A pre-coated dynamic membrane, a filtering device, and its preparation and application

Abstract

This invention discloses a pre-coated dynamic membrane, a filtration device, and its preparation and application. The main components of the pre-coated dynamic membrane include at least one of low bulk density boehmite powder, low bulk density boehmite powder, and low bulk density γ-alumina powder. When used for water filtration, the pre-coated dynamic membrane provided by this invention enables the effluent to reach the treatment level of an ultrafiltration membrane even with relatively poor influent water quality. The treated effluent has an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm. Compared with traditional solidified membranes, the requirements for influent water quality are significantly reduced, solving the problem of solidified membrane fouling. Compared with pre-coated membrane filters using ordinary pre-coated coatings, the effluent quality is better, reaching the level of ultrafiltration membranes, with less membrane powder consumption, less sludge production, and significantly reduced operating costs.

Description

Technical Field

[0001] This invention relates to a pre-coated dynamic membrane, a filtration device, and their preparation and application. Background Technology

[0002] Ceramic membranes, hollow fiber membranes, tubular membranes, and other solidified membranes are commonly used membrane technologies in water treatment. They are typically used in water supply treatment, sewage and wastewater treatment, chemical industry filtration, and food industry filtration. However, they suffer from problems such as easy membrane fouling and high requirements for influent water quality. Although current water treatment technologies have adopted many pretreatment facilities to alleviate membrane fouling to some extent, membrane lifespan is still relatively short, resulting in long pretreatment system processes, high investment, large amounts of reagents added, and high operating costs. In the treatment of oily wastewater in oil fields, where the oil injection water quality requirements are an oil content of 5 mg / L, a suspended solids content of 1 mg / L, and a particle size of 1 μm, the treatment process often adopts technologies such as "influent → sedimentation oil removal tank → air flotation oil removal → flowing sand filter → glauconite filter → hollow fiber ultrafiltration membrane" or "influent → buffer oil separator → air flotation device → biological treatment → sedimentation tank → hollow fiber membrane filtration". These technologies have problems such as long pretreatment processes, high operating costs, multiple filtration stages, easy fouling of membrane filters, and short membrane service life. At the same time, existing diatomaceous earth pre-coated membrane filters cannot meet the treatment requirements.

[0003] Pre-coated dynamic membrane technology is a technology to replace cured membranes. However, in traditional pre-coated dynamic membrane technology, when the pore size of the porous support layer is large (above 1.0 μm), there is a problem of poor water output. When the pore size of the porous support layer is small, it suffers from the same problem of easy fouling as cured membranes.

[0004] The pre-coated dynamic membrane consists of a porous support layer and a pre-coated layer formed by pre-coating materials. The pre-coating material is the key material for forming the pre-coating layer and is one of the key factors affecting the treatment effect. Existing pre-coating materials mainly fall into the following categories: ① metal oxides, such as zirconium dioxide, titanium dioxide, and manganese dioxide; ② hydroxides or hydrated oxides, such as iron hydroxide, magnesium hydroxide, and zinc hydroxide; ③ non-metallic minerals and inorganic powders, such as diatomaceous earth, kaolin, and activated carbon; ④ organic materials, such as ovalbumin, gamma globulin, gels, polymers, and humic acid.

[0005] The main problems with existing technologies using diatomaceous earth and other pre-coating materials and pre-coated dynamic membrane technologies are: high consumption of pre-coating materials (generally 800-1200 g / m³). 2The requirements for influent water quality, such as the content of suspended solids and petroleum, are relatively strict, and the effluent water quality is poor. For details, please refer to Zhou Wenqi, Xie Zhenfang. Optimization of process parameters for diatomaceous earth pre-coated membrane filtration [J]. Water Purification Technology, 2017, 36(5): 59-62, and Fu Lei, Gu Xiaofang, Yang Pingping, et al. Experimental study on the treatment of wastewater from Xinjiang oilfield by diatomaceous earth filter [J]. China Water & Wastewater, 2015, 31(7): 87-89.

[0006] Boehmite, also known as boehmite, has the chemical formula AlOOH·nH₂O (n = 0.08-0.62). The bulk density of both boehmite and gibbsite ranges from 0.08 to 1.2 g / cm³. 3 Generally, the bulk density is >0.6 g / cm³. 3 .

