Magnetic coagulant and preparation method and application thereof

Abstract

The present application relates to a kind of magnetic coagulant and its preparation method and application, the preparation method includes: after the dry and ground water supply sludge is mixed with wood vinegar solution and adds iron salt to obtain the first reaction liquid of the mass ratio of Al element and Fe element 1:1.5-2, carries out first reaction, obtains leaching solution A and precipitate B after reaction ends;Precipitate B is mixed with inorganic skeleton, add leaching solution A and 5-10% of the volume fraction of acetic acid in leaching solution A, uniformly mixed to obtain second reaction liquid, carries out high-pressure hydrothermal reaction to obtain precipitate C, precipitate C is washed and dried to obtain magnetic coagulant.The present application utilizes the water supply sludge generated in the process of tap water treatment to prepare magnetic coagulant, and the Fe, Al oxide on the surface of magnetic flocculant can be complexed with phosphate, effectively removing phosphorus pollutants in wastewater, and the adsorption and coagulation performance is stronger.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a magnetic coagulant, its preparation method, and its application. Background Technology

[0002] Water supply sludge is mainly formed by the sedimentation of excess coagulant from coagulation tanks, flocculation tanks and sedimentation tanks in water plants, and flocs formed by coagulant and impurities in natural water bodies such as clay, plant residues, and humus. Its inorganic components contain a large amount of silicon, iron, aluminum and a small amount of other components.

[0003] In existing technologies, iron and aluminum salt coagulants have limited effect on phosphorus adsorption in wastewater, and usually require a large dosage to achieve a good phosphorus removal effect. Moreover, after using metal salt coagulants, a certain amount of metal ions may remain in the treated water, which may deposit in the human body and cause harm to human health. Summary of the Invention

[0004] This invention provides a magnetic coagulant, its preparation method, and its application, which enables the utilization of wastewater sludge, and the resulting magnetic coagulant has a better adsorption effect.

[0005] In a first aspect, the present invention provides a method for preparing a magnetic coagulant, comprising:

[0006] The dried and ground water supply sludge was mixed with wood acetic acid solution and iron salt was added to obtain a first reaction solution with a mass ratio of Al to Fe of 1:1.5-2. The first reaction was carried out, and after the reaction was completed, leachate A and precipitate B were obtained. Precipitate B is mixed with an inorganic framework, and leachate A and acetic acid (5-10% by volume of leachate A) are added. The mixture is stirred evenly to obtain a second reaction solution. The solution is then subjected to a high-pressure hydrothermal reaction to obtain precipitate C. Precipitate C is washed and dried to obtain a magnetic coagulant.

[0007] In one optional embodiment, the water supply sludge, on a dry basis, contains 17-23% organic matter and the remainder is inorganic components. In the inorganic components, the content of SiO2 is 30-70%, the content of Fe2O3 is 15-35%, and the content of Al2O3 is 15-35%. The particle size of the water supply sludge after grinding is 100-150 μm; The ratio of the water supply sludge to the wood acetate solution is 1g:2-10ml; The iron salt includes one or more of ferric chloride and ferric nitrate.

[0008] In one optional embodiment, the first reaction includes reacting for 4-5 hours under ultrasonic conditions at 300-500 r / min, 50-70°C.

[0009] In one optional embodiment, the first reaction is carried out in an ultrasonic bath, and a stirrer is placed above the container of the first reaction liquid to allow the first reaction liquid to react for 4-5 hours under ultrasonic conditions at 300-500 r / min, 50-70°C.

[0010] In one alternative embodiment, the inorganic framework comprises 12-25% of the mass of precipitate B; The inorganic framework includes one or more of the following: kaolin, bentonite, diatomaceous earth, steel slag, fly ash, and blast furnace slag. The solid-liquid ratio of the mixture of precipitate B and inorganic framework to leachate A is 1g:15-30ml; In one optional embodiment, the second reaction solution further includes acetic acid, which accounts for 5-10% of the volume of the leachate A.

