This work investigates the membrane modification to enhance hydrophobicity aiming for applications as membrane contactors. The PVDF membranes were activated by NaOH and by plasma activation followed by grafting using three organosilanes. For the NaOH, the contact angle of original membranes (68°) was decreased from 44° to 31° with increasing NaOH concentration from 2.5M to 7.5M at 60°C for 3 h. The contact angle of NaOH treated membranes was increased to 100° after modification with 0.01M FAS‐C8 for 24 h. A needle‐like structure was observed on the membrane surface while there was no significant change in pore size and pore size distribution. Moreover, FTIR and XPS data showed Si peak and composition. The mechanical strength was improved. The surface modified membranes under helium plasma activation followed by grafting with 0.01M FAS‐C8 for 24 h showed higher contact angle, mechanical strength and surface roughness than that obtained by NaOH activation method while other physical properties did not change. The long‐term performance test for 15 days of operation was conducted. The modified membranes exhibited good stability and durability for CO2 absorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

This work investigated the membrane modification to increase hydrophilicity aiming for application in a photocatalytic membrane. The modified poly(vinylidene fluoride) (PVDF) flat sheet membrane was coated with titanium dioxide (TiO2). The chemical and physical changes of membranes were characterized by contact angle, scanning electron microscopy and porosity. The results found that TiO2 successfully modified the PVDF membrane by decreasing the contact angle from 127.1° to 114.3° on increasing the TiO2 concentration from 0.1 to 1.0 g/L. The contact angles were decreased with the increase of coating time. The water permeation after PVDF membrane modification decreased compared with the original membrane, whereas water fluxes increased with the increase of TiO2 concentration. TiO2 particles were observed on the membrane surface while the porosity of the membrane coated with TiO2 decreased. The optimum condition of membrane coating was obtained at 1.0 g/L of TiO2 and 60 min of coating time. The decolorization of RB 19 by photolysis and photolysis followed by filtration was less than 10%; in contrast, the decolorization of RB 19 by photocatalytic oxidation was as good as a photocatalytic membrane for 60 min. The TiO2 photocatalytic membrane is a feasible technology for RB 19 decolorization in wastewater.

This work investigates polyvinylidene fluoride (PVDF) membrane modification to enhance its hydrophilicity and antibacterial properties. PVDF membranes were coated with nanoparticles of titanium dioxide (TiO2-NP) and silver (AgNP) at different concentrations and coating times and characterized for their porosity, morphology, chemical functional groups and composition changes. The results showed the successfully modified PVDF membranes containing TiO2-NP and AgNP on their surfaces. When the coating time was increased from 8 to 24 h, the compositions of Ti and Ag of the modified membranes were increased from 1.39 ± 0.13 to 4.29 ± 0.16 and from 1.03 ± 0.07 to 3.62 ± 0.08, respectively. The water contact angle of the membranes was decreased with increasing the coating time and TiO2-NP/AgNP ratio. The surface roughness and permeate fluxes of coated membranes were increased due to increased hydrophilicity. Antimicrobial and antifouling properties were investigated by the reduction of Escherichia coli cells and the inhibition of biofilm formation on the membrane surface, respectively. Compared with that of the original PVDF membrane, the modified membranes exhibited antibacterial efficiency up to 94% against E. coli cells and inhibition up to 65% of the biofilm mass reduction. The findings showed hydrophilic improvement and an antimicrobial property for possible wastewater treatment without facing the eminent problem of biofouling.

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The decolorization of Reactive Blue 19 (RB 19) wastewater by an ozonation membrane contactor and Fenton oxidation was studied.

Hollow fiber membrane contactor is nowadays one of the alternative absorption processes for the conventional bubble column. In this work, the performances of microporous hollow fiber membranes for aeration and CO2 absorption were investigated and compared with a conventional bubble column. The membranes used in this work were adapted from filtration membranes which are significantly cheaper than conventional absorption membranes. The effects of operating variables such as average pore sizes, gas flow rates, liquid flow rates, number of hollow fiber membrane, and concentrations of chemical solution on the gas-liquid absorption rate were determined. For oxygen-water absorption, the overall mass transfer coefficient (kLa), which corresponding to the absorption rate, increased with the increase of membrane porous diameter. The kLa was also enhanced with the increase of the liquid flow rate and the number of membranes while the gas flow rate was rarely influent. For carbon dioxide absorption, the increase in liquid flow rate and the carbon dioxide concentration resulted in higher mass transfer rate. Moreover, adding sodium carbonate in absorbent improved the kLa value up to 2.2 folds, comparing with physical absorption. The comparison between the membrane contractor and a bubble column indicated that the utilization of filtration membranes had more efficiency comparing to bubble column due to its high surface area and adaptability when operating with the same size especially when using lower gas velocity rate.

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