Iranian Journal of Chemical Engineering (IJChE)

Abstract The SrO-CaO-Al₂O₃ nanocatalysts were prepared and optimized using the co-precipitation method. In this work parameters affecting the catalytic performance for the production of biodiesel from sunflower oil have been investigated. Thev response surface methodology (RSM) has been used to assess the impact of operational conditions on the production of biodiesel, with the biodiesel yield as the response variable. The catalyst was found to be calcined at 600 °C, with a 5-hour calcination time, 75 minutes of the aging time, and a precipitation temperature of 50 °C as optimal conditions for the production of biodiesel. The results showed that the optimal reaction conditions were CH₃OH/oil=12/1 at 60 ˚C with the concentration of 6wt.%of the catalyst and reaction time of 3 h at stirring speed of 600 rpm. Furthermore, the biodiesel yield reached 99% under optimal operational conditions. The SrO-CaO-Al₂O₃ nanocatalysts were characterized by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transforms-infrared spectroscopy (FT-IR), and N₂adsorption–desorption measurements methods. The kinetic study has been done and the first order kinetic model was found  in agreement with experimental results (R²= 0.998). From the kinetic studies, E_a=41.57 kJ.mol^–1 and A= 5.25×10⁵ L.mol^-1s^-1 were obtained.

Abstract The application of the agro-industrial waste as the feedstock helps to decrease the operational cost of the fermentation process. Soapstock is a by-product of the vegetable oil refinery and enriched with fatty acids including linoleic acid which has a high potential application in the production of biosurfactants. In this study, a dual carbon source system, including glucose and free fatty acids recovered from a sunflower soapstock, was used for the synthesis of sophorolipid (SL) by Candida catenulata. The production of SL showed a major dependence on the initial carbon sources and the concentration of urea as the nitrogen source. The inoculum size was another influential factor in the fermentation process. The optimization of these factors was evaluated by the one-factor-at-a-time and the response surface methodology (RSM). The one-factor-at-a-time approach gained the best SL productivity (Y₁) of about 52.08 mg L^-1 h^-1 and SL-to-biomass yield (Y₂) of 712 mg_SL g_cell^-1 at the inoculum size of 4% vv^-1, 100 g L^-1 of glucose, 80 g L^-1 of soapstock, and 7.5 g L^-1 of urea. While the RSM, due to considering interactional effects of the factors, obtained the best condition at 100 g L^-1 of glucose, 100 g L^-1 of the soapstock, 9.3 g L^-1 of urea, and an inoculum size of 6.3% vv^-1 with the Y₁ and Y₁ values of about 58.10 mg L^-1 h^-1 and 713 mg_SL g_cell^-1, respectively. The characterization of the produced SLs by the GC-MS analysis indicated that a di-acylated C16:1 acidic sophorolipid with an m/z ratio of 679 amu was the main product.

Abstract  In an Iranian zinc smelter plant, nickel and cadmium are removed from the electrolyte solution at the cold purification stage with the help of zinc powder. This study tries to investigate the optimal conditions for the removal of these impurities through the response surface methodology by examining the effects of effective parameters on the process. The results of the experiments showed that cadmium was cemented by zinc powder much more conveniently than nickel. The interplay of parameters showed that increasing the concentration of zinc powder can reduce the time and temperature of the entire reaction. It also neutralized the effect of the changes of pH and mixing speed. The optimum conditions for the simultaneous removal of nickel and cadmium were obtained at 75 °C, the pH of 4.5, the residence time of 45 min, the mixing speed of 500 rpm, and 2 g/l of zinc powder. Under optimal conditions, more than 99 % of nickel and cadmium were removed from the electrolyte solution.