[0007] γ-Alumina is a type of activated alumina, with the chemical formula γ-Al₂O₃. The bulk density of γ-alumina ranges from 0.07 to 3.0 g / cm³. 3 Generally, the bulk density is >0.6 g / cm³. 3 . Summary of the Invention

[0008] To at least partially address the problems of excessive pre-coating material usage, stringent requirements for influent water quality, and poor effluent water quality in existing pre-coated membrane materials and pre-coated dynamic membrane technologies, the inventors of this invention use low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder to prepare pre-coated dynamic membranes, thereby removing suspended solids, insoluble liquids, emulsified oils, and colloids from water or aqueous solutions, improving the quality of treated water and reducing sludge volume.

[0009] The low bulk density boehmite powder, boehmite powder, and γ-alumina powder used in this invention refer to powders with a bulk density of <0.6 g / cm³. 3 Boehmite powder, boehmite powder and γ-alumina powder.

[0010] As one aspect of the present invention, a pre-coated dynamic film is disclosed, the main components of which include at least one of low bulk density boehmite powder, low bulk density boehmite powder and low bulk density γ-alumina powder.

[0011] In a possible specific embodiment, the bulk density of the low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder is <0.6 g / cm³. 3 The pore volume is greater than 0.5 mL / g, and the median particle size is less than or equal to 100 μm.

[0012] In a possible specific implementation, the pre-coated dynamic film further contains a surface modifier.

[0013] As another aspect of the invention, a filtration device is provided, comprising a porous support layer and the aforementioned pre-coated dynamic membrane coated on the porous support layer.

[0014] In a possible specific embodiment, the amount of low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder in the pre-coated dynamic film is greater than or equal to 10 g / m³. 2 .

[0015] In possible specific embodiments, the porous support layer may be one of the following:

[0016] ① Woven wire mesh and sieves, such as stainless steel wire mesh, ordinary sieves, industrial filter cloth, sieve silk, stainless steel sintered mesh, etc.;

[0017] ② Organic membranes, also known as organic polymer membranes or high molecular weight membranes, include hollow fiber membranes, tubular membranes, organic powder sintered membrane tubes, etc.

[0018] ③ Inorganic membranes, commonly used ones include titanium powder sintered membranes, stainless steel powder sintered membrane tubes, silicon carbide membranes, porous carbon membranes, and ceramic membranes.

[0019] In a possible specific implementation, the pore size of the porous support layer used is 0.03 μm-50 μm.

[0020] In at least one specific embodiment, the filter device described above may be of the plate and frame type, the blade type, or the candle type.

[0021] As another aspect of the invention, the use of low bulk density boehmite powder, low bulk density boehmite powder and / or low bulk density γ-alumina powder in the preparation of pre-coated dynamic films is involved.

[0022] As another aspect of the invention, the use of low bulk density boehmite powder, low bulk density boehmite powder and / or low bulk density γ-alumina powder in the preparation of filtration devices is discussed.

[0023] As another aspect of the present invention, a method for preparing the above-mentioned pre-coated dynamic film is provided, comprising:

[0024] Low bulk density boehmite powder, low bulk density boehmite powder and / or low bulk density γ-alumina powder are dispersed in an aqueous solution;

[0025] The pre-coated dynamic membrane with separation function is formed on the surface or inside the pores of the porous support layer by filtration and coating onto the porous support layer.

[0026] As another aspect of the present invention, a filtration method is provided using the aforementioned pre-coated dynamic membrane.

[0027] When raw water is filtered using the pre-coated dynamic membrane provided by this invention, if the filtration resistance rises to a certain critical value or the effluent water quality fails to meet the requirements, the pre-coated filter cake layer and other pollutants are washed away by backwashing or other means, and then the next round of pre-coating, filtration and cleaning process begins.

[0028] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0029] The pre-coated dynamic membrane developed in this invention enables effluent to achieve ultrafiltration treatment levels even with poor influent water quality. The treated effluent has an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm. Compared to traditional solidified membranes, the requirements for influent water quality are significantly reduced, solving the problem of solidified membrane fouling. Compared to commonly used pre-coated membrane filters, the effluent quality is better, achieving ultrafiltration membrane levels, requiring less membrane powder, generating less sludge, and significantly reducing operating costs.

[0030] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description and claims. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0032] Through indoor and field experiments, the inventors discovered that ordinary boehmite powder, boehmite powder, and γ-alumina powder (bulk density > 0.6 g / cm³) 3 Similar to commonly used pre-coating materials such as diatomaceous earth, metal oxides, kaolin, and activated carbon, this material produces poor effluent quality when used in pre-coated dynamic membrane filtration. Low bulk density materials such as boehmite powder, gibbsite powder, and γ-alumina powder (bulk density <0.6 g / cm³) also exhibit poor effluent quality. 3 It has good effects, and the quality of the effluent can reach the level of ultrafiltration.

