Superhydrophobic Hollow Fiber Membrane Research Articles

Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation

In this study, we address the challenge of wetting and scaling in membrane distillation (MD) by developing a robust superhydrophobic poly(vinylidene fluoride) (PVDF) hollow fiber membrane. To achieve this, we utilized co-extrusion technology and subsequent fluorination treatment to create micro-nanoscale surfaces. The fabrication process involved extruding a SiO2 suspension onto the outermost layer of a triple-orifice spinneret to create a hierarchical structure, followed by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FAS) modification to lower the membrane surface energy. This resulted in a highly water-repellant membrane, as evidenced by contact angle measurements of 153°, 147°, and 141° for water, sodium dodecyl sulfate (SDS) solution (0.4 mM), and saline SDS solution (0.4 Mm SDS and 35 wt% NaCl), respectively, indicating increased resistance to liquid penetration. Through direct contact membrane distillation (DCMD) experiments, we demonstrated that the PVDF/FAS membrane exhibited excellent wetting resistance to seawater (3.5 wt% of NaCl) with SDS at varying concentrations. Furthermore, the membrane effectively hindered the CaSO4 scaling by reducing both heterogeneous nucleation and the tendency of bulk crystal deposition on the membrane outer surface. Overall, the developed approach for fabrication of superhydrophobic PVDF hollow fiber membrane presents a promising solution for facile and scalable manufacturing of anti-wetting and anti-scaling MD membranes. This advancement has significant implications for enhancing the practical application of MD technology.

Fabrication of a super hydrophobic polyvinylidene fluoride–hexadecyltrimethoxysilane hybrid membrane for carbon dioxide absorption in a membrane contactor

To obtain a super hydrophobic hollow fiber membrane for using in membrane contact absorption of carbon dioxide (CO2), hybrid polyvinylidene fluoride-hexadecyltrimethoxysilane (PVDF–HDTMS) membranes were fabricated via the non-solvent induced phase-inversion method with ammonia water as the non-solvent additive and dehydrofluorination reagent, and HDTMS as the hydrophobic modifier. The membranes exhibited super-hydrophobicity which was attributed to the formation of rough nanoscale microstructure and low surface free energy of the outer surface. The largest contact angle of water and diethanolamine (DEA) on the membrane outer surface attained 150°. Scanning electron microscopy images revealed that the membrane outer surfaces consisted of rough microscale hierarchical spherulitic particles with a nanoscale stereoscopic coralliform microstructure. Attenuated total reflectance–Fourier transform infrared spectroscopy of the membranes indicated that the HDTMS chains grafted in the PVDF were mainly located on the outer layer of the hollow fiber membranes. The membranes showed excellent CO2 mass transfer flux compared to our previously fabricated membrane with 8 wt % of phosphoric acid as the non-solvent additive in the dope (PVDF-PA-8). The membrane contactor with the membrane obtained by adding 1.5 wt% of HDTMS in the dope achieved the maximum CO2 mass transfer flux of 2.23 × 10−3 mol/m2s with the inlet gas (CO2/N2 = 19/81, v/v) at a flow rate of 20 mL/min and the absorbent liquid (1 mol/L DEA) at a flow rate of 50 mL/min. CO2 mass transfer flux of this membrane decreased by 17% after 17 days of operation and then remained stable.

NOx Removal from Air through Super Hydrophobic Hollow Fiber Membrane Contactors

NOx Removal from Air through Super Hydrophobic Hollow Fiber Membrane Contactors

N2O absorption through super hydrophobic hollow fiber membrane contactor

Dinitrogen monoxide (N2O) is mainly produced in Horticulture and farming activities, industrial processes and combustion of fossil fuels. N2O is one of the harmful emissions and its global warming potential is 310 times greater than CO2 on a molecular basis. This research aims to absorb N2O from its mixture with air through super hydrophobic hollow membrane contactor using a mixture of 0.5M HNO3 and 0.5 wt % H2O2 solutions as absorbent. In the experiment, the feed gas flowed through the shell side of the contactor, while absorbent solution flowed through the lumen fibers. Experimental results show that the amount of N2O absorbed and N2O absorption efficiency increased with the absorbent flow rate and the number of fibers in the contactor resulting from the increase in the turbulence and surface area for gas–liquid contact, respectively. The overall mass transfer coefficient and the flux increased with the absorbent flow rate due to the decrease of the mass transfer resistance in the liquid phase. However, the overall mass transfer coefficient and the flux decreased with the number of fibers in the contactor due to the decrease of the absorbent flow rate in a single fiber. The amount of N2O absorbed and the flux increased but the N2O absorption efficiency decreased with increasing the feed gas cross flow rate. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 362–366, 2019

