Browsing by Author "Shetty K, V.K."

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Biocomposite composed of PVA reinforced with cellulose microfibers isolated from biofuel industrial dissipate: Jatropha Curcus L. seed shell
(Elsevier Ltd, 2017) Manjula, M.; Srinikethan, G.; Shetty K, V.K.
Biofuel production by Jatropha Curcas L. (JC) seeds result in large quantities of unused seed shells contributing as an extensive potential source for cellulose production. Present work consummates on isolation of cellulose microfibers (CMF) from JC seed shell by chlorination treatment and were characterized using Scanning Electron Microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and 13C NMR. Removal of hemicellulose and lignin were confirmed from FTIR results. Cellulose microfibers with diameter 0.23-1.04 ?m demonstrated considerable increase in crystallinity and thermal stability by chlorination treatment. Procured cellulose microfibers were reinforced in Poly-vinyl Alcohol (PVA) by solution casting in water to form biocomposites. Mechanical properties and thermal stability of these biocomposites increased on addition of cellulose microfiber, ensuring the potentiality of cellulose fibers as filler in biocomposites which can reinstate traditional plastics. © 2017 Published by Elsevier Ltd.
Bioleaching of copper from electronic waste using Acinetobacter sp. Cr B2 in a pulsed plate column operated in batch and sequential batch mode
(Elsevier Ltd, 2017) Jagannath, A.; Shetty K, V.K.; Saidutta, M.B.
The amount of metal content present in electronic waste (e-waste) such as printed circuit boards (PCBs) exceeds that present in rich minerals thus allowing the use of PCBs as artificial ores. The copper content in PCBs is 10-30 mass %, which is the highest among all the metallic elements. The recovery of copper from e-waste serves dual fold benefit of conservation of metal resources and overcoming environmental hazard due to e-waste accumulation. In the currently reported study, a pulsed plate bioreactor in which the inter-plate spaces were packed with e-waste material was effectively employed for bioleaching of copper from e-waste using Acinetobacter sp. Cr B2. Various factors such as inoculum size, e-waste loading, frequency and amplitude of pulsation that significantly affected the bioleaching efficiency were studied. Inoculum size of 9% (v/v), frequency of 0.2 s-1, amplitude of 6.5 cm and total e-waste loading of 40 g with 10 g/stage were found to provide maximum bioleaching of Cu. Around 23% of Cu bioleaching was achieved under these conditions by batch mode of operation. Increasing the number of sequential cycles of operation in sequential batch mode further improved the bioleaching efficiency, by overcoming the maximum copper solubility and growth limitations of the single batch operation. With five cycles of sequential batch operation around 63% leaching of Cu could be achieved. The bioleaching was found to be mediated both by the action of extracellular enzymes and metabolites. The study demonstrated the potential application of pulsed plate bioreactor for larger scale application of copper bioleaching from PCBs. © 2017 Elsevier Ltd. All rights reserved.
Partial Purification and Characterization of Chromate Reductase of a Novel Ochrobactrum sp. Strain Cr-B4
(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2015) Hora, A.; Shetty K, V.K.
Hexavalent chromium contamination is a serious problem due to its high toxicity and carcinogenic effects on the biological systems. The enzymatic reduction of toxic Cr(VI) to the less toxic Cr(III) is an efficient technology for detoxification of Cr(VI)-contaminated industrial effluents. In this regard, a chromate reductase enzyme from a novel Ochrobactrum sp. strain Cr-B4, having the ability to detoxify Cr(VI) contaminated sites, has been partially purified and characterized. The molecular mass of this chromate reductase was found to be 31.53 kD, with a specific activity 14.26 U/mg without any addition of electron donors. The temperature and pH optima for chromate reductase activity were 40°C and 8.0, respectively. The activation energy (Ea) for the chromate reductase was found to be 34.7 kJ/mol up to 40°C and the activation energy for its deactivation (Ed) was found to be 79.6 kJ/mol over a temperature range of 50-80°C. The frequency factor for activation of chromate reductase was found to be 566.79 s-1, and for deactivation of chromate reductase it was found to be 265.66 × 103 s-1. The reductase activity of this enzyme was affected by the presence of various heavy metals and complexing agents, some of which (ethylenediamine tetraacetic acid [EDTA], mercaptoethanol, NaN3, Pb2+, Ni2+, Zn2+, and Cd2+) inhibited the enzyme activity, while metals like Cu2+ and Fe3+ significantly enhanced the reductase activity. The enzyme followed Michaelis-Menten kinetics with Km of 104.29 ?M and a Vmax of 4.64 ?M/min/mg. © 2015 Taylor and Francis Group, LLC.
Photocatalytic water disinfection under solar irradiation by Ag@TiO2 core-shell structured nanoparticles
(Elsevier Ltd, 2017) Sreeja, S.; Shetty K, V.K.
