Wetting of polymeric Hollow fiber membranes by chemical absorbents is one of the main challenges of gasliquid membrane contactors. This s tudy explored an appropriate method to fabricate a superhydrophobic polypropylene (PP) Hollow fiber membrane by incorporating fluorinated silica nanoparticles (fSiO2 NPs) on the PP membrane surface. The effect of the hydrophobic agent on the water repellent properties of the composite membrane was s tudied by varying (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane/ tetraethylorthosilicate) (PFOTES/TEOS) molar ratio from 0 to 1. The composite membranes were characterized using field emission scanning electron microscopy (FESEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR), contact angle, mechanical s trength and s tatic wettability. The obtained results showed that the surface hydrophobicity and mechanical s trength of the composite membranes increased compared to pure ones. The contact angle of 156°,was obtained when the (PFOTES/ TEOS) molar ratio was 0. 5. Furthermore, the CO2 absorption experiment was done to evaluate the performance of the fabricated membranes in a gas-liquid membrane contactor. The obtained results showed that the PP/fSiO2 composite membrane has more potential to be used in gas-liquid membrane contactors than commonly used polymeric membranes.

Hypothesis: Dehumidification of a gas stream was carried out by one of the newest separation techniques. Different processes have been proposed for gas humidification such as absorption process using an absorbent and adsorption process with higher capital and operating costs than the former. The former process is more common. Methods: For humidification/dehumidification process two Hollow fiber membrane contactor modules were made using polyetherimide Hollow fiber membranes. At first, the dry inlet gas was humidified in the first contactor module and then, the dehumidification process was performed by the second module. In dehumidification process, monoethylene glycol (as the absorbent) was allowed to flow through the shell side of the contactor while the wet gas flowed through the fibers. The different operating parameters such as the pressure and flow rate of the wet gas were studied in relation to the performance of dehumidification system. Findings: The results showed that by increasing the wet gas flow rate from 1 SLPM (standard liter per minute) to 3 SLPM, the water vapor absorption flux increased by 133%, indicating that the effect of decrease in gas phase mass transfer resistance in dehumidification process overcomes the effect of reduction in humidity content of the inlet gas to the dehumidification system. Furthermore, by increasing the gas pressure from 1 bar to 5 bar, the water vapor absorption flux decreased by 55% which showed that drop in humidity content of the inlet gas to dehumidification system (due to the pressure enhancement) affects the water vapor absorption process. Therefore, the operating conditions of the dehumidification process should be selected based on the effective parameters.

A steady state model was developed for a Hollow fiber membrane contactor to describe gas absorption performance. Countercurrent absorption of pure CO2, pure SO2, CO2-N2 and SO2-N2 mixtures in diethanolamine solution (DEA), and water as the absorbent were investigated. The model is able to predict gas phase concentration and the velocity profile in the axial direction inside the shell, as well as the liquid concentration profile in both the axial and radial direction inside the fibers. A numerical scheme was proposed to solve the simultaneous mathematical expressions that were obtained based on concepts of mass transfer, and the results were validated with experimental data found in the literature. Axial variations of gas velocity, gas concentration and a two dimensional concentration profile of the liquid phase were compared for three absorbing systems, including low (CO2-water), moderate (CO2-DEA) and high (SO2-water) absorption rates. The effect of chemical reaction on the importance of external resistance was also studied using this model. It was found that the shell side and membrane resistances are negligible in comparison with the liquid resistance in low absorption rates, for example in a CO2-water system, however they have significant effects when the chemical reaction is fast and the absorption rate is high, such as SO2-water system.

In Hollow fiber membrane fabrication process, a number of parameters such as dope compositions, flow rate, bore fluid type, flow rate, and air gap affect the structure and characteristics of membrane. Spinneret dimension as the effective parameter on the properties of a polyetherimide (PEI) Hollow fiber membrane and its performance in membrane contactor was examined. A polymer solution was used for fabrication of two PEI membranes under the same fabrication conditions, with variable-spinneret dimensions. Through the addition of water as a non-solvent into the polymer solution, the thermodynamic stability of the solution decreased and the phase-inversion process increased, and therefore, the effects of chain reorientation or chain relaxation on the structure of Hollow fiber membrane were minimized. The fabricated membranes were characterized by different tests and their performance in membrane contractor and in CO2 absorption test was evaluated in two events: 1-distilled water in lumen side and pure CO2 in shell side and 2-distilled water in shell side and pure CO2 in lumen side. The results showed that smaller dimension of spinneret enhanced the properties of membrane such as 250% increase in mean pore size and 300% increase in gas permeation rate. In addition, the smaller dimension of the spinneret formed more pores in the structure of membrane that could be related to the shorter diffusion distance of the coagulant. Furthermore, the CO2 absorption flux improved by 150%.

