A non-uniformly wettable hard particle filter bed

Abstract

The application discloses a kind of non-uniform wetting hard particle filter material layer, by super-hydrophobic super-oil-wettable hard particle filter material and natural hard particle filter material are mixed into 1:1 by mass ratio.The application is filled in filter column after two kinds of special wetting hard particle filter material is evenly mixed, constructs non-uniform wetting hard particle filter material layer, for separating oily sewage, continuous water phase is under the affinity of oil-wettable filter material surface under hydrophilic water, with smaller resistance through filter material layer, simultaneously, super-hydrophobic super-oil-wettable filter material is captured and adhered to oil phase in water, realize the effective separation of oily sewage;The non-uniform wetting hard particle filter material layer of the application can also effectively solve the problem that super-hydrophobic super-oil-wettable hard particle filter material surface is contaminated by oil dirt;The non-uniform wetting hard particle filter material layer of the application can quickly, efficiently, continuously filter large amount of emulsion degree high difficult to handle oily wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of non-uniform wettability hard particle filter layer. BACKGROUND

[0002] Petroleum sewage is the key source of environmental water pollution, and direct discharge of such oily sewage will inevitably cause ecological disaster and seriously threaten human health. Deep bed filtration is a commonly used method for treating oily wastewater, which mainly uses hard particles as filter material. The mechanism of the filtration process includes migration mechanism and adhesion mechanism, so the wettability of the filter material surface has a great influence on the oil removal performance. In recent years, researchers have paid attention to the use of special wettability to achieve controllable oil-water separation, which can selectively affinity water phase or oil phase, allowing one phase in sewage to pass freely, and retaining the other phase to achieve the purpose of oil-water separation.

[0003] The prior art is to modify the hard particle filter material into a single wettability filter bed. Since the super-hydrophobic super-oil-wet filter bed has strong affinity for oil, it can rely on the adhesion of oil droplets to achieve oil removal, and has high oil removal efficiency, but has high head loss (high resistance, requires external pressure to press the water down, can only treat stratified oil-water liquid with density heavier than water), and the material surface is easily contaminated by oil and loses separation performance. The super-hydrophilic underwater super-oleophobic filter has strong adhesion to water and weak adhesion to oil (can only treat stratified oil-water liquid with density lighter than water), and the surface is easy to form a water film, which hinders the adhesion of oil droplets and reduces the oil removal efficiency of the filter material, but has low head loss. SUMMARY

[0004] The purpose of the present application is to provide a non-uniform wettability hard particle filter layer, which can be used to treat oil-in-water type oily sewage, and can achieve continuous water phase passing through the filter layer with small resistance, and effective separation of oily sewage.

[0005] The technical solution of the present application is a non-uniform wettability hard particle filter layer, which is formed by mixing super-hydrophobic super-oil-wet hard particle filter material and natural hard particle filter material in a mass ratio of 1:1.

[0006] The super-hydrophobic super-oil-wet hard particle filter material is modified using the same type of natural hard particle filter material as the mixed natural hard particle filter material as the base material.

[0007] The natural hard particle filter material is one of serpentine, quartz sand, walnut shell, zeolite or glass slag.

[0008] The particle size of the super-hydrophobic super-oil-wet hard particle filter material and the natural hard particle filter material is 0.125-0.175 mm.

[0009] The super-hydrophobic super-oleophilic rigid particle filter material is prepared by the following method, specifically comprising the following steps:

[0010] (1) Pretreatment: The natural rigid particle filter material substrate is placed in anhydrous ethanol and deionized water respectively, and the surface attached floating dust and grease and other impurities are removed after ultrasonic cleaning, and then it is placed in a 100°C oven for drying for 5-8h; the pretreatment keeps the substrate surface clean;

