Research On The Preparation Of PVDF Hybrid Membrane Based On Functionalized Al₂O₃

In order to increase the compatibility between inorganic materials and polyvinylidene fluoride(PVDF) and prepare strong mechanical properties and good hydrophilic hybrid membranes, this paper made a research on the preparation of PVDF Hybrid Membrane based on functionalized Al2O3. This paper used vinyltrimethoxysilane modified nanoparticles of Al2O3, at the same time PVDF molecules were treated by the alkali and this made the PVDF molecules produced carbon-carbon double bond, and the addition of benzoyl peroxide(BPO) made the functionalized Al2O3 and modified PVDF produced chemical bonding. And then the modified Al2O3/PVDF hybrid membranes were prepared via thermally induced phase transition.In addition, the process and the process via thermally induced phase transition to make hybrid films were discussed by two angles of the thermodynamics and kinetics. The modified hybrid films were also applied to separate and purify soy protein solution. The main contents and results were as follows:The(2-cyanoethyl) triethoxysilane was used to modified nano-Al2O3, and the modify Al2O3 was prepared by further hydrolyzed hydrolyzation. The modified Al2O3/PVDF hybrid membrane was prepared via thermally induced phase transition. The results showed that: after modification the average particle of Al2O3 nanoparticles was reduced to 52.2 nm, the agglomeration was greatly reduced.The addition of modified Al2O3 made the crystal bal of hybrid membrane became smaller, and the density of crystal ball was increased and a large numbers of interface hole were produced, the membrane flux was greatly improved.The PVDF powder were treated by the alkali, at the same time the Al2O3 nanoparticles was modified by vinyltrimethoxysilane,and the double modified Al2O3/PVDF hybrid membranes were prepared via thermally induced phase transition the benzoyl peroxide(BPO) was added as initiator. The results showed that, after modification the PVDF molecules produced carbon-carbon double bond and the average particle of Al2O3 nanoparticles was reduced to 47.3 nm, and also produced carbon-carbon double bond. The addition of benzoyl peroxide(BPO) made the functionalized Al2O3 and modified PVDF produced chemical bonding.And the double modified Al2O3/PVDF hybrid membranes showed a better performance on mechanical property, reject rate, pure water influx compared with PVDF membrane. When the amount of modification Al2O3 was 5.0%, the pure water flux and tensile strength of hybrid membrane were reached 622.3 L·m-2·h-1 and 5.0 MPa,they increased 25.9%, 66.4% compared with pure PVDF membrane.The thermodynamic phase diagram and phase separation morphology via the thermally induced phase transitions of double modified Al2O3/PVDF/diluent system were stydied by differential scanning calorimetry instruments, hot stage optical microscopy. The effects of inorganic modified Al2O3 nanoparticles was also stydied. The results showed that: after modified by alkali, the degree of crystallinity of the polymer molecules in the system declined, the polymer system crystallization curve shift up, cloud point temperature rised, the liquid-liquid separation zone was enlarged. The addition of modified Al2O3 nanoparticles made the monotectic point moved right and thermodynamic instability of the system was increased. When the temperature droped near the cloud point temperature, double modified Al2O3/PVDF/diluent system began to appear liquid-liquid phase separation, polymer-lean phase began to gather and form dispersible droplet, as the temperature dropped further the droplet further grew up together and when the dilute of polymer-lean phase were extracted by solvent the micropores formed.The double modified Al2O3/PVDF hybrid membrane were used to separate and purify soybean extract liquor,and the influence to membrane flux recovery rate of different methods to clean hybrid membrane was also been studied. The results showed that, the anti-fouling performance of double modified Al2O3/PVDF membrane was significantly improved,when the transmembrane pressure was 0.15 MPa,the extract temperature was 55 ℃,material the concentration of material was 0.15g/m L, the membrane flux of double modified Al2O3/PVDF hybrid membranes reached 621.5 L·m-2·h-1 and the rejection of soy protein reached 89.5%, while after pure water cleaned, caustic washed, sodium hypochlorite solution washed, pickling, the flux recovery rate of the hybrid membranes reached 90.3%.