Optimization of process parameters and kinetic modelling for leaching of copper from oxidized copper ore in nitric acid solutions

The leaching behavior of Tunceli malachite mineral was investigated in nitric acid solutions by two steps to evaluate the effect of various experimental parameters.In the first step,the optimal conditions for the leaching process were determined,while in the second step,a kinetic evaluation for the process was performed.In the optimization experiments,the concentration of nitric acid,temperature,stirring speed,and solid-to-liquid ratio were selected as the independent variables,and the central composite design method(CCD)was applied to the experimental data.At the end of the experiments,the optimal values for the concentration of nitric acid,temperature,solid-to-liquid ratio and stirring speed were determined to be 0.5 mol/L,50℃,0.004 g/m L and 500 r/min,respectively.Under the optimal conditions,the leaching rate was found to be 99%for 120 min of reaction time.In the kinetic evaluation tests,the effects of the concentration of nitric acid,temperature,stirring speed,solid-to-liquid ratio and particle size on the leaching rate of copper from malachite were investigated.In these tests,it was determined that the leaching rate increased with the increase in the temperature,acid concentration and stirring speed,and with the decrease in the particle size and solid-to-liquid ratio.In consequence of the kinetic analysis,it was observed that the leaching kinetics followed the mixed kinetic model,and a mathematical model for the leaching process was introduced.The activation energy for this process was calculated to be 36.23 k J/mol.

Release of Anticancer Drug 5-Fluorouracil from Different Ionically Crosslinked Alginate Beads

In this research;the release of 5-Fluorouracil (5-FU) from different ionically crosslinked alginate (Alg) beads was investigated by using Fe3+, Al3+, Zn2+, and Ca2+, ions as crosslinking agent. The prepared beads were characterized by Fourier Transform Infrared Spectroscopy (FTIR) Differential Scanning Calorimetry (DSC) and Scanning Electron Micros-copy (SEM). The drug release studies were carried out at three pH values 1.2, 6.8 and 7.4 respectively each for two hours. The effects of the preparation conditions as crosslinker type, drug/polymer (w/w) ratio, crosslinker concentration and time of exposure to crosslinker on the release of 5-FU were investigated for 6 hours at 37℃. It was observed that 5-FU release from the beads followed the order of Fe > Zn > Al > Ca-Alg and increased with increasing drug/polymer ratio. At the end of 6 hours, the highest 5-FU release was found to be 90% (w/w) for Fe-Alg beads at the drug/polymer ratio of 1/8 (w/w), crosslinker concentration of 0.05 M, exposure time of 10 minutes respectively. The swelling measurements of the beads supported the release results. Release kinetics was described by Fickian and non-Fickian approaches.

Optical and electrical conductivity properties of rare earth elements(Sm, Y, La, Er) co-doped CeO_(2)

In this research,un-doped CeO_(2) and Ce_(0.85)La_(0.10)MO_(0.05)O_(2)(M:Sm,Er,Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported.Oxygen defects were created with the additives of rare earth ions.The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives.The synthesized products were characterized by X-ray diffraction(XRD) analysis,Brunauer-Emmett-Teller(BET) measurement,UV-vis diffuse reflectance spectroscopy(DRS),scanning electron microscopy(SEM),photoluminescence(PL)spectroscopy and electrochemical impedance spectroscopic(EIS).All synthesized compounds are found to be nano-structured and have cubic phase.The total conductivity of all samples was calculated.Hence,the total conductivity of un-doped CeO_(2),Ce_(0.85)La_(0.10)Y_(0.05)O_(2),Ce_(0.85)La_(0.10)Er_(0.05)O_(2) and Ce_(0.85)La_(0.10)Sm_(0.05)O_(2) is found to be 2.07×10^(-10),5.70×10^(-4),1.0×10^(-3) and 0.0747 S/cm,respectively.Also,bandgap energy(E_(g)) of these samples calculated from UV visible absorption spectra is discussed,and the optical results show variation between 3.2 and 2.15 eV.Additionally,the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type.Accordingly,photoluminescent emission spectra of Ce_(0.85)La_(0.10)Y_(0.05)O_(2),Ce_(0.85)La_(0.10)Er_(0.05)O_(2) and Ce_(0.85)La_(0.10)Sm_(0.05)O_(2) phosphors indicate that these phosphors have red,green and orange-red colors,respectively.

Activated carbon derived from radiation-processed durian shell for energy storage application

A lignocellulosic biomass,durian shell,modified by radiolytic oxidizing species from gamma and electron beam irradiations,has been used as a starting material for activated carbon(AC)production.Facile hydrothermal carbonization with ZnCl_(2)/FeCl_(3)and physical activation were employed in addition.The physicochemical and energy storage properties of the graphitic carbons were investigated using Field Emission Scanning Electron Microscope(FESEM),N_(2)adsorption-desorption,Brunauer-Emmett-Teller(BET),Fourier Transform Infrared Spectroscopy(FTIR),X-ray Diffraction(XRD),Raman spectroscopy,Cyclic Voltammetry(CV),Galvanostatic Charge-Discharge(GCD)and Electrochemical Impedance Spectroscopy(EIS).Biomass modification by radiolytic oxidizing species aided in improving the energy storage properties of the resultant ACs without significantly changing the textural qualities.The radiation type played an important role on the surface functional groups,basal plane,and pore structures of the graphitic materials.The energy storage mechanism was based on a combination of EDLC and pseudo capacitances with high Coulombic efficiency.The highest specific capacitance obtained was 325.20 F/g providing capacity retention of 94.79%after 10,000 cycles.A promising method of AC production for energy storage application has therefore been successfully demonstrated.

Optimization of Electrical Conductivity of SA-graphene Nanocomposites Using Response Surface Methodology

Synthesis and characterization of 4-{(E)-[(5-bromo-2-hydroxyphenyl)methylidene]amino}-N-carbamimidoylbenzene-1-sulfonamide(SA) and its composites with graphene(SA-GF) were performed. Compound SA and SA-GF were characterized by FTIR and 1H NMR. The GF dispersion in the composites was analyzed by means of scanning electron microscopy(SEM) for morphology. Thermal properties of SA and nanocomposites were investigated using differential thermal analysis(DTA) and thermogravimetric analysis(TGA). The optimum electrical conductivity of the new sulfonamide-based Schiff base was determined to be 1.78×10–5 S/cm at a frequency of 9923 Hz, an applied voltage of –19 V, a mass fraction of 9.38% for graphene loading using a central composite design in the response surface methodology. The significance of the selected parameters(frequency, voltage and GF amount) in the model was determined by the analysis of variance(ANOVA). The results showed that frequency and graphene loading represent important model terms and have considerable effects on the conductivity of SA.