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Wang X.,Kunming University of Science and Technology | Wang X.,Engineering Laboratory of Microwave Application and Equipment Technology | Srinivasakannan C.,The Petroleum Institute | Duan X.-H.,Hebei University of Technology | And 5 more authors.
Separation and Purification Technology | Year: 2013

The leaching kinetics of zinc residue, having total Zn content of 12.31%, along with other metallic components such as Fe and Pb, is leached using sulfuric acid as solvent, augmented with ultrasound is presented. The effects of variables such as the leaching temperature, sulfuric acid concentration, particle size, liquid/solid ratio and the ultrasound power have been assessed. The results show the maximum recovery of zinc to be 80% at an ultrasound power of 160 W, leaching temperature of 65 C, sulfuric acid concentration of 1.4 mol/L, particle size range of 74-89 μm and liquid/solid ratio of 4. The kinetics of leaching is modeled using shrinking core model and the rate controlling step is identified to be the diffusion through the product layer. The raw and the leached residue are characterized using XRD and SEM/EDX analysis. The activation energy is estimated to be 6.57 KJ/mol, while the order of reaction with respect to sulfuric acid concentration is 0.94 and particle size is 0.12 respectively. © 2013 Elsevier B.V. All rights reserved. Source


Wang X.,Kunming University of Science and Technology | Wang X.,Engineering Laboratory of Microwave Application and Equipment Technology | Ju S.-H.,Kunming University of Science and Technology | Ju S.-H.,Engineering Laboratory of Microwave Application and Equipment Technology | And 4 more authors.
High Temperature Materials and Processes | Year: 2013

The kinetics of carbothermic reduction of ZnFe2O4 in the temperature range 823-1223 K, was investigated in a microwave reactor. The mechanism of formation of ZnO and Fe3O4/FeO by decomposition of ZnFe2O4 was explained using the equilibrium calculations and thermodynamics analysis using HSC chemistry software 6.0. In addition the effect of parameters such as the decomposition temperature, C/ZnFe2O4 ratio, particle size and microwave power were assessed on the decomposition kinetics. Zn recovery as high as 98.83% could be achieved at a decomposition temperature of 1023 K, C/ZnFe 2O4 ratio of 1:3, particle size of +74-61 μm and microwave power of 1200 W. The kinetics of decomposition was found to be carbon gasification reaction controlled, with the activation energy of 39.21 kJ/mol. © [2013] by Walter de Gruyter Berlin Boston 2013. Source


Xin W.,Kunming University of Science and Technology | Xin W.,Engineering Laboratory of Microwave Application and Equipment Technology | Jin-Hui P.,Kunming University of Science and Technology | Jin-Hui P.,Engineering Laboratory of Microwave Application and Equipment Technology | And 3 more authors.
Journal of Microwave Power and Electromagnetic Energy | Year: 2013

Preparation of modified semi-coke has been achieved, using phosphoric acid as the modifying agent, by microwave heating from virgin semi-coke. Process optimization using a Central Composite Design (CCD) design of Response Surface Methodology (RSM) technique for the preparation of modifies semi-coke is presented in this paper. The optimum conditions for producing modified semi-coke were: concentration of phosphoric acid 2.04, heating time 20 minutes and temperature 587 °C, with the optimum iodine of 862 mg/g and yield of 47.48%. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy (SEM) and nitrogen adsorption isotherm. The BET surface area of modified semi-coke was estimated to be 989.60 m2/g, with the pore volume of 0.74 cm3/g and a pore diameter of 3.009 nm, with micro-pore volume contributing to 62.44%. The Methylene Blue monolayer adsorption capacity was found to be 98 mg/g at 332 K. The adsorption capacity of the modified semi-coke highlights its suitability for liquid phase adsorption application with a potential usage in waste water treatment. Source


Wang X.,Kunming University of Science and Technology | Wang X.,Engineering Laboratory of Microwave Application and Equipment Technology | Yang D.-J.,Kunming Metallurgy Research Institute | Ju S.-H.,Kunming University of Science and Technology | And 5 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2013

The kinetics of carbon reduction of ZnFe2O4 in the temperature range of 550-950 C was investigated in a microwave tank-type reactor. The mechanism of formation of ZnO and Fe3O4/FeO by the decomposition of ZnFe2O4 was detailed using the equilibrium calculations and thermodynamics analysis by HSC chemistry software 6.0. In addition, the effects of decomposition temperature, the C/ZnFe 2O4 ratio, the particle size and the microwave power were assessed on the kinetics of decomposition. Zn recovery as high as 97.93% could be achieved at a decomposition temperature of 750 C with C/ZnFe 2O4 ratio of 1:3, particle size of 61-74 μm and microwave power of 1200 W. The kinetics of decomposition was tested with different kinetic models and carbon gasification control mechanism was identified to be the appropriate mechanism. The activation energy for the carbon gasification reaction was estimated to be 38.21 kJ/mol. © 2013 The Nonferrous Metals Society of China. Source


Lu M.-N.,Kunming University of Science and Technology | Lu M.-N.,Key Laboratory of Unconventional Metallurgy | Lu M.-N.,Engineering Laboratory of Microwave Application and Equipment Technology | Lu M.-N.,State Key Laboratory Breed Base Of Complex Nonfer Metal Rsrc Cleaning Utilization In Yunnan Province | And 13 more authors.
Hydrometallurgy | Year: 2013

This preliminary study examined the role of microwave radiation on precipitation and aging of iron oxyhydroxides at 60 C. It was observed that due to rapid heating under microwave, transformation of two line ferrihydrite to α-Fe2O3 takes place within 4-10 h. This is in contrast to the usual aging temperature of > 100 C adopted in most conventional studies, and several days of aging. Besides rapid transformation, microwave helps forming nanoparticles, with crystallite size of ~ 60 nm as determined from X-ray diffractograms, and < 100 nm particles as observed under TEM. Rapid transformation also promotes formation of α-Fe 2O3 without the formation of intermediate γ-Fe 2O3. This study brought out the advantages of low temperature microwave assisted precipitation/aging as a low energy process to transform iron oxyhydroxides, with likely applications in slurry rheology, synthesis of nanoparticles, and adsorption. © 2013 Elsevier B.V. Source

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