Investigation of Different Membrane Porosities on the Permeate Flux of Direct Contact Membrane Distillation

In the present study the surface morphology of electrospun fibers at different polystyrene (PS) solution concentration was studied by SEM imaging to determine the best PS solution concentration yielding continuous uniform beadles fibers. Contact angle measurements of the optimum fabricatedPS-18 membrane confirmed the super hydrophobic property of the membrane that exhibited a static water contact angle of 145o. Numerical investigation of the performance of PS-18 membrane at different membrane thicknesses and porosities on direct contact membrane distillation showed that increasing the membrane porosity increases the permeate flux considerably.

Transendothelial Electrical Resistance Measurement across the Blood–Brain Barrier: A Critical Review of Methods

The blood–brain barrier (BBB) represents the tightest endothelial barrier within the cardiovascular system characterized by very low ionic permeability. Our aim was to describe the setups, electrodes, and instruments to measure electrical resistance across brain microvessels and culture models of the BBB, as well as critically assess the influence of often neglected physical and technical parameters such as temperature, viscosity, current density generated by different electrode types, surface size, circumference, and porosity of the culture insert membrane. We demonstrate that these physical and technical parameters greatly influence the measurement of transendothelial electrical resistance/resistivity (TEER) across BBB culture models resulting in severalfold differences in TEER values of the same biological model, especially in the low-TEER range. We show that elevated culture medium viscosity significantly increases, while higher membrane porosity decreases TEER values. TEER data measured by chopstick electrodes can be threefold higher than values measured by chamber electrodes due to different electrode size and geometry, resulting in current distribution inhomogeneity. An additional shunt resistance at the circumference of culture inserts results in lower TEER values. A detailed description of setups and technical parameters is crucial for the correct interpretation and comparison of TEER values of BBB models.

Synthesis and Evaluation of HSOD/PSF and SSOD/PSF Membranes for Removal of Phenol from Industrial Wastewater

Phenol is regarded as a major pollutant, as the toxicity levels are in the range of 9–25 mg/L for aquatic life and humans. This study embedded silica sodalite (SSOD) and hydroxy sodalite (HSOD) nanoparticles into polysulfone (PSF) for enhancement of its physicochemical properties for treatment of phenol-containing wastewater. The pure polysulfone membranes and sodalite-infused membranes were synthesized via phase inversion. To check the surface morphology, surface hydrophilicity, surface functionality, surface roughness and measure the mechanical properties of the membranes, characterization techniques such as Scanning Electron Microscope (SEM), contact angle measurements, Fourier Transform Infrared, Atomic Force Microscopy (AFM) nanotensile tests were used, respectively. The morphology of the composite membranes showed incorporation of the sodalite crystals decreased the membrane porosity. The results obtained showed the highest contact angle of 83.81° for pure PSF as compared to that of the composite membranes. The composite membranes with 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF showed mechanical enhancement as indicated by a 20.96% and 19.69% increase in ultimate tensile strength, respectively compared to pure PSF. The performance evaluation of the membranes was done using a dead-end filtration cell at varied feed pressure. Synthetic phenol-containing wastewater was prepared by dissolving one gram of phenol crystals in 1 L of deionized water and used in this study. Results showed higher flux for sodalite infused membranes than pure PSF for both pure and phenol-containing water. However, pure PSF showed the highest phenol rejection of 93.55% as compared to 63.65% and 64.75% achieved by 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF, respectively. The two sodalite infused membranes have shown enhanced mechanical properties and permeability during treatment of phenol in synthetic wastewater.

Intensification of CO2 absorption using MDEA-based nanofluid in a hollow fibre membrane contactor

Porous hollow fibres made of polyvinylidene fluoride were employed as membrane contactor for carbon dioxide (CO2) absorption in a gas–liquid mode with methyldiethanolamine (MDEA) based nanofluid absorbent. Both theoretical and experimental works were carried out in which a mechanistic model was developed that considers the mass transfer of components in all subdomains of the contactor module. Also, the model considers convectional mass transfer in shell and tube subdomains with the chemical reaction as well as Grazing and Brownian motion of nanoparticles effects. The predicted outputs of the developed model and simulations showed that the dispersion of CNT nanoparticles to MDEA-based solvent improves CO2 capture percentage compared to the pure solvent. In addition, the efficiency of CO2 capture for MDEA-based nanofluid was increased with rising MDEA content, liquid flow rate and membrane porosity. On the other hand, the enhancement of gas velocity and the membrane tortuosity led to reduced CO2 capture efficiency in the module. Moreover, it was revealed that the CNT nanoparticles effect on CO2 removal is higher in the presence of lower MDEA concentration (5%) in the solvent. The model was validated by comparing with the experimental data, and great agreement was obtained.