[0033] Example 1: Oily wastewater treatment.

[0034] With a bulk density of 0.58 g / cm³ 3γ-alumina powder with a pore volume of 0.7 mL / g and a median particle size of 50 μm was dispersed in clean water or filtered effluent. The powder was then pumped onto a candle-type titanium metal membrane tube with a substrate of 5 μm, a diameter of 13.5 mm, and a length of 250 mm to prepare a pre-coated dynamic membrane. The powder dosage was 50 g / m³. 2 A filtration device was obtained, namely the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. The turbidity of the influent to the experimental device was measured to be 31.6 NTU, the oil content to be 70.1 mg / L, the suspended solids to be 16.6 mg / L, and the median suspended particle diameter to be 4.15 μm. Furthermore, the turbidity of the effluent was measured to be 0.21 NTU, the oil content to be 0.79 mg / L, the suspended solids to be 0.31 mg / L, and the median suspended particle diameter to be 0.47 μm. This met the filtration level of an ultrafiltration membrane, with the treated effluent having an oil content to be less than 1.0 mg / L, suspended solids to be less than 1.0 mg / L, and a median suspended particle diameter to be less than 1.0 μm.

[0035] Comparative Example 1-1: Treatment of oily wastewater.

[0036] Diatomaceous earth with a median particle size of 50 μm was used as a pre-coating material, dispersed in clean water or filtered effluent, and then pumped onto a candle-shaped titanium metal membrane tube with a membrane substrate of 5 μm, a diameter of 13.5 mm, and a length of 250 mm to prepare a pre-coated dynamic membrane. The membrane powder dosage was 100 g / m³. 2 A filtration device was obtained, which is the experimental device for the comparative example. Using this experimental device, oily wastewater with the same influent water quality parameters as in Example 1 was filtered. The effluent water quality was turbidity 1.9 NTU, oil content 1.79 mg / L, suspended solids 2.44 mg / L, and median suspended particle diameter 1.97 μm. It can be concluded that when the influent water quality is relatively poor, the filtration level of the pre-coated dynamic membrane obtained by using diatomaceous earth with a median particle size of 50 μm as the pre-coating layer cannot reach the filtration level of the ultrafiltration membrane.

[0037] Comparative Examples 1-2: Treatment of oily wastewater.

[0038] Using a bulk density of 0.70 g / cm³ 3 A pre-coated dynamic membrane was prepared by dispersing γ-alumina powder with a pore volume of 0.3 mL / g and a median particle size of 25 μm in clean water or filtered effluent. The powder was then pumped onto a candle-shaped titanium metal membrane tube with a membrane substrate of 5 μm, a diameter of 13.5 mm, and a length of 250 mm. The powder dosage was 100 g / m³. 2A filtration device was obtained, which is the experimental device for this comparative example. Using this experimental device, oily wastewater with the same influent water quality parameters as in Example 1 was filtered. The effluent water quality was turbidity 1.7 NTU, oil content 1.51 mg / L, suspended solids 2.11 mg / L, and median suspended particle diameter 1.57 μm. It can be concluded that under relatively poor influent water quality, a bulk density of 0.70 g / cm³ is suitable. 3 The filtration level of the pre-coated dynamic membrane obtained by using γ-alumina powder with a pore volume of 0.3 mL / g and a median particle size of 25 μm as a pre-coating layer cannot reach that of the ultrafiltration membrane.

[0039] Example 2: Oily wastewater treatment.

[0040] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 5 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2 A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of influent turbidity of 30.1 NTU, oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and median suspended particle diameter of 3.95 μm, the effluent turbidity was measured to be 0.21 NTU, oil content of 0.8 mg / L, suspended solids content of 0.36 mg / L, and median suspended particle diameter of 0.47 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. The treated effluent had an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm.