[0011] (2) Roughening treatment: 1-10 parts of hydrophobic silica nanoparticles and 10-20 parts of polydimethylsiloxane (PDMS) are added dropwise to 400-500 parts of an organic solvent, stirred at room temperature, and then 1-10 parts of a resin curing agent (binder) is added, and continuous stirring is performed to obtain a roughening solution; the pretreated substrate is soaked in the roughening solution, taken out after soaking for 5-10min, and then semi-dried (semi-drying is beneficial to the surface loading of low surface energy substances); the roughening solution is PDMS and hydrophobic silica nanoparticles, PDMS provides adhesion for silica nanoparticles (adhesion to the substrate surface), on the other hand, the hydrophobicity of silica itself reduces the surface energy of the substrate, and is used for crosslinking with the hydrophobic modification solution to further improve the coating effect of the super-hydrophobic coating;

[0012] (3) Hydrophobic modification treatment: 1-10 parts of a surfactant (to enable uniform dispersion of siloxane in deionized water), 10-20 parts of concentrated ammonia water, and 10-20 parts of alkaline silica sol are added to 80-100 parts of deionized water, stirred uniformly, and then 10-30 parts of water-based fluorine-free silane is added, and stirred to obtain a hydrophobic modification liquid; the roughened rigid particle filter material and the hydrophobic modification liquid are placed in a 50-80°C vacuum rotating device at a mass-volume ratio of 1:1.5-5 (g:mL) and rotated for 50-80min (to evaporate water), to obtain a modified rigid particle filter material; the low surface energy substance and the hydroxyl groups on the surface of the filter material undergo dehydration condensation reaction to form multiple hydrophobic molecular chains, which intertwine to form a hydrophobic oleophilic film;

[0013] (4) Curing: the modified rigid particle filter material is taken out and dried in a vacuum oven; after drying, a super-hydrophobic super-oleophilic rigid particle filter material is obtained.

[0014] In step (2), the particle size of the hydrophobic silica nanoparticles is 7-40nm.

[0015] In step (2), the organic solvent is one of n-hexane, dichloromethane, dichloroethane, n-butane, ethyl acetate, butyl acetate, or acetone.

[0016] In step (3), the pH value of the alkaline silica sol is 8.5-10, and the particle size of silica in the silica sol is 5nm.

[0017] In step (3), the pH value of the hydrophobic modification solution is 8.5-10.

[0018] In step (3), the water-based fluorine-free silane is one of phenyltrimethoxysilane, trimethoxyethoxysilane or n-octyltriethoxysilane. The low surface energy substance used for hydrophobic modification is fluorine-free alkane-based silane, which is different from fluorine-containing long-chain polymer and is pollution-free to the environment. Phenyltrimethoxysilane (Maya Reagent) / n-octyltriethoxysilane (Anjie Chemical, Sats Chemical Technology (Shanghai) Co., Ltd.) / trimethoxyethoxysilane (Shanghai Mayre)

[0019] In step (4), the drying temperature is 200-300℃ and the drying time is 1-3h. The effect of drying temperature on the formation of the hydrophobic coating is that the hydrogen bond can be destroyed after the hydrolysis and condensation of silane, and the siloxane bond is completely dehydrated and cured.

[0020] The drying temperature has a great influence on the formation of the hydrophobic coating. In the process of coating formation, the siloxane bond generated after the hydrolysis and condensation of silane forms a hydrogen bond with the surface of the filter material, thereby forming a hydrophobic coating. When the drying temperature is high, the number of siloxane bonds in the generated hydrophobic coating will increase, and the number of hydrogen bonds will decrease, because high temperature will cause water molecules to lose, thereby dehydrating and curing to form siloxane bonds. If the drying temperature is too high, the water-based fluorine-free silane will decompose, and if the drying temperature is too low, the dehydration reaction will not be complete.

