Porous hydrophobic/hydrophilic composite membranes

A review on membrane applications and transport mechanisms in vacuum membrane distillation

The main aim of this article is to provide a state-of-the-art review of the experimental studies on vacuum membrane distillation (VMD) process. An introduction to the history of VMD is carried out along with the other membrane distillation configurations. Recent developments in process, characterization of membrane, module design, transport phenomena, and effect of operating parameters on permeate flux are discussed for VMD in detail. Several heat and mass transfer correlations obtained by various researchers for different VMD modules have been discussed. The impact of membrane fouling with its control in VMD is discussed in detail. In this paper, temperature polarization coefficient and concentration polarization coefficient are elaborated in detail. Integration of VMD with other membrane separation processes/industrial processes have been explained to improve the performance of the system and make it more energy efficient. A critical evaluation of the VMD literature is incorporated throughout this review.

Engineering Hydrophobic Organosilica Nanoparticle-Doped Nanofibers for Enhanced and Fouling Resistant Membrane Distillation

Engineering and scaling-up new materials for better water desalination are imperative to find alternative fresh water sources to meet future demands. Herein, the fabrication of hydrophobic poly(ether imide) composite nanofiber membranes doped with novel ethylene-pentafluorophenylene-based periodic mesoporous organosilica nanoparticles is reported for enhanced and fouling resistant membrane distillation. Novel organosilica nanoparticles were homogeneously incorporated into electrospun nanofiber membranes depicting a proportional increase of hydrophobicity to the particle contents. Direct contact membrane distillation experiments on the organosilica-doped membrane with only 5% doping showed an increase of flux of 140% compared to commercial membranes. The high porosity of organosilica nanoparticles was further utilized to load the eugenol antimicrobial agent which produced a dramatic enhancement of the antibiofouling properties of the membrane of 70% after 24 h.

A novel multi-stage direct contact membrane distillation module: Design, experimental and theoretical approaches

An economic desalination system with a small scale and footprint for remote areas, which have a limited and inadequate water supply, insufficient water treatment and low infrastructure, is strongly demanded in the desalination markets. Here, a direct contact membrane distillation (DCMD) process has the simplest configuration and potentially the highest permeate flux among all of the possible MD processes. This process can also be easily instituted in a multi-stage manner for enhanced compactness, productivity, versatility and cost-effectiveness. In this study, an innovative, multi-stage, DCMD module under countercurrent-flow configuration is first designed and then investigate both theoretically and experimentally to identify its feasibility and operability for desalination application. Model predictions and measured data for mean permeate flux are compared and shown to be in good agreement. The effect of the number of module stages on the mean permeate flux, performance ratio and daily water production of the MDCMD system has been theoretically identified at inlet feed and permeate flow rates of 1.5 l/min and inlet feed and permeate temperatures of 70 °C and 25 °C, respectively. The daily water production of a three-stage DCMD module with a membrane area of 0.01 m² at each stage is found to be 21.5 kg.

Composite Membrane with Underwater-Oleophobic Surface for Anti-Oil-Fouling Membrane Distillation

In this study, we fabricated a composite membrane for membrane distillation (MD) by modifying a commercial hydrophobic polyvinylidene fluoride (PVDF) membrane with a nanocomposite coating comprising silica nanoparticles, chitosan hydrogel and fluoro-polymer. The composite membrane exhibits asymmetric wettability, with the modified surface being in-air hydrophilic and underwater oleophobic, and the unmodified surface remaining hydrophobic. By comparing the performance of the composite membrane and the pristine PVDF membrane in direct contact MD experiments using a saline emulsion with 1000 ppm crude oil (in water), we showed that the fabricated composite membrane was significantly more resistant to oil fouling compared to the pristine hydrophobic PVDF membrane. Force spectroscopy was conducted for the interaction between an oil droplet and the membrane surface using a force tensiometer. The difference between the composite membrane and the pristine PVDF membrane in their interaction with an oil droplet served to explain the difference in the fouling propensities between these two membranes observed in MD experiments. The results from this study suggest that underwater oleophobic coating can effectively mitigate oil fouling in MD operations, and that the fabricated composite membrane with asymmetric wettability can enable MD to desalinate hypersaline wastewater with high concentrations of hydrophobic contaminants.

Hydrophobic polyvinylidene fluoride fibrous membranes with simultaneously water/windproof and breathable performance

Hydrophobic polyvinylidene fluoride fibrous membranes with good water/windproof and breathable performance, as well as robust mechanical property, would become a key material in many areas, especially in fabricating of protective clothing.

A comprehensive review: electrospinning technique for fabrication and surface modification of membranes for water treatment application

The review paper discusses the surface modification and fabrication of electrospun nanofibers for wastewater treatment.

Superhydrophobic modification of PVDF–SiO2 electrospun nanofiber membranes for vacuum membrane distillation

Superhydrophobic nanofiber membranes with high permeate fluxes and anti-wetting properties were prepared by hydrophobic modification of PVDF–SiO₂ nanofiber membranes.

Nanofiber based triple layer hydro-philic/-phobic membrane--a solution for pore wetting in membrane distillation

The innovative design and synthesis of nanofiber based hydro-philic/phobic membranes with a thin hydro-phobic nanofiber layer on the top and a thin hydrophilic nanofiber layer on the bottom of the conventional casted micro-porous layer which opens up a solution for membrane pore wetting and improves the pure water flux in membrane distillation.

Criteria for the selection of a support material to fabricate coated membranes for a life support device

The innovative design of coated membranes opens up wider applications for a life support device improving quality of life.

Hemoglobin immobilized with modified "fish-in-net" approach for the catalytic removal of aniline

Blood is a waste product of the slaughter industry, while its main component hemoglobin (Hb) is a pseudo-peroxidase which is able to oxidize polycyclic aromatic hydrocarbons (PAHs) in the presence of H(2)O(2). In order to use Hb for wastewater treatment, we encapsulated it in silica-based matrix by modified "fish-in-net" approach. The as-synthesized catalysts were characterized by SEM, TEM, BET and solid-state UV-vis spectroscopy. It was found that Hb was partially homogeneously dispersed in microspheres and showed more stable peroxidase-like activity than free Hb. Moreover, it had substantially increased storage stability as well as pH stability. It was used as biocatalyst to remove aniline in aqueous solution and gave a reduction of 65% aniline removal, while 76% in the presence of additive PEG. No significant activity loss was observed after ten runs. These experimental results suggest that the resultant product was a promising biocatalyst for aromatic wastewater treatment.