CN116023704A - Hydrophilic modified porous polyethylene pellets, preparation method thereof and application thereof in membrane bioreactor - Google Patents
Hydrophilic modified porous polyethylene pellets, preparation method thereof and application thereof in membrane bioreactor Download PDFInfo
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- 239000004698 Polyethylene Substances 0.000 title claims abstract description 151
- -1 polyethylene Polymers 0.000 title claims abstract description 148
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 145
- 239000008188 pellet Substances 0.000 title claims abstract description 134
- 239000012528 membrane Substances 0.000 title claims abstract description 43
- 238000002360 preparation method Methods 0.000 title abstract description 21
- 239000000243 solution Substances 0.000 claims abstract description 67
- 239000012954 diazonium Substances 0.000 claims abstract description 42
- 150000001989 diazonium salts Chemical class 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 29
- 238000001035 drying Methods 0.000 claims abstract description 20
- 239000000945 filler Substances 0.000 claims abstract description 20
- 239000010865 sewage Substances 0.000 claims abstract description 15
- 238000002791 soaking Methods 0.000 claims abstract description 15
- 229920001448 anionic polyelectrolyte Polymers 0.000 claims abstract description 13
- 239000000969 carrier Substances 0.000 claims abstract description 6
- 238000005406 washing Methods 0.000 claims abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 239000011148 porous material Substances 0.000 claims description 16
- 229920001577 copolymer Polymers 0.000 claims description 14
- 239000010802 sludge Substances 0.000 claims description 11
- 238000005273 aeration Methods 0.000 claims description 10
- 239000011324 bead Substances 0.000 claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 230000004907 flux Effects 0.000 claims description 8
- 230000014759 maintenance of location Effects 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 150000001336 alkenes Chemical class 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 229920001467 poly(styrenesulfonates) Polymers 0.000 claims description 4
- 229940006186 sodium polystyrene sulfonate Drugs 0.000 claims description 4
- 229920002845 Poly(methacrylic acid) Polymers 0.000 claims description 3
- 229920002125 Sokalan® Polymers 0.000 claims description 3
- 239000004584 polyacrylic acid Substances 0.000 claims description 3
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- 230000000694 effects Effects 0.000 abstract description 4
- 244000005700 microbiome Species 0.000 abstract description 3
- 239000002028 Biomass Substances 0.000 abstract description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 36
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 238000012986 modification Methods 0.000 description 15
- 230000004048 modification Effects 0.000 description 15
- 239000003054 catalyst Substances 0.000 description 14
- 239000002245 particle Substances 0.000 description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- CPOFMOWDMVWCLF-UHFFFAOYSA-N methyl(oxo)alumane Chemical compound C[Al]=O CPOFMOWDMVWCLF-UHFFFAOYSA-N 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 9
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 7
- 239000005977 Ethylene Substances 0.000 description 7
- 238000006116 polymerization reaction Methods 0.000 description 7
- BDJFCIOMKXVJJM-UHFFFAOYSA-N 2-methyloct-7-en-2-ol Chemical compound CC(C)(O)CCCCC=C BDJFCIOMKXVJJM-UHFFFAOYSA-N 0.000 description 6
- 238000011001 backwashing Methods 0.000 description 6
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 6
- 238000001179 sorption measurement Methods 0.000 description 6
- 229910001220 stainless steel Inorganic materials 0.000 description 6
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- 239000002994 raw material Substances 0.000 description 2
- 238000004438 BET method Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 125000003636 chemical group Chemical group 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 230000005660 hydrophilic surface Effects 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 238000009285 membrane fouling Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- 238000003756 stirring Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
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Abstract
The invention relates to a hydrophilically modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor. The preparation method of the hydrophilically modified porous polyethylene pellets comprises the following steps: soaking porous polyethylene pellets in hyperbranched diazonium salt solution, taking out, washing cleanly, drying to obtain porous polyethylene pellet carriers, soaking the porous polyethylene pellet carriers in anionic polyelectrolyte solution, taking out, and drying to obtain the hydrophilically modified porous polyethylene pellets. The hydrophilically modified porous polyethylene pellets can be used as a filler for membrane bioreactors. The hydrophilic modified porous polyethylene pellet surface can increase the adhesion rate of microorganisms, increase the active biomass and enhance the sewage treatment effect, and meanwhile, in the biochemical treatment process, the filler collides with the membrane surface in the membrane bioreactor, so that the membrane pollution is slowed down, and the back flushing period is prolonged.
Description
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a hydrophilic modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor.
Background
Chemical raw materials and products produced in the chemical industry are widely applied to various fields, make great contribution to national economy, and are one of the traditional prop industries in China. However, the chemical industry is a high pollution industry, the produced sewage contains high-concentration organic pollutants, standard emission is difficult to achieve through conventional method treatment, and the treatment difficulty is high.
