Preparation Of Nanometer Modified PVDF Membrane And Study On Its Performances Of Oily Wastewater Treatment

Now, the researchers and workers in the field of membrane separation technology are facing to a main subject, which is how to improve the membrane fluxes and enhance the membrane anti-fouling performances. And the betterment of membrane materials is the essential method to solve the pollution. In this dissertation, the PVDF ultrafiltration(UF) membranes modified by the inorganic nano-sized particles were prepared by the phase inversion process in order to improve the PVDF UF membrane hydrophilicity and anti-fouling performances in water and wastewater treatment. The membrane surface morphologies, cross-section structures and the pore structures and size inside the membranes were analyzed and detected by the Atomic Force Microscopy (AFM) and the Scanning Electron Microscopy (SEM); The crystallinities of UF membranes were investigated and analyzed by the X-ray Detector; The cup ultrafiltration set was employed to study the effects of nano-sized particles addition on the permeation performances of modified membranes; The contact angle between water and membrane surface was measured by contact angle measurement in order to characterize the hydrophlicity changing of the membrane surface; The membranes mechanical performances were measured by omnipotence electronic intensity measuring instrument (W-56). It shows that the addition of nano-sized particulars can not affect the modified membrane micro-structures and formed mechanism, significantly improved the membrane permeation abilities and enhanced the membrane anti-fouling performances without changing properties of the unmodified organic PVDF UF membrane.Little scale tubular UF membrane device equipped with the PVDF membranes modified by inorganic nano-sized particles and the unmodified PVDF membranes is used to treat with the waste water of oil filed. The effects of the operation pressure, wastewater concentration, wastewater temperature, and the circulation time on the membrane permeation properties were discussed. Additionally, the recovery ratio of membrane permeation flux was detected and calculated after chemical washing with 1% content of OP-10 surfactant solution. The experimental results show that the unmodified PVDF UF membrane and the inorganic nanometer modified PVDF UF membranes have the same performances in the oily wastewater treatment: the turbidity value is below 1 NTU, suspended solids (SS) content is below 0.4 mg.L-1, oil content is below 1.0 mg.L-1, polymer content is below 40.0 mg.L-1, retention ratios of chemical oxygen demand (COD) and total organic carbon (TOC) are 80%-94% and more than 90%, respectively. Under the same operation conditions (pressure 0.1MPa and temperature 40℃), the steady permeation fluxes of modified membranes PVDF330 and PVDF312 are respectively 1.24 times and 1.35 times than that of unmodified membrane PVDF000, which indicates that the permeation fluxes of modified membranes have been significantly improved. Additionally, the flux recovery ratios of nano-particles modified membranes after chemical washing with 1% content of OP-10 surfactant solution are also better than that of the unmodified membrane PVDF000.