Effect of Feed Gas Flow Rate on CO2 Absorption through Super Hydrophobic Hollow Fiber membrane Contactor

Carbon dioxide is pollutant in natural gas that could reduce the heating value of the natural gas and cause problem in transportation due to corrosive to the pipeline. This study aims to evaluate the effects of feed gas flow rate on CO2 absorption through super hydrophobic hollow fiber contactor. Polyethyleneglycol-300 (PEG-300) solution was used as absorbent in this study, whilst the feed gas used in the experiment was a mixture of 30% CO2 and 70% CH4. There are three super hydrophobic hollow fiber contactors sized 6 cm and 25 cm in diameter and length used in this study, which consists of 1000, 3000 and 5000 fibers, respectively. The super hydrophobic fiber membrane used is polypropylene-based with outer and inner diameter of about 525 and 235 μm, respectively. In the experiments, the feed gas was sent through the shell side of the membrane contactor, whilst the absorbent solution was pumped through the lumen fibers. The experimental results showed that the mass transfer coefficient, flux, absorption efficiency for CO2-N2 system and CO2 loading increased with the feed gas flow rate, but the absorption efficiency for CO2-N2 system decreased. The mass transfer coefficient and the flux, at the same feed gas flow rate, decreased with the number of fibers in the membrane contactor, but the CO2 absorption efficiency and the CO2 loading increased.

Effects of Absorbent Flow Rate on Co2 Absorption through a Super Hydrophobic Hollow Fiber Membrane Contactor

Effects of Absorbent Flow Rate on Co2 Absorption through a Super Hydrophobic Hollow Fiber Membrane Contactor

Surface modification to produce superhydrophobic hollow fiber membrane contactor to avoid membrane wetting for biogas purification under pressurized conditions

Abstract This article investigates CO2 removal from biogas (containing 40% CO2 and 60% CH4) using a hollow fiber membrane contactor (HFMC) with K2CO3 aqueous solutions as absorbent at elevated pressures up to 10 bar. Superhydrophobic PTFE membrane fibers (with a water contact angle of 158.4° and sliding angle of 1.3°) were fabricated by spraying silica nanoparticles on membrane surface and then used in membrane module for absorption experiments. The modified membrane outperformed the original membrane at elevated absorption pressures, and the highest CO2 removal efficiency and absorption flux reached 97.1% and 1.85 × 10−3 mol m−2 s−1, respectively. A 2D axisymmetric non-wetted mathematic model was developed to determine the membrane wetness conditions during absorption experiments. The model validation results indicated that when using aqueous K2CO3 solutions as absorbent the modified superhydrophobic membrane used in this study was able to prevent membrane wetting even at pressurized conditions up to 10 bar. This work showed that the superhydrophobic membranes modified by spray-deposition technique have great potential for application in HFMC to avoid membrane wetting for biogas purification under pressurized conditions.

Preparation of Super-hydrophobic Polypropylene Hollow Fiber Membrane

In order to improve the hydrophobicity of the superhydrophobic PP hollow fiber membrane and its application efficiency in membrane distillation, the method of solution coating was utilized in the surface modification of original PP hollow fiber membrane. The fabricated superhydrophobic hollow fiber membrane was applied in membrane distillation process. Water flux and salt rejection was evaluated to determine the efficiency of the modified fiber membrane. In addition, the effect of coating times on the superhydrophobicity was investigated. The results showed that after 6 times of surface coating, the water contact angle reached 154.5o and the salt rejection was enhanced from 99.0% to 99.9%.