The traditional sewage treatment process mainly adopts an activated sludge method, but the process has large occupied area, high energy consumption and poor effluent quality, and a large amount of excess sludge is easy to generate. Various novel sewage treatment technologies are developed at home and abroad to solve the problems.
Among them, MBR technology is widely focused by people because of small occupied area, excellent water output and small residual sludge. As the production process advances, the productivity of organic films increases and the cost decreases, limiting the technology mainly because of film contamination, which can seriously affect the stability and economy of the process. The means commonly used at present is chemical cleaning, but this can affect the service life of the membrane, increasing the operating costs. How to control membrane fouling is a current challenge.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a hydrophilic modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor. The preparation method of the porous polyethylene pellets adopts a method of copolymerizing ethylene and polar monomers, the porous polyethylene pellets are prepared and then subjected to hydrophilic treatment, the hydrophilic porous polyethylene pellets are used as the filler of a Membrane Bioreactor (MBR), the hydrophilic surface can improve the adhesion rate of microorganisms, the active biomass is improved, the sewage treatment effect is enhanced, and in the biochemical treatment process, the filler collides with the membrane surface in the membrane bioreactor, so that the membrane pollution is slowed down, and the physical back flushing period is prolonged.
One of the purposes of the invention is to provide a preparation method of hydrophilic modified porous polyethylene pellets, which comprises the following steps:
soaking porous polyethylene pellets in hyperbranched diazonium salt solution, taking out, washing cleanly, drying to obtain porous polyethylene pellet carriers, soaking the porous polyethylene pellet carriers in anionic polyelectrolyte solution, taking out, and drying to obtain the hydrophilically modified porous polyethylene pellets.
Preferably, the method comprises the steps of,
the porous polyethylene beads are olefin-olefin alcohol copolymers;
more preferably, the content of structural units corresponding to the olefin alcohol in the olefin-olefin alcohol copolymer is 0.4 to 5wt%; for example, it may be 0.4wt%, 0.8wt%, 1.2wt%, 1.6wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% and any range between any two values.
And/or the number of the groups of groups,
the porosity of the porous polyethylene pellets is 20-40%; for example, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40% and any range between any two values.
And/or the number of the groups of groups,
the average pore diameter of the porous polyethylene pellets is 3-10 um; such as 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, and any range between any two values.
And/or the number of the groups of groups,
the average grain diameter of the porous polyethylene pellets is 5-20 mm; for example, it may be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm and any range between any two values.
And/or the number of the groups of groups,
the specific surface area of the porous polyethylene pellets is 1000-1400 m 2 /m 3 For example, it may be 1050m 2 /m 3 、1100m 2 /m 3 、1150m 2 /m 3 、1200m 2 /m 3 、1250m 2 /m 3 、1300m 2 /m 3 、1350m 2 /m 3 、1400m 2 /m 3 And any range between any two values.
In the invention, the porous polyethylene pellets can be prepared by the existing preparation method, and the preferred preparation method is as follows:
ni using the catalyst shown in FIG. 1 1 Continuously drying 1L stainless steel polymerization kettle with mechanical stirring at 130deg.C for 6 hr, vacuumizing while it is hot, and using N 2 The air was replaced 3 times. 450-550ml of hexane is injected into a polymerization kettle, and 8-10 mg of catalyst Ni is added simultaneously 1 5 to 50mmol of 2-methyl-2-hydroxy-7-octene, 15 to 50mLAlEt 3 (triethylaluminum) (1.0 mol/L in hexane) and 3 to 30ml of Methylaluminoxane (MAO) (1.53 mol/L in toluene) at a temperature of 30 to 50 ℃,maintaining ethylene pressure of 8-10 atm, stirring and reacting for 30-60 min. Finally, neutralizing the ethanol solution acidified by 10wt% hydrochloric acid, and drying to obtain the porous polyethylene pellets.
Preferably, the method comprises the steps of,
the hyperbranched diazonium salt has the structural formula:
wherein m is the repeated number of chemical groups in brackets in the molecular formula, and the value range is 3-4; and/or the number of the groups of groups,
the anionic polyelectrolyte is selected from one or a combination of sodium polystyrene sulfonate, polyacrylic acid or polymethacrylic acid.
Preferably, the method comprises the steps of,
the concentration of the hyperbranched diazonium salt solution is 0.2-2 mg/mL; for example, the concentration may be in any range of 0.2mg/mL, 0.4mg/mL, 0.6mg/mL, 0.8mg/mL, 1mg/mL, 1.2mg/mL, 1.4mg/mL, 1.6mg/mL, 1.8mg/mL, 2mg/mL, and any range between any two values.
In the invention, the hyperbranched diazonium salt solution can be prepared by diluting a concentrated solution, and the storage temperature of the diluted hyperbranched diazonium salt solution is 2-8 ℃ so as to ensure the stability of the hyperbranched diazonium salt solution.
