Conference Papers
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Item Impact On Leaching Behaviour Of Toxic Metals In Ferrochrome Ash With Varying Ph Levels(American Institute of Physics Inc., 2022) Krishnamurthy, M.P.; Devatha, C.P.In the current investigation, leaching behaviour of cobalt (Co), copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), nickel (Ni), lead (Pb) and selenium (Se) from fresh and aged Ferrochrome Ash (FCA) samples were studied under various pH conditions (3-11). Results reveal that most of the elements follow oxyanionic leaching pattern where increase in pH increases the effluent concentration of elements. Leached As, Pb, Hg, Ni and Fe reached peak concentration at alkaline phases. Cd, Cr and Zn followed cationic leaching pattern where increase in pH decreases the concentration. Any specified pattern of leaching is not followed by Ca, Se, Co and Cu. Results of leaching test reveal that the high concentration of chromium leaching was found to be 156.18 and 155 mg/L, concentration of arsenic 13.46 and 12.89 mg/L, concentration of mercury 10.23 and 10.4 mg/L and lead concentration of 6.58 and 6.72 mg/L for fresh and aged FCA ashes respectively. Hence Cr, As, Hg and Pb are identified as significant hazardous pollutants and must not be discharged without being solidified/stabilized. Leached element concentration was not affected significantly by aging of the FCA. © 2022 American Institute of Physics Inc.. All rights reserved.Item Entrapment of Nickel in Ferrochrome Ash by Native Lysinibacilus sp Bacteria(Avestia Publishing, 2023) Kothuri, M.; Devatha, C.P.Nickel contamination in water is a significant environmental concern and causes several health effects such as allergies, cardiovascular diseases, and cancers in human beings. Ferrochrome ash is a fine dust generated as the waste from steel industry and pollutes the flow-through water by leaching nickel present in it. By providing a pre-disposal treatment of microbial induced calcite precipitation (MICP) to ferrochrome ash, the nickel leaching can be substantially reduced. Bacteria secrete the urease enzyme that decides the rate of urea hydrolysis reaction and they are the nucleation sites for the precipitation of calcium carbonate in calcium rich environment. During MICP, calcium carbonate entraps the nickel present in the ash. As a result, the nickel cannot escape the ash matrix and hence do not pollute the contacting water. This was confirmed by the atomic absorption spectrophotometric analysis (AAS) on leachates from treated and untreated ash. The analysis resulted in less nickel content from treated ash with highest treatment efficiency of 98% at LS 100. Results from SEM, FTIR, XRD, and TG implied that calcium carbonate developed in the ash due to MICP. © 2023, Avestia Publishing. All rights reserved.Item Statistical Modeling of Bacterial Statistical Modeling of Bacterial Culture Medium Composition Affecting Mineralization in Ferrochrome Ash(Springer Nature, 2024) Kothuri, M.; Devatha, C.P.Biomineralization is expected as an effective treatment technology to stabilize ferrochrome ash. It operates based on urea hydrolysis principle, and it requires an efficient medium for good bacterial growth and urease activity. An optimal medium is an ideal combination of protein, vitamin, and carbon source in the feed for bacteria. The objective of the current study is to optimize the medium and analyze the significance of its components on bacterial growth and urea hydrolysis. A central composite design (CCD) was developed with 20 experiments with different quantities of soybean (protein), yeast extract (vitamin), and dextrose (carbon) in the medium. Optical density at 600 nm and urease activity were determined after 12 h from inoculation and analyzed using response surface methodology (RSM) in Design-Expert software. Maximum urease activity of 27.83 mM of urea hydrolyzed/min and a maximum optical density of 1.92 were observed with the standard runs 4 and 10, respectively. According to the findings of the current study, the dosages of vitamin source and protein source were significantly affecting urease activity and optical density. It is inferred that the most crucial factor for optical density in the medium is protein dosage, and urease activity is vitamin dosage. Both bacterial growth and urea hydrolysis were minimally affected by the carbon dosage, suggesting that regulating the protein and vitamin doses, combined with a nominal carbon dose, results in an optimal growth medium for the biomineralization in ferrochrome ash. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.