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Choi, S.Y.,Nguyen, V.T.,Lee, J.c.,Kang, H.,Pandey, B.D. Elsevier Scientific Pub. Co 2014 Journal of hazardous materials Vol.278 No.-
The present paper is focused on solvent extraction of hazardous Cd(II) from acidic chloride media by Cyanex 921, a new extractant mixed with 10% (v/v) TBP in xylene. The optimum conditions for extraction and stripping of Cd(II) were investigated with an aqueous feed of 0.1mol/L Cd(II) in 2.0mol/L HCl. McCabe-Thiele diagram was in good agreement with the simulation studies, showing the quantitative extraction (99.9%) of Cd(II) within two counter-current stages utilizing 0.30mol/L Cyanex 921 at O/A ratio of 3/2 in 10min. Stoichiometry of the complexes extracted was determined and confirmed by numerical treatment and graphical method, revealing the formation of HCdCl<SUB>3</SUB>.2L and HCdCl<SUB>3</SUB>.4L for Cyanex 921(L) concentration in the range 0.03-0.1mol/L and 0.1-1.0mol/L, respectively. The thermodynamic parameters for the extraction of cadmium were also determined. The stripping efficiency of cadmium from the loaded organic with 0.10mol/L HCl was 99.6% in a three-stage counter-current process at an O/A ratio of 2/3. Cyanex 921 was successfully applied for the separation of Cd(II) from Ni(II) in the simulated leach liquor of spent Ni-Cd batteries. The study demonstrates the applicability of the present hydrometallurgical approach for the treatment of hazardous waste, the spent Ni-Cd batteries.
Optimizing the thiosulfate leaching of gold from printed circuit boards of discarded mobile phone
Ha, V.H.,Lee, J.c.,Huynh, T.H.,Jeong, J.,Pandey, B.D. Elsevier 2014 Hydrometallurgy Vol.149 No.-
An environmentally benign process involving thiosulfate leaching was developed in order to recover gold from the printed circuit boards (PCBs) of discarded mobile phone. The effect of concentration of the reagents such as thiosulfate, copper(II) and ammonia on the leaching of gold was investigated in the temperature range 20-50<SUP>o</SUP>C. Parameters were optimized through modeling of the leaching process using response surface methodology (RSM) based on central composite design (CCD). The optimum conditions for leaching of gold from PCBs were identified to be 72.71mM thiosulfate, 10.0mM copper(II) and 0.266M ammonia. The initial rate of gold leaching was found to be 2.395x10<SUP>-5</SUP>mol@?m<SUP>-2</SUP>@?s<SUP>-1</SUP> under the optimum conditions. As regards the kinetics of gold leaching, the pseudo-second order kinetic model with chemical control was found to be applicable in the low concentration range (40-60mM thiosulfate, 5-7mM copper(II) and 0.22-0.247M ammonia), compared to that of pseudo-first order kinetic model at mid concentration range of the reactants viz., 60-70mM thiosulfate, 7-9mM copper(II) and 0.247-0.263M ammonia. The apparent activation energy of the reaction in the temperature range 20-50<SUP>o</SUP>C was found to be 78.6kJ@?mol<SUP>-1</SUP>. The samples were characterized before and after leaching using scanning electron microscopy (SEM) which corroborated the chemical controlled leaching mechanism.
Rana, V.K.,Pandey, Asutosh K.,Singh, Raj Pal,Kumar, B.,Mishra, Satyendra,Ha, Chang-Sik 한국고분자학회 2010 Macromolecular Research Vol.18 No.8
Chitosan films with various compositions of silver nanoparticles were prepared by solution casting with an aqueous solution of chitosan and l-lactic acid. The chitosan/Ag nanocomposites were characterized by wide angle Xray diffraction (WAXD) and UV-vis spectroscopy. An analysis of the surface topography and size of the Ag nanoparticles (${\leq}$100 nm) were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Thermogravimetric analysis (TGA/DTA) confirmed the increase in thermal stability with increasing Ag nanoparticle content in the nanocomposites. Dynamic thermal analysis (DMA) was used to examine the phase relaxation behavior of chitosan and its nanocomposites. The conductivity of chitosan/Ag nanocomposites was considered with respect to the frequency. Contact angle measurements were used to characterize the surface twistability, surface cleanliness, and hydrophilic/hydrophobic nature of the surface.
Nguyen, Nghiem V.,Jeong, Jinki,Shin, Doyun,Kim, Byung-Su,Lee, Jae-chun,Pandey, B. D. The Japan Institute of Metals 2012 Materials Transactions Vol.53 No.4
<P>This research work focused on the simultaneous recovery of gold (40.5 mg/dm<SUP>3</SUP>) and iodine (748 mg/dm<SUP>3</SUP>) from the waste rinse water of the semiconductor industry using activated carbon. A batch study was conducted to optimize process parameters, such as contact time and carbon dose, for the recovery of gold and iodine from the waste water. The loading capacity of the activated carbon for adsorption of gold and iodine was found to be 33.5 mg Au/g carbon and 835 mg I<SUB>2</SUB>/g carbon, respectively. Gold was found to exist on the activated charcoal surface in two forms: ionic gold and elemental gold. Aqua regia was used to convert metallic gold to its ionic form, and the iodine and the small amount of ionic gold were removed from the activated carbon by elution with aqua regia. Gold was recovered from the eluate by reduction with hydrazine. Iodine from the diluted aqua regia was then precipitated by adding sodium hydrosulfite (Na<SUB>2</SUB>S<SUB>2</SUB>O<SUB>4</SUB>). A complete process flow sheet was developed to recover both gold and iodine from the waste water of the semiconductor industry, which conserves the resources while meeting environmental pollution requirements.</P>
Singh, Rani,Jain, Preeti,Pandey, N.K.,Saxena, V.K.,Saxena, M.,Singh, K.B.,Ahmed, K.A.,Singh, R.P. Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.7
In the present study, the impact of Salmonella Typhimurium on cell-mediated immunity (CMI) was investigated in 5 week-old immuno divergent broiler lines selected for the high and low response to phytohemagglutinin-P. The immune response was assessed in peripheral-blood mononuclear cells (PBMCs) induced with Salmonella Typhimurium at different time intervals (0 h, 0.5 h, 2 h, 4 h, 6 h, 12 h and 24 h). The differential mRNA expression patterns of IFN-${\gamma}$, IL-2 and iNOS were evaluated by quantitative real time PCR. In-vitro production of nitric oxide (NO) was also estimated in the culture supernatant and correlated with iNOS mRNA expression. Present study showed higher production of NO in the high cell-mediated line (HCMI) as compared to the low cell-mediated line (LCMI) upon stimulation with Salmonella Typhimurium. Correspondingly, higher mRNA expression of iNOS and IFN-${\gamma}$ were observed in high response birds (HCMI); but IL-2 was down regulated in this line compared to the low response birds (LCMI). Significantly (p<0.05) higher expression of iNOS, IFN-${\gamma}$ and higher production of NO in high line indicated that the selection for PHA-P response might be employed for increasing the immune competence against Salmonella Typhimurium in chicken flocks.