Impacts of hydrophilic nanofillers on separation performance of thin film nanocomposite reverse osmosis membrane

The membrane technology is still considered a costly method to produce potable water. In view of this, RO membrane with enhanced water permeability without trade-off in salt rejection is desirable as it could further reduce the cost for water desalination. In this study, thin film nanocomposite (TFN) membranes containing 0.05 or 0.10 w/v% hydrophilic nanofillers in polyamide layer were synthesized via interfacial polymerization of piperazine and trimesoyl chloride monomers. The resultant TFN membranes were characterized and compared with a control thin film composite (TFC) membrane. Results from the filtration experiments showed that TFN membranes exhibited higher water permeability, salt rejection and fouling resistance compared to that of the TFC membrane. Excessive amount of nanofillers incorporated in the membrane PA layer however negatively affected the cross-linking in the polymer matrix, thus deteriorating the membrane salt rejection. TFN membrane containing 0.05 w/v% of nanofillers showed better performances than the TFC membrane, recording a pure water flux of 11.2 L/m2∙he membsalt rejection of 95.4%, 97.3% and 97.5% against NaCl, Na2SO4 and MgSO4, respectively

Determination of Interleukin-6 and Tumor Necrosis Factor-alpha concentrations in Iranian-Khorasanian patients with preeclampsia

BACKGROUND: Our objective was to determine the role of Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha), markers of immune activation and endothelial dysfunction, in patients with preeclampsia. METHODS: Twenty four women with preeclampsia and eighteen antepartum normotensive pregnant women were recruited as controls. Serum levels of IL-6 and TNF-alpha were measured by enzyme-linked immunosorbent assay. We used independent-samples t test to assess the differences in the concentration of cytokines in preeclamptic patients and control subjects. RESULTS: IL-6 levels [mean (S.D.)] were significantly higher in preeclamptic women [5.8 (4.85) pg/ml] compared to normal pregnant women [3.01 (2.45) pg/ml] (p = 0.02). There was no significant change in concentration of TNF-alpha in preeclamptic women [53.8 (30.0) pg/ml] compared to normal pregnant women [51.9 (33.8) pg/ml] (p > 0.1). CONCLUSION: The results of this study show that IL-6 as a pro-inflammatory cytokine is present in higher concentration in women with preeclampsia. The study was undertaken in women with established preeclampsia and it is not possible to determine whether the increased concentration of IL-6 is a cause or consequence of the disease. Furthermore, these findings suggest that serum TNF-alpha level is not associated with preeclampsia

Antifouling properties of novel PSf and TNT composite membrane and study of effect of the flow direction on membrane washing

Antifouling properties of the polysulfone (PSf) and titanium nanotube (TNT) mixed matrix ultrafiltration membrane were investigated. The membrane was prepared by phase separation process using different concentrations of TNT and PSf. The pure water flux, protein removal and fouling parameters were studied to analyze the performance of the membrane. Morphology of the membrane was characterized by using scanning electron microscopy and atomic force microscopy. The most prominent observation was the significant improvement in water flux which attributed to improved hydrophilicity. The improvement of hydrophilicity was confirmed by water contact angle measurement and porosity measurements. This improvement in hydrophilicity is because of hydroxyl group present on TNT as determined by ATR-IR spectra. Fouling resistance of the membranes assessed by BSA solution filtration showed that 0.3 and 0.5 wt.% TNT loading membrane exhibited the best antifouling property that resulted in 100% flux recovery. The results also showed that 0.3 wt.% TNT loading membrane possessed the highest mean pore radius, porosity, and water flux. The effect of different washing directions in fouling experiment was reported. The perpendicular washing and parallel washing were carried out during fouling experiment and effects were discussed. The TNT nanocomposite membrane with parallel washing showed significant reusability during filtration

The potential of thin film nanocomposite membrane in reducing organic fouling in forward osmosis process

A major limiting factor of forward osmosis (FO) membrane, particularly in pressure retarded osmosis (PRO) mode, is fouling by natural organic matters. In this work, we investigated the effect of the nanocomposite substrate on the fouling of a thin film nanocomposite (TFN) membrane due to organic foulants in PRO mode. The TFN membrane was synthesized by coating a polyamide film over the surface of substrate made of polysulfone–titanium dioxide. The TFN membrane always showed much higher FO water flux than the typical thin film composite TFC membrane prepared from the pristine polysulfone substrate. Reduced internal concentration polarization following a significant decrease of the structural parameter in the nanocomposite substrate causes the mass transfer coefficient of the substrate to increase. In the PRO mode, BSA removal in the presence of Ca2 + confirmed that the TFN FO membrane could significantly mitigate fouling tendency compared to a typical TFC membrane. Results also showed that fouling in TFN FO is highly reversible, recovering > 92% permeate flux after a simple water rinse process. A complete study of the membrane fouling was reported with detailed scientific discussion. To the best of our knowledge, this is the first report on the effect of the nanocomposite membrane on membrane fouling in PRO mode

Long-term study of CO2 absorption by PVDF/ZSM-5 hollow fiber mixed matrix membrane in gas–liquid contacting process

In order to fabricate hollow fiber mixed matrix membrane (HFMMM) for long-term CO2 absorption process, ZSM-5 (Zeolite Socony Mobil-5) zeolite was modified using hexadecyltrichlorosilane for increasing hydrophobicity and then added to the polyvinylidene fluoride (PVDF) spinning dope. The in-house made HFMMMs were characterized in terms of gas permeance, overall porosity, average pore size, effective surface porosity, surface roughness, mechanical stability, and wetting resistance. The morphology of the HFMMMs was studied using SEM. The cross-sectional SEM images indicated that the membrane structure has changed from sponge-like to finger-like by ZSM-5 loading. The surface roughness increased by increasing ZSM-5 concentration in the spinning dope. The HFMMM spun from the spinning dope with 0.5 wt % of ZSM-5 zeolite showed that the CO2 absorption flux decreased 18.9% in the initial 115 h of the operation and then the absorption flux remained constant until the end of the operation. For plain PVDF HFM the absorption flux decreased 36% from the initial value in the first 15 h of the experiment. Thus it could be concluded that the long term stability of HFM was improved by the incorporation of ZSM-5

Study on CO2 stripping from water through novel surface modified PVDF hollow fiber membrane contactor

Dry-wet phased inversion method was used to fabricate polyvinylidene fluoride (PVDF) hollow fiber membranes. Different concentration of surface modifying macromolecules (SMM) i.e., 2, 4 and 6 wt.% were used as additives in the spinning dope. In the phase inversion SMM migrates to the membrane surface and changes the surface morphology with chemical properties on the membrane surface. This modification results into larger pore size, higher gas permeance, effective surface porosity and water contact angle. The surface modified membrane was used in membrane contactor for CO2 stripping from water by using self-fabricated gas-liquid membrane contactor module. The result of CO2 stripping experiment shows that the performance of surface modified membrane is better than plain PVDF membrane. CO2 desorption flux increased with respect to SMM concentration, considerably. The membrane fabricated with 6 wt.% SMM as additive showed higher CO2 desorption flux and efficiency of 2.1 x 10(-3) (mol m(-2) s(-1)) and 80%, respectively at 200 ml/min of liquid flow rate. For this membrane CO2 stripping flux was investigated for different liquid phase temperature. It was found that desorption flux increased by increasing liquid temperature and the highest stripping flux was obtained in the temperature of 90 degrees C. The enhancement of the gas flow rate increased the CO2 desorption flux but this change was negligible