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Poly(vinyl chloride) (PVC) hollow-fiber membranes were spun by a dry/wet phase-inversion technique from dopes containing 15 wt % PVC to achieve membranes with different pore sizes for ultrafiltration (UF) applications. The effects of the N,N-dimethylacetamide (DMAc) concentration in the internal coagulant on the structural morphology, separation performance, and mechanical properties of the produced PVC hollow fibers were investigated. The PVC membranes were characterized by scanning electron microscopy, average pore size, pore size distribution, void volume fraction measurements, and solubility parameter difference. Moreover, the UF experiments were conducted with pure water and aqueous solutions of poly(vinyl pyrrolidone) as feeds. The mechanical properties of the PVC hollow-fiber membranes were discussed in terms of the tensile strength and Young's modulus. It was found that the PVC membrane morphology changed from thin, fingerlike macrovoids at the inner edge to fully spongelike structure with DMAc concentration in the internal coagulant. The effective pores showed a wide distribution, between 0.2 and 1.1 lm, for the membranes prepared with H 2 O as the internal coagulant and a narrow distribution, between 0.114 and 0.135 lm, with 50 wt % DMAc. The results illustrate that the difference in the membrane performances was dependent on the DMAc concentration.

This study investigated the impact of implanting TiO2-NPs within a membrane to minimize the influence of long-term operation on the membrane characteristics. Four poly vinyle chloride-titanium oxide (PVC-TiO2-NPs) membranes were prepared to create an ultrafiltration membrane (UF) that would effectively treat actual refinery wastewater. The hypothesis of this work was that TiO2-NPs would function as a hydrophilic modification of the PVC membrane and excellent self-cleaning material, which in turn would greatly extend the membrane’s lifetime. The membranes were characterized via Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscope (AFM), and scanning electron microscope (SEM). The removal efficiency of turbidity, total suspended solid (TSS), oil and grease, heavy metals and chemical oxygen demand (COD) were investigated. Contact angle (CA) reduced by 12.7% and 27.5% on the top and bottom surfaces, respectively. The PVC membrane with TiO2-NPs had larger mean pore size on its surface and more holes with larger size inside the membrane structure. The addition of TiO2-NPs could remarkably enhance the antifouling property of the PVC membrane. The pure water permeability (PWP) of the membrane was enhanced by 95.3% with an increase of TiO2 to 1.5 gm/100gm. The PWP after backwashing was reduced from 22.3% for PVC to 10.1% with 1.5 gm TiO2-NPs. The long-term performance was improved from five days for PVC to 23 d with an increase in TiO2-NPs to 1.5 gm. The improvements of PVC-TiO2-NPs long-term were related to the enhancement of the hydrophilic character of the membrane and increase tensile strength due to the reinforcement effect of TiO2-NPs. These results clearly identify the impact of the TiO2-NPs content on the long-term PVC/TiO2-NPs performance and confirm our hypothesis that it is possible to use TiO2-NPs to effectively enhance the lifetime of membranes during their long-term operation.

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) hollow fiber membranes were prepared by using the phase inversion method. The effect of polyethylene glycol (PEG-600Mw) with different concentrations (i.e., 0, 5, 7, 10, 12, 15, 18, and 20 wt %) as a pore former on the preparation and characterization of PVDF-co-HFP hollow fibers was investigated. The hollow fiber membranes were characterized using scanning electron microscopy, atomic force microscopy, and porosity measurement. It was found that there is no significant effect of the PEG concentration on the dimensions of the hollow fibers, whereas the porosity of the hollow fibers increases with increase of PEG concentration. The cross-sectional structure changed from a sponge-like structure of the hollow fiber prepared from pure PVDF-co-HFP to a finger-like structure with small sponge-like layer in the middle of the cross section with increase of PEG concentration. A remarkable undescribed shape of the nodules with different sizes in the outer surfaces, which are denoted as ''twisted rope nodules,'' was observed. The mean surface roughness of the hollow fiber membranes decreased with an increase of PEG concentration in the polymer solution. The mean pore size of the hollow fibers gradually increased from 99.12 to 368.91 nm with increase of PEG concentration in polymer solution.polymer solution up to 20 wt % as shown in Table II, whereas the porosity of the hollow fibers prepared from pure PVDF-co-HFP was lower (i.e., e m ¼ 66.7%). Table II, it can be seen that the porosity of the PVDF-co-HFP reaches a maximum by using 12 wt % PEG in dope solution and then decreases. This behavior is due to the Figure 4. Topography and three-dimensional AFM images of the outer surfaces of the PVDF-co-HFP hollow fibers prepared at different PEG-600Mw concentrations: (a) 0 wt % PEG, (b) 5 wt % PEG, (c) 7 wt % PEG, (d) 10 wt % PEG, (e) 12 wt % PEG, (f) 15 wt % PEG, (g) 18 wt % PEG, and (h) 20 wt % PEG. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] ARTICLE WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP Moreover, from

