دوماهنامه مهندسی شیمی ایران
پیاپی 131 (بهمن و اسفند 1402)

Production of activated carbon by using agricultural wastage can greatly reduce production costs due to its cheapness and availability. In this study, activated carbon was produced using fig wood. Activation was performed using phosphoric acid with a ratio of 1:5 at 450°C. Activated carbon properties were obtained by using percentage yield and ash analysis, FTIR analysis, BET analysis, and SEM analysis. The percentages of yield and ash, the specific area and the total pore volume were 57.17%, 2.3%, 1004 (m2/g) and 0.844 (cm3/g) respectively. Based on adsorption-desorption analysis, the activated carbon was classified as two types I and II, with a combination of micropores and mesopores. The functional groups of activated carbon, including carboxylic acid, phenolic groups, etc., were found. The results of SEM analysis showed a microporous structure with frequent micropores.

In this work, the performance of a solar system, in more detail, the thermal photovoltaic system is investigated. Numerical study has been done through coding in MATLAB software and by simultaneously solving equations related to the electrical and thermal parts, which provides the possibility of performing various investigations on the system. It is noteworthy that the PV part of this code, which is entirely accurate, can also use independently for photovoltaic systems. Numerical study has three features: parametric study, and collector performance in one day and in one year. As the wind speed increases from zero to 14 m/s, the electrical efficiency increases by about 4%, the thermal efficiency decreases by about 22%, and the overall efficiency of the system decreases by 18%; Therefore, there is a possibility of drastic changes in the performance of the system with changes in wind speed. By increasing the amount of radiation from 350 to 1050 W/m2, the electrical, thermal and overall efficiency shows a 1% decrease, 16% increase and 14% increase, respectively. Assuming an increase in the ambient temperature from 5 to 60 oC, the electrical efficiency decreases by 2.5%, the thermal efficiency increases by 0.5% and the overall efficiency decreases by 2%. Also, the results show that the thermal output power of the photovoltaic thermal system varies between 280 and 460 Watts and the electrical output power varies between 120 and 190 Watts throughout the year

The composite solid propellant based on the three main components AP/Al/HTPB containing 19 wt.% of Aluminum has special physical, mechanical and combustion properties due to the high solid load. Increasing the solid load is done in order to improve the performance properties of solid propellant, such as specific impulse and volume combustion heat, which are requirements of space missions. On the other hand, increasing the solid load (reducing the binder system) leads to limitations in the production process, such as increasing the viscosity, reducing the pot life, and reducing the processability of the propellant slurry, and also reducing the quality of other propellant properties such as mechanical properties. In this study, the effect of ammonium perchlorate (AP) as one of the key parameters on the physical, mechanical and combustion properties of composite solid propellant has been studied experimentally. The results showed that by reducing the average size of AP particles, the density does not change significantly, the tensile strength and modulus increase and the elongation decreases, and the burning rate of the propellants increases slightly. The average density of propellants is 1792 kg/m3, For the propellant sample with the NCO/OH ratio = 0.88 and the mass average AP particle size equal to 251 μm, the ultimate tensile strength is 0.523 MPa, the maximum elongation is 35.1%, the modulus is 1.5 Mpa, and the burning rate at 65 bar is equal to 6.9 mm/sec.

Chemometrics science is effectively used for solving experimental problems and describing of experimental results in different fields using statistics and mathematics. Such applications of the method can be referred to solving the problems about optimization of the experimental methods. In the present research, ultrasonic irradiations was used for synthesis of zinc ferrite nanostructures. Also, starch as a green material was applied to reduce using of chemicals. Other novelty of the present study was application of the multivariate optimization method instead one-at-a-time usual methods. For achieving the purpose, at first the nanostructures were synthesized based on Box-Behnken design. Then, the results of X-ray diffraction were used as experimental responses for optimization of effective parameters on the synthesis of the nanostructures using response surface methodology. Finally, the optimized nanostructures were applied for investigation of electrocatalytic properties in tyrosine detection. The results showed the zinc ferrite nanostructures that were synthesized in the optimum conditions contain appropriate potential for trace analysis of tyrosine in complicated real samples.

In this work, the performance of a solar system, in more detail, the thermal photovoltaic system is investigated. Numerical study has been done through coding in MATLAB software and by simultaneously solving equations related to the electrical and thermal parts, which provides the possibility of performing various investigations on the system. It is noteworthy that the PV part of this code, which is entirely accurate, can also use independently for photovoltaic systems. Numerical study has three features: parametric study, and collector performance in one day and in one year. As the wind speed increases from zero to 14 m/s, the electrical efficiency increases by about 4%, the thermal efficiency decreases by about 22%, and the overall efficiency of the system decreases by 18%; Therefore, there is a possibility of drastic changes in the performance of the system with changes in wind speed. By increasing the amount of radiation from 350 to 1050 W/m2, the electrical, thermal and overall efficiency shows a 1% decrease, 16% increase and 14% increase, respectively. Assuming an increase in the ambient temperature from 5 to 60 oC, the electrical efficiency decreases by 2.5%, the thermal efficiency increases by 0.5% and the overall efficiency decreases by 2%. Also, the results show that the thermal output power of the photovoltaic thermal system varies between 280 and 460 Watts and the electrical output power varies between 120 and 190 Watts throughout the year.