[0021] The boiling point of the liquid can be reduced under vacuum, so that the solvent (water) can be removed at a lower temperature, thereby protecting the fluorine-free silane from being overheated or decomposed; at the same time, the dehydration can be accelerated, and the evaporation speed of water molecules can be accelerated under vacuum, so that the water can be removed from the liquid more quickly. At the same time, under the vacuum environment, the water molecules can evaporate directly from the surface of the solid, avoiding the phenomenon that the water forms droplets on the surface of the solid. Oxidation is prevented, and under the vacuum condition, the pressure of oxygen is reduced, so that the reaction between the silane and oxygen at high temperature can be avoided, thereby maintaining the purity and stability of the substance. The drying speed is accelerated: after the air in the vacuum rotary dryer is extracted, the evaporation and drying speed of the water can be accelerated, thereby shortening the drying time, improving the production efficiency, and the vacuum degree is set to 0.08 MPa; in the rotating process, the surface of the hard particles is continuously exposed to the vacuum environment, thereby improving the evaporation rate and drying efficiency of the solution. At the same time, rotation can promote the mixing and heat transfer between substances, so that the drying speed is more uniform and fast; under the vacuum environment, the evaporation of water can cause the temperature of the solution to decrease, thereby easily causing the condensation of the hydrophobic agent, and through rotation, the surface of the hard filter material can be continuously exposed to the vacuum environment, thereby avoiding condensation on the surface thereof; through rotation, the hydrophobic modifier can be uniformly loaded on the surface of the hard filter material, and the obtained coating is more uniformly wrapped on the surface of the filter material, and the rotating speed value is a constant value of 900 rmp.

[0022] The present application forms a non-uniform wetting filter bed by mixing hard particle filter material with super-hydrophobic super-oleophilic surface and natural hydrophilic underwater super-oleophobic hard particle filter material. The super-hydrophobic super-oleophilic modification of the hard particle filter material is achieved by roughening the surface of the hard particle to form a micro-nano composite structure, increasing the adhesion of low surface energy substances, and increasing the adhesion of low surface energy substances, greatly improving the coating of the super-hydrophobic coating on the surface of the hard particle. The high affinity of the super-hydrophobic super-oleophilic filter material surface for oil adheres oil to its surface, and the strong adhesion of the hydrophilic underwater super-oleophobic filter material to water and the low adhesion to oil, and the water film adsorbed reduces the pollution of the filter material surface by oil. The super-hydrophobic super-oleophilic hard particle filter material in the non-uniform wetting filter bed is adjacent to and uniformly distributed with the super-hydrophilic underwater super-oleophobic hard particle filter material, and the continuous water phase in the oil-containing sewage will migrate to the surface of the super-hydrophilic hard particle filter material with high surface energy, and penetrate to the lower layer of the filter bed under the action of capillary force and gravity; at the same time, the high affinity of the super-hydrophobic super-oleophilic filter material surface will destroy the surfactant-induced force between the oil and water phases and capture the oil droplets, and the small oil droplets will continue to coalesce on the super-oleophilic filter material surface to form large oil droplets, which will be trapped above the filter material, while the small oil droplets that are not captured will continue to flow to the middle and lower layers of the filter bed, and the middle and lower layers will continue to play a good role in capturing, adhering and trapping oil droplets, thereby having a good oil-water separation effect on oil-containing sewage of the oil-in-water type.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention uniformly mixes two special wettable hard granular filter media and fills them into a filter column to construct a non-uniform wettable hard granular filter media layer for separating oil-in-water type oily wastewater. The continuous aqueous phase passes through the filter media layer with less resistance under the affinity of the hydrophilic underwater oleophobic filter media surface. At the same time, the superhydrophobic and superoleophilic filter media captures and adheres to the oil phase in the water, thereby achieving effective separation of oily wastewater; (2) The non-uniform wettable hard granular filter media layer of the present invention can effectively solve the problem of The limitations of a single filter bed increase the probability of oil droplets penetrating the filter bed while improving the oil removal efficiency and reducing head loss, thereby reducing energy consumption; (3) The non-uniform wettable hard particle filter layer of the present invention can also achieve complete separation of oil substances in water when treating severely emulsified oily wastewater. Compared with the unmodified hard particle filter layer, the treatment effect is significantly improved; and it can still maintain excellent separation efficiency for oily wastewater with strong acidity and high salt concentration, thereby achieving rapid, efficient, continuous and large-volume filtration of highly emulsified and difficult-to-treat oily wastewater. Attached Figure Description

[0024] Figure 1 The hydrophobic and oleophilic properties of the superhydrophobic and superoleophilic quartz sand filter media and the unmodified quartz sand filter media in air are shown in Example 1.

