 3 Then the wastewater is introduced into the magnetic flocculation tank, and nanocrystalline magnetic powder is added to the wastewater in an amount of 0.001-0.004 kg / m 3 Finally, the wastewater is introduced into the reaction tank and the flocculant PAM is added in an amount of 0.002-0.004kg / m 3 After the reagent is added, react for 0.5-0.8h under stirring to form magnetic flocs; (4) Clarification: The wastewater is introduced into the clarification tank and clarified for 0.6-1h to separate the magnetic flocs and precipitate the remaining fine flocs. The effluent quality of the clarification tank meets environmental protection requirements, with turbidity of ≤5.0NTU, suspended solids ≤10mg / L, COD ≤10mg / L, and total bacteria ≤1000cfu / ml. The sludge from the clarification tank enters the next process; (5) Recovery of nano-crystal seed magnetic powder: The sludge containing nano-crystal seed magnetic powder discharged from the bottom of the clarification tank enters the seed recovery device, and the recovery efficiency reaches more than 85%; the recovered magnetic powder is reused in the preparation of new nano-crystal seed magnetic powder.

2. A nano-crystal seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater according to claim 1, characterized in that: Iron mud with an iron content of ≥65% by mass, of which the mass content of iron oxide is above 80%, the mass content of iron powder is above 18%, and the rest are impurities.

3. The nano-seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater according to claim 1, characterized in that: The dysprosium-containing rare earth oxide contains dysprosium oxide in an amount of ≥70% by mass.

4. The nano-seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater according to claim 1, characterized in that: The sodium citrate dihydrate adopts industrial grade purity.

5. The nano-seed magnetic flocculation precipitation process for improving the removal efficiency of suspended solids and turbidity in wastewater according to claim 1, characterized in that: The wastewater has a turbidity of 40-60 NTU, suspended solids of 100-150 mg / L, and a COD of 100-300 mg / L.