Study On Hydrophilic Modification And Formation Mechanism Of Pvdf/mmt Membranes For Oil/water Separations

The flat sheet PVDF/MMT membrane was prepared by L-S phase inversion method,with polyvinylidene fluoride (PVDF) as raw material and montmorillonite(MMT) as addition. The effects of concentration of additive MMT on the membrane pore size, porosity, water flux, rejection of PEG20000s were studied. The operation conditions: PVDF: MMT: DMAC = 14:7:79, and the time of solvent pre-evaporation is 1 minute. The max pure water flux of the membrane is 94.32 L·m-2·h-1, and the retention of Oil/Water compound is 68.5%.From the phase diagram, the effects of the temperature of coagulation bath,solvent,additive and contents on the membrane formation process were investigated. It had found that: Choosing DMAC, 7wt% MMT as addition, reduce temperature of coagulation bath has in favor of liquid-solid phase separation happened in the crystal polymer.In the membrane of sulfonating grafting experiment, The effects of the potassium hydroxide(KOH)/ ethanol(CH3 CH2OH) concentration, reaction time, mole ratio between acetic anhydride((CH3 CO) 2 O) and sulfuric acid (H2 SO4)on sulfonation degree were investigated. The experiment was indicated that the optimum sulfonating condition were as follows: KOH/ CH3 CH2OH concentration was 0.15g/mL, sulfonation time=150min, (CH3 CO) 2 O : H2 SO4=1.5:1(mole ration). Angle have reduced 49.56°, the retention of Oil/Water compound have increased by 88.26%, pure water flux of membrane have increased by 100.7 L·m-2·h-1. The results of the DSC curves showed that the crystal degree of PVDF decreased in the modification membrane. FT-IR show that the membrane have been grafted by sulfonic, Thus stretch intension increases,tenacity reduces,the adsorption function reduces.Resist to contaminate a function strengthening.