Faculty Publications
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Item Visible light assisted photocatalytic reduction of chromium (VI) using PANI/TiO2nanocomposite from aqueous solutions(American Institute of Physics Inc., 2023) Rathna, T.; JagadeeshBabu, J.P.Polyaniline (PANI)/TiO2 composite was prepared by in-situ chemical polymerisation of aniline monomer in the presence of ammonium persulfate (APS) and Degussa P25. The setbacks of TiO2 semiconductor catalysts like low visible light exploitation and aggregation of TiO2 nanoparticles can be avoided by incorporating PANI. The electron acceptability, electrically tuneable properties, optical and photoelectrical properties, chemical and thermal stability makes the conducting PANI a key for property enhancement of catalysts. The characterisation of nanocomposite was done using Attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET), Transmission electron spectroscopy (TEM) and Thermal gravimetric (TGA) analysis. This synergic effect of PANI-TiO2 was exploited for the removal of Cr(VI) from the wastewater in this work. PANI is rich in positively charged amino groups that can potentially adsorb Cr(VI) anions and convert to less toxic Cr(III) on the catalyst's surface. Suspended PANI/TiO2 reveals the excellent conversion (99.90%) of Cr(VI) in acidic pH under visible light irradiation. The emeraldine salt form of PANI is more reactive to Cr(VI) and the conversion to emeraldine base form is the endpoint of the reduction reaction. © 2023 Author(s).Item An investigation was carried out to examine the influence of chromium content on the plane strain fracture toughness of austempered ductile iron (ADI). ADIs containing 0, 0.3 and 0.5 wt.% chromium were austempered over a range of temperatures to produce different microstructures. The microstructures were characterized by optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and correlated with microstructure and chromium content. The chromium content was found to influence the fracture toughness through its influence on the processing window. Since the chromium addition shifts the processing window to shorter durations, the higher chromium alloys at higher austempering temperatures tend to fall outside of the processing window, resulting in less than optimum microstructure and inferior fracture toughness. A small chromium addition of 0.3 wt.% was found to be beneficial for the fracture toughness of ADI. © 2002 Elsevier Science B.V. All rights reserved.(Elsevier BV, Investigations on the fracture toughness of austempered ductile iron alloyed with chromium) Prasad Rao, P.; Putatunda, S.K.2003Item Characteristics of a novel Acinetobacter sp. and its kinetics in hexavalent chromium bioreduction(2012) Narayani, M.; Shetty K, K.V.Cr-B2, a Gram-uegadve hexavalent chromium [Cr(VI)] reducing bacteria, was isolated from the aerator water of an activated sludge process in the wastewater treatment facility of a dye and pigment based chemical industry. Cr-B2 exhibited a resistance for 1,100mg/l Cr(VI) and, similarly, resistance against other heavy metal ions such as Ni2+ (800 mg/l), Cu2+ (600 mg/l), Pb2+ (1,100 mg/l), Cd2+ (350 mg/l), Zn2+ (700 mg/l), and Fe3+ (1,000 mg/l), and against selected antibiotics. Cr-B2 was observed to efficiently reduce 200mg/l Cr(VI) completely in both nutrient and LB media, and could convert Cr(VI) to Cr(III) aerobically. Cr(VI) reduction kinetics followed allosteric enzyme kinetics. The Km values were found to be 43.11 mg/l for nutrient media and 38.05 mg/l for LB media. Vmax values of 13.17 mg/l/h and 12.53 mg/l/h were obtained for nutrient media and LB media, respectively, and the cooperativity coefficients (n) were found to be 8.47 and 3.49, respectively, indicating positive cooperativity in both cases. SEM analysis showed the formation of wrinkles and depressions in the cells when exposed to 800 mg/l Cr(VI) concentration. The organism was seen to exhibit pleomorphic behavior. Cr-B2 was identified on the basis of morphological, biochemical, and partial 16S rRNA gene sequencing chracterizations and found to be Acinetobacter sp. © The Korean Society for Microbiology and Biotechnology.Item Experimental investigation and artificial neural network-based modeling of batch reduction of hexavalent chromium by immobilized cells of newly isolated strain of chromium-resistant bacteria(2012) Shetty K, K.V.; Namitha, L.; Rao, S.N.; Narayani, M.The batch bioreduction of Cr(VI) by the cells of newly isolated chromium-resistant Acinetobacter sp. bacteria, immobilized on glass beads and Ca-alginate beads, was investigated. The rate of reduction and percentage reduction of Cr(VI) decrease with the increase in initial Cr(VI) concentration, indicating the inhibitory effect of Cr(VI). Efficiency of