Preparation method of super-hydrophobic super-oleophilic flame-retardant polyurethane sponge and application in oil-water separation

Abstract

The application belongs to the technical field of functional materials, and particularly relates to a preparation method of a polyurethane sponge with super-hydrophobic super-oleophilic and flame-retardant properties and application thereof in oil-water separation. The preparation method is as follows: a prepared nickel-cobalt hydrotalcite (NiCo-LDH) and ZIF-8 are dispersed in a polydimethylsiloxane (PDMS) diluent in a proper amount to form a dispersion liquid, and then a polyurethane sponge is immersed in the dispersion liquid, stirred for a period of time, and taken out for drying. The polyurethane sponge with super-hydrophobic super-oleophilic and flame-retardant properties is prepared by the method of immersion, the hydrophobic angle can reach 153.4 degrees, the burning time can be prolonged from the original 5s to 16s, the saturated oil absorption capacity can reach 26.6-82.9 times of the sponge itself, and the composite sponge can still achieve the super-hydrophobic state after 20 adsorption-extrusion cycles.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a method for preparing a polyurethane sponge with superhydrophobic and superoleophilic flame retardant properties and its application in oil-water separation. Background Technology

[0002] Oil spills, chemical leaks, and organic waste discharges often pose dangers such as fires and explosions, making it essential to find a reliable, effective, and environmentally friendly method for handling oil spills.

[0003] Several new materials and methods have been developed to achieve effective oil-water separation, including adsorption, dispersion, in-situ combustion, skimming, bioremediation, chemical dispersion, and filtration. However, most of these methods are time-consuming and labor-intensive, and may even cause secondary pollution. Among these, adsorption is a cost-effective and environmentally friendly method for removing oil and organic pollutants from water, and is therefore a more recommended approach. However, traditional adsorbent materials used to remove oil compounds and organic pollutants from water (such as cotton fabrics, zeolites, activated carbon, and fly ash) have almost all of the following drawbacks, including low oil recovery, poor absorption capacity, non-selective absorption, and difficulty in reusing. Therefore, the preparation of adsorbents with excellent superhydrophobic / superoleophilic surfaces is crucial for oil-water separation.

[0004] Novel three-dimensional (3D) porous materials are widely used in oil-water separation due to their high adsorption capacity, simple preparation, environmental friendliness, and low cost. These materials include polystyrene (PS) sponges, polyurethane (PU) sponges, polyvinyl alcohol (PVA) sponges, and melamine (MS) sponges. Among these, PU sponges are considered ideal as adsorbents due to their advantages such as light weight, low cost, large specific surface area, high porosity, and good adsorption repeatability. However, the hydrophilicity and flammability of PU sponges, and the toxic gases they produce when ignited, significantly limit their application. Summary of the Invention

[0005] To address the problems identified in the background section, this invention provides a simple, environmentally friendly, and easy-to-operate method for preparing superhydrophobic and superoleophilic flame-retardant polyurethane foam with high adsorption capacity, good separation efficiency, and high reusability. The technical solution adopted by this invention to solve the aforementioned technical problems includes the following steps:

[0006] (1) Cut commercially available polyurethane foam into 1×1×1cm pieces. 3 The cubes were ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes each, and then dried in an oven for later use.

[0007] (2) Dissolve 3g of cobalt nitrate hexahydrate and 4g of 2-methylimidazole in 100mL of anhydrous methanol, then stir and mix thoroughly for 20min and let stand for 24h. Centrifuge the solution after standing, wash it with anhydrous methanol and dry it in a vacuum drying oven at 35℃ to obtain ZIF-67.

[0008] (3) Dissolve 0.5g ZIF-67 in 200mL anhydrous ethanol by sonication for 20min, add 1.35g nickel nitrate hexahydrate, stir on a magnetic stirrer for 40min, transfer to an 80℃ oil bath for incubation for 48h, centrifuge, wash with deionized water and anhydrous ethanol 3 times each, and dry at 35℃ to obtain NiCo-LDH;

[0009] (4) Dissolve 1.488 g of zinc nitrate hexahydrate and 1.642 g of 2-methylimidazole in anhydrous methanol by stirring for 20 min respectively. Then mix the two solutions and stir on a magnetic stirrer for 2 h. After standing for 6 h, centrifuge, wash each solution 3 times with anhydrous methanol, and freeze dry to obtain ZIF-8.

