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.

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%.

This research focused on improving the antifouling properties and rejection performance of polyetherimide (PEI) nanofiltration membrane by chemical surface modification (surface coating). The hydrophilicity of the PEI nanofiltration membrane’, s surface was enhanced by anchoring guanidine on its surface which the used dosage of guanidine was considered as a variable (0. 5, 1, and 1. 5 g/L of guanidine concentration). ATR-FTIR, SEM, AFM, and water contact angle were used to characterize the surface-modified membranes. Also, dry milk powder solution was considered as an organic foulant to assess antifouling features of the fabricated membranes. According to the obtained results, the surfacemodified membrane with 0. 5 g/L of guanidine concentration was the optimal surface-modified membrane with pure water flux (PWF) and flux recovery ratio (FRR) of 11. 6 kg/m2. h and 88. 8%, respectively. Moreover, the capabilities of the optimal surface-modified membrane and the pristine membrane for rejecting AS5+ and Hg2+ in aqueous solution with concentrations of 20 ppm and 50 mg/L were compared. Based on the obtained results, the optimal surface-modified membrane rejected more than 98. 5 % of AS5+ and Hg2+ solutions with 20 and 50 mg/L of metal ion concentrations.

In this study, the combination of chemical, biological and membrane processes was investigated for landfill leachate treatment. In order to reduce the contamination level, the chemical coagulation process was used by coagulants such as aluminum sulfate and poly aluminum chloride. Also, the optimum pH range and concentration of the coagulant were determine following by the biological process of activated sludge. Finally, the leachate separation of the aerobic bioreactor was carried out by FO-MBR membrane process and the effect of powder activated carbon adsorbent was studied on this process. The results showed that the amount of COD in leachate decreased by 48% after pretreatment using coagulants (optimum concentration of 1 g/l and pH = 8). Then, the COD removal rate reached to 24% by using the aerobic activated sludge process under optimum aeration conditions, F/M = 0. 312 COD/MLSS. d ratio and 24h hydraulic retention time. In the last section, the usage of synthesized cellulose membrane in form of the frame and plate modules immersed in the aerobic bioreactor of the FO-MBR process, was examined. Furthermore, 2 g/l powder activated carbon adsorbent was used to improve the performance of this process and the reduction of membrane fouling, which improved the performance of the landfill leachate wastewater treatment system by increasing the COD removal rate from 74% to 92% as well as the changes in MLSS concentration during the 4-day FO-MBR process increased by 24% compared to the absence of adsorbent.

This study investigated the efficiency of membrane polyetheretherketone/polyetherimide modified with magnesium oxide nanoparticles to remove xylene and toluene from the air with gas chromatography. The influence of effective parameters such as sorbent dosage, extraction time, and extraction temperature of the sample was investigated and the optimum conditions were chosen. Various techniques including FT-IR, XRD, EDX, and SEM, were used to characterize this membrane. To optimize adsorption efficiency, factors such as xylene and toluene concentration, adsorbent dosage, temperature, and contact time were carefully fine-tuned. It was found that 50 mg of membranes has the best adsorption efficiency for both pollutants. The maximum adsorption capacities were found to be 163 mg/g for xylene and 200 mg/g for toluene on the PEEK/PEI nanocomposite adsorbent. Moreover, 190 mg/g for xylene and 230 mg/g for toluene were observed on the PEEK/PEI membrane modified with MgO nanoparticles. These results clearly demonstrate that PEEK/PEI membrane modified with MgO nanoparticles is a highly efficient adsorbent for eliminating xylene and toluene from air, making it a promising solution for air quality purification and environmental remediation applications.    

Palladium doped silica membranes were synthesized by the sol-gel method using two different procedures. The First palladium-doped silica membrane (M1) was synthesized with a coating of four layers of silica-palladium sol. The second membrane (M2) was synthesized with a coating of two silica layers followed by a coating of two silica-palladium layers. Scanning electron microscopy (SEM) proved the formation of uniform γ-alumina interlayers on the supports. SEM results for M1 showed that synthesis of a membrane with this procedure leads to the formation of crack on the membrane selective layer. Single gas permeation measurements of H2 and N2 were carried out at room temperature, 100 ° C and 550 ° C. Gas permeation results revealed that Knudsen diffusion was dominant in permeation of these gases through membrane M1 while the dominant mechanism in permeation of gases through membrane M2 was activated transport which has exhibited different behavior in comparison with M1. This result is due to the activated sublayers of membrane M2. In this case, H2 permeance increases and N2 permeance decreases with increasing temperature, leading to better separation perforamce of membrane M2 over M1 in separation of H. Therefore, using the activated silica sublayer in the synthesis of M2 can be used as a high potential method to synthesize a selective palladium-doped silica membrane.