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Dissolution kinetics of chromite overburden by using mineral acids
Gautam Roy Chaudhury,P. K. Swain,L. B. Sukla 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.6
different mineral acids were used to determine the kinetics of dissolution of Ni and Fe from chromiteas acid concentration, pulp density, temperature and particlesize. Both Fe and Ni dissolution followed 1st order irreversible kinetics. The activation energy was also measured. Uni-fied rate equations were established for Ni and Fe dissolution for two different mineral acids, HCl and H2SO4. The dis-solution reaction was observed to follow diffusion control-dense-constant size spherical particles.
Debabrata Pradhan,Jong-Gwan Ahn,Gautam Roy Chaudhury,Seoung-Won Lee,김동진 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.5
Bioleaching of spent catalyst were carried out using Acidithiobacillus type of microorganisms. Various leaching parameters like contact time, Fe(II) concentration, particle size, pulp densities, pH and temperature were studied in details. All the four metal ions like Ni, V, Mo and Al followed dual kinetics,i.e., initial faster followed by slower rate. The leaching kinetics of Ni and V observed to be higher compared to that of Mo and Al. The thermodynamic parameters like DG, DH and DS for all metals were calculated. The leaching kinetics followed first order rate. Rates of dissolution of Al, V and Ni increased,and Mo decreased with increase of Fe(II) addition whereas that of all metals decreased with increase of pulp density and particle size. Leaching kinetics of Al, Mo, V increased with decrease of pH. Variation of initial pH of the leaching medium showed an inadequate effect on Ni dissolution. The rate determining step found to be pore diffusion controlled. The correlation between observed and theoretical values of leaching efficiency for different parameters was evaluated usingMulti-Linear Regression Analyses which showed the significance of the leaching. A total of 5 factors were evaluated by data reduction technique using Principal Component Analysis. 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Percolation bacterial leaching of low-grade chalcopyrite using acidophilic microorganisms
Karanam Srinivasa Rao,Amrita Mishra,Devbrata Pradhan,Gautam Roy Chaudhury,Birendra Kumar Mohapatra,Trupti Das,Lala Bihari Sukla,Barada Kanta Mishra 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.3
Bioleaching studies were carried out in percolation columns using low-grade copper containing rock (granite). The lixiviant consisted of acidified ferric sulfate containing acidophilic microorganisms. The iron oxidizing strain was isolated from Malanjkhand mine water and after adaptation the iron oxidation observed to be 500 mg/L/h. Leaching parameters studied were lixiviant flow rate, particle size and bed height. It was observed that leaching efficiency increased with decrease of particle size and lixiviant flow rate. The precipitation of iron during leaching observed to be low as pH was maintained at 2. Based on the leaching kinetics, a unified rate equation was developed and shown as ra(dp)[−0.61 (F)−0.76 (Hb)0.97.]수식
Dissolution Kinetics of Complex Sulfides Using Acidophilic Microorganisms
Pradhan, Debabrata,Kim, Dong Jin,Chaudhury, Gautam Roy,Sohn, Jeong Soo,Lee, Seoung Won The Japan Institute of Metals 2010 Materials transactions Vol.51 No.2
<P>Bioleaching studies were conducted to evaluate a complex sulfide concentrate using an acidophilic microorganism. The leaching kinetics were found to vary based on pulp density, Fe and pH. In addition, the leaching efficiency increased as the Fe(II) concentration increased up to 20 kg·m<SUP>−3</SUP>, after which it decreased due to an increase in iron precipitation. Furthermore, the bacterial activity was good based on observation of the iron oxidation rate and pH and Eh studies. The leaching efficiencies decreased below 2 and 5% (w/v) in the pH and pulp density studies, respectively. Furthermore, the XRD analyses revealed the presence of various product layers, while the SEM-EDX analyses showed partial contact between different sulfide minerals that resulted in formation of a galvanic couple. The dissolution rate followed a product diffusion model. The diffusivity of Fe(III) for chalcopyrite and sphalerite were calculated.</P>
Kim, Dong-Jin,Pradhan, Debabrata,Chaudhury, Gautam Roy,Ahn, Jong-Gwan,Lee, Seoung-Won The Japan Institute of Metals 2009 Materials transactions Vol.50 No.9
<P>Bacterial leaching was applied to recover metal values from complex sulfide concentrates. The leaching kinetics were observed to depend on various leaching parameters, including Fe(II) concentration, pH and pulp density. The rate of leaching decreased with increase of iron precipitation rate. The leaching results indicated good bacterial activity. A Principle Component Analysis showed all the variables can be classified into four groups which account for more than 79.7% of the variance. The four groups were described as factors like leaching kinetics, bacterial activity, leaching parameters and bacterial metabolites.</P>