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>

Recent bioreduction of hexavalent chromium in wastewater treatment: A review

Debabrata Pradhan,Lala Behari Sukla,Matthew Sawyer,Pattanathu K.S.M. Rahman 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.55 No.-

Hexavalent chromium (Cr(VI)) in water is a proven carcinogen to different internal and external organs of the living organisms. There are different human activities incorporated to the anthropogenic sources in the environment enriching Cr(VI) of high concentration in the water system above the regulatory level. The physical, chemical and biological properties of chromium favour the dissolution in the water environment. This concerns the environmental researcher to tackle and mitigate. Chemical or biological techniques or a combination of the two have been used to remove Cr(VI) from polluted waters. Biological techniques include integrated bioremediation, such as the primary processes of direct bioreduction and biosorption, and secondary processes of microbial fuel cell, biostimulation, surface modified dry biomass and biochar adsorption, and engineered biofilm and cell free reductase. These techniques are used by a wide range of living organisms including bacteria, fungi, plants, plant leaves, plant nuts and algae. This group of living organisms transform and remove Cr(VI) from water during the cellular metabolisms, extracellular activities, physical and chemical adsorptions on the cell surface, and photosynthesis. Variation of different physical, chemical and environmental parameters affecting the efficiency of the bioremediation process have impacted on the design of bioreactors. There has been a recent development of a microbial fuel cell which use the proximity of Cr(VI) reduction as a cathode half cell for the generation of renewable energy and simulation of its’ removal from water.

Kinetics and statistical behavior of metals dissolution from spent petroleum catalyst using acidophilic iron oxidizing bacteria

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.

Comparison of Bioleaching Kinetics of Spent Catalyst by Adapted and Unadapted Iron & Sulfur Oxidizing Bacteria - Effect of Pulp Density; Particle Size; Temperature

( Debabrata Pradhan ),( Dong Jin Kim ),( Jong Gwan Ahn ),( Chandra Sekhar Gahan ),( Hun Saeng Chung ),( Seoung Won Lee ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.12

Bioleaching studies of metals from a spent catalyst were conducted using both adapted and unadapted bacterial cultures. The bacterium used in this experiment was Acidithiobacillus ferrooxidans. A comparison of the kinetics of leaching was made between the two cultures by varying the leaching parameters, including the pulp density, particle size and temperature. Both cultures showed similar effects with respect to the above parameters, but the leaching rates of all metals were higher with the adapted compared to the unadapted bacterial cultures. The leaching reactions were continued for 240 h in the case of the unadapted bacterial culture, but only for 40 h in the case of the adapted bacterial culture. The leaching reactions followed first order kinetics. In addition, the kinetics of leaching was concluded to be a diffusion control model; therefore, the product layers were impervious.

Bio-dissolution of Ni, V and Mo from spent petroleum catalyst using iron oxidizing bacteria.

Pradhan, Debabrata,Kim, Dong J,Roychaudhury, Gautam,Lee, Seoung W Marcel Dekker 2010 Journal of Environmental Science and Health. Part Vol.45 No.4

<P>Bioleaching studies of spent petroleum catalyst containing Ni, V and Mo were carried out using iron oxidizing bacteria. Various leaching parameters such as Fe(II) concentration, pulp density, pH, temperature and particle size were studied to evaluate their effects on the leaching efficiency as well as the kinetics of dissolution. The percentage of leaching of Ni and V were higher than Mo. The leaching process followed a diffusion controlled model and the product layer was observed to be impervious due to formation of ammonium jarosite (NH(4))Fe(3)(SO(4))(2)(OH)(6). Apart from this, the lower leaching efficiency of Mo was due to a hydrophobic coating of elemental sulfur over Mo matrix in the spent catalyst. The diffusivities of the attacking species for Ni, V and Mo were also calculated.</P>

Effect of Ni2+, V4+ and Mo6+ concentration on iron oxidation by Acidithiobacillus ferrooxidans

Debabrata Pradhan,Jong-Gwan Ahn,Seoung-Won Lee,김동진 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.3

The ferrous oxidation ability of Acidithiobacillus ferrooxidans was studied in the presence of Ni2+, V4+ and Mo6+ in 9 K media in order to implement the culture in the bioleaching of spent catalyst. The rate of iron oxidation decreased with increasing concentration of metal ions, but the rate of inhibition was metal-ion dependent. The tolerance limit was critical at a concentration of 25 g/L Ni2+, 5 g/L V4+ and 0.03 g/L Mo6+. The growth rate of microorganisms was negligible at concentrations of 6 g/L V4+ and 0.04 g/L Mo6+. Levels and degree of toxicity of these ions have been quantified in terms of a toxicity index (TI). The toxicity order of metal ions was found to be Mo6+>V4+>Ni2+. The significance and relevance of multi-metal ion tolerance in Acidithiobacillus ferrooxidans has been highlighted with respect to bioleaching of spent refinery catalyst.

