Filtration Performance Of FE3O4/PSF Hybrid Membrane And Its Application In Adsorption And Phosphorus Removal

Ultrafiltration is widely used in the separation of macromolecules in different fields,membrane materials are the key factors influencing the applicability and functionality of ultrafiltration membranes.In order to overcome the shortcomings of conventional single organic and inorganic membrane materials,composite matrix films formed by organic-inorganic hybridization become one of the hot topics in the field of membrane materials.In this paper,Fe₃O₄ nanoparticles were added into PSf casting solution to prepare Fe₃O₄/PSf by non-solvent induced phase separation process（NIPS）,the effect of Fe₃O₄ doping amount on the structure and filtration performance of matrix mixed membranes（MMMs）and the phosphorus adsorption property of MMMs under high doping amount were investigated.In this study,Fe₃O₄ nanoparticles were prepared by chemical co-precipitation method and solvothermal method and they both have typical Fe₃O₄ crystal characteristics,but the microstructure difference is significant.The particle size of co-precipitation-Fe₃O₄ was about 10 nm,smaller than that of solvothermal-Fe₃O₄,However,the former had poor dispersibility in the solvent due to agglomeration,and the size of aggregates formed was about 825 nm,which was higher than that of so-Fe₃O₄ with good dispersibility.Fe₃O₄ prepared by different methods can cause the difference of morphology structure of Fe₃O₄/PSf MMMs,mainly in:It can increase the structure of the finger-like pores in the membrane section,when the amount of Fe₃O₄ is small,and it will become wider as the increase of dosage;The effect of co-Fe₃O₄ on the formation of finger-like pores was more significant.After adding Fe₃O₄,the porosity of the MMMs increased significantly,and the average pore diameter of the membranes increased with the dosage of 1%and 8%.The structural changes resulted in a smaller filtration resistance and a significant filtration flux promotion.When the co-Fe₃O₄ content is 8%,the pure water flux of the MMMs is 663L/m2·h at 0.1MPa,which is 2 times of PSf membrane and 1.1 times of the same amount of so-Fe₃O₄ MMMs.However,the effect of Fe₃O₄ on the hydrophilicity of the membranes surface is not obvious.It has the minimum contact angle（71°）when the dosage is 1%and the maximum contact angle（85°）at 4%,the preparation method and dosage of Fe₃O₄ have little effect on it.The results showed that the MMMs exhibited strong hydrophobic character.Therefore,the flux will decline in the maximum up to 30L/m2·h when filtering 0.3g/L bovine serum albumin（BSA）solution,and after the hydraulic backwash,the pure water flux can only be restored to the initial flux of 21%.Although the Fe₃O₄ nanoparticles can obtain a PSf MMMs with high flux,the Fe₃O₄ preparation method has some influence on the microstructure of the Fe₃O₄/PSf MMMs.However,in the application performance don’t show significant differences.The MMMs is more suitable for drinking water treatment with relatively low pollution load.When the co-Fe₃O₄ doping content is increased to 60%,100%and 120%,the finger-like pore structure of the MMMs is more developed and the pore is more wider,the pure water flux can reach 785 L/m2·h.The adsorption performance of hybrid membrane on phosphate in water was investigated by shaking table experiment.As the Fe₃O₄ has the effective adsorption of the phosphate,and expose outside of MMMs,so the equilibrium adsorption capacity of the MMMs increased with the increase of Fe₃O₄ content.The equilibrium adsorption capacity of 120%-Fe₃O₄/PSf was 0.6281 mg-P/g（dry weight）when the initial phosphate concentration was 50 mg-P/L.The adsorption process can be reached within 3 hours,it can be fitted with pseudo-second-order kinetic model,and Freundlich adsorption isotherm.It can desorbed by O.Olmol/L NaOH solution.The solution with a phosphate concentration of 1 mg-P/L was filtered by 120%-Fe₃O₄/PSf MMMs,when the flow rate is 87L/m2·h,the adsorption equilibrium was reached after 31,and the equilibrium absorption capacity is 0.1719mg-P/L,compared with the sharking table experiment,the adsorption of filtration can not only improve the adsorption rate but also make the solution full contact with the Fe₃O₄ in the membrane pore,then improve the adsorption capacity.The Fe₃O₄/PSf MMMs with high doping content can be used for the removal and recovery of low concentration phosphorus in water.