[0010] (5) Dissolve PDMS and curing agent in 40 mL of n-hexane by ultrasonication for 30 min, add appropriate amount of NiCo-LDH in step (3) and ZIF-8 in step (4) by ultrasonication for 30 min, then add PU cleaned in step (1), stir on a magnetic stirrer (speed 180 rpm) for 50 min, take out the sponge and put it in a 120℃ oven to dry for 4 h to obtain superhydrophobic superoleophilic flame retardant polyurethane sponge.

[0011] The mass ratio of PDMS, curing agent, NiCo-LDH and ZIF-8 is 1:0.1:0.25-1:0.25-1.

[0012] The advantages of this invention compared to the prior art are:

[0013] 1. The superhydrophobic modification process of the present invention is simple, convenient, and low in cost. The main raw materials are non-toxic, harmless, green and environmentally friendly.

[0014] 2. The prepared modified superhydrophobic sponge has excellent saturated oil absorption capacity, oil-water separation efficiency and flame retardant properties.

[0015] 3. The hydrophobic, oleophilic, and flame-retardant sponge prepared by this invention has good mechanical properties and cyclic adsorption capacity, and can maintain its original appearance and adsorption performance after repeated extrusion and recycling. Attached image description:

[0016] Figure 1 This is a comparison chart of the hydrophobic angle, burning time, and saturated oil absorption data for n-hexane and chloroform of the sponges prepared in Examples 1-7 of this invention.

[0017] Figure 2 FESEM images of PU and NiCo-LDH / ZIF-8-PDMS-PU prepared in Example 1 of this invention.

[0018] Figure 3 (a) and (b) are state diagrams of water droplets and oil droplets falling on the original sponge and the surface of NiCo-LDH / ZIF-8-PDMS-PU, respectively, in Embodiment 1 of the present invention; (c) state diagram of water droplets on the cross section of NiCo-LDH / ZIF-8-PDMS-PU; (d) state diagram of the original sponge in water and NiCo-LDH / ZIF-8-PDMS-PU floating on the water; (e) state diagram of NiCo-LDH / ZIF-8-PDMS-PU exhibiting the underwater silver mirror phenomenon.

[0019] Figure 4 This is a time comparison chart of the combustion status of the original PU and NiCo-LDH / ZIF-8-PDMS-PU in Example 1 of the present invention.

[0020] Figure 5 This is a graph showing the saturation absorption data of NiCo-LDH / ZIF-8-PDMS-PU for various oils / organic reagents in Example 1 of the present invention.

[0021] Figure 6 This is a graph showing the hydrophobic angle data of NiCo-LDH / ZIF-8-PDMS-PU after soaking in different salt concentrations for 12 hours in Example 1 of the present invention.

[0022] Figure 7 This is a graph showing the hydrophobic angle data of NiCo-LDH / ZIF-8-PDMS-PU after soaking at different pH levels for 12 hours in Example 1 of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments, but is not limited thereto.

[0024] 1. Oil / organic solvent absorption capacity test

[0025] The oil absorption performance of the prepared NiCo-LDH / ZIF-8-PDMS-PU was tested by immersing it in various oils / organic solvents (such as petroleum ether, n-hexane, n-octane, heavy oil, tetrahydrofuran, benzene, toluene, dichloromethane, and trichloromethane) for 5 minutes. First, the NiCo-LDH / ZIF-8-PDMS-PU was weighed and recorded as m1. It was then immersed in 20 mL of oil or organic solvent for 5 minutes, and the sponge was removed and weighed, recorded as m2. The saturated absorption capacity of the sponge was denoted by Q. S This can be calculated using the following formula:

[0026] QS =(m2-m1) / m1

[0027] All test results are determined by averaging three samples to ensure data accuracy.

[0028] 2. Oil-water separation efficiency and reusability test

[0029] The reusability of NiCo-LDH / ZIF-8-PDMS-PU was tested using repeated absorption-extraction cycles. The mass of the sponge before oil absorption was recorded as m1. The sponge was then immersed in oil or organic solvent at ambient temperature for 5 minutes until it was saturated with oil; the mass of the sponge at this point was recorded as m2. The saturated sponge was then placed in a syringe, and the syringe was manually pushed to compress the sponge until all the absorbed oil was squeezed out without any oil droplets separating out. The mass of the sponge after desorption was recorded as m3 and used for the next cycle. Cycles were repeated 1-10 times, and the mass of the sponge before and after oil absorption and desorption was recorded for each cycle.