[0025] Figure 2 The hydrophobic angle of the superhydrophobic and superoleophilic quartz sand filter media in Example 1;

[0026] Figure 3 The positional distribution of the superhydrophobic and superoleophilic quartz sand filter media and the unmodified quartz sand filter media in Example 1 after being placed in water;

[0027] Figure 4 SEM images of the superhydrophobic and superoleophilic serpentine filter media and the unmodified serpentine filter media in Example 2;

[0028] Figure 5 The adsorption capacity of the superhydrophobic and superoleophilic zeolite filter media and the unmodified zeolite filter media in Example 3 for various organic substances;

[0029] Figure 6 These are optical photographs of the non-uniformly wettable walnut shell filter media layer and the unmodified walnut shell filter media layer after filtering a severely emulsified oil-in-water emulsion in Example 4.

[0030] Figure 7 The particle size distribution of the filtrate after filtering strongly acidic oily wastewater using a non-uniformly wettable quartz sand filter media layer and an unmodified quartz sand filter media layer in Example 5 is shown.

[0031] Figure 8The COD removal rate of the filtrate after filtering a high-salt-concentration oil-in-water emulsion using a non-uniformly wettable serpentine filter media layer and an unmodified serpentine filter media layer in Example 6 is shown. Detailed Implementation

[0032] Example 1

[0033] The preparation method of the superhydrophobic and superoleophilic quartz sand filter media of the present invention specifically includes the following steps:

[0034] (1) Pretreatment: Quartz sand was placed in anhydrous ethanol and deionized water in sequence and ultrasonically cleaned for 10 min each to remove floating dust and grease and other impurities attached to the surface. Then it was placed in a 100℃ oven to dry for 5 h. The selected quartz sand particle size was 0.125~0.175mm.

[0035] (2) Roughening treatment: 1 part of hydrophobic silica nanoparticles (Hydrophobic-170 type) and 10 parts of polydimethylsiloxane were added dropwise to 400 parts of n-hexane. After stirring at room temperature, 3 parts of epoxy resin curing agent were added and stirred continuously to obtain a roughening solution. The pretreated quartz sand was immersed in the roughening solution and taken out after 5 minutes to be semi-dry.

[0036] (3) Hydrophobic modification: 3 parts of cationic fluorocarbon surfactant, 10 parts of concentrated ammonia and 12 parts of alkaline silica sol were added to 80 parts of deionized water and stirred at room temperature for 10 min. Then, 10 parts of phenyltrimethoxysilane were added and stirred at room temperature for 30 min to obtain hydrophobic modification solution. The roughened hard particle filter media and the hydrophobic modification solution were placed in a vacuum rotating device at 70℃ and rotated for 55 min at a mass-volume ratio of 1:1.5 (g:mL) to obtain modified quartz sand filter media.

[0037] (4) Curing: Take out the modified quartz sand filter material and place it in a vacuum oven at 250°C for 1.5h to dry it under vacuum; thus obtaining superhydrophobic and superoleophilic quartz sand filter material.

[0038] Depend on Figures 1-2 It is known that unmodified raw quartz sand spreads rapidly in air with both water and oil, exhibiting hydrophilic and oleophilic properties. Modified superhydrophobic quartz sand, however, allows water droplets to maintain a spherical shape for an extended period, with a hydrophobic angle reaching 156°, while oil droplets spread rapidly. Figure 3 It can be seen that unmodified quartz sand sinks immediately in water, partly due to its inherent hydrophilicity, and partly due to the density of quartz sand (2.65 g / cm³). 3 Its density is higher than that of water (1.00 g / cm³). 3The superhydrophobic quartz sand can overcome its own gravity and float on the water surface due to its superhydrophobicity. Therefore, the modified quartz sand filter media has both superhydrophobicity and oleophilicity. The hydrophilic quartz sand filter media was successfully modified into a superhydrophobic and superoleophilic quartz sand filter media, and the water wetting angle increased from 0° to 156°.

