JOURNAL OF SEPARATION SCIENCE AND ENGINEERING
Year:2018 | Volume:10 | Issue:1 |Papers Count:8

Aqueous two-phase system is a well-known technique for separation of bio-molecules such as proteins and enzymes. Proline as an Amino acid has a lot of applications in different industries. In this research, proline partition coefficient in aqueous two-phase system of polymer-salt has been investigated. The system consists of polyethylene glycol as a polymer with different molecular weights and a biodegradable salt that is suitable for the environment, Dpotassium tartrate. Phase diagram (binodal curve) and tie lines were experimentally determined with different percentage of weight composition of polymer, salt and water from initial feed. Analysis of surface of two-phase area in binodal curve and tie line length were done. The best polymer and salt stock solution were suggested for phase diagram, and in that case increasing PEG molecular weight increases surface of two-phase area. Effect of PEG molecular weight, tie line length, polymer and salt concentration on proline partition coefficient has been investigated.

Supercritical fluids are recently used as a new method for producing nanoparticles. The purpose of this study is to thermodynamically model and solubility calculations of the gas anti-solvent process. For this purpose, a thermodynamic model based on the cubic-plus-association (CPA) equation of state (EoS) was applied to determine and predict the solubility of solid solutes in the process and to optimize the operational conditions. At the first, the optimum parameters of the CPA EoS were obtained for the pure compounds, using simultaneous regression of liquid density and vapor pressure data. Then, the binary interaction parameters were optimized using phase equilibrium experimental data. By applying these parameters, the modeling of the phase behaviour of six solidliquid-vapor (S-L-V) systems containing CO2 + toluene + naphthalene, CO2 + 1-propanol + salicylic acid, CO2 + ethyl acetate + salicylic acid, CO2 + ethanol + acetaminophen, CO2 + acetone + acetaminophen and CO2 + acetone + cholesterol was performed at the specific temperature and pressure ranges. The modeling results of this work were also compared with the literature data and the calculated results of the SRK EoS.

In the present study, a sophorolipid biosurfactant produced by Candida catenulata was used to extract hydrocarbons from a polluted soil collected from Naft Shahr oil-field. The critical micelle concentration was determined at 250 mg L-1 for the produced biosurfactant. Biosurfactant was efficient in leaching of hydrocarbons from contaminated soil due to the role of the surfactant in increasing the solubility of hydrocarbon in aquatic media. The effects of concentration of biosurfactant, temperature, and agitation speed were investigated on extraction yield using central composite design at 5 levels for each parameter. Data analysis and mathematical modeling were then performed using surface response methodology (RSM). The results showed agitation speed as the most effective factor followed by temperature and concentration of the biosurfactant. By optimizing the operating conditions of the process, the maximum removal efficiency of petroleum with 95. 51% was achieved under the following conditions: concentration of biosurfactant 220 mg L-1, temperature 55 ° C and agitation speed of 400 rpm.

In this research, in order to separate germanium from an aqueous solution containing tartaric acid, liquid-liquid extraction (LLX) and supported liquid membrane (SLM) were employed. In these systems, polytetrafluoroethylene (PTFE) as the membrane and Alamine 336 as the carrier/extractant were used. In the LLX system, the effect of concentrations of extractant, tartaric acid, and HCl as a strippant was studied. As a result, the germanium extraction efficiency increased 100% after reaching Alamine 336 concentration to 10 %v/v. At the tartaric acid concentration of 0. 275 mM, the highest germanium extraction (98. 6%) was obtained. According to the SLM experiments, the carrier concentration of 15 %v/v was enough for the efficient transport of germanium from feed to strip phase. In comparison with LLX system, despite transportation of all germanium species in the SLM system, the time of this process (20 h) is higher than that of the LLX system.