Abstract In this work, the demulsification of water-in-crude oil emulsions by dielectrophoresis via applying a non-uniform electric field in a lab-scale cylindrical cell was studied. The stability of emulsions was assessed through monitoring the size distribution of water droplets at 0, 3, 6, and 24 hours after the preparation of emulsion. The effect of operating parameters including the temperature, demulsifier concentration, water salinity, and time on the demulsification of water was investigated. Sodium dodecyl sulfate and sodium chloride were used as demulsifier and salt respectively. The experiments were designed by the response surface methodology (RSM) based on the central composite design (CCD). The operating parameters including the voltage, temperature, demulsifier concentration, salinity of water, and separation time were optimized. The contours and 3-D response surfaces of the water separation were acquired. A quadratic polynomial model, which was statistically highly significant (R²=0.9950, n=32), was provided by the RSM to predict the amount of the separated water. Comparison among the experimental and RSM-optimized values indicates a good agreement. The optimum amount of the water separation was obtained at the voltage of 15 kV, temperature of 60 °C, demulsifier concentration of 123 ppm, salinity of water of 12260 ppm, and separation time of 12.4 minutes. Under such conditions, the separation of water reached 98 %. The results obviously show that the electric field can be used as an appropriate means for the breakage of W/O emulsions.

Abstract In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence angles and diameters were examined. Microchannels with different confluence angles and diameters were examined. The effects of pH, temperature, and volumetric flow ratio and contact time of the two phases were investigated. The response surface methodology was used to optimize extraction yield of tannin from Quercus leaves in the employed microchannels. Based on this optimization, maximum yield was achieved at pH=2, temperature=33.1℃, volumetric flow ratio =1.2 and contact time of 25.35s. Results show that extraction-using microchannel has many advantages over traditional methods, including shorter time and higher economic efficiency. Moreover, microchannel provides smaller volume of fluids resulting in lower solvent consumption, lower waste production, shorter analytical times, smaller space requirements, and lower energy consumption.

Abstract In the present study, the effects of four factors including initial sulfide concentration (mg l-1 ), agitation speed (rpm), amount of inoculums (%) and sodium concentration (mg l-1) on removal efficiency (%R) and yield of sulfate production by Thioalkalivibrio versutus from synthetic spent caustic were investigated. For this purpose, experiments are designed by design of experiments (DOE) and Response Surface Methodology uses results of experiments to determine relationship between experimental factors and measured responses. The coefficient of determination (R2) was calculated as 0.9012 and 0.9544 for removal efficiency (%R) and yield of sulfate production (Y_(SO4/S)), respectively. The best local maximum was found to be at initial sulfide concentration 1500 mg/l, agitation speed 180 rpm, inoculum 8%, Na concentration 1.38 M , removal efficiency 96.99%, yield of sulfate production 2.65 and desirability of 0.909. According to these observations and results Thioalkalivibrio versutus is a suitable bacterium for oxidation of sulfide in spent caustic wastewater.

Abstract Magnetic silica aerogel in hydrophobic and hydrophilic forms were used as support to immobilize Candida rugosa lipase by adsorption method. Response surface methodology (RSM) was employed to study the effects of the three most important immobilization parameters, namely enzyme/support ratio (0.3-0.5, w/w), immobilization time (60-120 min) and alcohol percentage (20-40, %v/v) on the specific activity of immobilized lipase on the hydrophobic supports. For hydrophilic supports, alcohol percentage was removed as there was no need for pre-wetting step in enzyme immobilization process. Second order regression models with high coefficient determination (R2) values of higher than 0.98 were fitted to predict the response as function of immobilization parameters. The results indicated that for hydrophobic supports, optimum values for enzyme/support ratio, immobilization time and alcohol percentage were obtained at 0.45 (w/w), 94.27 min and 38.81 %, respectively, in which specific activity were predicted at 15.32 U/mg-protein. For hydrophilic supports, the optimum enzyme/support ratio and immobilization time were predicted at 0.47 (w/w) and 83.47 min, respectively. Specific activity in these conditions were obtained 11.21 U/mg-protein. As the difference between the experimental and predicted values was showed as non-significant, the response surface models employed could be considered as adequate.