The Ag core-TiO2 shell structured (Ag@TiO2) nanoparticles were found to be efficient in the disinfection of water under solar light irradiation both in free and immobilized form. Complete disinfection of 40 ? 108 CFU/mL Escherchia coli cells was achieved in 15 min by solar photocatalysis with 0.4 g/L Ag@TiO2 catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in solar disinfection. Photocatalysis rate was found to increase with increase in catalyst loading and with decrease in cell concentration. Ag@TiO2 nanoparticles showed their efficacy in the degradation of endotoxin, a harmful disinfection byproduct. Kinetics of solar disinfection with Ag@TiO2 nanoparticles followed Chick's law. The kinetics of endotoxin degradation followed zero order kinetics at high concentrations of endotoxin. However at lower concentrations, rate followed a nth order model with n = 6.99. A lower rate of photocatalytic disinfection with Ag@TiO2 nanoparticles immobilized on cellulose acetate as compared to that in their free form was observed, owing to diffusional and light penetration limitations. The re-growth of cells after photocatalytic disinfection was below the detectable limits, thus proving the potential of the process to produce safe drinking water. Ag@TiO2 nanoparticles can find potential application in solar water disinfection and the process which harnesses the solar energy may prove to be energy efficient and economical, thus can be easily adopted for large scale applications and portable drinking water treatment units for domestic applications. © 2017 Elsevier Ltd
Solar light-driven photocatalytic degradation of Anthraquinone dye-contaminated water by engineered Ag@TiO2 core–shell nanoparticles
(Bellwether Publishing, Ltd., 2015) Khanna, A.; Shetty K, V.K.
Abstract: The Ag core–TiO2 shell (Ag@TiO2) nanoparticles were synthesized by one-pot synthesis method followed by calcination and characterized using X-ray diffraction and transmission electron microscopy. The Ag@TiO2 core–shell-structured nanocatalyst was evaluated for its photocatalytic activity towards the degradation of Acid Blue-129 (AB-129), an Anthraquinone dye under solar light irradiations. The nanoparticles were engineered for efficient photocatalytic degradation of AB-129 by varying the parameters such as catalyst composition, calcination temperature, and calcination time. The catalyst composition with Ag to Ti molar ratio of 1:1.7, calcination temperature of 450°C, and time of 3 h were found to be the optimum for the efficient photocatalytic degradation of AB-129. The efficacy of Ag@TiO2 was compared with commercial TiO2, synthesized nano-TiO2, and Ag-doped TiO2 for the photocatalytic degradation of AB-129 and enhanced dye degradation was obtained with Ag@TiO2. This enhanced activity of Ag@TiO2 may be attributed to the trapping of conduction band electrons in Ag core and subsequent discharge on supply of air. Solar photocatalytic degradation of AB-129 dye using Ag@TiO2 followed Langmuir–Hinshelwood kinetics. Ag@TiO2 can be exploited as an efficient catalyst for the degradation of dye and textile industry wastewater. © 2014, © 2014 Balaban Desalination Publications. All rights reserved.
Solar photocatalytically active, engineered silver nanoparticle synthesis using aqueous extract of mesocarp of Cocos nucifera (Red Spicata Dwarf)
(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2017) Sumi, M.B.; Devadiga, A.; Shetty K, V.K.; Saidutta, M.B.
Silver nanoparticles synthesised using aqueous extract of Cocos nucifera (CN) mesocarp were evaluated for their photocatalytic activity under solar irradiation. The silver nanoparticles were synthesised by a green method of harnessing bioactive phytocomponents from the mesocarp of Cocos nucifera. Large-scale application of this process necessitates the manoeuvering of the process parameters for increasing the conversion of silver ions to nanoparticles. Process parameters influencing the morphological characteristics of silver nanoparticles such as precursor salt concentration and pH of the synthesis mixture were studied. The crystalline nanoparticles were characterised using UV-vis spectroscopy, XRD, FTIR, SEM and EDX analysis. CN extract and 5 mM silver nitrate solution at a ratio of 1:4 (v/v) in the synthesis mixture was found to be the optimum. Alkaline initial pH of the synthesis mixture was found to favour the synthesis of smaller sized monodispersed silver nanoparticles. Solar energy was harnessed for the photocatalytic degradation of Malachite green dye using silver nanoparticles obtained through the green synthesis method. Overall process aims at utilisation of naturally available resource for the synthesis of silver nanoparticles as well as the degradation of dyes using these nanoparticles, making it useful in the treatment of wastewater. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Synthesis of silver nanoparticles using medicinal Zizyphus xylopyrus bark extract
(Springer Nature, 2015) Babu, B.; Devadiga, A.; Shetty K, V.K.; Saidutta, M.B.
In the present paper, biosynthesis of silver nanoparticles using Zizyphus xylopyrus bark extract is reported. Z. xylopyrus bark extract is efficiently used for the biosynthesis of silver nanoparticles. UV–Visible spectroscopy showed surface plasmon resonance peaks in the range 413–420 nm confirming the formation of silver nanoparticles. Different factors affecting the synthesis of silver nanoparticles like methodology for the preparation of extract, concentration of silver nitrate solution used for biosynthesis and initial pH of the reaction mixture were studied. The extract prepared with 10 mM AgNO3 solution by reflux extraction method at optimum initial pH of 11, resulted in higher conversion of silver ions to silver nanoparticles as compared with those prepared by open heating or ultrasonication. SEM analysis showed that the biosynthesized nanoparticles are spherical in nature and ranged from 60 to 70 nm in size. EDX suggested that the silver nanoparticles must be capped by the organic components present in the plant extract. This simple process for the biosynthesis of silver nanoparticles using aqueous extract of Z. xylopyrus is a green technology without the usage of hazardous and toxic solvents and chemicals and hence is environment friendly. The process has several advantages with reference to cost, compatibility for its application in medical and drug delivery, as well as for large-scale commercial production. © 2014, The Author(s).