Study On Filtration And Antifouling Performance Of PVDF-silicon Nano-composite Membranes Enhanced By Coagulation

As a new and efficient separation technology,membrane separation technology has a wide application prospect in water treatment field,and has been one of the hotspots in recent years.However,in the field of water treatment,due to the chemical characteristics and structure of the ultrafiltration membrane,there are still many problems,such as low flux and membrane fouling,which has become a major obstacle to the using of ultrafiltration membrane.Among the membrane materials,PVDF has shown a great advantage in chemical stability,heat resistance and mechanical strength.However,since the PVDF belongs to hydrophobic material,it is liable to cause membrane fouling during the filtration of hydrophobic substances such as proteins and oils.Therefore,in this paper,the PVDF ultrafiltration membrane is hydrophilized and modified by silicon material with blending method to improve the flux and the ability of atifouling.The purification of Songhua river by coagulation-membrane progress has been discussed.In this paper,the mesoporous material SBA-15 and Si O2 nanoparticles have been used as additives to modify the PVDF ultrafiltration membrane,the effects and properties of the two modified membranes with the addition from 0.1% to 0.4% have been investigated and compared.What is more,the novel nanoparticle SBA-15-PVP has beensynthesized by using SBA-15,MAPTMS and NVP.The nanocomposite membrane of PVDF/SBA-15-PVP has been prepared by SBA-15-PVP and PVDF.The permeability,rejection and antifouling of the modified membrane have been tested by a dead-end stirred cell filtration system.The hydrophilicity of the modified membranes has been investigated by the measurement of the contact angle.The specific surface area and porosity of the membranes have been measured by BET.Some ways have been used to analyze the characteristics of nanomaterials and composite membranes.The effects of different nanomaterials and additions on the membrane structure during the phase transformation have been investigated.In addition,the water treatment efficiency of PVDF/SBA-15-PVP modified membrane and coagulationmembrane are investigated by Songhua River.The results have shown that.The results have shown that in the addition of 0.3%,the comprehensive properties of membranes are in the best condition.The membrane flux of PVDF/SBA-15 nanocomposite membranes is superior to PVDF/Si O2 in comparison with the membrane fluxes.Compared with the original membrane,the modified membranes have a more developed pore structure,so that the porosity and pore size of the modified membranes could be improved,which the permeation flux of the composite membrane has been improved.The hydrophilicity of the membrane surface has been enhanced by the synthesized SBA-15-PVP nanoparticles,the surface roughness of the membranes has been improved and the chemical composition of the membrane surface has been changed.The results of XPS and FTIR have shown that the surface modifying of SBA-15 by NVP is successful.Among the three modified particles,SBA-15-PVP nanoparticles are more excellent in hydrophilicity modification,and the modified particles have alleviated the agglomeration effect to a certain extent.During the exchange process of membrane-forming,the hydrophilic SBA-15-PVP particles migrate to the surface,while SBA-15 would prevent the loss of PVP,which is helpful to form more developed pores.The contact angles of modified membranes are decreased,the hydrophilicity and antifouling are improved,and the average pore diameter and porosity of the membrane are increased as well.The optimum dosage of Al2(SO4)3·18H2O is 30mg/L.In terms of the flux,the coagulation-modified membrane process>modified membrane filtration process>coagulation-pure membrane process>pure membrane filtration process.In general,PVDF/SBA-15-PVP nanocomposite membranes could achieve a higher raw water flux and maintain a better flux recovery rate.As for the remove of the pollutants in raw water,the PVDF/SBA-15-PVP modified nanocomposite membranes have shown a better effect on the turbidity,UV254,TOC,colloid,microbial,Ca,Mg,Al,Fe,Mn and other metal ions,especially for turbidity,the removal rate of more than 88% could be achieved.It is obvious that the PVDF/SBA-15-PVP nanocomposite membranes and the coagulation-membrane process have improved the purification effect of raw water.