Iranian journal of chemical engineering
Volume:21 Issue: 1, Winter 2024

The design of installations in the chemical industry requires knowledge of the thermodynamic properties of liquid mixtures. In the absence of experimental data, accurate predictive methods are needed. In this work, the refractive index and the surface tension are experimentally determined at different temperatures and atmospheric pressure, for the binary and ternary systems of benzyl alcohol, n-hexanol and water, less studied in the literature. Two models were developed for the correlation of excess surface tension with composition, normalized temperature and refractive index. The statistical processing of the experimental data with the multiple linear regression method allowed the development of a model for which, in the validation stage, the correlation coefficient was 0.9086 and the standard deviation was 4.36. With the best performing neural model, a correlation coefficient of 0.9727 and a standard deviation of 2.14 were obtained in the validation stage.

Humidification-dehumidification (HD) desalination has been identified as a sustainable, reliable, and energy-efficient technology for producing freshwater on a small scale. VP-HD systems operated at one-stage, multi-stage, and multi-feeding vacuum humidification-over atmospheric pressure dehumidification arrangements can be the recent modifications of an HD system. The present study offers a theoretical investigation and experimental verification of two VP-HD systems, encompassing both sub-atmospheric pressure humidification and over-atmospheric dehumidification. Two designs are evaluated, one comprising a three-stage humidification setup and the other featuring a three-feeding one-stage humidification apparatus. The results show which design has better performance than previous conventional and variable pressure HD systems. The parametric analysis reveals that an upsurge in freshwater generation is observed with an increase in air temperature, feed salinity, and a decrease in humidifier pressure. Additionally, an optimal water-to-air ratio is identified. The study further highlights that multi-stage humidification yields better results concerning freshwater productivity and specific power consumption. Three-stage humidification is found to be the most efficient in terms of freshwater production and specific power consumption, achieving the highest values of 1.93 L h-1 m-2 and 0.21 kWh L-1, respectively. The agreement between theoretical and experimental outcomes is deemed satisfactory.

Metal-organic frameworks (MOFs) have emerged as extended-network, highly tunable, crystalline hydrogen storage adsorbents. The uptake of H2 on Zn4O-based MOFs with different linkers was studied in the current work. The binding energies, consecutive binding energy and step energy of H2 adsorption on MOF-177, MOF-200 and a newly defined MOF (named NEW-MOF) have been calculated on different possible sorption sites, using DFT/Dmol3/PBE. The linkers have the same benzene ring in center, but different numbers of phenyl rings, including 3, 6 and 9 phenyl rings in MOF-177, MOF-200 and NEW-MOF around the center ring, respectively. Our study results showed that the binding energy of the H2 molecules with the linker NEW-MOF was -4.165 kcal/mol, more negative than those obtained for MOF-177 (-3.276 kcal/mol) and MOF-200 (-3.438 kcal/mol). The obtained thermo-favorability may be attributed to the less steric hindrance for adsorption of H2 on the MOF with the larger linker. Step energy results showed that the linkers of MOF-177, MOF-200 and NEW-MOF could adsorb 7, 9 and 12 number of H2 molecules, respectively. Results also disclosed adsorbed moles of H2 per 1×1×1 unit cell of the MOFs decreases with increasing the linker length according to the order of 0.263 (for MOF-177), 0.16 (for MOF-200) and 0.137 (for NEW-MOF), mainly due to reduced packing density of the active sites in the MOFs with larger linkers. The most negative binding energy was also tabulated for the perpendicular approaching of H2 molecules to the node of the central phenyl ring with the bonding distance of 3.19 Å from the linker.

In the present work, the effect of synthesis method (simultaneous impregnation and coprecipitation) and copper to nickel active phases loading were investigated in Ni-Cu-Al catalysts. The water/ethanol molar ratio of 6 and gas hourly space velocity (GHSV) of 20000 hr-1 were used in all the experiments. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The catalytic activity results revealed that 13Ni-6Cu/γ-Al2O3 impregnated catalyst was more active than co-precipitated one (13NiO-6CuO-81Al2O3) in the same amount of compositions of active metals and Al2O3, but by increasing the active phases (Cu and Ni) loading in co-precipitated catalysts (24NiO-31CuO-45Al2O3, 31NiO-24CuO-45Al2O3, 40NiO-15CuO-45 Al2O3 and 47NiO-8CuO-45Al2O3), they achieved a better performance than 13NiO-6CuO-81Al2O3 catalyst. The 40NiO-15CuO-45Al2O3 catalyst showed 99% ethanol conversion, as well as 303 hydrogen yield and 4% CO selectivity at 470oC. SEM images revealed agglomerated particles for the samples with high Al2O3 content and with increasing the active phase content in the catalyst the particle sizes decreased. The 40NiO-15CuO-45Al2O3 showed smallest particle size among the catalysts.

Constructed wetlands have been increasingly used as an effective method for removing heavy metals from wastewater. This study aimed to investigate the combined effect of sawdust and Hydraulic Retention Time (HRT) on the performance of vertical-flow constructed wetlands cultivated with Phragmites Australis to remove Pb and Co from oily wastewater. To this end, nine barrels were used to construct the wetlands, which were filled with coarse gravel, polluted soil, and varying percentages of sawdust (0%, 20%, and 40%). Phragmites Australis cuttings were then cultured inside the barrels and irrigated with heavy metal-contaminated oily wastewater for three different hydraulic retention times (5, 10, and 15 days). After the vegetation period, plant, soil, and wastewater samples were collected and analyzed for Co and Pb concentrations, from which transfer factor (TF), bioconcentration factor (BCF), and removal efficiency (%) were derived. Results showed that while both Pb and Co removal efficiencies were affected by HRT and sawdust, the removal efficiency of Pb (36.66%) was higher than that of Co (30.83%). TF was less than one and was not affected by HRT and sawdust, but the effect of HRT and sawdust on increasing BCF was significant. However, Phragmites Australis demonstrated suboptimal performance in the uptake and transfer of metals from the root to stem.

The preparation of ethylcellulose (EC) nanofibers (NFs) by the electrospinning method was optimized by Taguchi design. A Taguchi design was performed for electrospinning parameters such as EC concentration, voltage, ethanol/water ratio in the solvent, and feed rate in four levels (array L16).  EC solutions with a certain concentration were prepared in ethanol-water solvents with a certain ratio. The solutions were then stirred at a constant temperature for four hours and left overnight. Electrospinning parameters such as temperature 30 ˚C, distance between syringe needle and collector 10 cm, aluminum foil 20 micrometers as collector, collector speed 400 rpm, and electrospinning time 2.5 hours are constant in all electrospinning experiments, but voltage and feed rate were changed according to the experimental design. The resulting EC fibers were imaged by scanning electron microscopy (SEM). The SEM images of EC fibers were processed by Image J software, and the average diameter of EC fibers in each experiment was calculated. The results of the diameter of the electrospun EC fibers showed that all the fibers had a diameter of less than 100 nm. Also, the results of the diameter of EC fibers were analyzed based on the analysis of variance, and it was found that the ethanol/water ratio in the solvent (34.9%), the feed rate (23.5%), the voltage (22.1%), and the EC concentration (17.5%), respectively, had the greatest contribution to the diameter of EC fibers. Under optimal conditions, EC fibers with a diameter of 41 nm were prepared.