نشریه علوم و مهندسی جداسازی
سال نهم شماره 2 (پیاپی 18، پاییز و زمستان 1396)

CO2 adsorption as the most important greenhouse gas and the main cause of global warming has recently become as one of the major issues in the world. In this research, modification of Ca(OH)2 sorbent by adding hydrophilic and hydrophobic silica nanoparticles to improve the CO2 adsorption process is investigated. The experiments which are carried out in a gas–solid fluidized bed show that using the vapor of methanol and and 2-propanol alcohols have the most significant effect on fluidization behavior of Ca(OH)2-hydrophilic silica adsorbent. CO2 adsorption experiments by monitoring pH of pure water shows that modification increases the adsorption period to 3 times. In addition, the adsorbent modified by hydrophilic silica in the presence of alcohol shows more CO2 adsorption in comparison with adsorbent modified by hydrophobic silica. For more investigations SEM analysis and also Richardson-Zaki equation are used.

Ammonia is one of the most common pollutants in urban and industrial wastewaters and due to various problems it generates, it is necessary to remove it from wastewaters. In this study, a laboratory scale once-pass membrane contactor system was designed and constructed using PPO hollow fiber membranes and the effect of various operating parameters such as the feed passage side (the lumen-side or the shell-side), feed flow rate and temperature on the efficiency of the process for synthetic wastewater was investigated. Since the petrochemical units are of the main sources of wastewaters containing ammonia at high concentrations, in the second part of this study, the efficiency of the process to remove ammonia from Khorasan Petrochemical wastewater was also investigated. Experimental results showed that low feed flow rate, high feed temperature and feed passage through the lumen side increased the ammonia removal percentage. Also, the ammonia removal percentage variations with the feed velocity and temperature were the same as that of synthetic wastewater. By comparing the ammonia removal percentages of synthetic and real wastewaters, it was obtained that ammonia removal percentages for real petrochemical wastewater at 20 and 40 ºC, were respectively about 25 and 19% lower than that of synthetic wastewater.

In general, the non-sharp distillation columns sequence optimization problem is formulated as a MINLP with a non-linear objective function. This study is an attempt to provide a two- phase approach which categorizes the variables into two classes in order to simplification of the problem. A set of variables are managed and optimized by Genetic Algorithm, the other set of the remaining variables can be solved as a LP problem for estimated values of the first set. The study formulates some mathematical relationships between the first set of variables from the non-linear constraints so that by optimizing some of them, others are obtained with the assistance of the relationships. The method has the ability to obtain the best structure from the overall superstructure directly in short time without using any starting points for ternary separation. Three published examples were used to validate the proposed method.

Kinetics and mechanism of thorium (IV) transport through a bulk liquid membrane containing di(-2-ethylhexyl) phosphoric acid in kerosene were investigated. The type and concentration of acid in donor and acceptor phases, initial concentration of thorium in donor phase, carrier concentration, and contact time were studied. The optimum transport of thorium were obtained with 0.0001 M HCl in donor phase, 1.5 M H2SO4 in acceptor phase, 0.2 M D2EHPA in kerosene, 50 mg L-1 of thorium in donor phases, and contact time of order of 960 min. The kinetics of thorium (IV) transport were investigated assuming a consecutive, irreversible extraction and back-extraction reactions. The activation energy values of extraction and back-extraction reactions were calculated to be 29.94 kJ mol-1 and 20.55 kJ mol-1, respectively,which indicates that the extraction process was controlled by the mixed regime (both kinetic and diffusion), and the back-extraction process was mainly controlled by diffusion process.

In this research, T- shaped microchannels have been utilized for extraction of propionic acid from water using 1-octanol solvent. Effects of mixing channel length and fluid flow rate on the mass transfer characteristics between two phases were investigated. Experiments were performed in four microchannels with ýlengths of 10, 20, 30 and 40 cm at flow ratesý between 2 and 16 mL/min. Effect of increasing channel length on the overall mass transfer coefficient, extraction ýefficiency and pressure drop ýwas studied. Results showed that increasing mixing channel length enhances the mass transfer but it also increases the pressure drop in microchannels. In this regard, performance ratio criterion was defined which its value increased by increasing mixing channel length up to 30 cm and after that decreased. This research suggests that the use of continuous microfluidic systems for extraction of propionic acid from water can be a suitable replacement for conventional batch systems.

More than 80 percent of the water used in the flotation process Sarcheshmeh Copper Mine is provided from recycled water of tailing dam. Due to the water shortage problem in the current condition, evaporation is considered the most important factor of losses from this important resource. In this study, were introduced two chemicals including hexadecanol and octadecanol. The two chemicals have a significant impact in reducing evaporation from open water reservoirs of mine that these reservoirs is provided much of the water in the flotation circuit. In the following, the combination of these two substances were added to five different water samples and were examined its impact on the recovery of the three mineral, copper, pyrite and molybdenum and then, the significance of the observed differences flotation tests on water samples were analyzed using Duncan's multiple range test. The results showed, fatty alchohol not only have not been a negative impact on the recovery of three mineral copper, pyrite and molybdenum, but also have increased 0.1% recovery of copper and 3.5% molybdenum recovery. Moreover, have increased pyrite arrested an estimated 30%.

Membrane distillation is a separation method based on heat transfer due to vapour pressure gradient between the two sides of a microporous hydrophobic membrane. Owing to advantages such as low operating temperature and pressure, and insensitivity to the concentration of influent pollutants, it is considered as an appropriate membrane-based separation process to be integrated with other separation processes and has shown good performance on the desalination of brine. In this paper, the performance of direct contact membrane distillation for desalting produced water with a salinity of 100000 mg/L has been studied by adopting heat transfer model based on the Nusselt number and mass transfer model based on the Dusty gas model. The results indicate that increasing salinity from 35000 mg/L to 10000 mg/L reduces the volume of the product by only 10%, which is retrievable through increasing the feed temperature, raising the flow rate of the feed and permeate, and reducing the temperature of permeate.
The amount of error occurred in this model in comparison with the reported experimental data was lower than 14%, and economic projections made for a unit with the capacity of 11000 barrels of produced water per day indicate that the levelized cost of producing retreated water in this method is 1.95 $/m3, which is a reasonable number for hypersaline produced water.

Low dissolution rate of chalcopyrite as the main copper sulfide minerals is known as the main limiting problem for industrial application of this technology. Low dissolution rate of the chalcopyrite is the main limiting issue to industrialize microbial leaching of such a recalcitrant mineral. In the agitated reactors, the disslution rate of chalcopyrite could be influenced by the different parameters such as the pulp density and particle size. Therefore, the main objective of this study was to evaluate the role of pulp density and particle size on the kinetics and efficiency of bioleaching of chalcopyrite concentrate, using moderate thermophilic bacteria isolated from Sarcheshmeh copper complex.
From the results of this study, it can be pointed out that the pulp viscosity influenced by the pulp density and particle size could be increased with reduction of the particle size and the increased pulp density. Both parameters influence the dissolution rate and the copper recovery. Under optimal conditions (10% solid content and average particle size of 16 microns), more than 88% of copper could be bioleached.