نشریه علوم و مهندسی جداسازی
سال پانزدهم شماره 2 (پیاپی 30، پاییز و زمستان 1402)

Naphtha cracking processes call for low aromatic feedstocks to satisfy the operational considerations regarding the quality of their feedstocks. Therefore, the issue of the aromatics removal from petroleum fractions has become more serious. In this study, the experimental investigation and thermodynamic modeling of the liquid-liquid equilibria of the quinary system naphtha cut (including paraffinic, naphthenic, and aromatic species), sulfolane, and water, over the temperature range of 303.2 to 333.2 K, have been studied. The molecular representatives of paraffinic, naphthenic, and aromatic species of naphtha cut have been determined based on different objective functions. Physical properties estimation and modeling of equilibrium data reveal higher accuracy of vapor pressure- and viscosity-based objective functions in the structural modeling of naphtha cut. The root-mean-square deviations for the mentioned functions were determined to be about 1.47 and 1.48%, respectively. Thermodynamic modeling with the predictive UNIFAC model showed a good agreement with the experimental measurements. Also, the interaction coefficients extracted from the 75 ºC equilibrium data led to minimum deviation in the equilibrium modeling. Finally, the phase diagrams show the noticeable effect of water content and the small effect of temperature on the system equilibria.

One of the important sources of molybdenum is porphyry copper ores in which molybdenite is produced as a by-product. At the Sarcheshmeh Copper Complex, copper and molybdenum minerals float cumulatively. In this step, copper minerals are floated using sulfhydryl collectors and molybdenum mineral is floated with a collector such as Gasoline; Then, in the molybdenum processing plant, copper minerals are depressed using sodium sulfide, and the molybdenite is floated. One of the factors affecting in depress of minerals containing copper and iron is pH. In this study, the appropriate pH value and the best place to add the pH reducing agent were determined to increase the efficiency of the molybdenum flotation circuit. For this purpose, and according to the places where it is possible to add acid operation, the circuit was divided into three parts: rougher stage, third and fifth cleaning stage, and samples were collected from these parts. The results showed that by decreasing the pH in the fifth cleaning stage from 12 to 10.5, copper and iron recovery decreases and efficiency increases. Therefore, the best place to add sulfuric acid, is the fifth cleaning stage.

One of the widely used methods to remove acid gas is surface adsorption using solid molecular sieves. The advantages of H2S adsorption with molecular sieves can be seen in reversibility of the process, chemical and thermal stability, no secondary product, and high selectivity of H2S in these adsorbents. Therefore, in this study, Aspen-Adsim software was used to investigate the effect of various parameters on adsorption of H2S on 4A molecular sieve adsorbent. The desired bed is considered vertical and one-dimensional. The results related to the breakthrough curves and saturation time showed that maximum amount of adsorption occurred in early times. As the adsorption time increases, the rate of H2S adsorption decreases. The results of investigating the effect of operating parameters showed that increasing the tower pressure from 90 to 104 bar reduces the output H2S content by 21 ppm. Also, reducing the feed temperature showed significant results on amount of H2S absorption and the reduction of the output H2S content, so that for every one degree of temperature reduction in the feed gas temperature, the dew point temperature of the output was reduced by 1.6°C. Due to high amount of absorbent and its heat capacity compared to the amount of H2S in the gas phase, a slight temperature increase occurs along the tower so that the difference between inlet and outlet temperatures does not exceed 1˚C. According to the breakthrough curve, it was also determined that after 7920 seconds, the entire bed of the tower is saturated with H2S molecules.