[0011] In one optional embodiment, the high-pressure hydrothermal reaction process includes reacting the second reaction liquid at 200~250℃ and 200~350 r / min for 15~27 h.

[0012] In one alternative embodiment, the high-pressure hydrothermal reaction is carried out in a high-pressure reactor.

[0013] Secondly, the present invention provides a magnetic coagulant, which is prepared by the above-described preparation method.

[0014] Thirdly, the present invention provides an application of the above-mentioned magnetic coagulant in water treatment.

[0015] In one optional implementation, the application includes: directly adding magnetic coagulant to the coagulation tank of a waterworks for the removal of impurities and coagulation of tap water; Magnetic coagulants are directly added to the primary sedimentation tank of the wastewater treatment plant to adsorb, coagulate, and settle pollutants.

[0016] The technical solution of this invention has the following advantages: 1. The present invention provides a method for preparing a magnetic coagulant, comprising: mixing dried and ground water supply sludge with wood acetic acid solution and adding iron salt to obtain a first reaction solution with a mass ratio of Al to Fe of 1:1.5-2, performing a first reaction, and obtaining leachate A and precipitate B after the reaction is completed; mixing precipitate B with an inorganic framework, adding leachate A and acetic acid accounting for 5-10% of the volume of leachate A, mixing evenly to obtain a second reaction solution, performing a high-pressure hydrothermal reaction to obtain precipitate C, and washing and drying precipitate C to obtain a magnetic coagulant.

[0017] This invention utilizes the sludge generated during water treatment to prepare a magnetic coagulant, which can be applied to water treatment processes, realizing the utilization of sludge waste. This invention uses a hydrothermal method to synthesize multiphase nano-metal oxides loaded with Fe and Al metal salts on the surface of dried sludge products under specific system conditions, preparing a magnetic flocculant. This results in a magnetic coagulant with stronger stability and higher environmental adaptability. Furthermore, the organic matter in the sludge carbonizes during the high-pressure hydrothermal reaction, naturally creating pores and resulting in a higher specific surface area. The Fe and Al oxides on the surface of the magnetic flocculant can complex with phosphate ions, effectively removing phosphorus pollutants from wastewater, and exhibiting stronger adsorption and coagulation performance. Detailed Implementation

[0018] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0019] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0020] In this application document, the wood acetate is commercially available refined wood acetate suitable for agricultural use.

[0021] Example 1 This embodiment provides a method for preparing a magnetic coagulant, including: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 17%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 60%, 15% and 20% respectively, and the moisture content is 95%) was dried to constant weight in an oven at 105℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 95% water and 5% dry basis; the dry basis includes 17% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 60% SiO2, 15% Fe2O3, and 20% by mass of Al2O3.

[0022] The sieved sludge powder was added to a wood acetic acid solution at a ratio of 1g:5ml. Ferric chloride was then added until the Al to Fe ratio was 1:1.8 to obtain the first reaction solution. The first reaction solution was reacted at 400r / min, 60℃, and ultrasonic conditions for 4h. Solid-liquid separation was then performed to obtain leachate A and precipitate B. The wood acetic acid was a clear bamboo-derived wood vinegar obtained by dry distillation, condensation, static separation, and vacuum distillation purification. Its pH value was 2.7, the acetic acid mass concentration was 10%, the total phenol content was ≥0.5 wt%, and the tar residue was <0.1 wt%.

[0023] Mix precipitate B with diatomaceous earth accounting for 20% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:20ml, and add acetic acid accounting for 10% of the volume of leachate A. Mix well to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 250℃ and 300r / min for 20h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant D1.

[0024] Example 2 This embodiment provides a method for preparing a magnetic coagulant, including: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 23%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 50%, 10% and 20% respectively, and the moisture content is 90%) was dried to constant weight in an oven at 120℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 90% water and 10% dry basis; the dry basis includes 23% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 50% SiO2, 10% Fe2O3, and 20% by mass of Al2O3.

