Design Of Zinc Oxide Microspheres/Polysulfone Ultrafiltration Mixed Matrix Membranes And Their Behavior

Because of the inherent hydrophobicity of polysulfone?PSF?,contamination of organic matter and microorganisms can easily attach to surface of membranes,resulting in a sharp decrease in membrane separation performance and efficiency.In this study,we found that the enlargement of membrane permeability,antibacterial activity and mechanical properties can be realized with the addition of inorganic nano-antibacterial agent.Moreover,through changing the morphology of the antimicrobial agent nanoparticles,which can effectively limit the release of metal ions in the antimicrobial membranes during the separation process and improve the antibacterial duration.Herein,we design mixed matrix ultrafiltration membranes by employing polysulfone as membrane material,ZnO hollow microspheres?ZnO HSs?or L-dopa coated ZnO HSs as bacteriostatic agents via a phase transformation method.The main conclusions are listed as follows:?1?First of all,ZnO hollow microspheres were fabricated by a template method,and then different proportions of ZnO microspheres were incorporated into polysulfone membrane materials.Finally,the blended membranes were prepared by a phase inversion method.The morphology and properties of the membranes were characterized by scanning electron microscopy,contact angle test,tensile strength test,separation performance test,antibacterial property test and release of ions test.When the addition of dopa-ZnO hollow microspheres was 0.3%,the average pore size of the membrane was 33.7 nm and the porosity was 75.6%.The rejection rate can reach to 90.75% and the flux was enhanced to 158.85 L m^-2 h^-1 217.2%higher than that of the pure membrane.?2?The mechanical property was also analyzed with an uniaxial tension test.When the loading of dopa-ZnO hollow microspheres was 1.0 wt%,the mechanical strength of the hybrid membrane can reach to 5.08 Mpa,which indicates that the hybrid membrane prepared by the dopa-ZnO hollow microspheres can be applied in high-pressure environment.?3?The antibacterial activity of the blended membranes demonstrated that the diameter of inhibition zones of Staphylococcus aureus for ZnO nanoparticles,ZnO hollow microspheres and dopa-ZnO hollow microspheres were 11.2mm,10.3 and 9.4mm,respectively.The result indicates the morphology control and coating with L-dopa can be efficient routes for limiting the release of metal ions.?4?The leakage rate of metal ions was controlled by changing the morphology of the bacteriostatic agent.In order to obtain a long antibacteria efficiency,the release of zinc ions from the membrane should be controlled.The total leakage amount of Zn²⁺was only 0.095 mg L^-1 at first 24h in static systems during the test.Furthermore,the Zn²⁺leakage at the beginning of the filtration was only 3.18% of the total content of the hybrid membrane during filtration process.The results demonstrated that the dopa-ZnO hollow microspheres could inhibit the loss of Zn²⁺well and the prepared membranes exhibited long-lasting antimicrobial activity against Escherichia coli.