This paper projects the potential of waste beer yeast Saccharomyces cerevisiae in biosorbing lead from battery manufacturing industrial effluent. Experiments were carried out as a function of pH, biosorbent concentration, lead concentration and agitation speed. Specific lead uptake of 2.34 mg/g was recorded and the data gave good fits for Freundlich and Langmuir models with K f and Q max values of 0.5149 and 55.71 mg/g. The roles played by amines, carboxylic acids, phosphates, sulfhydryl group and lipids in lead biosorption were studied. Electrostatic attraction may be the mechanism of biosorption. The extent of contribution of the functional groups and lipids to lead biosorption was in the order: carboxylic acids > lipids > amines > phosphates. Blocking of sulfhydryl group did not have any significant effect on lead uptake.
Bioleaching of heavy metals from contaminated soil was carried out using indigenous sulfur oxidizing bacterium Acidithiobacillus thiooxidans. Experiments were carried out by varying sulfur/soil ratio from 0.03 to 0.33 to evaluate the optimum ratio for efficient bioleaching of heavy metals from soil. The influence of sulfur/soil ratio on the bioleaching efficiency was assessed based on decrease in pH, increase in oxidation-reduction potential, sulfate production and solubilization of heavy metals from the soil. Decrease in pH, increase in oxidation-reduction potential and sulfate production was found to be better with the increase in sulfur/soil ratio. While the final pH of the system with different sulfur/soil ratio was in the range of 4.1-0.7, oxidation reduction potential varied from 230 to 629 mV; sulfate production was in the range of 2,786-8,872 mg/l. Solubilization of chromium, zinc, copper, lead and cadmium from the contaminated soil was in the range of 11-99%. Findings of the study will help to optimize the ratio of sulfur/soil to achieve effective bioleaching of heavy metals from contaminated soils.
Experiments conducted by pre-treating the fermentation industrial waste biomass of Saccharomyces cerevisiae with laboratory grade chemicals like formaldehyde-formic acid, ethanol, triethyl phosphite-nitromethane, dithiopyridine and benzene helped in studying the roles played by amines, carboxylic acids, phosphates, sulfhydryl group and lipids present on the cell wall of the biomass in manganese biosorption. Potentiometric titration of S. cerevisiae revealed the presence of carboxyl, phosphate, amine groups. The extent of the contribution of the functional groups and lipids to manganese biosorption was in the order: carboxylic acids > amines > lipids > phosphates. Blocking of sulfhydryl group did not have any significant effect on manganese uptake.
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