[0039] Example 2

[0040] The preparation method of the superhydrophobic and superoleophilic serpentine filter media of the present invention specifically includes the following steps:

[0041] (1) Pretreatment: Serpentine was placed in anhydrous ethanol and deionized water in sequence and ultrasonically cleaned for 10 min each to remove surface dust and impurities such as grease. Then it was placed in a 100℃ oven to dry for 5 h. The selected serpentine particle size was 0.125~0.175mm.

[0042] (2) Roughening treatment: 3 parts of hydrophobic silica nanoparticles (Hydrophobic-260 type) and 10 parts of polydimethylsiloxane were added dropwise to 400 parts of dichloromethane. After stirring at room temperature, 5 parts of epoxy resin curing agent were added and stirred continuously to obtain a roughening solution. The pretreated serpentine was immersed in the roughening solution and taken out after 5 minutes to be semi-dry.

[0043] (3) Hydrophobic modification: 11 parts of nonionic fluorocarbon surfactant, 13 parts of concentrated ammonia and 13 parts of alkaline silica sol were added to 85 parts of deionized water and stirred at room temperature for 10 min. Then, 10 parts of trimethoxyethoxysilane were added and stirred at room temperature for 30 min to obtain hydrophobic modification solution. The roughened serpentine filter material and the hydrophobic modification solution were placed in a vacuum rotating device at 80℃ and rotated for 75 min at a mass-volume ratio of 1:2 (g:mL) to obtain modified serpentine filter material.

[0044] (4) Curing: Take out the modified serpentine filter material and place it in a vacuum oven at 250°C for 2 hours to dry it under vacuum; thus obtaining superhydrophobic and superoleophilic serpentine filter material.

[0045] Depend on Figure 4 It can be seen that the modified serpentine surface has an obvious micro-nano composite structure, while the unmodified original serpentine surface has irregular cuts and distinct edges, with obvious crystal structure characteristics, and the surface pores are not well developed. The overall surface is relatively smooth and clean, with a few fine particles attached.

[0046] Example 3

[0047] The preparation method of the superhydrophobic and superoleophilic zeolite filter media of the present invention specifically includes the following steps:

[0048] (1) Pretreatment: The zeolite was placed in anhydrous ethanol and deionized water in sequence and ultrasonically cleaned for 10 min each to remove the floating dust and grease and other impurities attached to the surface. Then it was placed in a 100℃ oven to dry for 5 h. The particle size of the selected zeolite was 0.125~0.175mm.

[0049] (2) Roughening treatment: 7 parts of hydrophobic silica nanoparticles (Hydrophobic-300 type) and 15 parts of polydimethylsiloxane were added dropwise to 450 parts of acetone, stirred at room temperature, and then 8 parts of epoxy resin curing agent were added. After continuous stirring, a roughening solution was obtained; the pretreated zeolite was immersed in the roughening solution and taken out after 7 minutes to be semi-dry.

[0050] (3) Hydrophobic modification: 15 parts of fluorinated surfactant, 18 parts of concentrated ammonia and 18 parts of alkaline silica sol were added to 85 parts of deionized water and stirred at room temperature for 10 min. Then, 15 parts of phenyltrimethoxysilane were added and stirred at room temperature for 30 min to obtain hydrophobic modified liquid. The roughened zeolite filter material and the hydrophobic modified liquid were placed in a vacuum rotating device at 80℃ and rotated for 75 min at a mass-volume ratio of 1:2.5 (g:mL) to obtain modified zeolite filter material.

[0051] (4) Curing: Take out the modified zeolite filter material and place it in a vacuum oven at 300°C for 2 hours to dry under vacuum; to obtain superhydrophobic and superoleophilic zeolite filter material.

[0052] Depend on Figure 5 It can be seen that the modified superhydrophobic and superoleophilic zeolite has a higher adsorption capacity for different organic substances than the unmodified zeolite, and it has almost no adhesion to water.