Abstract The ultrasound-assisted (UA) soybean oil methanolysis using KOH as a catalyst was studied at different reaction conditions in a microreactor. Box–Behnken experimental design, with three variables, was performed and the effects of three reaction variables i.e. reaction temperature, catalyst concentration and the methanol-to-oil molar ratio on fatty acid methyl ester (FAME) yield were evaluated by method of analysis of variance (ANOVA) and multiple regression. A quadratic polynomial model was obtained to predict the methyl ester yield. A yield of 97.1% for methyl ester was obtained at the deduced optimal conditions: reaction temperature of 47 °C, KOH catalyst concentration of 1.29% (w/w) and methanol-to-oil molar ratio of 6:1. Validation experiments confirmed the validity of the predicted model. At the optimal operation condition for the ultrasonic process, a higher yield of methyl esters was obtained in comparison with that of the non-ultrasonic layout. The results show that UA transesterification in microreactor minimizes the reaction time and temperature, alcohol-to-oil molar ratio as well as energy consumption.

Abstract By using response surface methodology, Batch shaking biosorption of cobalt (II) experiments were conducted in order to examine the combined effects of operating parameters. The results indicate that magnesium nitrate performed as an effective biosorbent surface modifier, which increases the rate of adsorption capacity. At optimal conditions (initial pH 7.0, temperature 45◦C, biosorbent concentration 0.1 g/100ml, and initial cobalt concentration 300mg/l for Mg-treated biomass) the biosorption capacity of the algae for cobalt was found to be 80.55 mg/g. The Langmuir and Freundlich isotherms were applied to the equilibrium data. The results are best fitted by the Freundlich model. Evaluation of the experimental data in terms of biosorption dynamics showed that the biosorption of cobalt (II) onto algal biomass followed the pseudo-second-order dynamics well. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic parameters (ΔG◦, ΔH◦ and ΔS◦) were also evaluated.

Abstract The ultra-high molecular weight polyethylene (UHMWPE) was prepared using titanium tetrachloride (TiCl4) supported by MgCl2 (ethoxide type), accompanied by triisobutylaluminium (TIBA) as co-catalyst. These all constituted the Ziegler–Natta
catalytic system. MgCl2 is one of the best supports for Ziegler-Natta catalyst in order to increase its yield.In the present study, the process variables were investigated through response surface methodology (RSM) to optimize the productivity of the catalyst and also the molecular weight of the polymer. Taking this into consideration a three-level Box-Behnken design for three factors with temperature (X1), monomer pressure (X 2), and [Al]/[Ti] molar ratio (X 3) as the independent variables were selected. Different molar ratio of [Al]/[Ti] is achieved by changing the amount of the co-catalyst.The dependent variables were productivity and molecular weights of the prepared polymers. Specifically, using these three parameters at three levels including 50, 60, and 70°C for temperature; 4, 6, and 8 bar for pressure; and 150, 250, and 350 for [Al]/[Ti] molar ratio. The RSM yielded optimum reaction conditions equal to: temperature of 55°C, pressure of 8 bar, and [Al]/[Ti] molar ratio of 230. Under these optimum conditions, the productivity and molecular weight were 2628 g PE/mmolTi.h and 5.09×10 6 g/mol, respectively.

