| The increasing water pollution and the shortage of available water resources have made water treatment technology more and more important.Pressure-driven membrane technology has attracted more and more attention in the wastewater treatment industry due to its low investment,low energy consumption,high rejection rate and environmental protection.However,the problem of membrane fouling has been an important reason for limiting the development of this technology.Membrane fouling will reduce the service life of the membrane and increase the cost of use.Therefore,the introduction of new methods to effectively reduce membrane fouling and to understand the mechanism of membrane fouling is the hotspot of this research.This paper attempts to improve the membrane anti-pollution research.A new method of in-situ electroless plating was introduced to modify the hydrophobic polyvinylidene fluoride?PVDF?membrane.A series of performance characterizations of the modified membranes were demonstrated and thermodynamic analysis based on the extended Derjaguin-Landau-verwey-overbeek?XDLVO?theory to combat contamination.The main findings are as follows:?1?A novel strategy combining radiation grafting of poly?acrylic acid??PAA?and electroless nickel oxide plating was proposed to improve performance of inherently hydrophobic poly?vinylidene fluoride??PVDF?membrane.Prior to plating,poly?acrylic acid??PAA?was firstly grafted onto the PVDF surface by irradiation to facilitate to absorb Ag+,which acted as the accelerant for in situ electroless nickel plating.Series analyses including scanning electron microscope?SEM?,atomic force microscope?AFM?,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?suggested the success and ease of coating PAA and nickel layer on the PVDF membranes by using the proposed strategy.Significant improvements of surface hydrophilicity and wettability of membrane,verified by the decrease of water contact angle from 75.5°to 47.1°and the increase of water content ratio from 61.4%to 109.9%,respectively,were achieved at plating time of 5min.With these improvements,the resulted PVDF-g-PAA-Ag@Ni membrane presented100%flux recovery and reduced fouling propensity when filtrating 0.1g/L sodium alginate?SA?solution.Moreover,involvement of silver in this strategy provided evident anti-bacterial activity of the modified membranes.?2?A novel conductive membrane prepared by coating polydopamine?PDA?and electroless NiO plating of the polyvinylidene fluoride?PVDF?membrane.The conductive membrane possessed improved hydrophilicity.Moreover,the conductive PVDF membrane integrating electric field voltage of 20 V simultaneously possessed high selectivity?97.93%rejection?and extremely high permeability(202.51±9.63 L·m-2·h-1 at 0.1Mpa)for filtration of Congo red?CR?solution,significantly breaking through the permeability-selectivity trade-off.The filtration performance was quite stable even after 6 filtration cycles,indicating the feasibility of the conductive membrane for long-term treatment of CR wastewater.In addition,the conductive membrane showed high antifouling ability to dye and microorganisms.The conductive membranes,together with the new strategy,offered in-depth insights into membrane fabrication.?3?Thermodynamic analysis of the membrane's antifouling properties was carried out by the extended Derjaguin-Landau-verwey-overbeek?XDLVO?theory.Thermodynamic analysis shows that,the change in the interaction energies caused by both the modified thermodynamic properties and the morphology of the surface is the reason for the improvement of the antifouling property of the modified membranes.This provides a potential solution for quantitatively adjusting the fouling resistance of the membrane. |
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