bioreduction can be improved by increasing the bioparticle loading or the initial biomass loading. Glass bioparticles have shown better performance as compared to Ca-alginate bioparticles in terms of batch Cr(VI) reduction achieved and the rate of reduction. Glass beads may be considered as better cell carrier particles for immobilization as compared to Ca-alginate beads. Around 90% reduction of 80 ppm Cr(VI) could be achieved after 24 h with initial biomass loading of 14.6 mg on glass beads. Artificial neural networkbased models are developed for prediction of batch Cr(VI) bioreduction using the cells immobilized on glass and Ca-alginate beads. © Springer Science+Business Media B.V. 2011.Item Behavior of Alloying Elements during Electro-Slag Remelting of Ultrahigh Strength Steel(2012) Bandyopadhyay, T.R.; Rao, P.K; Prabhu, N.The paper deals with the behavior of principal constituents of an ultrahigh strength steels during ESR. The multiple analyses show no significant variation in the concentrations of silicon, manganese, vanadium, molybdenum, sulphur and phosphorus while concentrations of carbon, chromium, aluminium and titanium in the ESR ingot are found to be within the range of ± 0.01, ± 0.12, ± 0.008 and ± 0.01% respectively. Silicon and manganese show a loss of 0- 55 and 2-13% respectively whereas the degree of desulphurization is in the range of 0 (in Ar shield) to 52 (in air). The lower carbon and chromium content of the electrode than the aimed value can be corrected by adding ferrochromium in-situ during ESR. The recovery of carbon from FeCr was nearly 100% in most of the melts while the recovery of chromium varied over a fairly wide range. The distributions of carbon and chromium are also uniform along the height and width of ESR ingots. The recovery of the inoculant titanium was relatively low at the bottom of the ingot and it increases with height and reached a constant value above 100-150 mm height. For the same addition of titanium, its recovery decreases during ESR with argon shielding. © Metallurgical and Mining Industry.Item The uptake mechanism of Cd(II), Cr(VI), Cu(II), Pb(II), and Zn(II) by mycelia and fruiting bodies of Galerina vittiformis(Hindawi Publishing Corporation 410 Park Avenue, 15th Floor, 287 pmb New York NY 10022, 2013) Damodaran, D.; Mohan Balakrishnan, R.M.; Shetty K, K.Optimum concentrations of heavy metals like copper, cadmium, lead, chromium, and zinc in soil are essential in carrying out various cellular activities in minimum concentrations and hence help in sustaining all life forms, although higher concentration of these metals is lethal to most of the life forms. Galerina vittiformis, a macrofungus, was found to accumulate these heavy metals into its fleshy fruiting body in the order Pb(II) > Cd(II) > Cu(II) > Zn(II) > Cr(VI) from 50 mg/kg soil. It possesses various ranges of potential cellular mechanisms that may be involved in detoxification of heavy metals and thus increases its tolerance to heavy metal stress, mainly by producing organic acids and phytochelatins (PCs). These components help in repairing stress damaged proteins and compartmentalisation of metals to vacuoles. The stress tolerance mechanism can be deduced by various analytical tools like SEM-EDX, FTIR, and LC-MS. Production of two kinds of phytochelatins was observed in the organism in response to metal stress. © 2013 Dilna Damodaran et al.Item Reduction of hexavalent chromium by a novel Ochrobactrum sp. - microbial characteristics and reduction kinetics(Wiley-VCH Verlag, 2014) Narayani, M.; Shetty K, K.A Gram negative hexavalent chromium (Cr(VI)) reducing bacteria, Ochrobactrum sp. Cr-B4 (genbank accession number: JF824998) was isolated from the aerator water of an activated sludge process of a wastewater treatment facility of a dye and pigment based specialty chemical industry. It showed a resistance for 1000mgL-1 Cr(VI). It exhibited resistance against other heavy metal ions like Ni2+ (900mgL-1), Cu2+ (500mgL-1), Pb2+ (800mgL-1), and Cd2+(250mgL-1), Zn2+ (700mgL-1), Fe3+ (800mgL-1), and against selected antibiotics. Cr-B4 could efficiently reduce 200mgL-1 Cr(VI) completely in nutrient and LB media and could convert Cr(VI) to Cr(III) efficiently. Cr(VI) reduction in nutrient media followed allosteric enzyme kinetics with Km values of 59.39mgL-1 and Vmax values of 47.03mgL-1h-1. The reduction in LB media followed Michaelis-Menten kinetics with Km values of 99.52mgL-1 and Vmax of 77.63mgL-1h-1. Scanning electron micrograms revealed the presence of extracellular polymeric secretions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Inhibitory and stimulating effect of single and multi-metal ions on hexavalent chromium reduction by Acinetobacter sp. Cr-B2(Kluwer Academic Publishers, 2014) Hora, A.; Shetty