And/or the number of the groups of groups,
the concentration of the anionic polyelectrolyte solution is 0.2-2 mg/mL; for example, the concentration may be in any range of 0.2mg/mL, 0.4mg/mL, 0.6mg/mL, 0.8mg/mL, 1mg/mL, 1.2mg/mL, 1.4mg/mL, 1.6mg/mL, 1.8mg/mL, 2mg/mL, and any range between any two values.
The soaking temperature of the porous polyethylene pellets in the hyperbranched diazonium salt solution is 2-6 ℃; for example, the temperature may be in any range between any two values of 2 ℃,3 ℃,4 ℃,5 ℃,6 ℃.
And/or the number of the groups of groups,
the soaking time of the porous polyethylene pellets in the hyperbranched diazonium salt solution is 0.5-1 h; for example, it may be in any range of 0.5h, 0.6h, 0.8h, 1h, and any range between any two values.
And/or the number of the groups of groups,
the soaking temperature of the porous polyethylene pellet carrier in the anionic polyelectrolyte solution is 2-6 ℃; for example, the temperature may be in any range between any two values of 2 ℃,3 ℃,4 ℃,5 ℃,6 ℃.
And/or the number of the groups of groups,
the soaking time of the porous polyethylene pellet carrier in the anionic polyelectrolyte solution is 0.5-2 h. For example, it may be in any range of 0.5h, 1h, 1.5h, 2h, and any range between any two values.
In the invention, the mass ratio of the porous polyethylene pellets to the hyperbranched diazonium salt solution has no special requirement, and the porous polyethylene pellets can be soaked in the hyperbranched diazonium salt solution. After soaking, the hyperbranched diazonium salt solution can be reused continuously if the concentration meets the requirement.
In the invention, the mass ratio of the porous polyethylene pellet carrier to the anionic polyelectrolyte solution has no special requirement, and the porous polyethylene pellet carrier can be soaked in the anionic polyelectrolyte solution. After the anion polyelectrolyte solution is soaked, if the concentration meets the requirement, the anion polyelectrolyte solution can be reused continuously.
It is a second object of the present invention to provide hydrophilically modified porous polyethylene beads prepared by the method for preparing hydrophilically modified porous polyethylene beads which are one of the objects of the present invention,
the porosity of the hydrophilically modified porous polyethylene pellets is 18-38%; for example, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, and any range between any two values.
And/or the number of the groups of groups,
the average pore diameter of the hydrophilically modified porous polyethylene pellets is 3-10 um; such as 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, and any range between any two values.
And/or the number of the groups of groups,
the average grain diameter of the hydrophilically modified porous polyethylene pellets is 5-20 mm; for example, it may be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm and any range between any two values.
And/or the number of the groups of groups,
the specific surface area of the hydrophilically modified porous polyethylene pellets is 1000-1400 m 2 /m 3 . For example, it may be 1050m 2 /m 3 、1100m 2 /m 3 、1150m 2 /m 3 、1200m 2 /m 3 、1250m 2 /m 3 、1300m 2 /m 3 、1350m 2 /m 3 、1400m 2 /m 3 And any range between any two values.
It is a further object of the present invention to provide the use of hydrophilically modified porous polyethylene beads as second object of the present invention in membrane bioreactors,
when the membrane bioreactor is used for sewage treatment, the filler is hydrophilic modified porous polyethylene pellets.
Preferably, the method comprises the steps of,
the membrane bioreactor is an immersed membrane bioreactor;
the adding amount of the hydrophilically modified porous polyethylene pellets is 5% -30% of the effective volume of the membrane bioreactor. For example, the ratio may be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30% or any range between any two values.
Preferably, the method comprises the steps of,
when the membrane bioreactor is used for sewage treatment,
the membrane flux range is 10-12L/(m) 2 H). For example, it may be 10L/(m) 2 ·h)、11L/(m 2 ·h)、12L/(m 2 H) and any range between any two values.
Preferably, the method comprises the steps of,
when the membrane bioreactor is used for sewage treatment,
the hydraulic retention time is 4-7 h; for example, it may be 4h, 5h, 6h, 7h, or any range between any two values.
And/or the number of the groups of groups,
the sludge concentration is 3.5-7 g/L. For example, it may be 3.5g/L, 4g/L, 4.5g/L, 5g/L, 5.5g/L, 6g/L, 6.5g/L, 7g/L, or any range between any two values.
Preferably, the method comprises the steps of,
when the membrane bioreactor is used for sewage treatment,
the aeration rate is 10-13L/min; for example, it may be 10L/min, 10.5/min, 11L/min, 11.5L/min, 12L/min, 12.5L/min, 13L/min, or any range between any two values.
