نشریه علوم و مهندسی جداسازی
سال یازدهم شماره 2 (پیاپی 22، پاییز و زمستان 1398)

The froth phase plays an important role in the recovery of minerals and the grade of concentrates in flotation machines. In the present work, the concept of bubble load was used to calculate the froth recovery. The results showed that the froth depth, aeration, and frother concentration are the most important operational parameters affecting the froth recovery in the flotation cell of hematite circuit of Gol Gohar Iron Ore. The results showed that increasing the aeration and frother concentration, and reducing the froth depth were caused to increase the froth recovery; For example, when aeration, frother and froth depth are respectively 146 m3/h, 150 ml/min and 5 cm, the froth recovery is more than 84%. Also, increasing the depth froth, aeration, and frother concentration were caused to increase the amount of sulfide minerals in the froth phase. Moreover increasing the aeration and frother concentration, and reducing the froth depth were caused to increase the amount of sulfide minerals in the concentrate.

The most common method of desalination is membrane method. Despite the large application, this method has weaknesses such as limited flux and low resistance to chlorine. In this research, a solution based on the use of functional graphene oxide with thionyl chloride(GO-OCl) in a polyamide membrane structure is suggested. To implement this idea, a new method was used to optimize the production of GO-OCl membrane using Constrain Mixture Design (CMD) (a design of experiment method). For execution, according to the CMD method, thirteen combinations of three materials: trimesoyl chloride, m-phenylenediamine and GO-COCl were selected. Then the membrane properties including salt rejection, resistance to chlorine and flux were measured. With using multi-objective optimization method, the optimal concentration was obtained, and the corresponding membrane was constructed. Comparison of the optimal membrane performance with pristine membrane showed that the flux of water was increased by 50.6%, salt rejection decreased by 3%, and chlorine resistance increased by 4.91%

The purpose of this research is to optimize the sulfur separation unit to increase sulfur production and simultaneously reduce the production of carbon dioxide based on the information of the unit for the separation of sulfur in the Ilam refinery. The input variables of the sulfur separation unit are the feed flow rate, airflow, furnace temperature, furnace pressure, first catalytic reactor temperature and the first catalytic reactor pressure. The mathematical model of the process was obtained using the surface response method (RSM) and the accuracy of the model was analyzed by analysis of variance. Finally, the operating conditions of the sulfur separation process were performed with numerical optimization method. The results showed that the most effective parameters are furnace temperature, air flow rate, and feed rate. The optimum points for the furnace temperature of 1039 °C, the airflow rate 469.38 kmol/h, and feed flow rate 1110.38 kmol/h were obtained which increased the sulfur production from 30% to 89% and decreased the production of dioxide Carbon from 55% to 8%.

In this study, the liquid-liquid equilibria for ternary systems of normal alkanes (consisting of nonane, undecane and tridecane) + methanol + methyl ethyl ketone have been investigated experimentally at the temperatures of 278.15, 288.15 and 298.15 K. The experiments of this study consist of the determination of the two-phase region and the tie lines of each of these three systems. The two phase regions were found by the titration method, based on the cloud point determination. The tie lines were found by using gas chromatography on the samples of the phases in equilibrium. The effects of temperature and the hydrocarbon chain length of the n-alkanes were also studied. In addition, the tie lines of each system were modeled by the NRTL (Non Random Two Liquid) model. The calculated values of root mean squared deviations (1.33, 1.71, 0.56 and 0.87) show the acceptable results of the used model in this study.

Sulfur is a toxic agent to most catalysts of the unit. Therefore, to eliminate the sulfur, the processes of hydrogenation and desulfurization should be performed on the feed gas. In this research, natural gas desulfurization process by zinc oxide adsorbent was model by using grain model. In order to analyze the adsorbent properties, two commercial samples were tested by BET, XRF, SEM and mercury porosimetry. The results showed that the model with an error of less than 2% corresponds to experimental data. The obtained results from sensitivity analysis indicated that the pellet porosity has the highest breakthrough time within 0.4-0.55. It was also found that by increasing of the bulk density, breakthrough time increases, but also it increases the pressure drop of the bed. Comparing the breakthrough time and conversion of commercial adsorbents samples, it was observed that Topsoe commercial adsorbent (1) had a better performance than Sud-chemie commercial adsorbent for specific operational conditions. The breakthrough time and the conversion of commercial adsorbent 1 has been calculated 215 days and 90%, respectively, and for commercial adsorption 2, 185 days and 87% respectively

Extraction of copper from sulphidic resources by hydrometallurgical methods is one of the greatest challenges in mining industries. Glycine is a new reagent for the leaching of copper and gold minerals, which has a high potential from treating copper sulphide concentrates and applying in the industry from environmental, technical and economic point of views. The aim of this research is to investigate the effect of pyrite content on the copper leaching from the chalcopyrite concentrate in a glycine medium. Leaching experiments and electrochemical analyses were carried out on the Sarcheshmeh copper flotation concentrate. Leaching experiments were performed at the three added pyrite to the concentrate (20% and 40% pyrite addition). Results showed that by increasing pyrite to concentrate mass ratio, copper extraction was enhanced significantly, in which by increasing pyrite addition from zero to 40%, at pH of 10.5, temperature of 60 ˚C, solid content of 5%, oxygen flowrate of 1 L.min-1 glycine concentration of 0.7 M and the stirring rate of 500 rpm copper extraction was increased from 50.6% to 73.8% (after 12 hours), while dissolved iron concentration was at a low level (<0.7%). Results of electrochemical analyses by cyclic voltammetry and polarization showed that maximum and minimum anodic oxidation currents were related to the copper concentrate and pyrite samples, respectively, which had a good accordance with the leaching results. This results show the high potential of glycine reagent to extract copper from pyritic concentrates.

Effect of magnetic field on the CO2 absorption in deionized water, water/Fe3O4, and water/Al2O3 nanofluids in a bubble column is studied. Effect of the other key parameters such as gas flowrate, nanoparticle type, magnetic field direction, and nanofluid concentration on the mass transfer rate and mass transfer coefficient has also been investigated. The results showed according to the polar nature of the water moleculs, by increasing the magnetic fielt to 1133 gauss, the mass transfer coefficient in pure water increases up to 6.7%. The enhancement can be achieved if the direction of the magnetic filed is parallel to the direction of the continious phase. By adding the nanopaticles to the pure water, the mass transfer coefficient and mass transfer rate increses. By increasing the water/Fe3O4 concentration the mass transfre coefficient increases, but in the water/Al2O3 nanofluid, by incerasing the nanofluid concentration up to 0.005%, the mass trasnfer coefficient increases, and then decreases.

Separation of sulfur dioxide by a new environmentally friendly method through its reduction to sulfur was investigated. Nickel catalyst was synthesized on two bases of alumina and activated carbon, using a wet impregnation method. Both catalyst series in two combinations of different percentages of nickel metal were synthesized, characterized and their performance in the reactor test in terms of conversion rate and selectivity for the desired product were compared. The effect of reaction temperature was investigated in the range of 550-800 °C. At low temperatures, activated carbon-nickel catalysts have better performance than the alumina-nickel catalyst. Effect of molar feed ratio of SO2/CH4= 3-1 was studied and stoichiometric feed ratio showed the best performance. Also, investigation of reaction time for catalysts showed a good long-term stability for SO2 reduction with methane in 8 hours. Keywords: SO2 reduction to sulfur, Separation of Sulfur Dioxide pollutant, Alumina-nickel catalyst, active carbon-nickel catalyst, catalist and reaction