Development of an Organ-on-a-Chip-Device for Study of Placental Pathologies

The human placenta plays a key role in reproduction and serves as a major interface for maternofetal exchange of nutrients. Study of human placenta pathology presents a great experimental challenge because it is not easily accessible. In this paper, a 3D placenta-on-a-chip model is developed by bioengineering techniques to simulate the placental interface between maternal and fetal blood in vitro. In this model, trophoblasts cells and human umbilical vein endothelial cells are cultured on the opposite sides of a porous polycarbonate membrane, which is sandwiched between two microfluidic channels. Glucose diffusion across this barrier is analyzed under shear flow conditions. Meanwhile, a numerical model of the 3D placenta-on-a-chip model is developed. Numerical results of concentration distributions and the convection–diffusion mass transport is compared to the results obtained from the experiments for validation. Finally, effects of flow rate and membrane porosity on glucose diffusion across the placental barrier are studied using the validated numerical model. The placental model developed here provides a potentially helpful tool to study a variety of other processes at the maternal–fetal interface, for example, effects of drugs or infections like malaria on transport of various substances across the placental barrier.

Legionella Detection in Water Networks as per ISO 11731:2017: Can Different Filter Pore Sizes and Direct Placement on Culture Media Influence Laboratory Results?

Determination of Legionella concentrations in water networks is useful for predicting legionellosis risks. The standard culture technique using concentration with membranes filters is the most commonly used method for environmental surveillance of Legionella. The aim of this study was to verify whether filtration with different filter pore sizes (0.2 and 0.45 µm) according to (ISO) 11731:2017, followed by directly placing them on culture media, can influence Legionella detection. Three laboratories participated in an experimental study that tested a known suspension of Legionella pneumophila (Lpn) serogroup 1 (ATCC 33152) (approximate final cell density of 15 CFU/mL). E. coli (ATCC 11775) and Pseudomonas aeruginosa (ATCC 25668) were included as control tests. The average (95% CI) percentage of recovery of Lpn was 65% using 0.45-µm filters and 15% using 0.2-µm filters (p < 0.0001). For control tests, the average (95% CI) percentage of recovery was higher with 0.45 vs. 0.2 µm filters: 97% vs. 64% for Escherichia coli (p < 0.00001) and 105% vs. 97% (p = 0.0244) for P. aeruginosa. Our results showed that the 0.45-µm filters provided the greatest detection of Legionella. Because the current national guidelines leave the choice of membrane porosity to the operator, experimental studies are important for directing operators towards a conscious choice to standardize Legionella environmental surveillance methods.

Separation of Acetic Acid and Water Using Reverse Osmosis Membranes

Reverse osmosis can potentially be used for separation of acetic acid from waste stream. However, the investigation on the separation of this binary mixture utilizing reverse osmosis is scarce. Thus, this study aims to evaluate the feasibility of lab-synthesized and commercially available reverse osmosis membranes to separate low acetic acid concentration from aqueous mixture. A commercially available AG membrane and three laboratory synthesized polysulfone (PSf) membranes were used in this work. Initial test for water permeation using dead end filtration found that 17.5 wt% PSf has the highest water permeability. As the polymer concentration decreases, the membrane porosity increases which decreases the resistance which enables the penetration of the permeant more easily through the membrane matrix resulting in higher water permeation when 17.5wt% PSf was used. Further modification by interfacial polymerization to form a thin polyamide layer on the porous support was seen to have had improved the membrane affinity towards water resulted in increased of permeation through the membrane matrix. However, the rejection was lower than that of the AG membrane. This indicates that, the increase in water permeation when 17.5wt%PSf was used is due to the high membrane porosity. This is evidence since 17.5wt%PSf has the highest water flux but lower acetic acid rejection compared to the commercial AG membrane. Low rejection of acetic acid when reverse osmosis membrane was applied indicates that other factor such as Donnan effect has to be further considered when synthesizing the membrane.