Abstract It was reported that the industrial application of Sub-Molten Salt method for production of potassium titanate from ilmenite concentrate is limited by feed particle size. Therefore, the objective of this study was to develop an improved approach for decomposition of ilmenite under industrial conditions. Using an ilmenite concentrate from Kahnooj Titanium Complex, experiments were performed at different conditions designed by the Response Surface Methodology (RSM) method. From the results of the tests, it can be noted that high conversion rate would be achieved even for particle size distribution similar to the industrial conditions. Statistical analysis of the results showed that conversion rate of titanium was significantly affected by process temperature. Optimized decomposition conditions were obtained at temperatures around 220 oC, KOH concentration of 84 wt%, KOH-to-ilmenite mass ratio of 9 and stirring rate of 800 rpm. Under these conditions, more than 96% of titanium can be recovered as potassium titanate. A quadratic model was obtained for the prediction of decomposition. Validity of the model was also experimentally confirmed. Observed effects of the relevant operating variables on conversion rate were consistent with a chemical reaction controlled kinetic model. Apparent activation energy for decomposition of ilmenite was found to be 80.15 kJmol−1.

Abstract The aim of the present work was to evaluate the effect of soy protein isolate (SPI)-gum arabic (GA) composite on the stability of beverage emulsion prepared as the orange oil-in-water (O/W) emulsion. Response surface methology (RSM) was used to study the influence of the two independent variables, each at three levels (homogenization speed
as x1 (1500, 15700, and 30000 rpm) and GA:SPI ratio as x2 (1, 0.6, and 0.2) on the two dependent variables namely, size of the emulsion droplet (EPS) as y 1 and emulsifying activity (EA) as y 2 . The results were discussed on the two empirical models obtained. Analysis of variance (ANOVA) showed a high coefficient of determination (R2 ) value of 0.937 and 0.979 for EPS and EA, respectively, ensuring a satisfactory adjustment of the second-order regression model with the experimental data. The negative sign for the regression coefficient of x1, indicated that size of the emulsion droplet increased with the decreased level of factor x1 from 30000 to 1500 rpm, while EA increased with increased levels of factor x1 . Thus, GA: SPI ratio with the lowest amount of GA along with the homogenization speed at high level, gave the smallest size of emulsion droplet (1μm). This size corresponded to the high emulsifying activity and stability. Sodium chloride and freeze-thaw cycling are two environmental factors affecting emulsion stability. Results of freeze-thaw cycling test showed a large decrease in the EA of the sample prepared with a low level of SPI:GA ratio and no dependence of the EA on the NaCl concentrations in the range of the tested levels was observed (50-150 mM). Long-term storage stability test (storing the emulsion samples at 4, 16, and 30ºC each for 8 days) showed the size of the emulsion droplet increased with the storage time. Results of use of SPI as a readily available plant source of protein for preparation of the encapsulant for orange oil-emulsion were encouraging, especially when one considers the dependence of the beverage industry on the unreliable source of supply of GA. RSM was successfully applied for the modeling of the emulsion preparation.

Abstract The increase in the usage of heavy metals in various industrial processes results in increasing heavy metal wastes that need further treatment. Cu and Zn remain hazardous even at low concentration and it is a clear necessity that they be removed from the effluent. The performance of oil palm frond (OPF) pre-treated with NaOH as a sorbent to remove Cu and Zn from aqueous solution was optimized in this study. 2 g of OPF was treated for 300 min in a 250 ml of 1.0 M NaOH solution to improve its sorption ability. Response Surface Methodology (RSM) based on the Three-Variable Composite Face Centered Design was employed as an experimental model to evaluate the effects of initial Zn and Cu concentration (5-100 mg/l), pH of the solution (2-9) and biomass loading (0.5-2.0 g) on the sorption process carried out at 25°C. The solution pH, initial metal concentration and biomass loading were used as the main process variables while the sorption performance was based on the removal efficiency. The coefficient of determination, R2, was found to be 0.96 and 0.97 for Cu and Zn removals, respectively. The initial concentration of 89 mg/l, biomass loading of 1.7 g and initial pH of 4.5 were found to be the optimum conditions for the maximum Cu removal of 91.0%, corresponding to sorption capacity of 11.9 mg/g. The optimum conditions for the highest Zn removal of 80.5 % or sorption capacity of 9.0 mg/g were found to be at an initial concentration of 76 mg/l, biomass loading of 1.7 and initial pH of 5.5.