Search

A novel composite forward osmosis (FO) membrane was fabricated by introducing a chitosan (CS) sublayer between nanofibers and polyamide (PA) layer, which was beneficial to forming thin and defect-free PA layer and improved binding strength between substrate and selective layer. Results exhibited low reverse salt flux (0.73 gMH) while maintained high water flux (85.4 LMH), which were better than that in other reports. In order to further improve permeability of membranes, oxidized multiwall carbon nanotubes (OMWNTs) were added into PA layer based on the optimized sublayer. The crosslinking degree of PA layer was reduced, leading to loose PA layers, which promoted the increase of water flux. After modifying, water flux reached 96.9 LMH without sacrificing salt rejection. It was worth mentioning that PAN/CS composite FO membrane, which could adjust microstructure of support layer and selective layer respectively, may provide a promising way for preparing membranes with anticipated separation performance.

Pore size plays a key role in the performances, such as transportation, filtration and separation, of bicomponentspunbond nonwoven geotextiles which fibrillated by hydroentanglement method. In this research work, samples of polyester (PET) - nylon6 (PA6) hollow segmented-pie bicomponentspunbond nonwoven materials were selected. A modified pore size prediction model has been proposed to predict the pore properties, and comparisons between theoretical and experimental results also discussed. The results show that the bicomponent fibers has been splitting into ultrafine fibers under the effect of the hydroentanglement method, and ultrafine fibers oriented mainly in the X-Y directions (plane direction). There is a good agreement between experimental results and experimental results, and the model of the pore size distribution is suit for the PET/PA6 bicomponentspunbond nonwoven geotextiles can be determined. The model provides a quantitative description of pore distribution for those nonwoven materials claimed to constitute with a series of types fiber.

Bicomponent spunbond technology is considered to be the most rapid process of ultrafine fiber nonwoven material. The cross-section of 70% PET and 30% PA6 bicomponent hollow-segmented pie filaments with diameter range from 2 D to 4 D was made by the bicomponent spunbond technology, and fibrillated by the high-pressure water jets at the same time bonded to microfiber nonwoven materials with the dense structure. The structure characteristics of materials were tested to study the feasibility for the air filter, including fineness of the fiber and pore size distribution of the webs. The filtration efficiency and filtration resistance of the webs were studied with the dioctyl phthalate particles in range of 0.3–2.7 micron at face velocity in range of 1.8–4.8 m/min. It was found that the hollow segmented-pie bicomponent fibers are splitted to microfibers and bonded mechanically by subjecting the web to high-pressure water jets, the total high pressure water jets energy was 5610.2 kJ/kg. The microfibers fibers gathered into fiber bundles on the surface of the webs were found from the 3D images. The filtration efficiency and filtration resistance of the webs followed typical behavior for fibrous filtration media, and the filtration efficiency and filtration resistance of the webs is increased with the weight increases.

Pore size distribution is the key factor of the nonwoven geotextiles for various functions including filtration, separation and reinforcement. The comparison of pore size distributions of spunbond-needle punched nonwoven geotextiles has been made among the theoretical, experimental and the virtual study based on a stochastic simulation. Moreover, the influence of fiber diameter, solid volume fraction, and the thickness of the nonwoven geotextiles on the pore size distribution of the nonwoven geotextiles has been investigated. It is demonstrated that the pore size distribution, which obtained using Geodict® based on a stochastic simulation, shows a good agreement with experimental data and theoretical, and it is feasible for the prediction of pore size distribution in spunbond-needle punched nonwoven geotextiles. The results show that increasing the solid volume fraction would decrease the pore size of the nonwoven geotextiles under the same filament diameter and same thickness of the webs. Increasing fiber diameter would cause the pore size decreasing, while thickness and solid volume fraction kept constant also found. The results also show that the pore size decreasing with the thickness of the nonwoven geotextiles increasing, while the constant of the solid volume fraction and filaments diameter.