Abstract
Composite PVDF-TiO2 membranes are studied extensively in literature as effective anti-fouling membranes with photocatalytic properties. Yet, a full understanding of how preparation parameters affect the final membrane structure, properties and performance has not been realized. In this study, PVDF-TiO2 membranes (20 wt% TiO2/PVDF) were fabricated via the non-solvent-induced phase separation (NIPS) method with an emphasis on the preparation temperature. Then, a systematic approach was employed to study the evolution of the membrane formation process and membrane properties when the preparation temperature changed, as well as to establish a link between them. Typical asymmetric membranes with a high porosity were obtained, along with a vast improvement in the permeate flux compared to the neat PVDF membranes, but a reduction in mechanical strength was also observed. Interestingly, upon the increase in preparation temperature, a significant transition in membrane morphology was observed, notably the gradual diminution of the finger-like macrovoids. Other membrane properties such as permeability, porosity, thermal and mechanical properties, and compression behavior were also influenced accordingly. Together, the establishment of the ternary phase diagrams, the study of solvent–nonsolvent exchange rate, and the direct microscopic observation of membrane formation during phase separation, helped explain such evolution in membrane properties.
Highlights
IntroductionA straightforward way to deal with this problem is to enhance the membrane fouling resistance by incorporating the original membrane material with one (or more) nanofiller that possesses anti-fouling properties, such as silver, silica, zeolite, or a carbon nanotube, etc
Our first aim is to examine the differences in the thermodynamic and kinetic aspects of the membrane formation process at different temperatures, along with an observation of the non-solvent entrance once the polymer is in contact with water, all of which determine the properties of the formed membranes
Since the cloud point method cannot quantify how fast the composition of the system changes, the cloud points here might result from both liquid–liquid and solid–liquid demixing of the polymer solution, especially for a semi-crystalline polymer such as PVDF
Summary
A straightforward way to deal with this problem is to enhance the membrane fouling resistance by incorporating the original membrane material with one (or more) nanofiller that possesses anti-fouling properties, such as silver, silica, zeolite, or a carbon nanotube, etc. These inorganic–organic hybrid membranes possess improved properties and performance compared to the original membranes, such as improved hydrophilicity and permeability, enhanced separation efficiencies or proton conductivity, and enhanced chemical stability or mechanical strength, etc. These inorganic–organic hybrid membranes possess improved properties and performance compared to the original membranes, such as improved hydrophilicity and permeability, enhanced separation efficiencies or proton conductivity, and enhanced chemical stability or mechanical strength, etc. [1,2]
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