فهرست مطالب mahdi pourafshari chenar

In this study, PES/Pebax composite membranes were prepared by coating the porous PES support layers by Pebax-1657. Film casting and pouring methods were used for coating Pebax layer. The effects of coating technique and conditions including coating solution concentration and curing temperature on CO2 and CH4 gas permeabilities of prepared composite membranes were investigated. SEM images were used to investigate the structure of the prepared membranes. Pure CH4 and CO2 gases were used to investigate the gas permeation properties of the prepared membranes at different trans-membrane pressures (1-11 bar) and feed temperatures (25-55°C). The obtained data showed that the prepared PES supports did not provide any CO2/CH4 selectivity. The results also showed the CO2/CH4 selectivity for the membrane prepared via pouring technique was higher than that of the film casting procedure due to the defect-free Pebax layer formation. CO2 and CH4 permeance increased as the feed temperature increased from 25 to 55°C. The results also showed that CO2 permeance increased from 6.8 to 10.1GPU with an increase in feed pressure from 2 to 12barg, while CH4 permeance remained almost constant and CO2/CH4 selectivity increased from 27 to 42.

Ammonia is one of the most common pollutants in urban and industrial wastewaters and due to various problems it generates, it is necessary to remove it from wastewaters. In this study, a laboratory scale once-pass membrane contactor system was designed and constructed using PPO hollow fiber membranes and the effect of various operating parameters such as the feed passage side (the lumen-side or the shell-side), feed flow rate and temperature on the efficiency of the process for synthetic wastewater was investigated. Since the petrochemical units are of the main sources of wastewaters containing ammonia at high concentrations, in the second part of this study, the efficiency of the process to remove ammonia from Khorasan Petrochemical wastewater was also investigated. Experimental results showed that low feed flow rate, high feed temperature and feed passage through the lumen side increased the ammonia removal percentage. Also, the ammonia removal percentage variations with the feed velocity and temperature were the same as that of synthetic wastewater. By comparing the ammonia removal percentages of synthetic and real wastewaters, it was obtained that ammonia removal percentages for real petrochemical wastewater at 20 and 40 ºC, were respectively about 25 and 19% lower than that of synthetic wastewater.

To investigate the adsorption property of H2 and CO2 on the organic ligand of C-MOF-5 (H2BDC) and T-MOF-5 (ZnO-doped H2BDC (ZnO-H2BDC)), Density functional theory (DFT) method was performed. First, the adsorption of ZnO on H2BDC resulted in examining binding energies, the charge transfer, density of states, dipole moments and adsorption geometries were investigated. The binding properties have been calculated and investigated theoretically for ZnO-doped H2BDC in terms of binding energies, band structures, Mulliken charges, and density of states (DOSs). According to obtained results, the H2BDC was strongly doped with ZnO. H2 and CO2 adsorption capacities for ZnO-doped H2BDC are significantly enhanced while there are low adsorption capacities for H2BDC. According to results, at least in the organic ligand of the MOF-5, the highest and lowest adsorption of CO2 (or H2) is attributed to the T-MOF-5 and C-MOF-5 respectively. Our calculations reveal that ZnO-doped H2BDC system (T-MOF-5) has much higher adsorption energy and higher net charge transfer value than pristine H2BDC (C-MOF-5). Also by changing in structure from cubic to tetragonal, the main site for H2 and CO2 adsorption was changed.

In the present investigation, nanosized silicalite-1 powder was first synthesized as a seed with mean diameter of 40 nm by the hydrothermal method. Seeding of nanosized zeolite crystals on the support surface is one of key steps in the secondary growth synthesis method. Therefore, in order to increase the quality of the zeolite membrane, subsequent seeding steps were investigated by dip-coating technique. The seeded supports and silicalite-1 nanoparticles were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), N2-BET adsorption/desorption isotherm,Fourier Transform Infrared Spectroscopy (FT-IR), Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimeter (DSC). Examination of the number of seeding steps showed that three subsequent seeding steps would improve the quality of seed layer.