Organic pollutants of wastewaters have always been one of the most important environmental challenges. Absorption of contaminants from aqueous solution by nano-bentonite is an efficient way due to smaller size and increased surface area of the particles. In this study, bentonite prepared from bentonite mines of Kheirabad was purified by sedimentation method. Magnetic nano composite was synthesized by coprecipitation method. The properties of nanocomposite was studied using FTIR, XRD, VSM, BET and TEM analyses. The adsorption process of TCP, a toxic carcinogen phenolic derivative (initial concentration of 100 mg/L) by pure bentonite and magnetic nano composites (1 gr/L) was evaluated at pH= 5, 23-25 0C and different times. The results indicated that the percentage of adsorption of TCP by magnetized bentonite nano composite due to increased surface area (108. 73 m2 g-1) and magnetized nano particles in 60 minutes was attained %96. 777, compared to pure bentonite which adsorbed %68. 25 of TCP in 3 hours.

This research investigates the effects of date-pit oil extraction conditions on the antioxidant activity of the extracted oil. The oil was extracted by maceration method using petroleum ether. The date seed powder was first sieved into three fractions with the average diameters of 497. 50, 892. 50, 1705 μ m. The oil of each fraction was extracted under certain conditions of solvent/powder ratio, temperature and agitation time. The antioxidant activity of the extracted oil was determined based on the IC50 through DPPH test. The effect of each condition in each time was assessed on the oil antioxidant activity. The highest antioxidant activity was obtained for both particles with mean diameter of 497. 50 and 1705 μ m depending on the applied conditions (solvent volume, temperature and the agitation time). The statistical analysis of the results using the step-by-step regression indicated the particle size and temperature are the most important factors as 86% of the antioxidant activity relates to these two parameters. In addition, the interaction effect of all parameters except temperature and agitation time was significant at the 99% level.

Coal is one of the most important sources of energy which is used in the production of coke, but presence of impurities including sulfur and ash in coal affect its properties and lead to environmental pollution. Hence, in this study, the reduction of the pyritic sulfur and ash content from coal using leaching method were investigated. The investigations indicated that among different leaching reagents, nitric acid had the highest effect in the reduction of sulfur. The influence of important factors showed that the removal value of pyritic sulfur increased with increasing the temperature, acid concentration and leaching time and the most removal percentage (91%) was obtained at leaching time of 75 min, acid concentration of 30% and temperature of 80 ° C. The pyritic sulfur dissolution kinetics was also examined according to shrinking core models and the results revealed that the dissolution rate was controlled by surface chemical reaction model with the activation energy of 32. 319 kJ/mol. In addition, the design of experiments method was used to determine the desirable conditions of factors affecting the reduction rate of ash content. The findings indicated that the highest removal percentage of ash was achieved under optimal conditions: nitric acid concentration of 30%, temperature of 80 ° C and leaching time of 40 min.

In this study, a surface dissolution method by sodium hydroxide was used to improve the floatability of ilmenite in the presence of olivine-pyroxene and tremolite-clinochlore. The results of microflotation and UV-Vis indicated that the flotation recovery and collector adsorption of ilmenite are increased about 9. 9% and 10. 3% after surface dissolution at pH=6. 3, respectively, while these parameters are decreased about 28. 1% and 27. 25% for olivine-pyroxene and 2. 6% and 13. 52% for tremolite-clinochlore, respectively. Also, the results of flotation showed that the recovery, grade and separation efficiency of ilmenite flotation from the aforementioned gangue minerals are improved after surface dissolution. It can be due to conversion of ferrous ions to ferric ones on the ilmenite surface and removing the iron, calcium and magnesium ions from the surface of gangue minerals. The IEP of all minerals are decreased after surface dissolution, but the Pzc value for ilmenite was increased in the presence of collector and pH=6. 3 while it was decreased for two gangue minerals. These results are in good agreements with FTIR results. Also, changing in physicochemical properties of these mineral surfaces via surface dissolution was resulted in a selective adsorbtion of oleate ions on the surface of those minerals. After surface dissolution, floatability and selectivity of ilmenite from gangue minerals are increased in a wide range of pH. Finally, the results of ilmenite flotation from gangue minerals showed that the surface dissolution can improve the metallurgical parameters of ilmenite separation.