Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method

Abstract

In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance Rt of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties.

Treatment of Palm Oil Mill Effluent Using Membrane Bioreactor: Novel Processes and Their Major Drawbacks

“…The by-product released through the metabolic activity of the living layer (biofilm) generates extracellular polymeric substance (EPS) [261]. The secreted EPS is a bio-adhesive material, which normally serves as the glue that fosters the formation of biofilm matrix on the membrane surface [254,262]. This indicates that the major constituents of biofilm are the bacteria cells and the EPS.…”

Characterization and Antibiofouling Performance Investigation of Hydrophobic Silver Nanocomposite Membranes: A Comparative Study

“…Since for both PVDF and PES the main drawback in applications is associated with the morphology and the structural properties causing fouling, this study is mainly devoted to the characterization of these factors. Although many researchers have investigated the hydrophilic modification and its effects on the membrane performance efficiency [ 11 , 15 , 26 ], less attention has been paid to the methods that create hydrophobic membranes capable of fouling reduction. In the present work, we examined the effect of hydrophobicity through physical coating on the biofouling resistance of PVDF and PES.…”

Fabrication of novel Janus membrane by nonsolvent thermally induced phase separation (NTIPS) for enhanced performance in membrane distillation

“…The homogeneous cellular-like pore structure of the hydrophilic layer can be attributed to the TIPS formation mechanism. This is due to the generally much faster heat transfer rate (dominant in TIPS) in the dope leading to the phase separation and crystallization in the polymer-rich phase, and eventually the formation of the cellular-like pores, which is similar to the typical bulk structure of hydrophilically modified PVDF/PVA membrane fabricated via TIPS process in the previous work [30]. Figure 4 gives the enlarged window between wave length of 1300 and 700 cm -1 .…”

“…The formation mechanisms of the PVDF toplayer and PVDF/PVA sub-layer were studied via morphological and crystalline analyses. Dope solution for hydrophilic sub-layer: based on a previous study on PVDF/PVA membranes [30], in this study a dope solution containing PVDF, PVA and CPL in a fixed weight ratio of 12.8: 3.2: 84 was prepared. The PVDF and PVA were dissolved into CPL at 150 o C under nitrogen protection and mechanical stirring for 2h to become homogeneous.…”