Study On Reinforced PVDF Hollow Fiber Membrane And Pretreatment Of RO Feeding Water Via Membrane Method

PVDF hollow fiber membrane and reinforced PVDF hollow fiber membrane were successfully prepared in this paper. Also pretreatment of RO feeding water via ultrafiltration was studied.The membrane forming solution viscosities of different PVDF initial concentrations at different temperatures were determined by rotating viscosity meter. Appropriate PVDF concentration and temperature range for forming PVDF hollow fiber membrane were determined. The effects of initial concentrations of PVDF and PVP and the membrane forming solution temperature on membrane morphology, porosity, mean pore size, water flux, tensile and bursting strengths were studied. The surface and intersection structures of PVDF hollow fiber membranes and reinforced ones were observed via SEM. Along with the increasing of PVDF initial concentration, the porosity, mean pore size and water flux of the membrane decreased while the tensile and bursting strengths of the membranes were improved. Meanwhile the structure beneath the outer skin of the membrane changed from pore like to sponge like gradually. Increasing of the membrane forming solution temperature led to the increasing of mean pore size and water flux of the membrane. Along with the increasing of PVP initial concentration, the size of the finger like pores decreased while the pore density and water flux of the membrane increased.Based on the study of PVDF hollow fiber membrane, PET thread reinforced PVDF hollow fiber membranes with high tensile strength were prepared for the first time at home. PET thread was integrated well into the PVDF membrane. The tensile strength of the reinforced membrane was improved 6.8 times on general PVDF membranes and could achieve as high as 10MPa. The reinforcement thread had little effect on other properties of the membrane.The factors that affect the running stability of ultrafiltration system and the effect of ultrafiltration treatment on water quality were also researched in this paper. It was found that flocculation and chemical enhanced backwash period had important influence on the running stability of ultrafiltration system. The turbidity, SDI value, iron ion and COD in the water could be reduced effectively via ultrafiltration. And use of flocculation agent PFS and bactericide NaClO had some negative effect on the SDI value of the product water.