نشریه علوم و مهندسی جداسازی
سال سیزدهم شماره 1 (پیاپی 25، بهار و تابستان 1400)

Multi-phase gravity separators are one of the most useful equipment used to separate immiscible phases in different industries. Debottlenecking of the separation process was investigated in this study, to improve the performance of an industrial three-phase boot separator. So, the effect of altering the inlet diverter (replacing the slopped inlet diverter with a vane inlet diverter), placing a baffle at the middle, and placing a mist extractor at the end of the separator, were considered. Results of this research showed that by using the new design, the performance of the separator improved so that the liquid amount at the gas outlet decreased by 83.8% compared to the current design of the industrial separator. This new design was successful in improving the flow behavior at the inlet zone, improving the droplet size distribution at the outlet zone, and preventing the impressive decrease of the separator performance while increasing the inlet flow rate.

The purpose of the study is to present a new process cycle based on a pre-pressure stage to improve the performance of the mercaptan removal process from the natural gas in South Pars Gas Company. The separation process was simulated based on Pressure-temperature swing adsorption (PTSA) method using Aspen Adsorption software. Results showed that consumption power of compressor has been decressed by 36.83% using improved cycle. Moreover, the amount of separation capacity of mercaptans has been gained by increasing the inlet feed flow rate and the second heating stage temperature in both cycles. The maximum separation capacity was obtained by 7.7% at the feed flow rate of 2.3 kmol/hr and by 7.9% at the temperature of 298°C. The results demonstrated that the effect of temperature on separation capacity is greater than the inlet feed flow rate.The maximum separation capacity was obtained by 7.7% at the feed flow rate of 2.3 kmol/hr and by 7.9% at the temperature of 298°C. The results demonstrated that the effect of temperature on separation capacity is greater than the inlet feed flow rate.

Column flotation, as a method with higher metallurgical performance is a better choice compared to the conventional mechanical cells for mineral processing. In this study, a 3D unsteady and two-phase flow computational fluid dynamics (CFD) simulation accompanied by experimental measurements was performed to calculate the flotation rate constant in a laboratory column flotation cell with a real ore feed at Sarcheshmeh Copper Complex. The population balance model (PBM) was applied to investigate the effect of bubble size on the flotation rate constant. The simulations were based on the Eulerian-Eulerian method and the k-ε dispersed turbulence model. To apply the local flow values to the kinetic model of flotation rate constant, different user-defined functions (UDFs) were applied. The flotation rate constants in the column flotation were predicted at different superficial gas velocities and particle sizes. CFD results were validated by comparison with the experimental data. The interfacial forces (lift and virtual mass) effect on the flotation rate constants’ prediction was assessed. The pulp density effect on the flotation rate constant was studied, indicating that increasing pulp concentration decreases the flotation rate constant. The superficial gas velocity effect on the gas holdup and bubble surface area flux was studied as well. Comparing simulation results and the experimental data reveals that the bubble size distribution effect on the predicted flotation rate constant is negligible.

In this study, the partitioning of glycine and arginine in aqueous two-phase systems (ATPSs) was measured. The aqueous two-phase systems containing polyethylene glycol with molecular weights of 8000 and 6000 (Da) and trisodium citrate and sodium sulfate were investigated. These systems have been studied at three different temperatures of 298, 303, and 308 K. The effect of different weight percentages of salt, the weight percentages of polymer, and temperature on the partitioning of glycine and arginine at ambient pressure was investigated. The results showed that the partition coefficients of glycine and arginine decreased with an increasing weight percentage of salt and polymer. Also, as the tie line length increases, the partitioning of amino acids decreases. The results showed that glycine in ATPS containing sodium sulfate (10 wt%) and polyethylene glycol (15 wt%, molecular weight 8000 Da) at 308 K has the highest partition coefficient in the top phase (2.013 ±0.101). Also, arginine in ATPS containing sodium triscitrate (14 wt%) and polyethylene glycol (25 wt%, molecular weight 6000 Da) at 308 K has the best partition coefficient (0.059 ± 0.005) in the bottom phase.

This paper presents a novel multistage hydrometallurgical process for copper and gold leaching from Sarcheshmeh Copper Complex (in Kerman, Iran) dust unit residue. To this end, 95.4% of copper and 90.2% of iron were leached in a three-step process using sulfuric acid in the presence of hydrogen peroxide, as the pretreatment. The solid residue from sulfuric acid pretreatment was applied to extract gold into the solution using acidic Thiourea leaching. To better understand the influence of different parameters on gold leaching using Thiourea and to reach maximum extraction, central composite design (CCD) was used through response surface methodology (RSM). The optimum conditions for gold leaching are as follows: Thiourea concentration = 20 g/L; temperature of leaching = 80 ˚C; and leaching time = 8 h. Under these conditions, the experimental leaching efficiency of gold was 44.2%. The presented mathematical model in the current study well explained the experimental data with the correlation coefficient value of 92.11% (R^2).