[0041] Comparative Example 2

[0042] Using a bulk density of 0.65 g / cm³ 3 A thin layer of borosilicate powder with a pore volume of 0.3 mL / g and a median particle size of 75 μm was used as a pre-coating layer. This pre-coated layer was dispersed in clean water or filtered produced water and then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 5 μm. This process achieved the preparation of a pre-coated dynamic membrane. The amount of membrane powder used was 100 g / m³. 2A filtration device was obtained, which is the experimental device of this embodiment. Using this experimental device, oily wastewater with the same influent water quality parameters as in Example 2 was filtered. The effluent water quality was turbidity 1.6 NTU, oil content 1.3 mg / L, suspended solids 1.7 mg / L, and median suspended particle diameter 1.63 μm. It can be concluded that under relatively poor influent water quality, a bulk density of 0.65 g / cm³ is suitable. 3 Using thin boehmite powder with a pore volume of 0.3 mL / g and a median particle size of 75 μm as a pre-coating layer, the filtration level of the pre-coated dynamic membrane cannot reach that of the ultrafiltration membrane.

[0043] Example 3: Oily wastewater treatment.

[0044] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a 13.5 mm diameter, 250 mm long stainless steel membrane tube with a membrane substrate of 1 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2 A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of an influent oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and a median suspended particle diameter of 3.95 μm, the effluent was found to have an oil content of 0.3 mg / L, a suspended solids content of 0.29 mg / L, and a median suspended particle diameter of 0.391 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. The treated effluent had an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm.

[0045] Example 4: Oily wastewater treatment.

[0046] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a stainless steel membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 7 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of an influent oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and a median suspended particle diameter of 3.95 μm, the effluent oil content was 0.70 mg / L, suspended solids of 0.36 mg / L, and median suspended particle diameter of 0.580 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. After treatment, the effluent oil content was less than 1.0 mg / L, suspended solids were less than 1.0 mg / L, and the median suspended particle diameter was less than 1.0 μm.

[0047] Example 5: Oily wastewater treatment.

[0048] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a stainless steel membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 10 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2 A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of an influent oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and a median suspended particle diameter of 3.95 μm, the effluent oil content was 0.70 mg / L, suspended solids content was 0.41 mg / L, and the median suspended particle diameter was 0.621 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. After treatment, the effluent oil content was less than 1.0 mg / L, suspended solids were less than 1.0 mg / L, and the median suspended particle diameter was less than 1.0 μm.

[0049] Example 6: Oily wastewater treatment.

[0050] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 20 μm to prepare a pre-coated dynamic membrane. The powder dosage was 50 g / m³. 2A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of an influent oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and a median suspended particle diameter of 3.95 μm, the effluent oil content was 0.9 mg / L, suspended solids content was 0.51 mg / L, and median suspended particle diameter was 0.663 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. After treatment, the effluent oil content was less than 1.0 mg / L, suspended solids were less than 1.0 mg / L, and the median suspended particle diameter was less than 1.0 μm.

[0051] Example 7: Oily wastewater treatment.

[0052] The bulk density is 0.19 g / cm³. 3 Boehmite powder with a pore volume of 0.8 mL / g and a median particle size of 100 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a candle-shaped stainless steel membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 50 μm to prepare a pre-coated dynamic membrane. The powder dosage was 100 g / m³. 2 A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Under the conditions of an influent oil content of 50.1 mg / L, suspended solids of 12.6 mg / L, and a median suspended particle diameter of 3.95 μm, the effluent was found to have an oil content of 0.9 mg / L, a suspended solids content of 0.53 mg / L, and a median suspended particle diameter of 0.730 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. The treated effluent had an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm.

[0053] Example 8: Treatment of oily wastewater.

[0054] The bulk density is 0.18 g / cm³. 3 A pseudoboehmite powder with a pore volume of 0.8 mL / g and a median particle size of 75 μm was dispersed in clean water or filtered produced water. The powder was then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 5 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2A filtration device was obtained, namely the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. The turbidity of the influent to the experimental device was 29.5 NTU, the oil content was 40.2 mg / L, the suspended solids were 13.6 mg / L, and the median suspended particle diameter was 3.76 μm. The turbidity of the effluent was 0.23 NTU, the oil content was 0.67 mg / L, the suspended solids were 0.36 mg / L, and the median suspended particle diameter was 0.49 μm. It can be concluded that even with relatively poor influent water quality, the filtration level of the pre-coated dynamic membrane reached that of an ultrafiltration membrane. The treated effluent had an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm.

