Preparation Of Inorganic Nanofluids/Polylactic Acid Janus Fibrous Membrane On Application Research

Polylactic acid(PLA)is a biodegradable thermoplastic polymer material with good biocompatibility,environmental friendliness,high modulus and high strength.However,pure PLA has disadvantages such as high brittleness and poor hydrophilicity,which limit its further applications.At present,researchers usually use polymer particles and inorganic nanoparticles to modify PLA.Meanwhile,electrospinning was used to compound or blend PLA with functional materials and spin into fibrous membranes,which gave PLA multifunctionality and expand its applications.In this paper,organic long-chain ions were used to modify the surface of inorganic nanoparticles to prepare solvent-free nanofluids.After blending with PLA,electrospinning was used to construct functional Janus PLA fibrous membranes,which are used in water treatment such as oil-water emulsions separation and solar desalination.The main research contents are as follows:1.SiO₂ nanofluids composed of SiO₂ nanoparticles as the core,siloxane and polyoxyethylene ether organic long chains as the crown layer,were prepared by ion exchange reaction.The SiO₂ nanofluids,carbon nanotubes and PLA solution were blended separately to prepare functional Janus PLA fibrous membranes by electrospinning.The results of FTIR,DSC and XRD show that CNTs have little effect on PLA.The results of TEM and WCA show that SiO₂ nanofluids are uniformly dispersed in membranes and wettability of membrane was improved.The difference between the two sides(the difference in contact angle was greater than 140°)was beneficial to the separation of the oil-water emulsions.The separation effect of Janus PLA fibrous membranes for several oil-water emulsions,showed that it had a good separation effects.The fluxes of Janus PLA fibrous membranes for water/carbon tetrachloride emulsion,water/n-hexane emulsion and water/pe troleum ether emulsion were 1630 L m^-2 h^-1,1456.77 L m^-2 h^-1 and 1485.48 L m^-2 h^-1,respectively.After 12 cycles,the flux stabilization and separation efficiency were 81%and 99.1%,83%and 99%,82%and 99.2%,respectively.The flux of Janus PLA fibrous membranes for carbon tetrachloride/water emulsion,n-hexane/water emulsion and petroleum ether/water emulsion increased from 966.5 L m^-2 h^-1 to1142.2 L m^-2 h^-1.After 11 cycles,the flux remained at 91-92%of the initial and the separation efficiency were 99-99.5%.The incorporation of CNTs into PLA increased the surface roughness of the fibrous membrane,improved the hydrophobicity of the surface,and made the contact angle difference between water and oil larger.The amphiphilic SiO₂ nanofluids migrates to fiber surface to make the PLA fibrous membrane superhydrophilic.The formed hydration layer generated between water and the PLA/SiO₂ nfs fibers interface had a strong repelling effect on the formation of a filter cake by oil pollution.2.TiO₂ nanofluids composed of TiO₂ nanoparticles as the core,siloxane and polyoxyethylene ether flexible long chains as the crown layer,were prepared by ion exchange reaction.The TiO₂ nanofluids and polyethylene oxide(PEO)are blended with PLA solution,PLA composite fibrous membranes were prepared by electrospinning.Then,PEO was washed and etched to obtain the porous fibrous membrane.Finally,the mixed solution of MXene/PDMS was sprayed on the surface of the fibrous membrane.Thus,Janus PLA fibrous membranes were prepared,which was hydrophilic and hydrophobic,respectively.The wettability and solar absorption ability of the membranes were tested by WCA and UV-Vis-NIR spectroscopy.The results showed that Janus PLA fibrous menbranes have excellent hydrophilicity and solar absorption effect.The Janus PLA fibrous membranes were tested and evaluated to have good photothermal conversion effect.Under 1 sun irradiation,the evaporation rate of Janus PLA fibrous membrane was 0.98 kg m^-2 h^-1,and the efficiency was about 60%.Five of Na Cl solutions with different concentrations to simulate seawater samples from different sea areas were desalinated by Janus PLA fibrous membrane,the Na⁺concentrations were decreased about 4 orders of magnitude.Simulates the concentration of major ions(Na⁺,K⁺,Ca²⁺,Mg²⁺)in offshore seawater,and the ion concentration after desalination(<10 mg L^-1)is much lower than the standard for freshwater ion threshold established by the WHO(Na⁺<200mg L^-1).The organic long chain in TiO₂ nanofluids exchanges with the ions in seawater,and the organic crown layer remains dynamically stable,preventing the accumulation and precipitation of salt,so that Janus PLA fibrous membrane has a better salt rejection effect.During ion exchange,the quaternary ammonium salts were exposed in the TiO₂ nanofluids,which inhibited the growth and reproduction of bacteria and made Janus PLA fibrous membrane antibacterial.