نشریه علوم و مهندسی جداسازی
سال دوم شماره 1 (پیاپی 3، بهار و تابستان 1389)

In this work, numerical simulation of liquid separation process through hollow-fiber membrane contactors (HFMCs) using computational fluid dynamics (CFD) is investigated. Simulations are based on solving conservation equations for solute in the membrane contactor. Simulations are performed for separation of caffeine from water by subcritical carbon dioxide in a 3-fiber membrane module. Simulation results were compared with the experimental data reported in literature to evaluate the accuracy of the developed model. The modeling findings showed an average deviation of 13% with the experimental data. Effect of physical parameters of membrane on the separation of caffeine was investigated to obtain optimum conditions. The simulation results revealed that physical parameters of membrane such as porosity to tortuosity ratio and inner diameter of fiber have remarkable influence on the separation efficiency.

In this work, feasibility of using a non polar adsorbent known as exfoliated graphite (EG) for the separation of polar/non-polar mixture of MTBE/MEOH has been studied. In the case of removal of methanol from MTBE, four main effecting parameters were recognized to study their effect on the adsorption capability of EG. Two parameters of high temperature of thermal treatment and nitric acid/sulfuric acid ratio were related to the synthesis process of adsorbent, whereas MTBE/MEOH ratio in the solution and adsorbent to the solution ratio were other factors related to adsorption stage. To decrease the number of required experiments and determining the contribution of each factor, the Taguchi method was used for design of the experiments. By application of L16 orthogonal array, optimum condition for eliminating MTBE was predicted. According to the obtained results, EG was able to eliminate MTBE from MEOH effectively and at optimum condition, the removal percentage of MTBE was 80.

The main objective of this research was to study the bioleaching of Sarcheshmeh chalcopyrite copper concentrate by mixed iron- and sulfur- oxidizing bacteria. Experiments were designed using a full factorial design program. The effects of temperature, pH, nutrient medium and silver ions on the iron and copper recovery from chalcopyrite concentrate as well as on the cell concentration were considered. The experiments were carried out at a pulp density of 10% (w/v) using shake flasks in incubator (150 rpm) for 30 days. Several models have been developed between the target variables and relevant parameters by means of variance analysis using the Design-Expert software. It was found that the maximum copper recovery can be achieved under the following optimum conditions: T= 50°C; initial pH= 1.8; nutrient medium= Norris; silver concentration, 30 mg/L.

A 2D mathematical model with two approaches for unsteady CO2 permeation through a flat sheet polymeric gas separation membrane was developed. This model considered axial and radial transport in the membrane. Modeling results for CO2 transport, were compared with experimental data measured for the acrylonitrile butadiene styrene/poly vinyl acetate blend membrane. Gas permeability in various polymeric compositions and the effect of pressure on permeability are the main objectives of the comparisons. The model predictions were in excellent agreement with the experimental data.

Temperature overlapping is always considered in petroleum rectification. In this study, a mechanism is suggested to remove the temperature overlapping in distillation curve for rectification units which their feeds are liquefied petroleum. In this mechanism, firstly the unit is simulated and then is optimized by defining an objective function. Finally, operating conditions were determined without temperature overlapping in the distillation curve. Steps for defining the objective function are also presented. Optimization of a petroleum refinery by the presented mechanism shows considerable reduction in temperature overlapping of the distilled products and pushing them into appropriate operating range. Furthermore, applying the optimized conditions to the unit will be beneficial by 2958486 $/yr

Different methods for recycling aluminum slag have been used and the best method for turning it into refractory material is presented. The results show that the best method for recycling aluminum slag includes; grinding, sorting and sieving, leaching and calcination of aluminum slag at temperature higher than 1250 ºC. By use of a suitable method, low melting point phases such as aluminum in slag composition are decreased or deleted. Efficiency of this procedure is approved by chemical and phase analyzes. Such a procedure for recycling aluminum slag is enables protection of environment together with using slag as refractory material for lightweight castables. Also, aluminum oxide as secondary product of this method can be obtained.

In this study, adsorption of methylene blue from aqueous solution on carbon nanotubes was investigated. Experimental data at three temperatures of 290, 300 and 310 K were fitted to equilibrium models and at 300K with kinetics models. It was found that the Langmuir isotherm is the best fit with isothermal data and the kinetic data could be successfully fitted by McKay and Ho as a pseudo-second order model. The effects of different experimental parameters, such as contact time, solution pH, initial concentration of methylene blue and dose of adsorbent were investigated as effective parameters. Ninety groups of the experimental data for developing a neural network were used. The inputs data were initial solution concentration, dose of adsorbent, initial pH of the solution, contact time and temperature while the final methylene blue concentration in the solution was the output of the network. Finally, the network was optimized using the genetic algorithm. The results were compared with the experimental data and a very good agreement was observed.

In this paper, an appropriate, accurate and fast method for automated separation of plastic resins from post consumer plastic wastes is presented. The principle of sorting system operation is based on Near Infrared (NIR) reflectance spectroscopy. In this system, the plastic samples are fed on the sorting conveyor. When the samples are crossing from the near of conveyor end, their NIR reflectance spectrum is taken by a rapid spectrometer device. The control unit takes the second derivative of spectrum graph and then recognizes the sample material by analyzing this graph. Finally the target plastic resin is thrown to proper location by compressed air jet. According to current study, it is possible to separate PET, HDPE, PVC, PP and PS resins automatically by LabVIEW software. The accuracy of this method has been demonstrated for different resins. Also the effect of various parameters such as surface pollution, sample thickness and existence of label and cap has been studied on identification system. Experimental results, have confirmed the high accuracy of this new method.

During the past two decades the use of lignocelluloses fiber for biocomposite production has been the focus of many investigations. In order to reduce the lignin and hemicelluloses of the crude fibers, the fibers are often treated with different chemicals. The chemical treatments should enhance the physical and mechanical properties of the fibers and increase the adhesive force between the matrix and the biofibers. In this research, NaOH, KOH, and HCl were used in different concentrations for purifying date tree fibers. The percentage of pure fiber, ash content, coefficient of friction, diameter, and the tensile strength of the fiber prepared by different treatments were determined and statistically compared. The Weibull distribution model was used to investigate the variation in tensile strength of the fibers. The results indicated that the purification methods decreased the lignin content between 20 to 50, the ash content from 37 to 75% and the diameter of the fibers between 37 to 62%. The tensile strength of the fibers increased between 15 to 60%. The Weibull analysis of the data indicated that the distribution of tensile strength in purified fibers was more uniform than the untreated fibers.