And/or the number of the groups of groups,
the dissolved oxygen is 4.5-5.5 mg/L. For example, it may be 4.5mg/L, 4.7 mg/min, 4.9mg/L, 5.1mg/L, 5.3mg/L, 5.5mg/L and any range between any two values.
Compared with the prior art, the invention has at least the following advantages:
1) In the preparation method of the porous polyethylene pellets, the spherical polymer with good shape is directly prepared by selecting unsaturated carboxylic acid monomers, catalysts and proper polymerization processes without the subsequent processing steps of pelleting and the like. The porous polyethylene pellets provided by the invention have a porous structure, and can be directly used as a filler after hydrophilic modification. Compared with the existing high molecular filler, the porous polyethylene pellets of the invention omits the polymer foaming process, and have the advantages of simpler preparation process and lower production cost.
2) The hydrophilic modification method for the porous polyethylene pellets based on the hyperbranched diazonium salt utilizes the multi-functional group property and high reaction activity of the hyperbranched diazonium salt to fix the anionic polyelectrolyte on the surfaces of the porous polyethylene pellets, realizes the hydrophilic modification of the porous polyethylene pellets, has the characteristics of simple steps, easy operation and the like, and is beneficial to realizing industrialization.
3) The invention takes the hydrophilically modified porous polyethylene pellets as the MBR filler, and has the advantages of quick microorganism adsorption, improved effluent quality of an MBR system and prolonged backwashing period.
4) After the porous polyethylene pellets are subjected to hydrophilic modification, the porous polyethylene pellets subjected to hydrophilic modification are dispersed in sewage more uniformly, and in the biochemical treatment process, the probability of collision between the filler and the surface of the membrane is larger, so that membrane pollution is more favorably slowed down, and the backwashing period is prolonged.
Drawings
FIG. 1 shows a catalyst Ni used for preparing porous polyethylene according to the present invention 1 Is a structural formula of (a).
Detailed Description
The present invention is described in detail below with reference to the specific drawings and examples, and it is necessary to point out that the following examples are given for further illustration of the present invention only and are not to be construed as limiting the scope of the present invention, since numerous insubstantial modifications and adaptations of the invention to those skilled in the art will still fall within the scope of the present invention.
The raw material sources are as follows:
the porous polyethylene pellets used in the examples were self-made and the preparation method was as described in the following examples.
EPP foamed polypropylene materials used in the comparative examples were purchased from Jiangsu-Kagaku Chen plastics technology Co.
The testing method comprises the following steps:
in the invention, the surface of the porous polyethylene pellets subjected to hydrophilic modification is a curved surface, so that the contact angle cannot be tested. The contact angle in the present invention is a contact angle measured after the PE sheet was modified according to the same hydrophilic modification conditions as in each example in order to illustrate the effect of the hydrophilic modification of the present invention.
The contact angle is the included angle between the solid-liquid interface and the gas-liquid interface from the inside of the liquid at the solid-liquid-gas interface, and is generally indicated by theta, and the size of the contact angle can reflect the wetting condition of the liquid on the solid surface, and the smaller the contact angle, the better the wetting. When theta is less than 90 degrees, the water is partially wetted or wetted, and the water is hydrophilic; when θ=90°, it is the boundary line of wetting or not; when theta is more than 90 degrees, the water-repellent fabric is not wetted and is hydrophobic.
In the present invention, the specific surface area is measured by the BET method;
the average particle size is measured by a Markov laser particle size analyzer;
the average pore diameter is measured by a gas adsorption method;
the porosity was measured by mercury porosimetry.
Example 1
The invention provides a hydrophilically modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor, comprising the following steps:
(1) Preparation of porous polyethylene pellets: continuously drying 1L stainless steel polymerization kettle with mechanical stirring at 130deg.C for 6 hr, vacuumizing while it is hot, and using N 2 The air was replaced 3 times. 500mL of hexane was injected into the polymerizer, while 8.0mg of Ni catalyst was added 1 (the catalyst structure is shown in FIG. 1), 15mmol of 2-methyl-2-hydroxy-7-octene, 15mLAlEt 3 (1.0 mol/L hexane solution), 6.5mL Methylaluminoxane (MAO) (1.53 mol/L toluene solution), and the reaction was stirred for 30 minutes at 30℃under an ethylene pressure of 10 atm. Finally, the porous polyethylene pellets are obtained by neutralization with an ethanol solution acidified with 10wt% hydrochloric acid.
The porous polyethylene pellets prepared by the method are olefin-olefin alcohol copolymers, and the content of structural units corresponding to olefin alcohol in the olefin-olefin alcohol copolymers is 0.4 weight percent; specific surface area of 1035m 2 /m 3 The average particle diameter was 6mm, the average pore diameter was 4um, and the porosity was 21%.