[0053] Example 4

[0054] The non-uniform wettable hard particulate filter media layer of the present invention is obtained by uniformly mixing 30 parts by weight of superhydrophobic and superoleophilic walnut shell filter media with 30 parts by weight of pretreated natural walnut shell filter media; the particle size of the selected walnut shells is 0.125-0.175 mm.

[0055] The superhydrophobic and superoleophilic walnut shell filter media is prepared by the following method, specifically including the following steps:

[0056] (1) Pretreatment: The walnut shells were placed in anhydrous ethanol and deionized water in turn, and ultrasonically cleaned for 10 min each to remove the floating dust and grease and other impurities attached to the surface. Then they were placed in a 100℃ oven to dry for 5 h.

[0057] (2) Roughening treatment: 8 parts of hydrophobic silica nanoparticles (Hydrophobic-300 type) and 15 parts of polydimethylsiloxane were added dropwise into 450 parts of acetone, stirred at room temperature, then 8 parts of epoxy resin curing agent was added, and after continuous stirring, a roughening solution was obtained; the pretreated walnut shell was soaked in the roughening solution, and after 8 min, it was taken out to semi-drying;

[0058] (3) Hydrophobic modification: 15 parts of fluorine surfactant, 18 parts of concentrated ammonia water and 18 parts of alkaline silica sol were added into 90 parts of deionized water, stirred at room temperature for 10 min, then 15 parts of trimethoxyethoxysilane was added, stirred at room temperature for 30 min, and a hydrophobic modification liquid was obtained; the roughened walnut shell filter material was placed in a vacuum rotating device at 80°C with the hydrophobic modification liquid at a mass-volume ratio of 1:2.5 (g:mL) for 75 min, and a modified walnut shell filter material was obtained;

[0059] (4) Curing: the modified walnut shell filter material was taken out and placed in a vacuum oven at 300°C for 2h vacuum drying; and a super-hydrophobic super-oleophilic walnut shell filter material was obtained.

[0060] As shown in Figure 6 , the non-uniform wetting walnut shell filter material layer can completely separate the oil-containing sewage, and the filtrate is in a clear state. The unmodified walnut shell filter material layer (formed by 60 parts of pretreated natural walnut shell filter material) filters part of the oil droplets, and the filtrate still appears milky white. The non-uniform wetting walnut shell filter material layer has excellent oil-water separation effect on the emulsified oil-containing sewage.

[0061] The oil-in-water emulsion is in a milky white state because the oil droplets are stably present in the water phase in a fine and uniform state. The unmodified walnut shell filter material has a hydrophilic underwater super-oleophobic property on the surface, and during filtration, the continuous water phase can easily wet the filter material to form a water film, thereby hindering the wetting and adhesion of oil on the surface of the filter material, affecting the oil removal efficiency, and thus the filtrate still appears milky white. In the filtration of the non-uniform wetting filter bed, the continuous water phase in the oil-containing sewage will migrate to the surface of the hydrophilic walnut shell filter material and penetrate to the lower layer of the filter bed under the action of capillary force and its own gravity; at the same time, the high affinity of the super-hydrophobic super-oleophilic walnut shell filter material surface will destroy the surfactant-induced force between the oil and water phases and capture the oil droplets, and the tiny oil droplets will continue to coalesce on the surface of the super-oleophilic filter material to form large oil droplets, which are trapped above the filter material; when the surface of a certain super-oleophilic filter material is completely wetted and adhered by oil droplets, the oil droplets that migrate to the surface will either coalesce on the surface of the filter material or flow to the next layer of filter material with the water flow, and the middle and lower layers will continue to play a good role in capturing, adhering and trapping oil droplets, thereby having a good oil-water separation effect on the oil-in-water type oil-containing sewage.

