توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Investigation the effects of pulp density on the uranium bioleaching in stirred tank reactor
نویسنده(ها): ، ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۶
Uranium bioleaching was carried out with low grade uranium ore from anomaly II of Saghand in Yazd. The bacterial which was used for these experiments was the native strain of Acidithiobacillus ferrooxidans. In these experiments, the effect of pulp density on the efficiency of uranium bioleaching was examined. It is observed that increasing the pulp density cause increasing the lag time of bacterial growth and leaching time and in a given time cause lower uranium extraction. In these experiments the uranium extraction percentage reached to 99% after 7 days for 5% (w\v) pulp density at both agitation speeds of 400 (rpm) and 600 (rpm) and 96% and 97% after 8 and 9 days for 15% (w\v) pulp density at agitation speeds of 400 (rpm) and 600 (rpm), respectively.<\div>

۲Coalescence of Water Drops in Oils under Pulsatile Electric Fields
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۱۵
The coalescence of water drops in oils may be enhanced by the application of an electric field. However, the process of coalescence could cause secondary drop formation, a feature which is undesirable as it reduces the efficiency of water separation. In this work the effect of pulsed electric field is evaluated. With pulsatile electric fields higher field strengths can be applied for systems having a high water content without causing field breakdown. Three waveform types, i.e. square, sinusoidal and sawtooth waves have been applied to drop–interface coalescence and their effect analysed. It is shown that the sinusoidal and sawtooth waveforms are most effective in reducing the secondary droplets formation<\div>

۳application of response surface methodology for optimazation of PVDF hollow fiber membrane in DCMD and AGMD performance
اطلاعات انتشار: دومین همایش ملی غشا و فرایندهای غشایی، سال
تعداد صفحات: ۵
Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by the dry\wet jet spinning phase inversion technique. the Box–Behnken design method were applied for study the fibers under different polymer concentrations, BaCl2 salt concentrations and air gap length to optimize mean outer surface pore size, overall porosity and hydrophobicity. The prepared membranes were characterized through SEM observation and contact angle test. An optimal hollow fiber membrane was finally fabricated using the determined optimum spinning conditions: polymer concentration of 22 %w\w, BaCl2 concentration of 2.9 %w\w and air gap of 34.5 cm. The optimum fiber was tested for desalination by direct contact and air gap membrane distillation (DCMD and AGMD). The permeate flux of this fiber at different concentrations and temperatures of feed was tested for comparison. At optimal MD condition (feed concentration of 0.5 mol\lit and temperature of 80 °C), optimum fiber synthesis was compared with a fiber prepared at the same spinning condition but without salt additive. Permeation flux was improved in optimal fiber from 13.750 kg\m2.hr to 20.101 and from 10.212 to 13.367 with salt rejection of 99.9% for DCMD and AGMD respectively.<\div>

۴Dual–layer hydrophilic\hydrophobic PVDF–HFP electrospun membranes synthesis for Air Gap Membrane Distillation (AGMD)
اطلاعات انتشار: دومین همایش ملی غشا و فرایندهای غشایی، سال
تعداد صفحات: ۷
The main challenges for membranes used in membrane distillation (MD) are well–designed porous structure and hydrophobic surface property. Hydrophobic nanofiber membranes possess high hydrophobicity, high surface porosity and adjustable pore sizes and membrane thickness, which make them an attractive candidate as MD membranes. Compared to traditional phase inversion techniques for membrane fabrication, electrospinning allows the formation of interconnected pores with uniform pore size and porosities exceeding 90%.In this study, a electrospun nanofiber polyvinylidenefluoride–co–hexafluoropropylene (PVDF–HFP) flat–sheet composite membrane using commercial hydrophilic polyester nonwoven as a support layer was prepared for MD applications. This composite nanofiber membrane has been characterized by a series of measurements (scanning electron microscopy (SEM),contact angle and porosity measurements and air gap MD (AGMD) setup were used) and benchmarcked against commercial PVDF flat–sheet membrane for MD applications. The electrospun layer of the membrane which fabricated by using optimized process parameters was obtained with mean pore size, porosity, contact angle, and thickness of 435 nm, 81%, 140° and 105 μm, respectively. Fabricated membrane was tested for desalination by air–gap MD and water flux value of 13.2 L\m2.h was obtained with a salt rejection of 98.4%. The present composite nanofiber membrane showed better flux performance and salt rejection compared to a commercial flat–sheet membrane (Flux = 8 L\m2h and SR = 95% ) The result suggest the potential of the nanofibrous membrane for AGMD applications.<\div>

۵improvement of hollow fiber membrane characteristics and performance by using of chloride salt additives
اطلاعات انتشار: دومین همایش ملی غشا و فرایندهای غشایی، سال
تعداد صفحات: ۵
Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by the dry\wet jet spinning phase inversion technique. Fibers used for MD process must have at least one hydrophobic surface and high overall porosity with small pore sizes. DiMethylACetamide (DMAC) was used as polymer solvent and several chloride salts (NaCl, KCl, CaCl2 and BaCl2) are not dissolved by DMAC were used as pore forming additive in dope solution that improved porosity in fibers structure. Four experiments were performed for determination of optimum salt between these salts that increase the overall porosity while keep pore sizes in hollow fiber structure smaller than 0.4 micrometer. Other spinning parameters were maintained the same at these experiments. Salt particle sizes in DMAC were measured by Dynamic Light Scattering (DLS). The prepared membranes were characterized through Scanning Electron Microscope (SEM) observation and contact angle test. Finally the optimum membrane were tested for desalination by direct contact membrane distillation and compared with fiber that produced at same spinning parameters and without salt additive. An optimal hollow fiber membrane was fabricated using the BaCl2 particles with contact angle of 93.8, overall porosity of 85% and pore size of 0.29μm. This optimum membrane exhibits the highest permeate flux (16.902 Kg\m2hr compared to 11.015) and salt rejection factor of 99.9%.<\div>

۶hydrophobic pvdf hollow fiber membrane synthesis for direct contact membrane distillation DCMD
نویسنده(ها): ، ، ،
اطلاعات انتشار: دومین همایش ملی غشا و فرایندهای غشایی، سال
تعداد صفحات: ۵
Polyvinylidene fluoride (PVDF) hollow fibers membrane were prepared by the dry\wet jet spinning phase inversion technique. For synthesis of this membrane, the methanol was used as a non–solvent for producing more porous fibers. The Membrane was fabricated at optimum condition; polymer concentration (16% wt), methanol concentration (4% wt) air gap (10 cm), bore fluid rate (10 ml\min). The prepared membrane was characterized through SEM observation and contact angel test. The fiber prepared at this condition has 0.31 μm of mean pore size, 81% of overall porosity and 115º of surface contact angel. Membrane Distillation (MD) process is mainly investigates for desalination, waste water treatment and other applications which water is the major component present in the feed solution to be separates. In this work, hollow fibers were tested for desalination by direct contact membrane distillation and the permeation flux was improved from 12.8 kg\m2.hr (without methanol) to 16.3 kg\m2.hr (with methanol) and 99.3% salt rejection of feed solution (1 molNaCl\lit and temperature of 80 ºC) was obtained<\div>
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