[0025] The sieved sludge powder was added to a wood acetic acid solution at a ratio of 1g:2ml. Ferric nitrate was then added until the Al to Fe ratio was 1:2 to obtain the first reaction solution. The first reaction solution was reacted at 300r / min, 70℃, and ultrasonic conditions for 5h. Solid-liquid separation was then performed to obtain leachate A and precipitate B. The wood acetic acid was a clear bamboo-derived wood vinegar obtained by dry distillation, condensation, static separation, and vacuum distillation purification. Its pH value was 2.7, the acetic acid mass concentration was 10%, the total phenol content was ≥0.5 wt%, and the tar residue was <0.1 wt%.

[0026] Mix precipitate B with blast furnace slag accounting for 25% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:15ml, and add acetic acid accounting for 5% of the volume of leachate A. Mix evenly to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 200℃ and 350r / min for 27h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant D2.

[0027] Example 3 This embodiment provides a method for preparing a magnetic coagulant, including: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 20%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 70%, 12% and 12% respectively, and the moisture content is 99%) was dried to constant weight in an oven at 80℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 99% water and 1% dry basis; the dry basis includes 20% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 70% SiO2, 12% Fe2O3, and 12% Al2O3 by mass, respectively.

[0028] The sieved sludge powder was added to a wood acetic acid solution at a ratio of 1g:10ml. Ferric chloride was then added until the ratio of Al to Fe was 1:1.5 to obtain the first reaction solution. The first reaction solution was reacted at 500r / min, 50℃, and ultrasonic conditions for 4h. Solid-liquid separation was then performed to obtain leachate A and precipitate B. The wood acetic acid was a clear bamboo-derived wood vinegar obtained by dry distillation, condensation, static separation, and vacuum distillation purification. Its pH value was 2.7, the acetic acid mass concentration was 10%, the total phenol content was ≥0.5 wt%, and the tar residue was <0.1 wt%.

[0029] Mix precipitate B with diatomaceous earth accounting for 12% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:30ml, and add acetic acid accounting for 10% of the volume of leachate A. Mix well to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 250℃ and 300r / min for 15h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant D3.

[0030] Comparative Example 1 This comparative example provides a method for preparing a magnetic coagulant, comprising: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 17%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 60%, 15% and 20% respectively, and the moisture content is 95%) was dried to constant weight in an oven at 105℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 95% water and 5% dry basis; the dry basis includes 17% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 60% SiO2, 15% Fe2O3, and 20% by mass of Al2O3.

[0031] The sieved sludge powder for water supply was added to a wood acetic acid solution at a ratio of 1g:5ml to obtain the first reaction solution. The first reaction solution was reacted at 400r / min, 60℃ and ultrasonic conditions for 4h. Solid-liquid separation was performed to obtain leachate A and precipitate B. The wood acetic acid was a clear bamboo-source wood vinegar obtained by dry distillation, condensation, static separation and vacuum distillation purification. Its pH value was 2.7, the acetic acid mass concentration was 10%, the total phenol content was ≥0.5 wt% and the tar residue was <0.1 wt%.

[0032] Mix precipitate B with diatomaceous earth accounting for 20% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:20ml, and add acetic acid accounting for 10% of the volume of leachate A. Mix well to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 250℃ and 300r / min for 20h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant E1.

[0033] Comparative Example 2 This comparative example provides a method for preparing a magnetic coagulant, comprising: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 17%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 60%, 15% and 20% respectively, and the moisture content is 95%) was dried to constant weight in an oven at 105℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 95% water and 5% dry basis; the dry basis includes 17% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 60% SiO2, 15% Fe2O3, and 20% by mass of Al2O3.