[0030] The first saturation oil absorption rate is denoted as k. a，1 k a，1 = [(m2-m1) / m1]×100%

[0031] The nth saturation oil absorption rate is denoted as k. a，n k a，n =[(m 3n-1 -m 3n-2 ) / m 3n-2 ]×100%

[0032] The efficiency of the first separation is denoted as η, i.e., η = (m2 - m3) / (m2 - m1).

[0033] The efficiency of the nth separation is denoted as η. n , that is, η n =(m 3n-1 -m 3n ) / (m 3n-1 -m 3n-2 )

[0034] 3. Environmental stability test

[0035] NiCo-LDH / ZIF-8-PDMS-PU was soaked in acidic or alkaline solutions with pH values ​​of 1, 3, 5, 7, 9, 11, and 13 for 12 hours. The sponges were then removed, rinsed with anhydrous ethanol, dried, and their water contact angles were measured. Similarly, NiCo-LDH / ZIF-8-PDMS-PU was soaked in NaCl solutions with concentrations of 1.5%, 2.5%, 3.5%, 4.5%, and 5.5% for 12 hours. The sponges were then removed, rinsed with anhydrous ethanol, dried, and their water contact angles were measured.

[0036] Example 1

[0037] (1) Cut commercially available polyurethane foam into 1×1×1cm pieces. 3 The cubes were ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes each, and then dried in an oven for later use.

[0038] (2) 3g of cobalt nitrate hexahydrate and 4g of 2-methylimidazole were added to 100mL of anhydrous methanol and stirred for 20min to dissolve, resulting in solution A and solution B. Solution A was quickly added to solution B and stirred for 20min. The solution was then allowed to stand for 24h. After standing, the solution was centrifuged and washed three times with anhydrous methanol. The solution was then dried in a vacuum drying oven at 35℃ to obtain ZIF-67. 0.5g of ZIF-67 was added to 200mL of anhydrous ethanol and sonicated for 20min. 1.35g of nickel nitrate hexahydrate was added and stirred for 40min. The solution was then incubated at 80℃ for 2 days. After centrifugation, the solution was washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 35℃ to obtain NiCo-LDH.

[0039] (3) 1.488 g of zinc nitrate hexahydrate and 1.642 g of 2-methylimidazole were added to 100 mL of anhydrous methanol and stirred for 20 min to obtain solution A and solution B. Solution A was added to solution B and stirred for 2 h. After standing for 6 h, the mixture was centrifuged and washed three times with anhydrous methanol. After freeze-drying, ZIF-8 was obtained.

[0040] (4) Add 0.5g of polydimethylsiloxane with vinyl active groups (Dow Corning PDMS) and 0.05g of curing agent (hydrogen-containing polydimethylsiloxane Dow Corning Sylgard 184) to 40mL of n-hexane, sonicate for 30min, add 0.25g of NiCo-LDH and 0.25g of ZIF-8, sonicate for 30min, add the cleaned PU, stir at 180rpm for 50min, remove the sponge and dry it in an oven at 120℃ for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0041] Example 2

[0042] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0043] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0044] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0045] (4) Add 0.25g PDMS and 0.025g curing agent to 40mL n-hexane, sonicate for 30min, add 0.125g NiCo-LDH and 0.125g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0046] Example 3

[0047] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0048] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0049] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0050] (4) Add 0.75g PDMS and 0.075g curing agent to 40mL n-hexane, sonicate for 30min, add 0.325g NiCo-LDH and 0.325g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0051] Example 4

[0052] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0053] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0054] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0055] (4) Add 1g PDMS and 0.1g curing agent to 40mL n-hexane, sonicate for 30min, add 0.5g NiCo-LDH and 0.5g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU;

[0056] Example 5

[0057] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0058] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0059] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0060] (4) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.125g NiCo-LDH and 0.125g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0061] Example 6

[0062] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0063] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0064] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0065] (4) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.325g NiCo-LDH and 0.325g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU;

[0066] Example 7

[0067] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0068] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0069] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0070] (4) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.5g NiCo-LDH and 0.5g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0071] Example 8

[0072] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0073] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0074] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0075] (4) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.375g NiCo-LDH and 0.125g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0076] The combustion time is 15s, the hydrophobic angle is 152.3°, the oil absorption of chloroform is 78.5234g / g, and the oil absorption of n-hexane is 25.3284g / g.

[0077] Example 9

[0078] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0079] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0080] (3) The preparation steps for ZIF-8 are the same as in Example 3;

[0081] (4) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.125g NiCo-LDH and 0.375g ZIF-8, sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH / ZIF-8-PDMS-PU.