Hypothesis: Gas-liquid membrane contactors have been considered as one of the potential alternatives for CO2 removal compared to conventional technologies. However, membranes wetting with liquid absorbents during this process limits membrane contactors application, which indicates the need for the use of hydrophobic membranes in these systems. In recent years, the use of nanoparticles to increase the hydrophobicity of polymer membrane surfaces and fabrication of nanocomposite membranes has been considerably investigated by researchers. Methods: In order to reduce the wetting problem of membranes, in the present work, methyl grafted silica nanoparticles (CH3SiO2 NPs) were used to increase surface hydrophobicity of the polypropylene (PP) Hollow fiber membranes, which were synthesized by the sol-gel method. Prepared membranes were characterized by ATRFTIR, XRD, FE-SEM, contact angle, mechanical strength and breakthrough pressure. Findings: The obtained results from ATR-FTIR analysis confirmed the presence of methyl grafted silica NPs on the surface of PP membrane. The results of the contact angle measurement showed that for nanocomposite membranes by increasing the MTES/TEOS molar ratio from 1 to 4, the contact angle increased from 125° to 164° ; however, the contact angle decreased with further increase in the molar ratio of MTES/ TEOS. Also, with the precision in the results of mechanical strength measurement, it can be seen that the synthesis of NPs on the membrane surface as well as in the cross-section increased the tensile strength of the membrane to 12. 8 MPa. Finally, the performance of membranes was investigated in the membrane contactors for CO2 absorption, which results in a significant decrease in the flux for pure membranes compared with nanocomposite membranes.

n this study, computational fluid dynamics simulation of liquid-liquid extraction of zinc was performed using trifluoroacetylacetone as a solvent in the Hollow fiber membrane contactor. Mass and momentum balance equations (Navier-Stokes) were used to express the transport of zinc solutes through the membrane contactor. After applying the conditions, the governing equations were simulated using the finite element method. After validating the results, simulation was performed to study the distribution of zinc concentration in two-dimensional and three-dimensional form, as well as to investigate the effect of different parameters such as distribution coefficient and current intensity on the extraction efficiency. The results showed that by increasing the partition coefficient from 1 to 10, the amount of single-pass extraction increased from 10 to 100 percent. Also, the extraction efficiency in the counter-current flow of pipe and shell is 9% higher than in the co-current flow. Furthermore, this study showed that computational fluid dynamics could be used as an effective tool for the development of membrane-based extraction processes.

The presence of pharmaceutical wastewater can pose significant challenges to the environment. Since conventional wastewater treatment processes are not efficient for the complete separation of drug materials, solvent extraction through a Hollow fiber membrane contactor could be a promising alternative. In this study, a developed polysulfone (PSF) Hollow fiber membrane was fabricated using a non-solvent phase separation (NIPS) method to extract penicillin G from aqueous solutions in the membrane contactor system. From the characterization experiments, the prepared polysulfone membrane demonstrates an outer surface contact angle of 69.6°, critical water entry pressure (CEPw) of 250 kPa, total porosity of 72.2%, and collapsing pressure of 500 kPa. The extraction of penicillin G from the aqueous phase was performed with a 5% w/w solution of Aliquat 336. The effect of the operating parameters on the extraction flux of penicillin G was investigated using the response surface method (RSM). The optimum penicillin G flux of 1.46×10-3 kg/m2s was found at an operating pressure of 100 kPa, an aqueous phase flowrate of 70.5 ml/min, and an organic phase flowrate of 200 ml/min. Therefore, the developed PSF Hollow fiber membrane contactor can be considered a proper choice to remove antibiotics (penicillin G) from aqueous solutions.

The increasing trend of pollutant gases emission into the atmosphere, particularly greenhouse gases, such as carbon dioxide (CO2) and their role in global warming, has led to numerous investigations to separate these gases. For this purpose, the Hollow fiber membrane contactor (HFMC) technology, possessing advantages over traditional separation processes, has drawn a great deal of attention. Some of these advantages include consumption of less energy, low footprint, providing high contact area for mass transfer, and easier scale up. Therefore, compared to traditional separation methods, such as chemical absorption in packed columns, adsorption, and cryogenic distillation, HFMC might be considered as a proper alternative for separation of pollutant gases, more specifically CO2, which is the most important greenhouse gas. In this paper, technical characteristics and effective parameters on separation performance of HFMC along with a number of studies conducted by foreign and internal researchers have been investigated and some active companies involving in this field have been also introduced.

In the present study, developed polysulfone (PSF) Hollow fiber membranes were fabricated via a phase-inversion process. In order to enhance the membrane porosity, non-solvent additives such as polyvinylpyrrolidone (PVP) and poly ethyleneglycol (PEG) were introduced into the polymer solutions. The prepared membranes were used in the membrane contactor modules for dehydration of nitrogen gas stream by triethylene glycol (TEG). The membranes were characterized in terms of scanning electron microscopy (SEM), nitrogen permeation, overall porosity, collapsing pressure and wetting pressure. From SEM analysis, the membranes prepared by PVP and PEG presented a porous structure with smaller finger-like cavities compared to the plain membrane. Results of gas permeation test showed that the developed PSF-PVP membrane had mean pore size of 112 nm and N2 permeance of 16900 GPU. Due to open structure of the PSF-PVP membrane, a good overall porosity of about 76% was obtained. The prepared membranes by PVP and PEG showed higher collapsing pressure due to the formation of smaller finger-likes and a thicker spongy sublayer. From dehydration test at liquid flow rate of 250 ml/min, the maximum vapor absorption flux of 6. 6×10-7 m3/m2 s was achieved for the PSF-PVP membrane which was about 10% and 6. 5% higher than the flux of the plain membrane and PSF-PEG membrane, respectively.