(2) Hydrophilic modification of the surface of the porous polyethylene pellets: and (3) measuring a certain volume of hyperbranched diazonium salt solution, diluting the hyperbranched diazonium salt solution to 50 times by using water, and obtaining the diluted hyperbranched diazonium salt (m is 3 in the structural formula of the hyperbranched diazonium salt) solution, wherein the concentration is 0.2mg/mL. And then stored under the condition of below 8 ℃ to ensure the stability of the hyperbranched diazonium salt solution. Immersing porous polyethylene pellets in the diluted hyperbranched diazonium salt solution for 0.5h at the temperature of 2 ℃, taking out, cleaning by using water, and quickly drying by using cold air at the temperature of 7 ℃; and (3) obtaining a porous polyethylene pellet carrier, immersing the porous polyethylene pellet carrier in a sodium polystyrene sulfonate solution with the concentration of 0.2mg/mL for 2 hours at the temperature of 2 ℃ to achieve saturated adsorption, taking out and drying to obtain the hydrophilically modified porous polyethylene pellet.
The specific surface area of the hydrophilically modified porous polyethylene pellets prepared by the above method is 1035m 2 /m 3 The average particle diameter was 6mm, the average pore diameter was 4um, and the porosity was 20%. Under the same conditions, the surface of the PE sheet is modified, and the contact angle is 68 degrees.
In the present invention, since the hydrophilic layer thickness on the surface of the hydrophilically modified porous polyethylene pellets is in the order of nanometers, the differences in specific surface area, average particle diameter, average pore diameter and porosity of the hydrophilically modified porous polyethylene pellets are not significant as compared with those of the non-hydrophilically modified porous polyethylene pellets, and in the present invention, the specific surface area, average particle diameter and average pore diameter of the hydrophilically modified porous polyethylene pellets described above are considered to be approximately equal, and the same data as those of the non-hydrophilically modified porous polyethylene pellets, and the same is true in the following examples, which will not be described in detail. However, the porosity of the hydrophilically modified porous polyethylene pellets is slightly reduced compared to the porosity of the non-hydrophilically modified porous polyethylene pellets.
(3) Hydrophilic modified porous polyethylene pellets are used for MBR unit packing: the hydrophilically modified porous polyethylene pellets are used as the filler of an immersed MBR device, the adding amount of the hydrophilically modified porous polyethylene pellets is 10% of the effective volume of the immersed MBR device, the COD of water inflow is 300mg/L, and the membrane flux is 12L/(m) 2 H), the Hydraulic Retention Time (HRT) is 5h, the sludge concentration (MLSS) is 4g/L, the aeration quantity is 12.5L/min, the aeration mode adopts microporous aeration, the dissolved oxygen is 5mg/L, and the COD of the effluent is 18mg/L after stable operation. When the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 10 days.
Example 2
The invention provides a hydrophilically modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor, comprising the following steps:
(1) Preparation of porous polyethylene pellets: will be equipped with an organicMechanically stirred 1L stainless steel polymerizers were dried continuously at 130℃for 6h, evacuated while hot and N-terminally heated 2 The air was replaced 3 times. 500mL of hexane was injected into the polymerizer, while 9.0mg of Ni catalyst was added 1 (catalyst structure shown in FIG. 1), 30mmol of 2-methyl-2-hydroxy-7-octene, 30mLAlEt 3 (1.0 mol/L hexane solution), 15mL of Methylaluminoxane (MAO) (1.53 mol/L toluene solution), and maintaining an ethylene pressure of 8atm at 50℃were stirred and reacted for 60 minutes, and finally neutralized with an ethanol solution acidified with 10wt% hydrochloric acid to obtain porous polyethylene pellets.
The porous polyethylene pellets prepared by the method are olefin-olefin alcohol copolymers, and the content of structural units corresponding to olefin alcohol in the olefin-olefin alcohol copolymers is 2.6wt%; specific surface area of 1376m 2 /m 3 The average particle diameter was 15mm, the average pore diameter was 8um, and the porosity was 29%.
(2) Hydrophilic modification of the surface of the porous polyethylene pellets: and (3) measuring a certain volume of hyperbranched diazonium salt solution, diluting the hyperbranched diazonium salt solution to 10 times by using water, and obtaining the diluted hyperbranched diazonium salt solution (m is 3 in the structural formula of the hyperbranched diazonium salt), wherein the concentration is 2mg/mL. And then stored at 8 ℃ to ensure the stability of the hyperbranched diazonium salt solution. Immersing porous polyethylene pellets in the diluted hyperbranched diazonium salt solution for 1h at the temperature of 6 ℃, taking out, cleaning by using water, and quickly drying by using cold air at the temperature of 7 ℃; and (3) obtaining a porous polyethylene pellet carrier, immersing the porous polyethylene pellet carrier in a polyacrylic acid solution with the concentration of 2mg/mL for 0.5h at the temperature of 6 ℃ to achieve saturated adsorption, taking out and drying to obtain the hydrophilically modified porous polyethylene pellet.