[0062] Example 5

[0063] The preparation method of the super-hydrophobic super-oleophilic quartz sand filter material specifically comprises the following steps:

[0064] (1) Pretreatment: the quartz sand is sequentially placed in anhydrous ethanol and deionized water, and is ultrasonically cleaned for 10 minutes respectively, so as to remove floating dust and grease and other impurities attached to the surface, and then is dried in a 100℃ oven for 5 hours; the particle size of the selected quartz sand is 0.125-0.175mm;

[0065] (2) Roughening treatment: 9 parts of hydrophobic silica nanoparticles (Hydrophobic-380 type) and 20 parts of polydimethylsiloxane are added dropwise into 500 parts of butyl acetate, and after stirring at room temperature, 10 parts of an epoxy resin curing agent is added, and after continuous stirring, a roughening solution is obtained; the pretreated quartz sand is soaked in the roughening solution, and after 9 minutes, it is taken out to be semi-dried;

[0066] (3) Hydrophobic modification: 15 parts of an aqueous anionic surfactant, 10 parts of concentrated ammonia water and 12 parts of alkaline silica sol are added into 95 parts of deionized water, and after stirring at room temperature for 10 minutes, 20 parts of n-octyl ethoxy silane is added, and after stirring at room temperature for 30 minutes, a hydrophobic modification liquid is obtained; the roughened hard particle filter material and the hydrophobic modification liquid are placed in a vacuum rotating device at 80℃ for 80 minutes at a mass-volume ratio of 1:2 (g:mL), and a modified quartz sand filter material is obtained;

[0067] (4) Curing: the modified quartz sand filter material is taken out and placed in a vacuum oven for vacuum drying at 240℃ for 2 hours; a super-hydrophobic super-oleophilic quartz sand filter material is obtained.

[0068] 35 parts of the super-hydrophobic super-oleophilic quartz sand filter material and 35 parts of the pretreated natural quartz sand filter material are uniformly mixed and packed in a filter column to obtain a non-uniformly wet quartz sand filter material layer.

[0069] As shown in Figure 7 , the non-uniformly wet quartz sand filter material layer still maintains excellent removal performance for the oil-in-water emulsion with strong acidity (pH=1), and no oil droplet distribution is observed in the filter particle size distribution diagram, while a large number of oil droplets exist in the filtrate filtered by the unmodified quartz sand filter material layer (the unmodified quartz sand filter material layer is formed by 70 parts of the pretreated natural quartz sand filter material).

[0070] The prepared super-hydrophobic filter material has good chemical stability, maintains its super-hydrophobic performance in acidic oil-containing wastewater, and the gas film formed can effectively block the erosion of the acidic solution, so it still maintains excellent removal performance for the oil-in-water emulsion with strong acidity (pH=1).

[0071] Example 6

[0072] The preparation method of the super-hydrophobic super-oleophilic serpentine filter material specifically comprises the following steps:

[0073] (1) Pretreatment: the serpentine is sequentially placed in anhydrous ethanol and deionized water, and is ultrasonically cleaned for 10 minutes respectively, so as to remove floating dust and grease and other impurities attached to the surface, and then is dried in a 100℃ oven for 5 hours; the particle size of the selected serpentine is 0.125-0.175mm;

[0074] (2) Roughening treatment: 10 parts of hydrophobic silica nanoparticles (type Hydrophobic-260) and 10 parts of polydimethylsiloxane are added dropwise into 400 parts of ethyl acetate, and after stirring at room temperature, 5 parts of an epoxy resin curing agent is added, and after continuous stirring, a roughening solution is obtained; the pretreated serpentine is soaked in the roughening solution, and after 10 minutes, it is taken out to be semi-dried;

[0075] (3) Hydrophobic modification: 5 parts of non-ionic fluorocarbon surfactant, 13 parts of concentrated ammonia water and 13 parts of alkaline silica sol are added into 80 parts of deionized water, and after stirring at room temperature for 10 minutes, 10 parts of n-octyl triethoxysilane is added, and after stirring at room temperature for 30 minutes, a hydrophobic modification liquid is obtained; the roughened serpentine filter material and the hydrophobic modification liquid are placed in a vacuum rotating device at 80℃ with a mass-volume ratio of 1:2.5 (g:mL) and rotated for 80 minutes to obtain modified serpentine filter material;

[0076] (4) Curing: the modified serpentine filter material is taken out and placed in a vacuum oven for vacuum drying at 250℃ for 2 hours; and a super-hydrophobic super-oleophilic serpentine filter material is obtained.