[0055] Comparative Example 8-1

[0056] Using a bulk density of 0.63 g / cm³ 3 A pseudoboehmite powder with a pore volume of 0.3 mL / g and a median particle size of 75 μm was used as a pre-coating layer. This pre-coated layer was dispersed in clean water or filtered produced water and then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 5 μm. This process achieved the preparation of a pre-coated dynamic membrane. The amount of membrane powder used was 100 g / m³. 2 A filtration device was obtained, which is the experimental device of this embodiment. Then, produced water from an oilfield, i.e., oily wastewater, was filtered. Using this experimental device, oily wastewater with the same influent water quality parameters as in Example 1 was filtered. The effluent water quality was turbidity 1.5 NTU, oil content 1.2 mg / L, suspended solids 1.8 mg / L, and median suspended particle diameter 1.57 μm. It can be concluded that under relatively poor influent water quality, a bulk density of 0.63 g / cm³ is suitable. 3 The filtration level of the pre-coated dynamic membrane obtained by using boehmite powder with a pore volume of 0.3 mL / g and a median particle size of 75 μm as the pre-coating material cannot reach that of the ultrafiltration membrane.

[0057] Example 9: Water supply treatment.

[0058] With a bulk density of 0.4 g / cm³ 3 γ-alumina powder with a pore volume of 0.8 mL / g and a median particle size of 50 μm was dispersed in clean water or filtered effluent. The powder was then pumped onto a candle-type titanium metal membrane tube with a diameter of 13.5 mm and a length of 250 mm and a membrane substrate of 5 μm to prepare a pre-coated dynamic membrane. The powder dosage was 30 g / m³. 2The filtration device, namely the experimental device of this embodiment, was obtained. Then, river water was filtered. The turbidity of the influent to the experimental device was measured to be 29.5 NTU, and the turbidity of the effluent was measured to be 0.12 NTU. It can be concluded that when the turbidity of the influent is relatively high, the filtration level of the pre-coated dynamic membrane reaches the filtration level of the ultrafiltration membrane.

[0059] In this embodiment of the invention, a pre-coated dynamic membrane, whose main components include low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder, is used to filter raw water to remove suspended solids, insoluble liquids, emulsified oils, and colloids, thereby improving the quality of treated water and reducing sludge volume. When the filtration resistance rises to a certain critical value or the effluent quality fails to meet requirements, the pre-coated filter cake layer and other pollutants are washed away by backwashing or other means. Then, the next round of pre-coating, filtration, and cleaning processes begins.

[0060] In this embodiment of the invention, the inventors discovered that when a bulk density of <0.6 g / cm³ is used... 3 When boehmite powder with a pore volume greater than 0.5 mL / g, low bulk density boehmite powder, and low bulk density γ-alumina powder are used as pre-coating materials, the filtration effect of the pre-coated dynamic membrane decreases significantly after the median particle size of the powder is greater than 100 μm.

[0061] In this embodiment of the invention, the inventors discovered that the amount of low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder in the pre-coated dynamic film is less than 10 g / m³. 2 At that time, the filtration effect of the pre-coated dynamic membrane decreased significantly.

[0062] The pre-coated dynamic membrane provided in this embodiment of the invention also contains a surface modifier. The powder weight percentage of the surface modifier can be, for example, 0.1%-10%. When surface modification is performed on low bulk density boehmite powder, boehmite powder, and γ-alumina powder using a surface modifier with a powder weight percentage of 0.1%-10%, the filtration effect of the surface-modified pre-coated dynamic membrane is not much different from that of the unmodified pre-coated dynamic membrane, and it can still achieve the filtration level of an ultrafiltration membrane.

[0063] The surface modifiers used in the embodiments of the present invention may include one or more of the following agents:

[0064] ①Carboxyl-containing compounds, such as polyacrylic acid and its salts, polymaleic acid and its salts, oxalic acid and its salts, tartaric acid and its salts, citric acid and its salts, higher fatty acids and their salts, polyepoxysuccinic acid, polyaspartic acid, sodium carboxymethyl starch, sodium carboxymethyl cellulose, sodium gluconate, sodium gluconate, sodium benzoate, etc.

[0065] ② Compounds containing sulfonic acid groups or sulfate ester groups, such as sodium styrene sulfonate, sodium benzene sulfonate, sodium alkylbenzene sulfonate, sodium alkyl sulfonate, etc.;

[0066] ③ Compounds containing phosphonic acid groups or phosphonic acid ester groups, such as ethylenediaminetetramethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, hydroxypropyl distarch phosphate, hydroxyphosphonic acid acetic acid, alkyl phosphate salts, trisodium phosphate, sodium polyphosphate, sodium hexametaphosphate, etc.