The hydrophilic modified porous polyethylene pellets prepared by the method have a specific surface area of 1376m 2 /m 3 The average particle diameter is 15mm, the average pore diameter is 8um, the porosity is 27%, and the contact angle is 67 degrees when the PE sheet is subjected to surface modification under the same conditions.
(3) Hydrophilic modified porous polyethylene pellets are used for MBR unit packing: the hydrophilically modified porous polyethylene pellets are used as the filler of an immersed MBR device, and the hydrophilically modified porous polyethylene pellets are addedThe amount is 20% of the effective volume of the immersed MBR device, the COD of the inflow water is 300mg/L, and the membrane flux is 10L/(m) 2 H), the Hydraulic Retention Time (HRT) is 4h, the sludge concentration (MLSS) is 6g/L, the aeration quantity is 13L/min, the dissolved oxygen is 5mg/L, the COD of the effluent is 15mg/L after stable operation, when the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 11 days.
Example 3
The invention provides a hydrophilically modified porous polyethylene pellet, a preparation method thereof and application thereof in a membrane bioreactor, comprising the following steps:
(1) Preparation of porous polyethylene pellets: continuously drying 1L stainless steel polymerization kettle with mechanical stirring at 130deg.C for 6 hr, vacuumizing while it is hot, and using N 2 The air was replaced 3 times. 500mL of hexane was injected into the polymerizer while 10mg of Ni catalyst was added 1 (catalyst structure shown in FIG. 1), 50mmol of 2-methyl-2-hydroxy-7-octene, 40mLAlEt 3 (1.0 mol/L hexane solution), 30mL of Methylaluminoxane (MAO) (1.53 mol/L toluene solution), and maintaining an ethylene pressure of 9atm at 40℃were stirred and reacted for 45 minutes, and finally neutralized with an ethanol solution acidified with 10wt% hydrochloric acid to obtain porous polyethylene pellets.
The porous polyethylene pellets prepared by the method are olefin-olefin alcohol copolymers, and the content of structural units corresponding to olefin alcohol in the olefin-olefin alcohol copolymers is 4.8wt%; specific surface area 1215m 2 /m 3 The average particle diameter was 10mm, the average pore diameter was 9um, and the porosity was 39%.
(2) Hydrophilic modification of the surface of the porous polyethylene pellets: and (3) measuring a certain volume of hyperbranched diazonium salt solution, diluting the hyperbranched diazonium salt solution to 25 times by using water, and obtaining the diluted hyperbranched diazonium salt solution (m is 4 in the structural formula of the hyperbranched diazonium salt), wherein the concentration is 0.4mg/mL. And then stored at 7 ℃ to ensure the stability of the hyperbranched diazonium salt solution. Immersing porous polyethylene pellets in the diluted hyperbranched diazonium salt solution for 0.8h at the temperature of 5 ℃, taking out, cleaning by using water, and quickly drying by using cold air at the temperature of 7 ℃; and (3) obtaining a porous polyethylene pellet carrier, immersing the porous polyethylene pellet carrier in a polymethacrylic acid solution with the concentration of 1mg/mL for 1h at the temperature of 5 ℃ to achieve saturated adsorption, taking out and drying to obtain the hydrophilically modified porous polyethylene pellet.
The specific surface area of the hydrophilically modified porous polyethylene pellets prepared by the above method is 1215m 2 /m 3 The average particle diameter is 10mm, the average pore diameter is 9um, the porosity is 36 percent, and the contact angle is 65 degrees when the PE sheet is subjected to surface modification under the same conditions.
(3) Hydrophilic modified porous polyethylene pellets are used for MBR unit packing: the hydrophilically modified porous polyethylene pellets are used as the filler of an immersed MBR device, the adding amount of the hydrophilically modified porous polyethylene pellets is 25% of the effective volume of the immersed MBR device, the COD of water inflow is 300mg/L, and the membrane flux is 11L/(m) 2 H), the Hydraulic Retention Time (HRT) is 4h, the sludge concentration (MLSS) is 5.5g/L, the aeration amount is 11L/min, the dissolved oxygen is 5.5mg/L, the COD of the effluent is 14mg/L after stable operation, when the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 12 days.
Example 4
(1) Preparation of porous polyethylene pellets: continuously drying 1L stainless steel polymerization kettle with mechanical stirring at 130deg.C for 6 hr, vacuumizing while it is hot, and using N 2 The air was replaced 3 times. 500mL of hexane was injected into the polymerizer while 10mg of Ni catalyst was added 1 (catalyst structure shown in FIG. 1), 40mmol of 2-methyl-2-hydroxy-7-octene, 30mLAlEt 3 (1.0 mol/L hexane solution), 25mL of Methylaluminoxane (MAO) (1.53 mol/L toluene solution), and maintaining an ethylene pressure of 10atm at 40℃were stirred and reacted for 60 minutes, and finally neutralized with an ethanol solution acidified with 10wt% hydrochloric acid to obtain porous polyethylene pellets.
