Gautam Roy Chaudhury

Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms

Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters

Kinetics of SO4−2 reduction under different growth media by sulfate reducing bacteria

Sulfate Reducing Bacteria (SRB) were used to reduce the SO4−2 concentration in waste water. The growth pattern of SRB was found by varying the concentration of nutrients and the biomass. The specific reaction constant was evaluated in each case.

Assessment of the significant parameters influencing the bio-oxidation and bio-precipitation of iron from industrial leach liquor

Abstract In the present study, iron oxidation and precipitation experiments were carried out using Acidithiobacillus ferrooxidans. Experiments were conducted in a specially designed bioreactor in batch as well as in continuous mode in order to evaluate the iron oxidation and precipitationparameters. The four basic parameters studied were pH, biomass, Fe(II) and Fe(III) concentration. Iron oxidation rate was observed to follow first order kinetics. The specific growth rate and dependence factorwere determined for each parameter. An Eh–pH diagram was developed to findout the theoretical conditions for iron precipitation. It was observed that by increasing the pH, the iron precipitation rate increased and at pH 2˙7 and 2˙9 precipitation was more than 90%. Iron oxidation and precipitation studies were carried out in a continuous mode and the processwas observed to be effective at a dilution rate of 35 ml/15 min. The technique was also tested using two different leach liquorsobtained from treating Zn tailings and lateritic nickel ore. Iron could be successfully precipitated in a crystalline form from the leach liquor using this process.

Trend in chemical composition of precipitation during 2005–2009 at a rural station of Bhubaneswar, eastern India

Precipitation samples collected during 2005–2009 from a rural forest station of Bhubaneswar were analyzed for their chemical composition. The samples were collected through a wet-only (WO) collector and two bulk (B1 and B2) collectors. The ions were evenly balanced indicating good data quality. The overall pH of rainwater was slightly acidic and ~47% of all rain events during the period were acidic (pH < 5.6). Multilinear regression analysis showed relation between the free acidity (H+) and other components in rainwater. Enrichment factors (EF) of the major components with respect to their sources such as marine and crustal were calculated. Maximum EF was observed for NO3− for both marine and crustal sources for all the three collectors. Source apportionments were also carried for the ions. Trend analysis showed continuous increase in most of the ions over years during the study period driven by anthropogenic emissions. Statistical/factorial analysis established correlation among different ions.

Use of Thiobacillus ferrooxidans for iron oxidation and precipitation

Fe(II) oxidation reaction was carried out using an acidophilic microorganism, Thiobacillus ferrooxidans. Four different parameters such as pH, Fe(II), Fe(III) and biomass concentration were studied. The oxida-tion reaction follows a pseudo first order rate equation. Apparent reaction rate constants were calculated. Unified rate equation was developed using the four parameters. Along with oxidation, a part of the iron also was precipitated. The extent of Fe(III) precipitation in each case was calculated.

Emission of nitrous oxide and methane from alluvial soil through incubation

AbstractMethane and nitrous oxide emission from alluvial soil under incubation using varying doses of urea and water content were studied for Tangibanta and Sorada. The N2O emission was observed to increase with time and tapers off after attaining the peak. The theoretical emission was evaluated using empirical equations and matches well with the experimental values. The CH4 and N2O emission both increased with the increase in Water Filled Pore Space (WFPS) and urea concentration. The nitrification and denitrification reaction rates were determined with and without acetylene. Michaelis-Menten equation was used to evaluate the Km and Vmax values. The rate of emission of N2O increased with increase of WFPS and urea concentration whereas the emission factor showed a reverse trend. The CH4 emission rate was observed to be comparatively low with respect to N2O emission rate around a factor of 10.