Nanoporous Polyether Sulfone Membrane, Preparation and Characterization: Effect of Porosity and Mean Pore Size on Performance

Flat sheet membranes were prepared by phase inversion technique using polyether sulfone (PES) dissolved in dimethylacetamide (DMAc) with and without adding polyvinylpyrrolidone (PVP) or polyethyleneglycol (PEG). The characteristics of the prepared membranes were evaluated using Scanning Electron Microscope (SEM) images, Atomic Force Microscopy (AFM), and Optical Contact Angle (OCA) measurements, and porosity tests. The porosity test and SEM images show that increasing additives to a certain value increases the porosity of the membrane. Also, as the coagulation bath temperature is increased, the porosity of the membrane is increased. The roughness of the membrane is increased by increasing the additive concentration. The analysis of AFM images confirms the nanoporous structure of the prepared membranes, and that the membranes with appropriate pore size distribution can be prepared by the applied method. Permeability tests using single-layer membranes show that the direct relationship between porosity and the flux of pure water or salt solution is dominated by the effect of applied additive while the salt rejection shows an inverse relationship with the mean pore size regardless of the applied additive. The salt permeation flux is a function of total porosity while the salt rejection is a function of surface porosity. Pervaporation tests show that both permeation flux and enrichment factor depend on the total porosity of the support membrane

Performance of octadecylamine-functionalized graphene oxide nanosheets in polydimethylsiloxane mixed matrix membranes for removal of toluene from water by pervaporation

Functionalized and reduced graphene oxide nanosheets with octadecylamine (rGOODA) were incorporated in polydimethylsiloxane (PDMS) membranes to be used in pervaporation for removal of toluene from water. The properties of the functionalized nanosheets were characterized by FTIR, XRD, Raman, SEM, and TGA analyses. The prepared mixed matrix membranes (MMMs) were characterized using contact angle, AFM, SEM-EDX, TGA, solvent uptake tests. The membranes contained reduced graphene oxide (rGO) represented 111% increment in the enrichment factor compared to that of the bare-PDMS owing to Π-Π interaction of graphene nanosheets and the toluene's aromatic ring as well as high aspect ratio of rGO that causes more tortuous pathways for water permeation. By incorporating rGOODA in the MMMs, the separation factor was increased about 164% rather than that of rGO-contained membrane, which could be mainly attributed to closer Hansen solubility parameter of the functionalized nanosheets to that of toluene, water repelling of the membrane due to more hydrophobicity and steric hindrance of the functionalized nanosheets, their well dispersion which causes more compatibility with the polymeric matrix. The pervaporative performance of membranes with different filler contents were investigated as a function of operational temperatures and feed concentrations. The prepared MMM with 0.4 wt% rGOODA presented the best performance at 30 °C and 150 ppm toluene concentration

Phase Behavior of Nitrate Based Ionic Liquids with Thiophene and Alkanes

In this study, the extraction of thiophene from alkane compounds (hexane, heptane, and octane) was investigated by using 1-butyl 3- methylimidazolium nitrate ([Bmim]­[NO₃]) and 1-methyl 3-octylimidazolium nitrate ([Omim]­[NO₃]). Liquid–liquid equilibrium (LLE) data for ternary systems of ionic liquid + thiophene + alkane were reported at atmospheric pressure and 298.15 K. The calculated selectivity and solute distribution coefficient values from the experimental data demonstrate that the selectivities increase with increasing alkane chain length while the solute distribution coefficients decrease. Moreover, the selectivity values for the systems containing [Bmim]­[NO₃] are higher than those containing [Omim]­[NO₃]. This implies that [Bmim]­[NO₃] is a more suitable solvent than [Omim]­[NO₃] for desulfurization of alkane. The nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models were used to correlate the experimental data. The results show both models can correlate the experimental data with good accuracies

Dehydration of isopropanol by poly(vinyl alcohol) hybrid membrane containing oxygen-plasma treated graphene oxide in pervaporation process

