Preparation Of Layered Compound Composite Aerogel And Its Application In Dyes Adsorption And Oil-water Separation

In this article,the epoxy/graphene oxide/layered double hydrogen?EP/GO/LDH?composite aerogel was prepared by hydrothermal and freeze drying combined with high temperature curing.Polyimide/MXene?PI/MXene?composite aerogel was prepared via solution blending and freeze-drying techniques combined with thermal imide technology.The microstructure of aerogel was studied by XRD,FTIR and SEM.The thermal stability and combustion characteristics of aerogel were studied by TG and MCC.The mechanical properties of aerogel were studied by mechanical test.By studying the adsorption capacity,adsorption kinetics and thermodynamics of organic dyes by EP/GO and EP/GO/LDH composite aerogel,the adsorption mechanism of organic dyes by aerogel was revealed.By exploring the adsorption capacity of PI/MXene for oil and organic solvents,cyclic compression adsorption behavior and adsorption behavior under extreme conditions,it is revealed that PI/MXene composite aerogel has high adsorption flux,long service life,excellent cyclic adsorption capacity and excellent reusability under extreme conditions.The application of aerogel in dye adsorption and oil-water separation was expanded.The main research contents include:?1?Application of EP/GP/LDH composite aerogel in dye wastewater.EP/GO/LDH hydrogel was prepared through the hydrothermal approach and by combining the freeze-drying and high temperature curing procedures,the EP/GO/LDH composite aerogel with three-dimensional porous structure was fabricated.By comparing to the pristine EP/GO aerogel,with 1.7 wt%of the LDH,the stress increase of the composite aerogel can reach up to 283%under 70%strain.Besides,after 10times of cyclic compression tests,the original shape of the aerogel?5.1 wt%LDH?was retained,and the residue height was 91%?9%reduction?.This is because the LDH laminates support the porous structure so that the load forces can be transferred to the disordered LDH laminates.TGA analysis suggests that,compared with pure EP/GO,the thermal decomposition rate of EP/GO/LDH composite aerogel in the high temperature region was significantly reduced,and the residual amount increased with the increase of LDH content.High adsorption capacity of EP/GO/LDH on organic dyes.According to the tests results analysis,the equilibrium adsorption capacity of the EP/GO/LDH?5.1%wt LDH?which is 48.166mg·g^-1 is higher than that of the pure EP/GO which is 26.452 mg·^g-1and the adsorption capacity of the EP/GO/LDH can achieve 85%of the equilibrium adsorption capacity within 8 hours.In addition,it is found that the adsorption ability of EP/GO/LDH on the anionic dyes is higher than that on the cationic dyes.With the adsorption ability order from highest to the lowest,the capacity of EP/GO/LDH?5.1wt%?to the methyl orange,con go red,rhodamine B and methylene blue are 40.108,38.842,9.38 and 8.282 mg·g^-1,respectively.The adsorption of anionic dyes by EP/GO aerogel conforms to the first-order kinetics,indicating that the adsorption behavior is mainly physical adsorption.The adsorption of anionic dyes by EP/GO/LDH composite aerogel conforms to both primary and secondary kinetics,indicating that the adsorption behavior is both physical adsorption and chemical adsorption.The adsorption of cationic dyes by EP/GO/LDH composite aerogel was more in line with the first-order kinetics,and the adsorption behavior was mainly physical adsorption.The adsorption of anionic dyes by EP/GO aerogel conforms to the Langmuir isothermal adsorption model,indicating that the adsorption behavior tends to be monolayer adsorption.The adsorption of EP/GO/LDH?5.1%?to anion dyes was consistent with the Langmuir and Freundlich isothermal adsorption models,indicating that the adsorption behavior was monolayer adsorption and multilayer adsorption.The adsorption of cationic dye by EP/GO/LDH?5.1%?was more consistent with the Langmuir isothermal adsorption model,indicating that the adsorption behavior was inclined to monolayer adsorption.?2?Application of PI/MXene composite aerogel in oil-water adsorption separation.The N-N-dimethylacetamide and 4,4'-oxydianiline were used as the raw materials to fabricate the polyamide acid.The MXene?Ti₃C₂T_x?dispersion was prepared via etching the Ti₃Al C₂followed by ultra-sonication exfoliation.The firm,light and surface hydrophobic polyimide/MXene?PI/MXene?composite aerogel was manufactured through the freeze-drying and thermal imidization of the polyamide/MXene blending solution.SEM images showed that the surface structure of aerogel was compact and complete,and the internal structure was orderly and interconnected.Under the 80%strain,the aerogel compressive strength decreases as the addition of the MXene increases.Compared with the PI/MXene-1?mass ratio of 20.8:1?,the PI/MXene-4?mass ratio of 2.6:1?compressive stress declines approximately 11 times.Moreover,after 50 cycles of compression and release of the PI/MXene aerogel,the aerogel is able to regain the original height,which shows the super elasticity and the extraordinary fatigue resistance properties.The strong interaction between the PI chains and the MXene nanosheets enables the increase in the compressive property.With the comparison of the pure PI membrane and pure MXene aerogel to the surface unmodified PI/MXene aerogel,the water contact angle of the PI/MXene aerogel improves significantly with a value of 119°?PI/MXene-3,mass ratio 5.2:1?,and the water contact Angle increased with the increase of PI content.This is attributing to many polar groups of PI were involved in the reaction,reducing the hydrophilicity of aerogels,and the surface structure of aerogels was dense.High adsorption capacity to the organic liquids is found in the surface unmodified composite aerogels with the adsorbing about 18 times their own weight to waste pump oil and 58 times their own weight to pump oil.It is also observed that,the PI/MXene composite aerogel can rapidly separate the chloroform,soybean oil and liquid paraffin from the oil-water system.From the cyclic adsorption test results,the composite aerogel shows great reusability.Thermally stable composite aerogels also exhibit excellent recyclability in extreme environments.PI/MXene-3 aerogel?weight ratio 5.2:1?cannot be ignited by alcohol lamp.compared to the pure MXene,the peak heat release rate?PHRR?and total heat release?THR?of the PI/MXene composite aerogel are extremely lower,which indicates the outstanding fire retardancy of the aerogel.