[0082] The combustion time is 14.5s, the hydrophobic angle is 151.8°, the oil absorption of chloroform is 76.3258g / g, and the oil absorption of n-hexane is 25.1032g / g.

[0083] Comparative Example 1

[0084] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0085] (2) The preparation steps for NiCo-LDH are the same as in Example 2;

[0086] (3) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.5g NiCo-LDH and sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain NiCo-LDH-PDMS-PU.

[0087] The combustion time is 14s, the hydrophobic angle is 150.3°, the oil absorption of chloroform is 72.2589g / g, and the oil absorption of n-hexane is 23.4561g / g.

[0088] Comparative Example 2

[0089] (1) The preparation steps for sponge cleaning are the same as in Example 1;

[0090] (2) The preparation steps for ZIF-8 are the same as in Example 3;

[0091] (3) Add 0.5g PDMS and 0.05g curing agent to 40mL n-hexane, sonicate for 30min, add 0.5g ZIF-8 and sonicate for 30min, add cleaned PU, stir at 180rpm for 50min, take out the sponge and put it in a 120℃ oven to dry for 4h to obtain ZIF-8-PDMS-PU.

[0092] The combustion time is 14s, the hydrophobic angle is 151.4°, the oil absorption of chloroform is 73.5741g / g, and the oil absorption of n-hexane is 23.8657g / g.

Claims

1. A method for preparing a polyurethane sponge with superhydrophobic and superoleophilic flame-retardant properties, characterized in that, The preparation method steps are as follows: (1) The polyurethane sponge was cut into 1 x 1 x 1 cm cubes, sequentially cleaned with anhydrous ethanol, deionized water by ultrasonic, and dried in an oven for use; 3 ​ (2) Dissolve cobalt nitrate hexahydrate and 2-methylimidazole in anhydrous methanol respectively, then mix and stir and let stand. Centrifuge the solution after standing, wash with anhydrous methanol and dry in a vacuum drying oven to obtain ZIF-67. (3) Dissolve ZIF-67 in anhydrous ethanol by ultrasonication, add nickel nitrate hexahydrate, stir on a magnetic stirrer, transfer to an oil bath for incubation, centrifuge, wash with deionized water and anhydrous ethanol in sequence, and dry to obtain NiCo-LDH. (4) Dissolve zinc nitrate hexahydrate and 2-methylimidazole separately in anhydrous methanol, then mix the two solutions and stir on a magnetic stirrer. After standing, centrifuge, wash with anhydrous methanol, freeze dry to obtain ZIF-8. (5) Dissolve PDMS and curing agent in n-hexane by ultrasonication, add NiCo-LDH from step (3) and ZIF-8 from step (4) by ultrasonication, then add PU cleaned in step (1), stir on a magnetic stirrer, take out the sponge and put it in an oven to dry, and obtain superhydrophobic and superoleophilic flame-retardant polyurethane sponge. PDMS is a polydimethylsiloxane with vinyl active groups; the curing agent is a polydimethylsiloxane with hydrogen groups.

2. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (2), when preparing ZIF-67, the mass ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 3:4, the amount of anhydrous methanol used is 100 mL, the stirring time after mixing is 20 min, the standing time is 24 h, and the vacuum drying temperature is 35 °C.

3. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (3), when preparing NiCo-LDH, the mass ratio of ZIF-67 to nickel nitrate hexahydrate is 1:2.7, and the ultrasonic dissolution time is 20 min.

4. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (3), the stirring time is 40 min, the oil bath incubation time is 48 h, the temperature is 80℃, the washing is 3 times, and the drying temperature is 35℃.

5. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (4), when preparing ZIF-8, the mass ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1.488:1.

642. After mixing, the stirring time is 2 hours, the standing time is 6 hours, and the mixture is washed 3 times.

6. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (5), the mass ratio of PDMS, curing agent, NiCo-LDH and ZIF-8 is 1:0.1:0.25-1:0.25-1.

7. The method for preparing the superhydrophobic and superoleophilic flame-retardant polyurethane sponge as described in claim 1, characterized in that: In step (5), the ultrasonic time is 30 min, the stirring time is 50 min, the rotation speed is 180 rpm, the drying temperature is 120℃, and the time is 4 h.

8. A superhydrophobic and superoleophilic flame-retardant polyurethane sponge prepared by the method according to any one of claims 1-7.

9. An application of a superhydrophobic and superoleophilic flame-retardant polyurethane sponge prepared by the method according to any one of claims 1-7, characterized in that, The polyurethane foam is used for oil-water separation.

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