[0034] The sieved sludge powder was added to a wood acetic acid solution at a ratio of 1g:5ml. Ferric chloride was then added until the Al to Fe ratio was 1:1.8 to obtain the first reaction solution. The first reaction solution was reacted at 400r / min, 60℃, and ultrasonic conditions for 4h. Solid-liquid separation was then performed to obtain leachate A and precipitate B. The wood acetic acid was a clear bamboo-derived wood vinegar obtained by dry distillation, condensation, static separation, and vacuum distillation purification. Its pH value was 2.7, the acetic acid mass concentration was 10%, the total phenol content was ≥0.5 wt%, and the tar residue was <0.1 wt%.

[0035] Mix precipitate B with diatomaceous earth accounting for 20% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:20ml, and mix evenly to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 250℃ and 300r / min for 20h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant E2.

[0036] Comparative Example 3 This comparative example provides a method for preparing a magnetic coagulant, comprising: The water supply sludge (based on dry weight, the organic matter content of the water supply sludge is 17%, the contents of SiO2, Fe2O3 and Al2O3 in the inorganic components are 60%, 15% and 20% respectively, and the moisture content is 95%) was dried to constant weight in an oven at 105℃, then ground and passed through a 200-mesh sieve. Specifically, the water supply sludge comprises 95% water and 5% dry basis; the dry basis includes 17% organic matter by mass, with the remainder being inorganic components; and the inorganic components contain 60% SiO2, 15% Fe2O3, and 20% by mass of Al2O3.

[0037] The sieved sludge powder was added to a dilute hydrochloric acid solution at a ratio of 1g:5ml. Ferric chloride was then added until the ratio of Al to Fe was 1:1.8 to obtain the first reaction solution. The first reaction solution was reacted at 400r / min, 60℃ and ultrasonic conditions for 4h. Solid-liquid separation was then performed to obtain leachate A and precipitate B. Mix precipitate B with diatomaceous earth accounting for 20% of the mass of precipitate B, add leachate A to the mixture at a solid-liquid ratio of 1g:20ml, and add acetic acid accounting for 10% of the volume of leachate A. Mix well to obtain the second reaction solution. The second reaction solution was placed in a polytetrafluoroethylene high-pressure reactor and reacted at 250℃ and 300r / min for 20h. After cooling to room temperature, solid-liquid separation was performed to obtain precipitate C. Precipitate C was washed with ethanol and deionized water and then dried in an oven to obtain magnetic coagulant E3.

[0038] Experimental Example 1 The magnetic coagulant prepared according to this invention was used to treat domestic sewage. The initial domestic sewage had SS of 203 mg / L, COD of 328 mg / L, total phosphorus of 3.56 mg / L, and turbidity of 230 NTU. The coagulant was added to the sewage at a ratio of 200 mg: 1 L, stirred at 200 r / min for 5 min, then stirred at 50 r / min for 10 min, followed by sedimentation for 15 min. The precipitate was then used to recover the magnetic coagulant using a magnetic separator.

[0039] The magnetic recovery rate is the mass ratio of the recovered coagulant to the initial coagulant.

[0040] The determination of suspended solids (SS) was carried out according to the "Determination of Suspended Solids in Water - Gravimetric Method" (GB / T 11901-89), the determination of chemical oxygen demand (COD) was carried out according to the "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ 828-2017), the determination of total phosphorus was carried out according to the "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method" (GB / T 11893-89), and the determination of turbidity was carried out according to the "Determination of Turbidity in Water" (HJ 1075-2019).

[0041] The treatment effect of pollutants in the supernatant and the magnetic recovery rate are shown in the table below.

[0042] Table 1: Results of Coagulant Effect Measurement in Each Example and Comparative Example

[0043] The experimental comparison between D1-D3 coagulants and no coagulant shows that the magnetic coagulant prepared by this invention has a very good adsorption effect on pollutants in domestic sewage, and the magnetic recovery rate is extremely high when the coagulant after pollutant adsorption is recovered by a magnetic separator after sedimentation.