[0077] 35 parts of the super-hydrophobic super-oleophilic serpentine filter material and 35 parts of the pretreated natural serpentine filter material are uniformly mixed and packed in a filter column to obtain a non-uniform wetting serpentine filter material layer.

[0078] As shown in Figure 8 , the non-uniform wetting serpentine filter material layer has excellent removal performance on the adsorption performance of oil-containing wastewater with high salt concentration, and the COD removal rate of the unmodified serpentine filter material layer is much lower than that of the non-uniform wetting serpentine filter material layer.

[0079] The prepared super-hydrophobic filter material has good chemical stability, maintains its super-hydrophobic performance in high-salt oil-containing wastewater, and the air film formed can effectively block the corrosion of the salt solution, so it still maintains excellent removal performance on the oil-in-water emulsion with high salt.

[0080] Comparative Example 1

[0081] A non-uniform wettability rigid particle filter layer is obtained by mixing 30 parts by mass of the super-hydrophobic and super-oleophilic rigid particle filter material prepared by the prior art CN 114875659 A with 30 parts of the pretreated natural walnut shell filter material to obtain the filter layer. The emulsified oily sewage is treated and separated in the same manner as in Example 4, and the results show that the filtrate is in a slightly turbid state.

[0082] In the separation of emulsified oily sewage, the oil-water separation performance of Comparative Example 1 is not as good as that of Example 4 because the capture ability of Comparative Example 1 for small oil droplets in the water phase is weak, which leads to the fact that these small oil droplets cannot adhere to the surface of the filter material and coalesce into large oil droplets, but pass through the filter bed and follow the water phase into the filtrate, so that part of the small oil droplets is still dispersed in the filtrate.

Claims

1. A layer of non-uniformly wettable hard particulate filter material, characterized by, The super-hydrophobic super-oil-wettable walnut shell filter material is prepared by mixing 30 parts of super-hydrophobic super-oil-wettable walnut shell filter material with 30 parts of pretreated natural walnut shell filter material uniformly; the particle size of the walnut shell is 0.125-0.175 mm; The super-hydrophobic super-oil-wettable walnut shell filter material is prepared by the following method, which comprises the following steps: (1) Pretreatment: the walnut shell is sequentially placed in anhydrous ethanol and deionized water, and is ultrasonically cleaned for 10 min, respectively, so as to remove floating dust and oil and other impurities attached to the surface, and then is placed in a 100°C oven for drying for 5 h; (2) Roughening treatment: 8 parts of hydrophobic silica nanoparticles and 15 parts of polydimethylsiloxane are added dropwise into 450 parts of acetone, and after stirring at room temperature, 8 parts of epoxy resin curing agent is added, and after continuous stirring, a roughening solution is obtained; the pretreated walnut shell is soaked in the roughening solution, and after 8 min, it is taken out to be semi-dried; (3) Hydrophobic modification: 15 parts of fluorine surfactant, 18 parts of concentrated ammonia water and 18 parts of alkaline silica sol are added into 90 parts of deionized water, and after stirring at room temperature for 10 min, 15 parts of trimethoxyethoxysilane is added, and after stirring at room temperature for 30 min, a hydrophobic modification liquid is obtained; the roughened walnut shell filter material and the hydrophobic modification liquid are placed in a vacuum rotating device at 80°C with a mass-volume ratio of 1:2.5 (g:mL) for 75 min to obtain modified walnut shell filter material; the pH value of the alkaline silica sol is 8.5-10; (4) Curing: the modified walnut shell filter material is taken out and placed in a vacuum oven for vacuum drying at 300°C for 2 h; and the super-hydrophobic super-oil-wettable walnut shell filter material is obtained.

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