K, V.Potential application of chromium reducing bacteria for industrial scale wastewater treatment demands that effect of presence of other metal ions on rate of Cr(VI) reduction be investigated, as industrial wastewaters contain many toxic metal ions. In the current study, the effect of different heavy metal ions (nickel, zinc, cadmium, copper, lead, iron) on chromium reduction by a novel strain of Acinetobacter sp. Cr-B2 that shows high tolerance up to 1,100 mg/L and high Cr(VI) reducing capacity was investigated. The alteration in Cr(VI) reduction capacity of Cr-B2 was studied both in presence of individual metal ions and in the presence of multi-metal ions at different concentrations. The study showed that the Cr(VI) reduction rates decreased in presence of Ni2+, Zn2+ and Cd2+ when present individually. Pb2+ at lower concentration did not show significant effect while Cu2+ and Fe3+ stimulated the rate of Cr(VI) reduction. In the studies on multi-metal ions, it was observed that in presence of Cu2+ and Fe3+, the inhibiting effect of Ni2+, Zn2+, Cd2+ and Pb2+ on Cr(VI) reduction was reduced. Each of these metals affect the overall rate of Cr(VI) reduction by Cr-B2. This work highlights the need to consider the presence of other heavy metal ions in wastewater when assessing the bioreduction of Cr(VI) and while designing the bioreactors for the purpose, as rate of reduction is altered by their presence. © 2014, Springer Science+Business Media Dordrecht.Item Hydrous Cerium Oxide Nanoparticles Impregnated Enteromorpha sp. for the Removal of Hexavalent Chromium from Aqueous Solutions(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2016) Selvasembian, S.; Selvaraju, N.; Raj Mohan, B.; Muhammed Anzil, P.K.; Amith, K.D.; Ushakumary, E.R.A novel nanobiocomposite, hydrous cerium oxide nanoparticles impregnated Enteromorpha sp. (HCONIE) was used effectively for the adsorption of Cr(VI) from aqueous solutions. The chemical and structural characteristics of the nanobiocomposite were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. Adsorption studies were determined as a function of pH, contact time, initial concentration of Cr(VI), HCONIE dose, and temperature. The equilibrium adsorption data were modeled using two parameter isotherms, including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Jovanovic, Halsey, and Harkin-Jura. Adsorption data were well described by the Freundlich and Halsey isotherm. The kinetics data were analyzed using adsorption kinetic models like the pseudo-first-order, pseudo-second-order and intraparticle diffusion equation. Kinetic data showed good agreement with the pseudo-second-order kinetic model. The obtained thermodynamic parameters showed that the adsorption of Cr(VI) onto the HCONIE was exothermic in nature. The presence of foreign ions showed a decreased effect on the adsorption capacity of HCONIE towards Cr(VI) removal. The desorption study was carried out with 0.1 and 0.5 M of three different desorbing agents. The study suggests that HCONIE nanobiocomposite could be used for the removal of Cr(VI) from aqueous solution. © 2015 American Society of Civil Engineers.Item Surface treated Pteris vittata L. pinnae powder used as an efficient biosorbent of Pb(II), Cd(II), and Cr(VI) from aqueous solution(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2018) Prabhu, S.G.; Srinikethan, G.; Hegde, S.Biosorption is a surface-dependent phenomenon. Surface modifications by chemical treatment methods could either improve or reduce the biosorption capacity of potential biosorbents. In the present work, pristine Pteris vittata L. pinnae (PPV) powder was treated separately with sodium hydroxide (NaOH), calcium chloride (CaCl2), and nitric acid (HNO3). The pristine and treated biosorbents were used to assess the biosorption of Pb(II), Cd(II), and Cr(VI) as a function of pH. Kinetics and adsorption isotherms were studied. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscope combined with energy dispersive x-ray (SEM-EDX) spectroscopic techniques were used to characterize the biosorbents before and after chemical treatments. The possible functional groups contributing to the metal sorption were identified. Results revealed favorable biosorption of Pb(II), Cd(II), and Cr(VI) described by pseudo-second order kinetics. NaOH-treated P. vittata (NPV) showed higher biosorption capacity for Pb(II) and Cd(II) compared to that of PPV. ATR-FTIR studies indicated that -OH, -COOH, and -NH2 groups were mainly involved in Cr(VI) and -OH in Pb(II) and Cd(II) biosorption. The enhanced efficiency of NPV and CaCl2 treated P. vittata (CPV) in the uptake of Pb(II) and Cd(II) compared to PPV can be associated with their altered physicochemical characters. © 2018, © 2018 Taylor & Francis Group, LLC.