The porous polyethylene pellets prepared by the method are olefin-olefin alcohol copolymers, and the content of structural units corresponding to olefin alcohol in the olefin-olefin alcohol copolymers is 4wt%; specific surface area of 1335m 2 /m 3 The average particle diameter was 20mm, the average pore diameter was 10 μm, and the porosity was 30%.
(2) Hydrophilic modification of the surface of the porous polyethylene pellets: and measuring a certain volume of hyperbranched diazonium salt solution, diluting the hyperbranched diazonium salt solution to 50 times by using water, and obtaining the diluted hyperbranched diazonium salt solution (m is 4 in the structural formula of the hyperbranched diazonium salt), wherein the concentration is 1.5mg/mL. And then stored under the condition of below 8 ℃ to ensure the stability of the hyperbranched diazonium salt solution. Immersing porous polyethylene pellets in the diluted hyperbranched diazonium salt solution for 1h at the temperature of 4 ℃, taking out, cleaning by using water, and quickly drying by using cold air at the temperature of 7 ℃; and (3) obtaining a porous polyethylene pellet carrier, immersing the porous polyethylene pellet carrier in a sodium polystyrene sulfonate solution with the concentration of 1.5mg/mL for 1.3 hours at the temperature of 4 ℃ to achieve saturated adsorption, taking out and drying to obtain the hydrophilically modified porous polyethylene pellet.
The specific surface area of the hydrophilically modified porous polyethylene pellets prepared by the above method is 1335m 2 /m 3 The average particle diameter is 20mm, the average pore diameter is 10um, the porosity is 27%, and the contact angle is 63 degrees when the PE sheet is subjected to surface modification under the same conditions.
(3) Hydrophilic modified porous polyethylene pellets are used for MBR unit packing: the hydrophilically modified porous polyethylene pellets are used as the filler of an immersed MBR device, the adding amount of the hydrophilically modified porous polyethylene pellets is 30% of the effective volume of the immersed MBR device, the COD of water inflow is 300mg/L, and the membrane flux is 10L/(m) 2 H), the Hydraulic Retention Time (HRT) is 7h, the sludge concentration (MLSS) is 7g/L, the aeration amount is 10L/min, the dissolved oxygen is 4.5mg/L, the COD of the effluent is 15.5mg/L after stable operation, when the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 11 days.
Comparative example 1
In comparative example 1, the MBR system was not charged with filler, and the same operation conditions as in example 1 were adopted, the COD of the effluent was 23mg/L, and the backwashing time was 4 days.
As can be seen from the comparison, after the hydrophilic porous polyethylene pellets are used as the filler, the COD removal rate is improved from 92.3% to 94%, and the backwashing period is prolonged by more than one time.
Comparative example 2
In comparative example 2, the MBR system was not charged with filler, and the same operation conditions as in example 2 were adopted, the COD of the effluent was 25mg/L, and the backwashing time was 3 days.
Comparative example 3
In comparative example 3, the MBR system was not charged with the filler, and the same operation conditions as in example 3 were adopted, the COD of the effluent was 27mg/L, and the backwashing time was 3 days.
Comparative example 4
(1) Preparation of porous polyethylene pellets: continuously drying 1L stainless steel polymerization kettle with mechanical stirring at 130deg.C for 6 hr, vacuumizing while it is hot, and using N 2 The air was replaced 3 times. 500mL of hexane was injected into the polymerizer while 10mg of Ni catalyst was added 1 (catalyst structure shown in FIG. 1), 50mmol of 2-methyl-2-hydroxy-7-octene, 40mLAlEt 3 (1.0 mol/L hexane solution), 30mL of Methylaluminoxane (MAO) (1.53 mol/L toluene solution), and maintaining an ethylene pressure of 9atm at 40℃were stirred and reacted for 45 minutes, and finally neutralized with an ethanol solution acidified with 10wt% hydrochloric acid to obtain porous polyethylene pellets.
The porous polyethylene pellets prepared by the method are olefin-olefin alcohol copolymers, and the content of structural units corresponding to olefin alcohol in the olefin-olefin alcohol copolymers is 4.8wt%; specific surface area 1215m 2 /m 3 The average particle diameter was 10mm, the average pore diameter was 9um, the porosity was 39%, and the contact angle measured on a PE sheet was 98.
(2) Porous polyethylene pellets were used in MBR device: porous polyethylene pellets are used as the filler of the immersed MBR device, the adding amount of the porous polyethylene pellets is 25% of the effective volume of the immersed MBR device, the COD of inflow water is 300mg/L, and the membrane flux is 11L/(m) 2 H), the Hydraulic Retention Time (HRT) is 4h, the sludge concentration (MLSS) is 5.5g/L, the aeration amount is 11L/min, the dissolved oxygen is 5.5mg/L, the COD of the effluent is 23mg/L after stable operation, when the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 8 days.