In this research, solvent extraction of neodymium from nitric acid media using D2EHPA and Cyanex 301 was investigated. Different parameters affecting on the extraction of neodymium such as contact time, pH, nitrate ion, extractant concentration and temperature were studied. The effect of various acids on the stripping of organic phase was also investigated. Results indicated that the addition of Cyanex 301 to D2EHPA in the organic phase will be improved the extraction efficiency of D2EHPA. The best synergistic enhancement factor was obtained 9.3 in the fraction mole of 0.3 for Cyanex 301. The effect of equilibrium pH on the distribution ratio of neodymium showed that two moles of H+ were released during the extraction process. The variation of extractant concentration on the extraction of neodymium at fixed concentration of other extractant indicated that the extracted complex was as NdH5A2B6(o). Finally, extraction mechanism, equilibrium constant, and thermodynamic parameters (H, S, and G) of extraction process were investigated.

In this study, the adsorption of cerium and lanthanum ions from aqueous solutions was investigated using Amberlite XAD-7 resin impregnated with bis (2,4,4–trimethylpentyl) phosphinic acid (Cyanex-272) in the batch system. The characterization of provided resin was performed by SEM and FTIR analysis. The effect of important parameters such as pH, contact time, temperature and initial concentration of metal ions in the solution on the adsorption process of cerium and lanthanum from aqueous solution were investigated. The results showed that with increasing the pH of solution, the adsorption of cerium and lanthanum increased and the maximum adsorption occurred at pH=6. Langmuir, Freundlich and Temkin isotherm models were applied to describe the equilibrium data. The results showed the agreement of the experimental data for Ce and La elements with Langmuir isotherm (R2 (Ce) =0.999, R2 (La) =0.998). The maximum adsorption capacity of resin for cerium and lanthanum was 11.17 and 6.48 mg.g-1, respectively. The kinetic study was performed using pseudo-first order, the pseudo-second order and intraparticle diffusion models. According to the results, kinetic data for Ce and La adsorption were fitted well to a pseudo-second-order rate equation (R2 (Ce) =0.966, R2 (La) =0.985). The thermodynamic parameters of the adsorption process such as standard enthalpy (ΔH°), Gibbs free energy (ΔG°) and entropy (ΔS°) were studied at different temperatures. The positive value of enthalpy and negative value of Gibbs free energy indicates that the cerium and lanthanum adsorption reaction is spontaneous and endothermic.

In this study, the removal of chemical oxygen demand in the wastewater of the textile and dyeing plant of Jey Industrial Zone using UV/H2O2 process in the presence of titanium dioxide and iron ion (II) catalysts was investigated. The experiments were performed by an advanced oxidation process in the presence and or absence of UV light. The effect of operating variables such as time (30, 90 and 150 min), UV lamp power (0, 15 and 30W), hydrogen peroxide concentration (100, 500 and 900mg/L), and catalyst concentration (values for titanium dioxide of 100, 500 and 900mg/L and for iron ion (II) of 10, 50 and 90mg/L) at pH=3 were investigated on the reduction of chemical oxygen demand of textile wastewater. All experiments were performed in a glass reactor at a temperature of 25 °C and on a magnetic stirrer at a suitable speed, and 27 experiments (for each type of catalyst) were randomly tested using the Box-Behnken design method. The results show that in the UV/H2O2/Fe2+ process, at time of 138min, the UV lamp power of 30W, the concentration of hydrogen peroxide of 677mg/L, and the concentration of iron ion of 50mg/L, the maximum rate of removal of chemical oxygen demand was equal to 90.20%. While in the UV/H2O2/TiO2 process, the highest rate of chemical oxygen demand removal was about 100% in time of 148min, the UV lamp power of 30W, the concentration of hydrogen peroxide of 710mg/L, and the concentration of titanium dioxide of 593mg/L.

In the process of zinc hydrometallurgy, many impurities such as nickel, cobalt, and cadmium, are removed, but magnesium remains with zinc in the electrowinning stage and its concentration increases during the process. The aim of this study is to reduce the concentration of magnesium in zinc leaching solution. XRD analysis showed that the prepared zinc oxidised sample contains smithsonite and hemimorphite as valuable minerals and dolomite and calcite as tailings. The sample contains 8.27% zinc and 8.15% magnesium. Here, alkaline zinc sulfate precipitation was carried out to bring magnesium to the permissible level in electrowinning solution. In acidic leaching, effective factors such as pH, temperature, solid percent and leaching time optimized to achieve maximum zinc recovery. In alkaline zinc sulfate precipitation, effective factors such as pH, temperature and retention time examined for selective precipitation of alkaline zinc sulfate. Recovery of zinc in one leaching step reached to 70.81% at pH=2, temperature of 60°C, solid percent of 10% and leaching time of 120 minutes. The leach residue was then dissolved at pH=3 for 60 minutes, in which the total recovery of zinc increased to 86.32%. Under optimal conditions of 90°C, pH =6.5-7, zinc recovery was found to be 99.90% in the precipitate, while the amount of magnesium precipitation was 3.6%. After re-dissolution of alkaline zinc sulfate, the amount of magnesium in the solution found to be 1.3 g/l, which was much less than the allowable magnesium level in solution used for electrowinning (10-15 g/l).