نشریه علوم و مهندسی جداسازی
سال چهاردهم شماره 1 (پیاپی 27، بهار و تابستان 1401)

Adsorption is an effective method for the treatment of dyed wastewater contaminants the aqueous environments. In this study, an alginate-based foam adsorbent was prepared via freeze-drying and post-cross-linking method and then used to remove methylene blue dye from aqueous solutions. Characterization using different analyzes, kinetics, isotherm, swelling, and regeneration experiments, and the parameters affecting the dye adsorption process such as dye concentration (2-10 mg/L), pH (3-11) were investigated. The findings obtained from the adsorption process indicated that the adsorption of methylene blue using synthetic adsorbents has good conformity with conventional kinetic and isotherm models and the kinetics and isotherm are adjusted with the pseudo-second-order and the Freundlich models, respectively. The adsorption capacity of methylene blue was 3.80 mg/g with 97% removal efficiency for alginate-based foam. With the increase in initial solution pH and dye concentration, better adsorption performance was observed. The prepared adsorbent presented remarkable chemical stability and was readily recyclable after three reuse cycles.

The development and increase of industrial activities lead to the proliferation of toxic metals in the environment and humans are exposed to these metals. The results of this study are as follows: the optimal pH for the percentage of adsorption was determined to be 8, the amount of adsorbent was 0.04 g, the isotherm of Radoskovich for (XAD-4-DETA) was the most suitable linear regression The maximum adsorption capacity of Dubin was 73.1 mg/g at ambient temperature, the synthetic adsorption model was quasi second order and the type of penetration into the adsorbent cavities was both controlled by the film resistance and increased by the intraparticulate penetration by increasing the ionic strength of the Solution due to the reduction in metal activity in the solution and the formation of complexes with anions present. In real samples because the samples themselves contain ions. The percentage of adsorption for the adsorbent was reduced by approximately 20%.

In this study, in order to improve the adsorption capacity of CaO in the calcium looping process, the natural ores supplied from Bukan mines was modified by citric acid monohydrate using sol-gel method to prepare a porous CaO adsorbent. Primary and modified adsorbents were investigated by conventional analysis methods including XRD, FTIR and SEM. The capture rate of CO2 was measured using TGA analysis under pure CO2 atmosphere and finally the fluidity behavior of the appropriate sample was investigated in terms of CO2 adsorption capacity. Capture tests performed on CaO adsorbents showed that the difference in the CO2 capture capacity of the primary and modified adsorbents was the highest at the carbonation temperature of 500 °C and reached about 14.625%. This result was in consistent with the SEM pictures obtained from adsorbents, so that a more porous structure was observed in the case of modified adsorbent rather than of the initial one. To study the fluidization behavior and improve its performance, the modified adsorbent was selected and mixed with 5, 7.5 and 10 weight percent of hydrophobic silica nanoparticles. With increasing weight percentage of silica, the cannels created at low gas velocities gradually disappeared and expanded up to 2.02 times the initial height at gas velocity of 4.5 cm/s. Finally, using of citric acid monohydrate as a modifier of the structure of CaO adsorbent and silica nanoparticles as a factor of improving the fluidity of this adsorbent was suggested.

The aim of this study was to produce porous nanomaterials with a high specific surface area to increase the separation capacity of the cationic surfactant of cetyltrimethylammonium bromide (CTAB) from water. To this end,, meso and micro-porous carbon fiber / ZIF-8 nanocomposites were produced in situ without the use of surfactants by a simple and cost-effective method of sediment synthesis with superhydrophobicity and high specific surface area. Nanocomposite capacity analyzes were studied quantitatively and qualitatively by standard methods. According to the results, ZIF-8 particles with a crystal size of 27 nm and an average size of 30 to 50 nm were obtained. A rough surface with a ZIF-8 coating thickness of between 0.1-1 microns was obtained for carbon fiber / ZIF-8 nanocomposites. According to the research findings, the maximum adsorption of 388 mg / g for surfactant by fiber-carbon nanocomposite / ZIF-8 with a specific surface area of ​​260 m2 / g and the porosity of micropores and mesopores with an average size of 1.6 nm and 3/8 was obtained. Superhydrophobicity of carbon fiber nanocomposite / ZIF-8 with wettability angle with water of 150 ° and electrostatic collisions were identified as the dominant mechanisms of surfactant separation. The performance of the adsorbent in static and dynamic systems with the effect of different parameters was investigated in this study. The adsorption mechanism of the surfactant on the adsorbent was interpreted by the Langmuir adsorption isotherm model, and the first-order kinetics is the control mechanism of the adsorbent behavior over time.

The main goal of this study is to investigate the influence of functionalization of silica nanoparticles on the structural properties and gas separation performance of the poly (ether-block-amide) based mixed matrix membranes containing silica nanoparticles. For this purpose, first silica nanoparticles were modified by carboxylic functional groups and used for the preparation of mixed matrix membranes. The prepared membranes were analyzed using the XRD, DSC, FTIR, SEM and gas permeation tests. The results showed that the chemical modification of silica nanoparticles and the incorporating of carboxyl groups on its surface had a strong interaction with the polymer matrix and improved the filler distribution in the membrane matrix. It was observed that by loading 4%wt of silica nanoparticles functionalized with carboxyl groups in the polymer matrix increases the gas permeability at different pressures. The membranes containing 4%wt modified silica nanoparticles had the permeability of CO2, O2 and N2 equal 43.1, 2.8 and 0.42 Barrer, respectively, and the selectivity of O2/N2 (6.71) and CO2/N2 (103.3) at the pressure of 3 bar.

In this study, for the first time, nanofiltration membranes containing cellulose acetate butyrate polymer and MXene nanoparticles were prepared and used to remove dye and salt from water. MXene nanoparticles were synthesized from Ti3AlC2 precursor and the existence of a layered structure as well as the formation of OH-functional group in them was proved. Then, Cellulose acetate butyrate nanofiltration membranes were prepared from MXene nanoparticles at concentrations of 0 to 4 wt.% and various characterizations were performed on the mentioned prepared membranes. The results showed that increase in concentration of MXene nanoparticles results in formation of membranes with higher porosity, hydrophilicity, pure water flux and flux recovery ratio. Also, with the addition of MXene to the polymer and increase in its concentration up to 3 wt.%, mechanical properties, including tensile strength, elastic modulus and elongation at breakpoint increased, while further increase in nanoparticle concentration decreased these properties. In all membranes up to 3 wt.% of nanoparticles, the rejection of methylene blue and methyl orange dyes as well as rejection of divalent salt were above 90%.

In the present study, polyetersulfone membrane was modified with ferric chloride nanocomposite to improve membrane performance in removing contaminants. Choline chloride ion liquid was used for the first time. In order to determine the properties and morphology, FTIR, contact angle, porosity, BET, TGA, DSC, SEM, transmission flux and membrane clogging analysis were investigated. In order to find the optimal removal conditions, pH and temperature were selected as effective variables and the necessary experiments were designed and performed using Design Expert software and response surface method. The results showed that the best performance of orange 7 dye removal with a membrane of 0.5 wt% nanocomposite and a concentration of 5 μM contaminant at pH 6.7 and a temperature of 33.9 ⁰C, which removes 97.6% of the contaminant. The forecasting model and the results were in good agreement. Water permeability in the modified membranes increased due to changes in the structure and hydrophilicity of the membrane surface, which led to a decrease in clogging and an increase in the amount of return flux compared to the pure membrane.