Comparative example 5
Commercial EPP foamed polypropylene material is used as the filler of the immersed MBR device, and the adding amount of the EPP foamed polypropylene material is 25 percent of the effective volume of the immersed MBR deviceCOD of the inlet water is 300mg/L, and the membrane flux is 11L/(m) 2 H), the Hydraulic Retention Time (HRT) is 4h, the sludge concentration (MLSS) is 5.5g/L, the aeration amount is 11L/min, the dissolved oxygen is 5.5mg/L, the COD of the effluent is 22mg/L after stable operation, when the effluent is circulated, back flushing is carried out when the transmembrane pressure difference reaches 45kPa, and the back flushing time of the MBR reactor is 8 days.
Claims (10)
1. A method for preparing hydrophilically modified porous polyethylene beads, comprising the steps of:
soaking porous polyethylene pellets in hyperbranched diazonium salt solution, taking out, washing cleanly, drying to obtain porous polyethylene pellet carriers, soaking the porous polyethylene pellet carriers in anionic polyelectrolyte solution, taking out, and drying to obtain the hydrophilically modified porous polyethylene pellets.
2. The method for producing hydrophilically-modified porous polyethylene beads according to claim 1, wherein,
the porous polyethylene beads are olefin-olefin alcohol copolymers;
preferably, the content of the structural units corresponding to the alkene alcohol in the alkene-alkene alcohol copolymer is 0.4 to 5wt%; and/or the number of the groups of groups,
the average pore diameter of the porous polyethylene pellets is 3-10 um; and/or the number of the groups of groups,
the average grain diameter of the porous polyethylene pellets is 5-20 mm; and/or the number of the groups of groups,
the porosity of the porous polyethylene pellets is 20-40%; and/or the number of the groups of groups,
the specific surface area of the hydrophilically modified porous polyethylene pellets is 1000-1400 m 2 /m 3 。
3. The method for producing hydrophilically-modified porous polyethylene beads according to claim 1, wherein,
the hyperbranched diazonium salt has the structural formula:
wherein the value range of m is 3-4; and/or the number of the groups of groups,
the anionic polyelectrolyte is selected from one or a combination of sodium polystyrene sulfonate, polyacrylic acid or polymethacrylic acid.
4. The method for producing hydrophilically-modified porous polyethylene beads according to claim 1, wherein,
the concentration of the hyperbranched diazonium salt solution is 0.2-2 mg/mL; and/or the number of the groups of groups,
the concentration of the anionic polyelectrolyte solution is 0.2-2 mg/mL; and/or the number of the groups of groups,
the soaking temperature of the porous polyethylene pellets in the hyperbranched diazonium salt solution is 2-6 ℃; the soaking time is 0.5-1 h; and/or the number of the groups of groups,
the soaking temperature of the porous polyethylene pellet carrier in the anionic polyelectrolyte solution is 2-6 ℃; the soaking time is 0.5-2 h.
5. The hydrophilically modified porous polyethylene pellets produced by the process for producing hydrophilically modified porous polyethylene pellets as claimed in any of claims 1 to 4,
the average grain diameter of the hydrophilically modified porous polyethylene pellets is 5-20 mm; and/or the number of the groups of groups,
the porosity of the hydrophilically modified porous polyethylene pellets is 18-38%; and/or the number of the groups of groups,
the average pore diameter of the hydrophilically modified porous polyethylene pellets is 3-10 um; and/or the number of the groups of groups,
the specific surface area of the hydrophilically modified porous polyethylene pellets is 1000-1400 m 2 /m 3 。
6. The use of hydrophilically modified porous polyethylene beads according to claim 5 in membrane bioreactors,
when the membrane bioreactor is used for sewage treatment, the filler is hydrophilic modified porous polyethylene pellets.
7. The use according to claim 6, wherein,
the membrane bioreactor is an immersed membrane bioreactor;
the adding amount of the hydrophilically modified porous polyethylene pellets is 5% -30% of the effective volume of the membrane bioreactor.
8. The use according to claim 6, wherein,
when the membrane bioreactor is used for sewage treatment,
the membrane flux range is 10-12L/(m) 2 ·h)。
9. The use according to claim 6, wherein,
when the membrane bioreactor is used for sewage treatment,
the hydraulic retention time is 4-7 h; and/or the number of the groups of groups,
the sludge concentration is 3.5-7 g/L.
10. The use according to claim 6, wherein,
when the membrane bioreactor is used for sewage treatment,
the aeration rate is 10-13L/min; and/or the number of the groups of groups,
the dissolved oxygen is 4.5-5.5 mg/L.
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