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In this work, a flat-sheet blend membrane was fabricated by a traditional phase inversion method, using the polymer blends poly phenyl sulfone (PPSU) and polyether sulfone (PES) for the ultrafiltration (UF) application. It was hypothesized that adding PES to the PPSU polymer blend would improve the properties of the PPSU membrane. The effect of the PES concentration on the blend membrane properties was investigated extensively. The characteristics of PPSU-PES blend membranes were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), contact angle measure, and contaminant (dye) elimination efficiency. This study showed that PES clearly affected the structural formation of the blended membranes. A considerable increase in the average roughness (about 93%) was observed with the addition of 4% PES, with a higher mean pore size accompanied by a rise in the pores' density on the surface of the membrane. The addition of up to 4% PES had a significant influence on the hydrophilic character of the PPSU-PES membrane, by lowering the value of the contact angle (CA) (i.e., to 56.9 • ). The performance of the PPSU-PES composite membranes' UF performance was systematically investigated, and the membrane pure water permeability (PWP) was enhanced by 25% with the addition of 4% PES. The best separation removal factor achieved in the current investigation for dye (Drupel Black NT) was 96.62% for a PPSU-PES (16:4 wt./wt.%) membrane with a 50% feed dye concentration.Membranes 2020, 10, 47 2 of 17 the removal of a variety of dye molecules from industrial effluents. Hence, a number of investigations have reported using UF and nanofiltration technologies in textile manufacturing industries [4].Alventosa-deLara et al.[5] studied the influence of trans-membrane pressure (TMP) and cross-flow velocity (CFV) on the ultrafiltration (UF) ceramic membrane performance for various concentrations of dye (50-500 ppm). They concluded that the permeate flux increases with a higher TMP and CFV as well as with a low concentration of feed, up to a maximum flux of 0.267 m 3 /(m 2 h). Moreover, the efficiency of the UF treatment was estimated by the dye rejection coefficient. Alventosa-deLara et al. [5] reported considerable dye rejection, regardless of the examined conditions, with steady-state rejection higher than 79.9% for 50 ppm and approximately 73.2% for 500 ppm. Moideen et al.[6] prepared a polysulfone-poly phenyl sulfone (PSF-PPSU blend UF membrane for Pb 2+ and Cd 2+ heavy metal removal, and the blend membrane displayed improved performance and hydrophilicity as well as an antifouling feature, as compared with the pristine PSF polymer membrane. Contaminant (e.g., heavy metals) rejection was completed by complexing the metal ions with polyaziridine, which has displayed a good rejection of 99.5% and 95.5% of Pb 2+ and Cd 2+ , respectively. Since 2012, poly phenyl sulfone (PPSU) emerged as an excellent polymer material for membrane fabrication due to its advantageous characteristics, especially for NF application [...

The present work reports the performance of three types of polyethersulfone (PES) membrane in the removal of highly polluting and toxic lead Pb2+ and cadmium Cd2+ ions from a single salt. This study investigated the effect of operating variables, including pH, types of PES membrane, and feed concentration, on the separation process. The transport parameters and mass transfer coefficient (k) of the membranes were estimated using the combined film theory-solution-diffusion (CFSD), combined film theory-Spiegler-Kedem (CFSK), and combined film theory-finely-porous (CFFP) membrane transport models. Various parameters were used to estimate the enrichment factors, concentration polarization modulus, and Péclet number. The pH values significantly affected the permeation flux of the Pb2+ solution but only had a slight effect on the Cd2+ solution. However, Cd2+ rejection was highly improved by increasing the pH value. The rejection of the PES membranes increased greatly as the heavy metal concentration rose, while the heavy metal concentration moderately affected the permeation flux. The maximum rejection of Pb2+ in a single-salt solution was 99%, 97.5%, and 98% for a feed solution containing 10 mg Pb/L at pH 6, 6.2, and 5.7, for PES1, PES2, and PES3, respectively. The maximum rejection of Cd2+ in single-salt solutions was 78%, 50.2%, and 44% for a feed solution containing 10 mg Cd/L at pH 6.5, 6.2, and 6.5, for PES1, PES2, and PES3, respectively. The analysis of the experimental data using the CFSD, CFSK, and CFFP models showed a good agreement between the theoretical and experimental results. The effective membrane thickness and active skin layer thickness were evaluated using the CFFP model, indicating that the Péclet number is important for determining the mechanism of separation by diffusion.

Among many contaminants in wastewater, organic phenol compounds presented a major concern to endanger the water resources safety. In the present study, blend nanofiltration (NF) membranes comprising polyphenylsulfone (PPSU) and polyethersulfone (PES) were prepared via the non-induced phase separation and their performance was examined against 4-Nitrophenol (4-NP). The PES ratio in the dope solution was varied from 6 to 9 wt.% to probe the impact of PES on the retention and permeation characteristics of the final membranes. A series of experimental tools were employed to estimate the characteristics of the membranes, including surface and cross-section, hydrophilicity, pore size and pore size distribution. Performance evaluation of the NF membranes was conducted considering two operational variables; pH and initial feed solution. About 99% removal of 4-NP along with 6.2 L/m2.h.bar was achieved at the optimum operating conditions as revealed by optimization and mathematical modelling.