Oil is considered an important source of energy in the world and still no suitable available and reliable source of energy has replaced it. Crude oil despite all its benefits has a high potential for environmental damage. Oil sludge is the most important waste of the oil industry which is known as a complex and dangerous organic substance due to its various compounds, and it is considered a special and dangerous waste in many countries, which can be treated using effective technologies such as The use of supercritical fluids, pyrolysis, centrifuge, etc. is recycled.In this research, oil sludge is placed in the hydrothermal oxidation reactor along with KOH and deionized water, so that the oxidation process takes place. The reactor has the ability to withstand critical water temperature and pressure conditions. Three factors of temperature with the range of 320 to 380 degrees Celsius, reaction time of 30 to 600 seconds and weight ratio of catalyst to oil sludge from 0 to 0.05 were investigated as reaction variables and the test response in the test is the COD of water remaining from oxidation in ppm. According to the results COD removal efficiency is in the range of 70.3 to 92.2%.92.2% yield at 380C temperature and 600 second residence time and 0.05 mass ratio of catalyst to initial feed as the highest yield and 70.3% yield at 320C temperature and 30 second residence time and 0.05 mass ratio of catalyst to initial feed. The title is the lowest return.

The separation of Pyrrhotite from Magnetite in the presence of Pyrite and ferrous ions was ‎investigated. Electrochemical investigations are used because iron sulfides are semiconductors. In ‎this research, at first, cyclic voltammetry studies have been conducted to investigate the ‎electrochemical interactions between pyrrhotite and magnetite in the presence of pyrite, ferrous ‎ions, and sodium isopropyl xanthate (SIPX). Based on these studies, the undesirable formation ‎of dixanthogen on the pyrrhotite electrode has justified the inappropriate flotation of pyrrhotite ‎in traditional flotation conditions (pH close to 7 and pulp rest potential). Redox potential control ‎has been used to achieve the desirable sulfur reduction rate. Flotation tests have been performed ‎on different pulp potentials and pH close to neutral conditions. The best result to reduce the total ‎sulfur has been obtained in Eh of 250 to 320 mV vs Ag/AgCl, absence of ferrous ions, the size of ‎magnetite particles at d_80 ,74 microns, 1.5 g/liter xanthate collector, preparation time equals 7 ‎minutes, and pH 6.‎

Mineralogy and chemical composition are the main indicators for selecting operational parameters for copper leaching from mineral resources and smelting furnace dust. The main goal of this research is to evaluate the dust composition of chalcopyrite concentrate smelting furnaces to improve copper leaching efficiency. In this regard, for four months, samples were taken daily from the dust of the smelting furnaces of Sarcheshme copper complex. Using X-ray diffraction analysis, X-ray fluorescence spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and reflective light microscopy, the composition of the samples was determined, and leaching tests were designed and implemented to determine the main operational parameters.The results of this study showed that the grain size distribution of the samples did not change significantly during the sampling period, but the amount of some elements such as arsenic was variable and fluctuated between 0.17 and 3.90%. The changes of copper and iron were also about 2%. The results of leaching tests of flash furnace dust showed that the solid percentage, acid concentration and temperature are the most important operating parameters. Under the optimal operating conditions, about 65% of copper is dissolved without the use of an oxidizer within a maximum of 60 minutes. By using a two-stage electrochemical process, the conditions for extracting more than 95% of copper from flash furnace dust are provided.

removal of volatile organic compounds is one of the most challenging issues according to the new environmental policies. considering the disadvantages of these compounds and the important effects on the environment and life of organisms, proper treatment and prevention of these compounds to the environment is important. in this research, separation of ethanol as a volatile organic compound using PDMS pure membrane and PDMS/ TiO2 nanocomposite membranes with different percentages of nanoparticles during pervaporation permeation was investigated. the effect of temperature, ethanol concentration and the effect of increasing the percentage of nanoparticles on pervaporation performance was studied. scanning electron microscopy (SEM) was used to study the structure and morphology of membranes, CA analysis (contact angle) to evaluate the membrane hydrophobicity, TGA analysis to investigate the thermal resistance of membranes and FTIR analysis to observe the membranes 'and chemical bonds. according to the results, increasing the temperature leads to increase in the movement and molecular mobility followed by increase in total flux. by increasing the flux of water ، the separation factor is reduced. on the other hand, separation factor is a function of feed concentration and the separation factor decreases considerably by increasing the amount of ethanol in feed. by adding nanoparticles to the membrane, at first, we see increase in membrane selectivity and then decrease it. this can be due to agglomeration of nanoparticles at high concentration. in general, nanocomposite membranes containing 0.1 % of nanoparticles with selectivity of 11.2 % and permeate flux 1230 showed the best selectivity.