Poly(vinyl alcohol) (PVA)/polyethersulfone (PES) composite membranes were fabricated using two PVA polymers with molecular weights of 50,000 and 15,000 and different crosslinker agents. The membrane with the top layer consisting PVA 50,000 and formaldehyde as the crosslinker were found to have a better separation factor than the others for pervaporative dehydration of isopropanol. While adding 1.0 wt% graphene oxide could represent a better pervaporation separation factor, 248.7% higher than that of the unfilled membrane, treating the graphene oxide nanosheets using cold plasma irradiation under oxygen atmosphere could yield 47.5% higher separation factor compared to the membrane containing untreated nanosheets owing to higher functional groups on the treated nanosheets that enhance the crosslinking density of the membrane. The best plasma treatment conditions in the selected range were found as 60 s irradiation under 0.3 mbar pressure and device power of 25 watts. The superior performance of the optimal membrane fabricated in the present study was confirmed by comparing the values of normalized pervaporation water index with those in previous studies

Oxidative Desulfurization of Model Diesel Using Ionic Liquid 1‑Octyl-3-methylimidazolium Hydrogen Sulfate: An Investigation of the Ultrasonic Irradiation Effect on Performance

A Brønsted acidic ionic liquid (IL), 1-octyl-3-methylimidazolium hydrogen sulfate ([Omim]­[HSO₄]), was prepared and utilized as the extractant and catalyst to study the oxidative desulfurization of dibenzothiophene (DBT) in <i>n</i>-decane as the model oil. The effects of the alkyl chain length of the IL cation, temperature, H₂O₂/DBT molar ratio (O/S), IL/oil mass ratio, initial S-content, and sulfur species on the sulfur removal of the model oil were investigated. Complete removal of DBT was observed by [Omim]­[HSO₄], O/S molar ratio of 5, and IL/oil mass ratio of 1:2 after 70 min at 25 °C. The order of observed oxidizing reactivity for different sulfur species was as follows: DBT > benzothiophene (BT) > thiophene (TH) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The IL could be reused six times without a significant decrease in the desulfurization activity. The kinetics of oxidative desulfurization for DBT by [Omim]­[HSO₄] was found to be pseudo-first-order with an apparent rate constant of 0.0734 min^–1 (at 298 K) and the apparent activation energy of 24.51 kJ/mol. The ultrasound-assisted oxidative desulfurization (UAOD) process was also applied and represented a high desulfurization performance for the model oil in a fast reaction. The effects of various parameters, including irradiation time, settling time, O/S molar ratio, and IL/model oil mass ratio, on the UAOD process were studied. The complete sulfur removal efficiency could be reached after 3 min of ultrasonic irradiation with an ultrasonic power of 30 W, ultrasonic frequency of 20 kHz, O/S molar ratio of 5, and IL/oil mass ratio of 1:2. It was observed that the application of ultrasonic irradiation allows the desulfurization process to be performed in a shorter time. The sulfur removal of real diesel was 77.2% in the ODS process, and 76.3% in the UAOD process under the optimal conditions

Control of the visible and UV light water splitting and photocatalysis of nitrogen doped TiO2 thin films deposited by reactive magnetron sputtering

International audienceN-doped TiO2 thin films have been prepared by reactive RF magnetron sputtering at different pressures and with different compositions using a dual reactive gas mixture of nitrogen and oxygen. The morphological, optical, photo-electrochemical and photocatalytic properties have been studied in order to investigate the white light and visible light photoactivities of the films. Significant control over the band gap energy in the films was achieved by varying the deposition parameters. Photoelectrochemical characterization revealed improved white light photocurrent generation in nitrogen doped films prepared at low pressures. However, the visible light photocurrent generation showed improvement for all deposition pressures, and changed accordingly with the nitrogen incorporation. Photocatalytic measurements of a common chemical pollutant NMP (N-methyl-2-pyrrolidone) under different irradiation conditions provided evidence of improved photoactivity for samples prepared at high pressure, due to the increased active surface area and optimal nitrogen doping levels. Overall, this study showed a simple method to produce highly controllable nitrogen doping in different sites within TiO2 showing improved visible light photoactivity and photo induced pollutant degradation. More interestingly, by investigating the effect of different nitrogen sites in nitrogen doped TiO2, we have shown that the optimized conditions for photocatalysis do not correspond to those for water splitting