A series of polyethersulfone-TiO 2 (PES/TiO 2) film photocatalysts were prepared by a phase inversion technique and subsequently used in the photodegradation of methyl orange dye (MO). The photoactivity of the films increased with increasing TiO 2 content up to 13 wt% (PT-13). The photodegradation of MO followed pseudo first-order kinetics and complete removal of MO was almost achieved in acidic conditions. The PT-13 film was found to retain its high degradation efficiency even after 5 cycles indicating the stability of the film photocatalyst.
Complete CO 2 /CH 4 gas separation was aimed in this study. Accordingly, asymmetric neat polysulfone (PSF) and PSF/polyvinylpyrrolidone (PVP) blend membranes were prepared by wet/wet phase inversion technique. The effects of two different variables such as type of external nonsolvent and type of solvent on morphology and gas separation ability of neat PSF membranes were examined. Moreover, the influence of PVP concentration on structure, thermal properties, and gas separation properties of PSF/PVP blend membrane were tested. The SEM results presented the variation in membrane morphology in different membrane preparation conditions. Atomic forced microscopic images displayed that surface roughness parameters increased significantly in higher PVP loading and then gas separation properties of membrane improved. Thermal gravimetric analysis confirms higher thermal stability of membrane in higher PVP loading. Differential scanning calorimetric results prove miscibility and compatibility of PSF and PVP in the blend membrane. The permeation results indicate that, the CO 2 permeance through prepared PSF membrane reached the maximum (275 6 1 GPU) using 1-methyl-2-pyrrolidone as a solvent and butanol (BuOH) as an external nonsolvent. While, a higher CO 2 /CH 4 selectivity (5.75 6 0.1) was obtained using N-N-dimethyl-acetamide (DMAc) as a solvent and propanol (PrOH) as an external nonsolvent. The obtained results show that PSF/PVP blend membrane containing 10 wt % of PVP was able to separate CO 2 from CH 4 completely up to three bar as feed pressure.
Preparation and characterization of novel polysulfone/zinc oxide (PSf/ZnO) mixed matrix membranes (MMMs) with different ZnO loadings for high selective CO 2 /CH 4 separation were aimed in this study. Scanning electron microscopy photographs demonstrated that spongy and small tear like pores in plain PSf membrane (0 wt % of ZnO) replaced with large tear like pores close to surface layer by increasing ZnO content up to 0.1 and 1 wt %. In contrast, a dense and less free volume structure was obtained in membranes having 3 and 5 wt % of ZnO. Membrane porosity increased from 28.68 to 50.51% with increasing ZnO content from 0 to 1 wt %. Then, a reduction in porosity was observed for membranes containing 3 and 5 wt % of ZnO. Atomic force microscopy images presented variation in membrane surface roughness. Surface roughness decreased from 67.64 nm for plain PSf to 47.86 nm for membrane containing 1 wt % of ZnO. While, surface roughness increased and reached to 115.5 and 122.4 nm for MMMs having 3 and 5 wt % of ZnO. Gas separation properties of PSf/ZnO MMMs were examined and CO 2 /CH 4 selectivity of MMMs containing 3 and 5 wt % of ZnO were 22.29 and 54.29, respectively, in 1 bar feed pressure.
Novel mixed matrix membranes were prepared from polysulfone (PSf), talc and Fe 3 O 4 -talc nanocomposite by phase inversion technique. PSf/Fe 3 O 4 -talc membranes showed higher lead and nickel rejections compared to PSf/talc membranes, which reaches to 99.4 and 96.2% for lead and nickel ions, respectively, at feed pH 5 and lower rejections at pH 3.5 and 2. Higher surface area in Fe 3 O 4 -talc nanocomposite than talc could be considered as a main reason of higher heavy metals removal in PSf/Fe 3 O 4 -talc membranes. The heavy metals removal enhances with the increase in nanocomposite content from 7 to 9 wt.% because higher numbers of vacant sites in membrane morphology were available for adsorption. Heavy metals rejection reduces in higher nanocomposite concentrations (11 and 13 wt.%) due to the formation of macrovoids in membrane substructure. In addition, a reduction in the metal ion rejection was recognized by enhancement in feed solution concentration and applied pressure. This is caused by difficulty for the remaining vacant sites to be filled with the heavy metal ions because of repulsive forces between the adsorbed solute molecules on the surface and solute in bulk phase. The interactions of lead and nickel ions with nanocomposite placed on the membrane top layer were revealed by the scanning electron microscopy with energy dispersive X-rays.
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