نشریه علوم و مهندسی جداسازی
سال سیزدهم شماره 2 (پیاپی 26، پاییز و زمستان 1400)

In the flotation of sulfide minerals, pH and reagent dosage is very important. In the majority of copper flotation circuits, based on an idea, the pH is higher than standard values to increase the froth stability. In this study, to determine the effect of pH and reagent dosages on the froth stability, flotation tests based on the Taguchi design (L27) were performed on a sample of flotation circuit of the Mohammadabad-E-Delijan copper company, and froth stability (froth half-life time) was measured. The results showed that, unlike the idea, pH does not have a significant effect on the froth stability. Also, it was shown that froth stability was affected by collector’s (Z11 and TC15), and Dowfroth250 (frother) dosages and was not affected by MIBC (frother) dosage. Finally, the highest froth stability was resulted when pH was 11.2, Z11, TC15, Dowfroth250, and MIBC dosages were 20, 15, 20, and 15 g/t, respectively.

In this study, a comprehensive comparative analysis between various adsorption kinetic and mass transfer models were carried out to investigate and predict the adsorption process of ketorolactromethamine drug pollutant onto the porous UiO-66 metal organic framework. Primarily, a new kinetic model was developed and compared with Elovich and four different form of Pseudo second order kinetics. Moreover, various mass transfer models such as Weber and Morris, liquid film diffusion, Bangham's and Burt and McKay et al models were utilized for determination of mass transfer mechanism of drug molecules onto the adsorbent. Measured experimental data in laboratory were fitted with the abovementioned models and the results showed that Pseudo second order (Form 1) and subsequently developed new kinetic models, with R^2valuse of 0.999 and 0.994, respectively, could be utilized as the best models for description of the adsorption rate. In addition, investigation of the results of the mass transfer models illustrated that both film diffusion and intraparticle diffusion had an important roles in the mass transfer mechanism and the boundary layer thickness and its effectiveness increases with increasing the drug concentration in adsorption process.

In this research, the degradation performance of toluene has been evaluated by the design and construction of a fixed-bed photocatalytic reactor. The role of effective operational parameters was investigated, and obtained results indicated that the designed system could degrade toluene up to %95.30 at optimal conditions. The simulation of the reactor was carried out using a three-dimensional CFD to the prediction of the hydrodynamic behavior and determination of the toluene concentration along the reactor. Findings showed that the proposed model could predict the degradation rate of toluene along the reactor. The comparison of the designed system performance with other systems revealed that the current system not only could degrade toluene with higher concentration at a shorter time but also requires less photocatalyst mass per unit area, which is very important economically. The results of this study can be used in the design of photocatalytic reactors for action on an industrial scale.

In this research, mathematical modeling for the absorption process of carbon dioxide and hydrogen sulfide gases using silica-water nanofluid has been performed in a packed bed column. A laboratory apparatus consisting of two towers packed with plastic Raschig rings was prepared for the absorption and desorption process. Experimental tests were performed for three flow rates of 3, 7 and 15 LPM for gas and 0.35, 0.50 and 1 LPM for liquid and the molar fraction of CO2 and H2S in two phases of gas and the liquid are measured. The modeling of the process was done using the overall and partial mass balance equations. Comparison of the obtained model results with the experimental results shows a close correlation between the experimental data and the model and the average relative error was about 10%. Using the obtained model, the component concentration, transferred molar flux and mass flux for liquid and gas are plotted along the column. The results show that with increasing the gas flow rate, both the rate of mass transfer and the slope of the molar fraction gas components were increased. On the other hand, the mass transfer flux in higher gas flow rates achieved to more than twofold. Also, the mass transfer of carbon dioxide was higher than that of hydrogen sulfide, which is due to the higher concentration of carbon dioxide in the inlet gas.

In recent years, the removal of carbon dioxide as the most important greenhouse gas has been noticed. In this study, the performance of potash-glycerol hybrid solvent in the process of carbon dioxide absorption was investigated using a microreactor. Experiments have been done under different conditions include: flow of inlet solvent (4-8 ml/min), potassium hydroxide concentration (0.3- 0.7 M) and glycerol concentration (0-30 wt.%) at constant temperature of 40 °C, and the percentage of carbon dioxide absorption and the overall volumetric mass transfer coefficient based on gas phase (KGav) have been considered as response. According to the results, with increasing glycerol concentration as physical solvent from 0 to 30 wt. %, the absorption efficiency increases from 59.13 to 66.1%. Also, by increasing glycerol concentration despite increased fluid viscosity, the overall volumetric mass transfer coefficient increases from 55.50 to 66.53 kmol/m3.hr.kPa. Comparison of the reported values for KGav in this study with the values published for monoethanolamine in the packed tower shows that the overall volumetric mass transfer coefficient in the microreactor is about 60 times larger, indicating better microreactor mass transfer performance.

Clinoptilolite is a natural zeolite which is prone to use in the removal of contaminants due to its abundance, cheapness, suitable specific surface area and surface functional groups. In this research, the removal of iron and phosphate ions in aqueous solution has been investigated using natural clinoptilolite zeolite. The amount of removal of these contaminants has been investigated by the adsorbent in conditions such as the type of corrective method, the concentration of adsorbent to the contaminant, contact time and different pH. Modification of the adsorbent with acidic solutions results in the removal of 87% of iron at pH = 6.2 and D/C = 40, and 91% of phosphate at pH = 5.4 and D/C = 40. The ratio of adsorbent concentration to pollutant and pH have also been investigated as important factors in this study. Examination of different adsorption isotherm models showed that Langmuir model is suitable for phosphate with the maximum adsorption capacity of 62.25 mg/g and Freundlich model is suitable for iron with the maximum adsorption capacity of 48.35 mg/g. The present study showed that clinoptilolite can be used as an effective and inexpensive adsorbent to remove iron and phosphate from aqueous solutions.

In separation operations using the distillation process, the packed towers are considered for their advantages such as high efficiency. In this study, the separation of deuterium oxide (D2O) (heavy water) and hydrogen oxide (H2O) (ordinary water) was investigated using a packed tower under relative vacuum conditions. In these experiments, heavy water with 10%, 50% and 90% concentrations was used and the separation was examined using Dixon-like packing made of stainless steel. For this purpose, a factorial experiment was designed in which the effects of heavy water concentration, pressure and return flow on the height equivalent of the theoretical tray (HETP) in the tower were investigated. According to the results, the effect of concentration was more than the other two variables and with the optimization, it was concluded that if all variables are at their minimum, the lowest (best) equivalent height will be obtained. The experiments also showed that the pressure parameter in the studied range had no effect on the rate of separation, although its interaction with other factors was evaluated as significant.

The membrane technology has experimentally and theoretically attracted much attention by researchers as a way to reduce the increasing emission of carbon dioxide to the atmosphere due to the high competitiveness in separation performance and economics. In this work, the modified Maxwell model and modified Lewis-Nielsen model are developed to predict the experimental gas separation performance of polyimide/silica nanoparticles and polysulfone/silica nanoparticles mixed matrix membranes. The developed modified models consider the crucial role of interfacial voids between inorganic nanoparticles and the polymer matrix. The prediction accuracy of developed models is evaluated and compared with that of conventional models such as the Maxwell model, Bruggeman model, Lewis-Nielsen model and Pal model. The modified Maxwell model, developed in this work, considering the role of interfacial voids, can accurately predict the experimental gas permeability data of MMMs with error values lower than 6%. However, the error is obtained around 30% for conventional models.