[0067] ④ Ammonium compounds, such as primary amine salts, secondary amine salts, and quaternary amine salts;

[0068] ⑤ Compounds containing thiol groups, such as thiocarbonates, etc.;

[0069] ⑥ Compounds containing two or more of the following groups: carboxyl, sulfonic acid, phosphoric acid, mercapto, and ammonium groups, such as hydroxyphosphonic acid acetic acid, 3-allyl-2-hydroxypropylsulfonic acid, methylamine dimethylphosphonic acid, hydroxamic acid and its salts, sulfonated succinates and sulfonated succinamide salts, etc.

[0070] ⑦ Natural or naturally modified anionic compounds, such as tannins, anionic starch, lignin, sodium alginate, etc.

[0071] ⑧ Inorganic modifiers, such as metal chlorides, metal sulfates, metal nitrates, organic acid salts and esters, silica and its salts, carbonates, aluminates, zirconium oxide, titanium oxide, aluminum oxide, zinc oxide, etc.

[0072] The pre-coated dynamic membrane developed in this invention enables effluent to achieve ultrafiltration treatment levels even with poor influent water quality. The treated effluent has an oil content of less than 1.0 mg / L, suspended solids of less than 1.0 mg / L, and a median suspended particle diameter of less than 1.0 μm. Compared to traditional solidified membranes, the requirements for influent water quality are significantly reduced, solving the problem of solidified membrane fouling. Compared to commonly used pre-coated membrane filters, the effluent quality is better, achieving ultrafiltration membrane levels, requiring less membrane powder, generating less sludge, and significantly reducing operating costs.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All modifications or applications made in accordance with the above embodiments are within the scope of protection of this technical solution.

[0074] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details based on all the teachings disclosed, and all such changes are within the scope of protection of this invention. The full scope of this invention is given by the appended claims and any equivalents thereof.

Claims

1. A pre-coated dynamic film, characterized in that, Its main components include at least one of low bulk density boehmite powder, low bulk density boehmite powder and low bulk density γ-alumina powder. The bulk density of the low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder is <0.6 g / cm³. 3 The pore volume is greater than 0.5 mL / g, and the median particle size is less than or equal to 100 μm.

2. The pre-coated dynamic film as described in claim 1, characterized in that, It also contains surface modifiers.

3. A filtration device, characterized in that, The membrane comprising a porous support layer and a pre-coated dynamic membrane as described in any one of claims 1-2 coated on the porous support layer.

4. The filtration device as described in claim 3, characterized in that, The amount of low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder in the pre-coated dynamic membrane is greater than or equal to 10 g / m³. 2 .

5. The filtration device as described in claim 4, characterized in that, The porous support layer includes one or more of the following types: Woven mesh, sieve mesh, organic membranes and inorganic membranes.

6. The filtration device as described in claim 5, characterized in that, The pore size of the porous support layer is 0.03μm-50μm.

7. The filtration device according to any one of claims 3-6, characterized in that, The filter device is of the plate and frame type, blade type, or candle type.

8. The application of a low bulk density boehmite powder, a low bulk density boehmite powder, and / or a low bulk density γ-alumina powder in the preparation of a pre-coated dynamic film; The bulk density of the low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder is <0.6 g / cm³. 3 The pore volume is greater than 0.5 mL / g, and the median particle size is less than or equal to 100 μm.

9. The application of a low bulk density boehmite powder, a low bulk density boehmite powder, and / or a low bulk density γ-alumina powder in the preparation of a filtration device; The bulk density of the low bulk density boehmite powder, low bulk density boehmite powder, and / or low bulk density γ-alumina powder is <0.6 g / cm³. 3 The pore volume is greater than 0.5 mL / g, and the median particle size is less than or equal to 100 μm.

10. A method for preparing the pre-coated dynamic film according to any one of claims 1-2, characterized in that, include: At least one of low bulk density boehmite powder, low bulk density boehmite powder and low bulk density γ-alumina powder is dispersed in an aqueous solution; The pre-coated dynamic membrane with separation function is formed on the surface or inside the pores of the porous support layer by filtration and coating onto the porous support layer.

11. A filtering method, characterized in that, Use the pre-coated dynamic film according to any one of claims 1-2.

12. The filtering method as described in claim 11, characterized in that, Also includes: When the filtration resistance exceeds the preset critical value or the effluent water quality exceeds the preset requirements, the pre-coated dynamic membrane and pollutants are washed away by backwashing, and the pre-coated dynamic membrane is recoated.