M. Asadrokht, A. R. Zakeri,
Volume 36, Issue 1 (6-2017)
Abstract
Despite a great thermodynamic driving force, copper cementation by aluminum from sulfate solutions involves a relatively slow kinetics due to the presence of the passive oxide film on the surface of aluminum. The previous studies have confirmed the positive effect of the presence of small amounts of chloride ion on reducing the scale of this problem. In this paper, the effect of concurrent ball milling on the kinetics of this process has been investigated. The cementation experiments were carried out in a polyamide jar with alumina balls inside by planetary ball milling. The studied parameters were ball number (0, 4), temperature (25-55 °C) and time (0-240 s). All experiments were conducted at constant condition of [Cu2+] = 6 g/L, [Cl−] = 75 mg/L, rotation speed of 160 rpm, average aluminum particle size of 279 µm and [H+] = 1.94×10-3. The results showed that concurrent ball milling reduces the induction period of the cementation process to less than 120 s. The apparent rate constant of cementation showed the positive influence of simultaneous milling on the kinetics of the studied cementation process. Moreover, activation energies of the induction and main periods were calculated to be respectively 86 and 26 kJ.mol-1, indicating the shift of the reaction mechanism from chemical control to mass transfer control.
M. H. Bakhshi, A. Zakeri,
Volume 36, Issue 4 (3-2018)
Abstract
Electrowinning is one of the methods for recovery of nickel metal from pregnant leach solutions. In industrial practice, the Ni content in electrolytes is usually above 80 g/L. However, many nickel solutions obtained from processing of secondary nickel resources are much less concentrated and this makes the electrowinning of such solutions difficult. In the present study, Nickel electrowinning from 30 g/L sulfate solutions has been investigated and the effect of the parameters such as current density (CD), temperature (T) and boric acid concentration (BA) on the current efficiency and nickel deposit quality has been determined using a central composite design methodology. The statistical analysis of experimental results revealed the significant factors and a proper model was obtained for each response variable. The results revealed two important negative interaction effects of T´BA and CD´BA which means that increasing temperature and current density could result in a higher current efficiency and satisfactory Ni deposit quality only at lower boric acid concentrations. By using overlaid contour plot method for multiple response optimization, the optimum condition for attaining current efficiencies of >95% and a smooth and compact Ni deposit quality was determined as CD = 2-2.5 A/dm2, T = 25-30 °C, and BA = 10 g/L.
V. Mohammadpour, M. Soltanieh, Dr. M. Adeli,
Volume 37, Issue 1 (6-2018)
Abstract
In the present study, alkali roasting and oxalic acid leaching were used to extract titanium dioxide from ilmenite, and the effect of ethanol and ascorbic acid on the purity and recovery of titanium dioxide was investigated. In this research, ilmenite was alkali roasted with sodium carbonate for 4 hours at 900˚C. Then, the roasted ilmenite was leached with distilled water for 1 hour at room temperature. Finally, leaching with a mixture of 0.47M oxalic acid and different amounts of ascorbic acid and ethanol was performed at 65˚C. The results showed that using ethanol caused an increase in the amount of recovery and ascorbic acid increased the purity of the extracted titanium dioxide; also, the presence of these two factors at the same time simultaneously increased the amount of purity and recovery of the final product. Eventually, by choosing 0.47M oxalic acid, 0.005M ascorbic acid, and 48% ethanol as the appropriate conditions for leaching media and increasing the leaching time and temperature to 16 hours and 80˚C, it was possible to get titanium dioxide purities which were as high as 93.3% and 90.9%, respectively.
A. Vahedi, H. Nadimi, D. Haghshenas Fatmesari, S. Firoozi,
Volume 37, Issue 3 (12-2018)
Abstract
The aim of this study was to investigate the effect of tartrate ion (C4H4O62-) on the extraction and separation of zinc and cadmium using D2EHPA extractant. The presence of tartrate ion in the solution caused the shift of the extraction curve of zinc and cadmium to the more alkaline pH; however, the shifting rate for the cadmium extraction curve was more significant. In the absence of tartrate ion, ΔpH50% value was equal to 0.65. If 0.2 M tartrate ion were added to the aqueous phase, ΔpH50% value would increase to 1.09. The FT-IR analysis of organic phase showed that tartrate ion absorbed the organic phase along with zinc and cadmium. "Slope analysis method" also showed that 0.25 M and 0.5 M tartrate ion participated in the zinc-tartrate and cadmium-tartrate complex formation, respectively; however, extraction number was changed with increasing the tartrate ion concentration.
H. Mirzaaei Ghasabe, A. Zakeri, Sh. Mirdamadi, M. Ghorbanzadeh,
Volume 37, Issue 3 (12-2018)
Abstract
In this study, the recovery of lithium from the cathode of the spent Li-ion batteries of the LiNixMnyCozO2 type was investigated. After complete discharging and dismantling, the cathodic section was cut and its aluminum content was selectively dissolved in 2.5 M NaOH solution at room temperature for 2 hr. In the next step, selective dissolution of lithium by oxalic acid from the de-aluminized cathode material was investigated and optimized using the response surface methodology of the central composite design. The effect of three parameters of time (35-100 min), temperature (40-70 °C), and oxalic acid concentration (0.5-1.2 M) on the lithium recovery percentage and manganese concentration was studied as the response variables. According to the statistical analysis of the results and the developed models, an optimum condition (T = 70 °C, t = 122 min and oxalic acid concentration of 1.1 M) was suggested and verified experimentally, resulting in the lithium recovery of about 95% and Mn2+ concentration of about 110 mg/L.
M. Soltani, A. Seifoddini, S. Hasani,
Volume 39, Issue 1 (5-2020)
Abstract
In this research, the effect of heating rate on oxidation kinetics of magnesium powder particles under non-isothermal conditions was studied. For this purpose, differential thermal analysis (DTA) and thermogravimetry analysis (TGA) was done on magnesium powder particles at three heating rates of 5, 10 and 20 K min-1 up to 1000 °C under air atmosphere. Also, in order to better understand the oxidation process of magnesium powder, three temperatures were selected according to the DTA curve at a heating rate of 20 K min-1. Then, samples of magnesium powder were heated up to these three temperatures with heating rate of 20 K min-1 and were subjected to X-ray diffraction (XRD) and scanning electron microscopy (SEM) for phase and microstructural analysis. Then, kinetic studies were performed using some isoconversional methods such as Starink and Friedman as well as direct and indirect fitting methods. The activation energy (E) and pre-exponential factor (lnA) for oxidation of magnesium powder were in the range of 327-956 kJ mol-1 and 45-135 min-1, respectively. The reaction models for heating rates of 5, 10 and 20 K min-1 were obtained to be A3/2, R2 and D1, respectively.
