Preparation Of Smart Responsive P-Fe₃O₄-PDA@MF Foam And Its Oil-water Separation Performance

The environmental pollution caused by oil leakage and oil-bearing wastewater from industrial production is threatening the global ecosystem.Therefore,it is urgent to solve the problem of water pollution with high efficiency,energy saving and recyclable oil-water separation materials.Although a variety of strategies and methods have been proposed and the corresponding separation materials have been designed to deal with the problem of water pollution at home and abroad,the recovery of oil spill or treatment of oily wastewater usually needs to face more complex wastewater status or harsh operating conditions.For example,spilled crude is difficult to recover at room temperature;In the process of oil spill recovery,the oil is flammable,and there is a huge potential fire hazard;After the successful treatment of oil spill or oily wastewater,oil and materials cannot be recovered at low energy consumption,and potentially harmful bacteria and microorganisms may multiply in water,or even spread through water vectors,endangering human health.The problems described above seriously hinder the application of many traditional separation materials.To this end,this study designed and developed a multi-response P-Fe₃O₄-PDA@MF oil-water separation foam,which can achieve a controllable wettability switch to separate oil-containing wastewater,effectively improve the recovery rate of high-viscosity crude oil through photothermal conversion,and provide an integrated method of filtering bacteria-containing wastewater and sterilization,and can effectively deal with fire warning.The main contents of this paper are as follows:(1)Preparation and characterization of multi-responsive P-Fe₃O₄-PDA@MF foam:In this study,Fe₃O₄ nanoparticles(NPs)was deposited into the porous foam based on melamine 3D porous foam(MF)through the chelation of polydopamine(PDA),and a thermo-responsive and p H-responsive poly(NIPAAm-co-DMAEMA)copolymer layer was modified in the MF foam by in situ free radical polymerization,then P-Fe₃O₄-PDA@MF foam was obtained by silanization of hexadecyltrimethoxysilane(HDTMS).The characterization results of SEM,XRD,ATR-FTIR,EDS,and XPS show that the multi-responsive P-Fe₃O₄-PDA@MF foam was successfully prepared.(2)Study on oil absorption and desorption performance of multi-responsive P-Fe₃O₄-PDA@MF foam:The photothermal effect of PDA/Fe₃O₄ NPs stimulated the thermal response of P-Fe₃O₄-PDA@MF foam,and the wettability of the foam was changed from hydrophilic/lipophilic to hydrophobic(WCA=145.3±0.1°)/lipophilic,achieving oil absorption on and under water,and showing a high adsorption capacity for a variety of organic solvents and oils(18.42?43.83 g·g^-1),and the mechanism of oil absorption process of foam was revealed by analyzing thermodynamic equation and thermosensitive conformation of foam surface molecules.After oil absorption,the foam changed to hydrophilic/underwater oleophobic under p H response(p H=1),and the underwater oil contact angle of light oil(cyclohexane)and heavy oil(1,2-dichloroethane)were above 150°,which enabled the oil to be desorbed automatically from the foam,and the oil recovery rate of various organic solvents was up to 98.4%.Moreover,the oil recovery rate of oil(1,2-dichloroethane)can still reach 91.9%after 10 cycles of absorption and desorption,which has high oil recovery and recycling property.The intrinsic mechanism of p H-responsive desorption of oil in P-Fe₃O₄-PDA@MF foam was revealed by XPS test and thermodynamic model of liquid transfer.(3)Study on photothermal adsorption and desorption properties of multi-responsive P-Fe₃O₄-PDA@MF foam with high viscosity crude oil:Compared with unmodified MF,the excellent photothermal effect of PDA and Fe₃O₄ NPs made the foam heat up to 75.2°C within10 min of irradiation,and the viscosity of the crude oil with high viscosity decreased from 1.3910⁵ m Pa·s to 71.77 m Pa·s,which greatly improved the recovery capacity of spilled oil(12.8g·g^-1)and the continuous adsorption capacity of spilled oil after the foam was connected to the peristaltic pump.Further study on the desorption of the foam after adsorption of high viscosity crude oil,the results showed that due to the p H response characteristics of P-Fe₃O₄-PDA@MF foam,it also showed excellent desorption performance(88.7%)for crude oil.(4)Study on separation of bacteria-containing emulsions and photothermal antibacterial/anti-adhesion properties of multi-responsive P-Fe₃O₄-PDA@MF foam:P-Fe₃O₄-PDA@MF foams can effectively separate oil/bacteria from oil-in-water emulsions,and the separation efficiency was close to 100%.Further,the temperature of P-Fe₃O₄-PDA@MF foam was increased to 74.6°C and 70.3°C respectively by using xenon lamp to simulate sunlight at3.0 k W·m^–2 light intensity for 90 min.The results of bacterial plate counting,SEM,TEM and fluorescence microscopy showed that the bactericidal rates of the foam against Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli)were nearly 100%under the action of photo-heat transfer.The combination of SEM,fluorescence microscopy,oil adhesion and oil contact angle tests underwater showed that P-Fe₃O₄-PDA@MF foam has low oil adhesion below the minimum critical solution temperature(LCST),which was helpful to prevent bacterial adhesion.Finally,the mechanism of P-Fe₃O₄-PDA@MF foam of retaining bacteria,photothermal sterilization,and anti-bacterial adhesion was revealed by constructing a model diagram of the process of treating the bacteria-containing emulsion with three steps.(5)Research on oil absorption to extinguish fire and fire alarm performance of multi-responsive P-Fe₃O₄-PDA@MF foam:The results of combustion test,thermogravimetric test and microcalorimetric(MCC)test showed that the P-Fe₃O₄-PDA@MF foam could self-extinguishing after oil absorption combustion,and the initial weight loss temperature(T₀)of290.5°C was significantly higher than that of PU foam(213.1°C),showing good thermal stability and lower heat release capacity.The excellent magnetic responsiveness of multi-responsive foam(saturation magnetization of 6.40 emu·g^-1)can be used for magnetic control of rapid oil absorption and fire extinguishing,significantly reduce the temperature around the ignition point,and reduce the risk of fire spread.The mechanism of oil absorption and flame retardancy was further revealed by SEM and multi-responsive foam oil absorption and fire extinguishing process model.The high porosity of foam,thermal barrier of Fe₃O₄ NPs and N₂release from melamine at high temperature were important reasons for the efficient flame retardancy of foam.By connecting to a 60 V power supply and connecting small bulbs in series,the P-Fe₃O₄-PDA@MF foam enabled rapid fire warning and response.