Transport Analysis of Anti-Wetting Composite Fibrous Membranes for Membrane Distillation

Composite electrospun fibrous membranes are widely studied for the application of membrane distillation. It is an effective approach to enhance the membrane distillation performance in terms of anti-wetting surface and permeate flux by fabricating composite fibrous membranes (CFMs) with a thin skin layer on a thick supporting layer. In this work, various membranes prepared with different pore sizes and porosities by polyacrylonitrile and polyvinylpyrrolidone were prepared. The membrane characteristics and membrane distillation performance were tested. The mass transfer across the membranes was analyzed experimentally and theoretically in detail. It is shown that the skin layer significantly increases liquid entry pressure of the CFM by 5 times. All the membranes have a similar permeate flux. The permeate flux of membranes is stable at 19.2 ± 1.2 kg/m2/h, and the salt rejection ratios remain above 99.98% at 78 ± 1 °C for 11 h. The pore size and porosity of membranes have an insignificant effect on the temperature distribution of membrane. The porosity and pore size of the skin layer have an insignificant effect on the mass transfer process of the CFM. The mass transfer process of the CFM is governed by the supporting layer.

Regulating phase-change temperatures of form-stable phase-change ternary composite fibrous membranes consisting of polystyrene nanofibers and fatty acid eutectics via co-electrospinning method

The fatty acid ternary eutectics such as capric-lauric-myristic acid, capric-lauric-palmitic acid, capric-lauric-stearic acid, capric-myristic-palmitic acid, capric-myristic-stearic acid, and capric-palmitic-stearic acid and quaternary eutectics such as capric-lauric-myristic-palmitic acid, capric-lauric-myristic-stearic acid, capric-lauric-palmitic-stearic acid, capric-myristic-palmitic-stearic acid, and lauric-myristic-palmitic-stearic acid were selected as solid-liquid phase-change materials (PCMs). And then the innovative ternary eutectic/polystyrene (PS)/ternary eutectic and ternary eutectic/PS/quaternary eutectic form-stable phase-change composite fibrous membranes (PCCFMs) were directly prepared by the co-electrospinning method under the same spinning parameters. The as-prepared form-stable PCCFMs exhibited three-dimensional fibrous network structure with the average fiber diameter of about 410–780 nm according to the scanning electron microscopy images. The adhesion among nanofiber intersections was observed occasionally. The differential scanning calorimetry results showed that fatty acid eutectics have been successfully combined into the form-stable PCCFMs, and their melting peak temperatures mostly ranged from 15°C to 21°C with a temperature interval of 1°C. Moreover, the phase-change enthalpies reached about 40–61 kJ kg−1. It is concluded that these electrospun form-stable PCCFMs with appropriate phase-change temperatures could be considered as potential PCMs to be applied in thermo-regulating fibers and textiles.

Preparation and characterization of composite fibrous membranes for oil spill cleanup

In this study, polyacrylonitrile (PAN) electrospun fibrous membranes were manufactured and applied for oil spill cleanup. Two kinds of composite fibrous membranes composed of PAN electrospun fibrous membranes and polyethylene/polyethylene terephthalate (PE/PET) core-shell fiber nonwoven fabric were fabricated. The fibrous structure, mechanical properties and surface wettability for water and oil, as well as oil absorption capacities and dynamic oil retention of the membranes, were investigated in detail. The addition of nonwoven fabric significantly enhanced the tensile strength of the PAN fibrous membranes. The oil absorption mechanisms of different membranes were studied as well. The sandwich structure composite fibrous membranes exhibited excellent mechanical property and oil absorption capacity, making it a promising candidate for treatment of oily wastewater.

Nanocrystalline Cellulose/Polyvinylpyrrolidone Fibrous Composites Prepared by Electrospinning and Thermal Crosslinking

Nanocellulose/polyvinylpyrrolidone (nCel/PVP) fibrous composite materials containing rod-like nanocrystalline cellulose particles with the lengths varying in the range from 100 to 2000 nm were prepared by using DC electrospinning. The particle size had a strong effect on the precursor viscosity, process efficiency, and resulting fiber diameter. The thermal crosslinking of nCel/PVP composite nanofibers with up to 1.0 : 8.0 nCel/PVP weight ratio resulted in fibrous membranes with textural, air transport, and mass swelling properties varying significantly with the size of cellulose particles. The presence of nCel particles increased the oxidation resistance of PVP during the crosslinking and affected the morphological changes of nCel/PVP fibrous membranes in aqueous solutions. Particles with the smallest size improved the strength of the membrane but decreased its mass swelling capacity, whereas the larger particles led to a more porous and flexible, but mechanically weaker, membrane structure with a higher swelling ability. Thus, by using the nCel particles of different size and shape, the properties of nCel/PVP composite fibrous membranes can be tailored to a specific application.