Biohydrogen production by microorganisms including Clostridium and Enterobacter are covered. Artificial microbial consortia have no complications as the pure culture. Further avails the effect of environments interaction on each other and yield of hydrogen production. The present review paper discloses the pathway of hydrogen production by Enterobacter and Clostridium, the rate of growth of the microorganism, The potential of carbohydrate substrate metabolism, pH and temperature influence, and the ratio of experimental to theoretical yield under anaerobic conditions. Enterobacter by Pyruvate formate-lyase (PFL) and Clostridium Pyruvate-ferredoxin oxidoreductase (PFOR) yield 2 mol / mol glucose and 4 mol / mol glucose. On the count of the present comparison 1.36 to 2.205 mol /mol glucose produced by Enterobacter and Clostridium, respectively, 38% discrepancy of practical yield is observed. For hydrogen production Clostridium needs strict anaerobic environments and L-cysteine are added, while Enterobacter in consortia uses oxygen and as a result the production cost is reduced. The consortia are potential to metabolize simple and complex carbon sources like glucose, starch wastewater and lignocellulose wastes. Moreover, reasonably high inoculate ratio of Enterobacter, pH, and, temperature ranges of 5-7 and 30-39°C are effective for biohydrogen production.
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Carbon dioxide absorption is one of the ways to reduce greenhouse gases. This study investigates carbon dioxide absorption by methyldiethanolamine-piperazine aqueous solution using a microchannel. The Design Expert software was used to check and analyze the results. The effect of the parameters of amine concentration (30-50 wt.%), temperature (20-40°C), solvent flow entering the microreactor (3-9 ml/min) and carbon dioxide concentration (5-15 vol.%) on the overall mass transfer coefficient was evaluated. The importance of the input variables for this response is in the order of liquid flow > amine concentration > temperature. Liquid flow intensity is the most effective input variable because there is a direct relationship between liquid flow intensity and the succession of absorption sites. The highest value of the overall mass transfer coefficient was reported as 202.50 kmol/m3.h.kPa. This value was obtained in operating conditions: concentration of 40 wt.% of solvent, flow intensity of 9 ml/min of solvent, operating temperature of 40 degrees Celsius and input concentration of 10 vol.% of carbon dioxide gas.

This research addressed the experimental optimization of the operating conditions to decrement the concentration polarization on the reverse osmosis (RO) membrane. Regarding the number and diversity of the effective parameters (salt concentration, pressure, flow rate, and pH) of desalination process, Taguchi design of experiment (DoE) was employed to decrease the number of texts and costs. The contribution of various parameters and optimal conditions to achieve the highest desalination were determined using Taguchi DoE and ANOVA as implemented in Minitab 16 software. The RO desalination increased in various conditions by prolonging the time for tests 5, 4, and 6. The best desalination performance of the polyamide composite membrane (97.24%) was achieved for salt concentration, pressure, flow rate , and pH of 1500 ppm, 10 bar, 0.5 L/min, and 7, respectively. The highest water flux through the polyamide composite membrane during the RO process was 41.04 L/m2hr which was observed in test 6. Such an enhancement in the water flux can be assigned to the decrease in the concentration polarization on the polyamide composite membrane.

In this research, the production of xanthan biopolymer in two substrates of olive mill wastewater (OMW) and pre-treated OMW by coagulation -flocculation methods was investigated. Aluminum, iron ions, and lime have been used as coagulants . The use of 4 g/L FeCl3 has caused the highest removal efficiency of COD and PPH about 24 and 31% respectively. Considering the reasonable price of lime and its effect in creating alkalinity the combination of various coagulants with lime was also investigated. The results show that the combination increases the pollutant removal efficiency by two folds and also reduces the amount of coagulant consumption. For example, the combination of 4 g/L of lime with 3 g/L of FeCl3 removes 48 and 65 percent of COD and PPH, respectively. In order to investigate the effect of reducing the concentration of PPH on the xanthan production , the growth of the microorganism Xanthomonas campestris and the production of xanthan in different concentrations of raw OMW and pre-treated OMW were investigated. The results show that the pre-treatment process increases the xanthan production. So that the maximum amount of xanthan produced in raw OMW at the concentration of 40% is equal to 4 g/L, and this much in pre-treated OMW is 13 g/L at a concentration of 70%. Therefore, the use of pre-treatment methods and the reduction of toxic biological compounds in OMW, in addition to the significant increase in the amount of xanthan produced, also leads to a decrease in the dilution of the wastewater.