[0044] Wood acetate contains reducing substances, and some components decompose and transform into reducing agents under hydrothermal reaction conditions, thus reducing Fe under these dual effects. 3+ Fe is generated 2+ The final product is magnetite (Fe3O4); the appropriate amount of acetic acid added to the second reaction solution replenishes the acidic environment and ensures the Fe... 3+ The iron acetate complex is fully dissolved and complexed to form an iron acetate complex, and the reaction environment is optimized to promote the Fe... 3+ Reduction and magnetite formation.

[0045] Compared to D1-D3 coagulants, E1 coagulant has a poorer adsorption effect and a lower magnetic recovery rate. This is because no iron salt was added during the preparation of the first reaction solution of E1 coagulant, resulting in a lower iron content in E1 coagulant, which in turn makes the coagulant less magnetic and has weaker coagulation performance.

[0046] During the preparation of E2 coagulant, acetic acid was not added when preparing the second reaction solution, resulting in insufficient acidity of the solution, which caused some Fe to be released. 3+ Precipitation affects reactivity, therefore Fe 3+ Insufficient reduction results in less magnetite formation, leading to weak magnetic properties and poor coagulation performance in the prepared coagulant.

[0047] During the preparation of E3 coagulant, the acid used in the preparation of the first reaction solution is dilute hydrochloric acid, which does not have reducing properties, causing Fe... 3+ It is basically not reduced, and very little magnetite is generated, resulting in a coagulant with weak magnetic properties and poor coagulation performance.

[0048] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a magnetic coagulant, characterized in that, include: The dried and ground water supply sludge was mixed with wood acetic acid solution and iron salt was added to obtain a first reaction solution with a mass ratio of Al to Fe of 1:1.5-2. The first reaction was carried out, and after the reaction was completed, leachate A and precipitate B were obtained. Precipitate B is mixed with an inorganic framework, and leachate A and acetic acid (5-10% by volume of leachate A) are added. The mixture is stirred evenly to obtain a second reaction solution. The solution is then subjected to a high-pressure hydrothermal reaction to obtain precipitate C. Precipitate C is washed and dried to obtain a magnetic coagulant.

2. The preparation method according to claim 1, characterized in that, The water supply sludge, on a dry basis, contains 17-23% organic matter, with the remainder being inorganic components. In the inorganic components, the content of SiO2 is 30-70%, the content of Fe2O3 is 15-35%, and the content of Al2O3 is 15-35%. And / or, the particle size of the water supply sludge after grinding is 100-150 μm; And / or, the ratio of the water supply sludge to the wood acetic acid solution is 1g:2-10ml; And / or, the iron salt includes one or more of ferric chloride and ferric nitrate.

3. The preparation method according to claim 1 or 2, characterized in that, The first reaction includes reacting for 4-5 hours under ultrasonic conditions at 300-500 r / min and 50-70℃.

4. The preparation method according to claim 1, characterized in that, The inorganic framework comprises 12-25% of the mass of precipitate B; And / or, the inorganic framework includes one or more of kaolin, bentonite, diatomaceous earth, steel slag, fly ash, and blast furnace slag; And / or, the solid-liquid ratio of the mixture of precipitate B and inorganic framework to leachate A is 1g:15-30ml.

5. The preparation method according to claim 1, characterized in that, The high-pressure hydrothermal reaction process includes: reacting the second reaction liquid at 200~250℃ and 200~350 r / min for 15~27 h.

6. The preparation method according to claim 5, characterized in that, The high-pressure hydrothermal reaction is carried out in a high-pressure reactor.

7. A magnetic coagulant, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The application of the magnetic coagulant as described in claim 7 in water treatment.

9. The application according to claim 8, characterized in that, include: Magnetic coagulants are added directly to the coagulation tank of a waterworks for the removal of impurities and coagulation of tap water. And / or, magnetic coagulants are directly added to the primary sedimentation tank of the wastewater treatment plant to adsorb, coagulate and settle pollutants.

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