Interfacial electronic structures of metallic nanoparticles on bare- and functionalized-Au nanoisland templates, and on transition metal oxide supports

손영구,Debabrata Pradhan,K. T. Leung 한국진공학회 2011 한국진공학회 학술발표회초록집 Vol.40 No.0

AgX (X = Cl, Br, I)/BiOX nanoplates and microspheres for pure and mixed (methyl orange, rhodamine B and methylene blue) dyes

이승원,박요한,Debabrata Pradhan,손영구 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.35 No.-

The loading of AgX (X = Cl, Br and I) into BiOX nanoplates and microspheres was demonstrated, and thentheir adsorption and photocatalytic performances were studied using rhodamine B (RhB) and a morecomplicated mixed dye (methyl orange + RhB + methylene blue) system under UV and visible light. Theadsorption performances were highly dependent on morphology, nature of material, dye system, andAgX-loading. Photocatalytic activity was also found to be dependent on the wavelength of incident light. The detailed approach to a more complicated system provides new insights that can aid in design ofappropriate photocatalysts for a more complicated polluted target.

Electrical and optical properties of semiconducting camphoric carbon films

Maheshwar Sharon,Debabrata Pradhan,Yoshinori Ando,Xinluo Zhao 한국물리학회 2002 Current Applied Physics Vol.2 No.6

In situ variation in resistance of camphoric carbon versus time of pyrolysis, temperature of pyrolysis and eect of sintering arestudied to perceive the time required for the completion of pyrolysis and the activation energy from the electrical conductance plot.Variation in the electrical conductance versus temperature and activation energies derived from these measurements, are repro-ducible when lm is thermally treated below 750.C. Thermal treatment above 750.change in the conductance prole as well as decreases its band gap to 0.1 eV. Camphor pyrolyzed at 650.C gives semiconductingcarbon with optical band gaps 1 eV (direct) and 0.8 eV (indirect). Increase in pyrolysis temperature also shifts G-band of Ramanspectrum from 1605 to 1586 cm. 1 i.e., towards value corresponding to graphitic carbon. SEM micrograph of camphoric lm showsabsence of any carbon nanobeads or bers as normally observed with camphoric carbon pyrolysed in this temperature range.

Extraction of Valuable Metals from Spent Desulfurizing Catalyst

김동진,백승배,이성원,Pradhan, Debabrata,Kim, Dong-Jin,Baik, Seung-Bai,Lee, Seoung-Won 한국자원리싸이클링학회 2011 資源 리싸이클링 Vol.20 No.3

황산으로 탈황 폐촉매를 침출한 결과 황산농도 1 M, 반응시간 1 hr인 실험조건에서 Ni 및 V은 95% 이상, 그리고 Mo은 30%가 침출되었다. 탈황 폐촉매의 Mo matrix 특성으로 인하여 다른 금속에 비하여 Mo의 침출율이 낮았으며, 본 침출반응은 확산반응에 의하여 제어되는 것으로 판단된다. Mo을 완전히 침출하기 위하여 유황성분이 제거된 폐촉매로 침출실험을 실시하였다. 1M 황산으로 처리후 탄산나트륨으로 세척시 Ni, Mo 그리고 V의 침출율은 99% 이었다. Ni 2 g/L; V 9 g/L, Mo 0.6 g/L 조성의 침출액을 LIX 841로 용매추출한 조건에서 A:O 비 5:2, 2단계로 처리시 Mo은 98% 이상 추출되었으며 A:O 비 5:3, 2단계로 처리시 V은 82%가 추출되었다. Sulphuric acid leaching was conducted to extract the metal values from spent refinery catalyst. More than 95% of Ni and V and 30% of Mo could be leached out in 1 M sulphuric acid and 1 hr of leaching time. The decrease in Mo leaching was due to typical characteristic of Mo matrix. The activation energies of the leaching reactions showed the dissolution process follows a diffusion control mechanism. In order to leach out all Mo, further the leaching experiments were conducted with sulfur free spent refinery catalyst. For sulfur free spent refinery catalyst, a two step process of leaching with 1 M sulphuric acid followed by sodium carbonate washing showed better leaching than a two step leaching process with sodium carbonate followed by sulphuric acid washing, with almost 99% leaching of Ni, Mo and V. Solvent extraction using LIX 841 were conducted for a leach liquor containing Ni, 2 g/L; V, 9 g/L, Mo, 0.6 g/L. More than 98% of Mo was extracted from the leach liquor at A:O ratio of 5:2 in a 2 stage process. Similarly V was extracted at A:O ratio of 5:3 in a 2 stage process with 82% of total V extraction.