Study On The Properties Of Hydrophilic PVDF Membranes Modified By Ag₃PO₄/Inorganic Nanocomposites

In recent years,membrane separation technology has been widely used in wastewater treatment due to its high effluent quality and simple operation in the water treatment process.As an excellent polymer material,PVDF has the advantages of thermal stability,chemical stability and high mechanical strength,and plays a vital role in membrane preparation materials.At the same time,the PVDF membrane has strong hydrophobicity,which is easy to cause direct pollution of proteins and other organic substances in the sewage treatment process and requires a large driving force in the operation process.All adove problems will increase the running cost.Therefore,PVDF membranes were modified by blending?1?nano-Ag/ZrO₂,?2?Ag₃PO₄/ZrO₂,?3?Ag₃PO₄/TiO₂ and?4?Ag₃PO₄/SiO₂,and prepared by immersion precipitation method.The synthesis of composite materials and the composition of modified PVDF membranes were studied by XRD;The surface morphology of the membranes was measured by SEM;UV-vis response spectrum of the composites was studied by UV-vis;The hydrophilic properties of PVDF membrane and modified PVDF membranes was explored via angle measuring instrument;the filtration experiments test the membrane water flux,rejection,anti-organic pollution performance,flux recovery and relative attenuation rate;The membrane bioreactor was used to study the degradation effect of PVDF membrane on RhB dye wastewater under simulated sunlight,and the photo-response of PVDF membrane modified by composite material was further verified.This experimental study has the following conclusions:?1?The Ag/ZrO₂-PVDF membrane was prepared by nano-scale zirconia and in-situ synthesis of nano-silver as modified substances.The experimental results of modified Ag/ZrO₂-PVDF membrane showed that with the increase of hydrophilic substances,the pore size of the membrane was gradually increased,so did the number of the pores.When the ZrO₂content reaches 1%,the formation of the pores of the membrane was caused by agglomeration,resulting in a decrease in the number of membrane pores.As the content of hydrophilic polymer increased,the contact angle decreased by 15.35°,and the water flux increased significantly from 28.43 L/m²h to 143.2 L/m²h.After BSA was used as an organic pollutant to contaminate the membrane,the flux recovery of the membrane increased with the increase of hydrophilicity,indicating that the antifouling performance of the modified Ag/ZrO₂-PVDF membrane was improved.It is found that the modification of PVDF membrane by in-situ precipitation synthesis of Ag is an effective method to improve membrane antimicrobial contamination by the inhibition zone method.?2?The PVDF membrane was modified by of in-situ synthesized Ag₃PO₄/ZrO₂ in different content.Ag₃PO₄/ZrO₂ was successfully blended into PVDF membrane shown in XRD analysis.The SEM image analysis indicated that the membrane pore size increased and evenly distributed on the surface and inside of the membrane with the content of modified substances.When Ag₃PO₄/ZrO₂ content reached 1%,the presence of Ag₃PO₄/ZrO₂ particles in the pores was observed.The UV-vis spectrum showed that Ag₃PO₄/ZrO₂ showed a significant red shift compared to pure ZrO₂,and the absorption of visible light was significantly enhanced.The PVDF membrane contact angle was reduced from 82.72°to52.04°,and the pure water flux increased from 30.43 L/m²h of pure PVDF to 171.97 L/m²h of Ag₃PO₄/ZrO₂?0.5%?membrane after modification,indicating the hydrophilicity of the PVDF membrane was significantly enhanced after modification.The experimental study on the circulating pollution showed that the anti-organic contamination of PVDF membrane was significantly enhanced after modification.When the content of Ag₃PO₄/ZrO₂ reached 0.5%,the PVDF membrane performance was the best.The photocatalytic experiment was carried out after the membrane bioreactor was stable.The experimental results revealed that the removal rate of RhB by the reactor with Ag₃PO₄/ZrO₂-PVDF?0.5%?as the membrane module reached 98.5%,indicating its good photocatalytic performance.?3?The PVDF membrane was modified by Ag₃PO₄/TiO₂ and prepared by different in-situ precipitation methods.It was found by XRD pattern that Ag₃PO₄/TiO₂ was compounded and modified to PVDF membrane succussfully;The SEM image analysis showed that the pore size of the membrane increased gradually and was evenly distributed on the surface of the membrane as the content of modified substances increased.The UV-vis pattern showed that the Ag₃PO₄/TiO₂ had a significant red shift compared to pure TiO₂.The absorption capacity of visible light was significantly enhanced.The PVDF membrane contact angle after modification was reduced from 82.72°to 52.38°,and the pure water flux increased from 30.43 L/m²h of pure PVDF to 171.97 L/m²h of Ag₃PO₄/TiO₂?0.5%?membrane.The hydrophilicity of the PVDF membrane was significantly enhanced after modification.The experimental study on the circulating pollution showed that the anti-organic contamination of the PVDF membrane was significantly enhanced after modification.When the Ag₃PO₄/TiO₂content reached 0.5%,the membrane performance was the best.In the membrane bioreactor with Ag₃PO₄/TiO₂-PVDF?0.5%?as the membrane module,the removal rate of RhB in the target concentration of dye wastewater under photocatalytic conditions was 98.5%,which was significantly higher than that of the simple membrane bioreactor,so that Ag₃PO₄/TiO₂-PVDF has significant catalytic oxidation ability to RhB under photocatalytic conditions.?4?In this chapter,The PVDF membrane was modified by different contents of Ag₃PO₄/SiO₂ prepared by in-situ precipitation method.XRD analysis showed that Ag₃PO₄/SiO₂ was successfully blended with modified PVDF membrane.The SEM image analysis showed that the pore diameter of the membrane gradually increased and was uniformly distributed on the surface and inside of the membrane as the content of the modified substance increases.When the content of Ag₃PO₄/SiO₂ reaches 1%,the membrane solution was viscous due to excessive modification of the material,and the membrane phase was broken due to accelerated phase transformation.The UV-vis spectrum showed that Ag₃PO₄/SiO₂ had a distinct red shift compared to pure SiO₂,the absorption of visible light was significantly enhanced.The PVDF membrane contact angle after modification was reduced from 82.72°to 57.35°,and the pure water flux increased from 30.43 L/m²h of pure PVDF to 62.77 L/m²h of Ag₃PO₄/SiO₂?0.5%?membrane,indicating the hydrophilicity of the PVDF membrane after modification was significantly enhanced.The experimental study of the circulating pollution showed that the anti-organic contamination of the PVDF membrane was significantly enhanced after modification,and the membrane performance was the best when the Ag₃PO₄/SiO₂ content reached 0.5%.After the reactor was operated stably,the removal rate of RhB by Ag₃PO₄/SiO₂-PVDF?1%?in the target concentration of dyeing wastewater reached 77.5%under photocatalytic conditions.The experiment showed that the photocatalytic performance of Ag₃PO₄/SiO₂-PVDF was effective.