Beads-on-string structural nanofiber membrane with ultrahigh flux for membrane distillation
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Membrane Distillation
Polyvinylidene fluoride
Polyvinylidene fluoride
Membrane Distillation
Lycopodium
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Abstract Hydrophobic polyvinylidene fluoride (PVDF) hollow fibre composite membranes were prepared by the dilute solution coating process to build a special surface structure that was similar to the dual micro‐nano structure on the lotus leaf. Poly(vinylidene fluoride‐co‐hexafluoropropene) was chosen as the hydrophobic polymer candidate in dilute solution. Membrane morphology and surface hydrophobicity were evaluated by scanning electron microscopy and dynamic water contact angle measurement. The prepared PVDF hollow fibre membranes were employed to separate dyes (Congo Red and Methylene Blue) from water by vacuum membrane distillation. The effects of operational conditions (feed temperature, vacuum pressure and feed flow rate) on the vacuum membrane distillation performance of different PVDF membranes were investigated. The results indicated that the water contact angle values of PVDF composite membrane surfaces improved from 93.6° to 130.8°, which was mainly attributed to the formation of micro‐nano rods. This structure was similar to the dual micro‐nano structure on the lotus leaf. Under test feed temperature, vacuum pressure and feed flow rate conditions, the dye rejection rate of Congo Red and Methylene Blue by the hydrophobic PVDF hollow fibre membrane remained above 99.5% and 99%, which was higher than that of the pristine PVDF membrane (99% and 98%, respectively). In addition, the hydrophobic PVDF hollow fibre composite membrane showed higher permeation flux under different conditions compared with the pristine PVDF membrane, which was attributed to membrane surface hydrophobicity and the electrostatic interactions between dyes and the PVDF membrane surface.
Polyvinylidene fluoride
Membrane Distillation
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Membrane Distillation
Surface Modification
Glow discharge
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Membrane distillation (MD) is one of the novel separation methods used in water and wastewater treatment processes. MD is a thermal driven process which has the potential to be integrated with renewable energy source and can be operated at very low pressure. Polyvinylidene fluoride (PVDF) is a hydrophobic polymeric material which is commonly used to prepare MD membrane. In this study, surface modifying macromolecule (SMM) was added as additive into PVDF dope solution and then the hollow fiber membrane was prepared using phase inversion process. The membrane was characterized with respect to morphology and permeates flux at different temperatures. The results revealed that the PVDF membrane blended with SMM exhibited higher permeate flux than PVDF neat membrane did, mainly due to the better pore size distribution and thinner skin layer. This finding indicated the role of SMM in modifying the properties of PVDF membrane for MD process.
Polyvinylidene fluoride
Membrane Distillation
Phase inversion
Hollow fiber membrane
Surface Modification
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Membrane Distillation
Surface Modification
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The objective of this study was to use the membrane distillation process for saline water desalination using available commercial membranes and evaluate their performance in desalination. Direct contact membrane distillation with membrane of 0.014 m 2 dimensions was used.Available commercial hydrophobic membrane with various pore sizes manufactured by different suppliers, were used. For all membranes, flux experiments were carried out at the same conditions. Results show that PTFE membranes with pore size of 0.45 and 1.0µm provides better performance. Also, the effect of support layer on flux and salt rejection surveyed. PTFE membrane with pore size of 0.45µm and scrim support had higher flux and salt rejection. Experiments showed that PTFE membrane with active layer thickness of 0.005 mm has higher flux and salt rejection. In all cases high salt rejection, more than 99% could be reached.
Membrane Distillation
Saline water
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Polyvinylidene fluoride
Membrane Distillation
Polydimethylsiloxane
Biofouling
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To date, membrane distillation (MD) has been regarded as a potential candidate in treating textile effluents as this thermally-driven membrane process has unique advantages over pressure-driven membrane processes. However, the main challenge for the MD process to be practically used in textile industry is the difficulty of getting a membrane with desirable characteristics. In this work, polyvinylidene fluoride incorporated Cloisite 15A hollow fiber composite membranes were developed for textile wastewater treatment using direct contact membrane distillation (DCMD) system. The effects of polymer concentrations, types of additives and Cloisite 15A clay loadings on the membrane properties and its DCMD performance were investigated. Membrane made of 12 wt% PVDF was found to be the best performing membrane based on its overall separation performance in comparison to the membranes prepared with higher PVDF concentration. In terms of additive, ethylene glycol (EG) was found to be better pore former agent as compared to polyvinylpyrrolidone (PVP). The 12 wt% PVDF membrane with EG as additive was further modified by Cloisite 15A at different loadings. Results showed that the PVDF membrane incorporated with 3 wt% Cloisite 15A (PVDF-3% C15A) was the best composite membrane in terms of permeate flux (10.13 ± 0.18 kg m-2 h-1) and dye rejection (>99%). Its membrane contact angle, wetting pressure, mean pore size and surface roughness was reported to improve upon addition of 3 wt% Cloisite 15A. Besides, this membrane also exhibited the highest thermal stability, mechanical strength and overall porosity compared to other composite membranes. In view of this, PVDF-3% C15A membrane was selected for further studied using synthetic dyeing solutions containing dyes and salts. With respect to separation performance, higher rejections were able to achieve in all experimental tests, regardless of operating conditions, which indicate the potential of PVDF-3% C15A membrane in producing purified water from synthetic dyeing solutions. The membrane was further subjected to another experiment using real textile wastewater collected from a textile factory located in Kulai, Johor. The treated water was analyzed with respect to biological oxygen demand (BOD5), chemical oxygen demand (COD), total dissolved solid (TDS), color, turbidity and conductivity. Higher permeate flux (36.82 ± 1.96 kg m-2 h-1) with excellent removal efficiency (>90%) was recorded for each measured analytical parameter during textile wastewater treatment. The stability of the membrane was also assessed for up to 40-h. Results showed that a significant flux decline was observed during the longterm operation, owing to fouling resulted from cake layer formed at the outer surface of the membrane. Nevertheless, the quality of permeate could be practically maintained at not less than 72% removal for both COD and color. As a conclusion, it can be said that the in-house made PVDF-Cloisite 15A composite membrane can facilitate the development of textile wastewater treatment if several issues such as membrane fouling and pore wetting can be further addressed.
Polyvinylidene fluoride
Membrane Distillation
Polyvinylpyrrolidone
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The formation of biofouling on membrane surfaces is a critical factor that affects the efficiency of desalination processes, because it creates operational problems and increases the energy and cleaning requirements.This research studies the efficacy of different membranes in inhibiting the adhesion of proteins and bacteria on their surface.The adhesion of bovine serum albumin (BSA) and of Escherichia coli DH5α was studied on four membrane types: polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone and polyamide.Evaluation was performed by using 1 g L -1 BSA and a suspension of 10 5 CFU mL -1 of E. coli on both static and dynamic setup.Subsequently, the membranes were mildly washed with distilled water to remove weakly attached cells and the concentration of the fouling agent was determined.The results indicate that the adhesion of both agents is stronger on the hydrophilic membrane surfaces compared to the hydrophobic ones.
Polyvinylidene fluoride
Membrane Distillation
Hollow fiber membrane
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Polyvinylidene fluoride
Membrane Distillation
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