The current study deals with Cr(VI) removal using unmodified alumina nanoparticles of two different sizes (NA1: mean hydrodynamic diameter = 75.3 ± 2.8 nm; NA2: mean hydrodynamic diameter = 229.8 ± 3.3 nm). The equilibrium adsorption capacities, 73.2 and 59.4 mg of Cr(VI)/g of adsorbent, were noted for NA1 and NA2, respectively, under optimized conditions (pH 7.0, temperature = 27 °C, initial Cr(VI) concentration = 20 mg L-1, adsorbent dosage = 0.1g L-1) but different contact times (120 min for NA1, 180 min for NA2). For both sorbents, the equilibrium adsorption data fitted well with the Langmuir isotherm model. The adsorbent NA1 followed a pseudo-second-order kinetics, whereas NA2 followed pseudo-first-order kinetics. Surface characterization studies (zeta potential measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectroscopy) substantiated oxyanionic binding on the sorbent surface. The EPR and XRD spectroscopy confirmed the existence of reduced Cr(III) on the adsorbent surface. The applicability of the sorbent in Cr(VI)-contaminated water was studied. © 2012 American Chemical Society.

Chandra Sekaran N

Centre for Nanobiotechnology

Vellore Campus

Amitava Mukherjee

Paul M.L

Samuel J

Das S.B

Swaroop S

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Industrial & Engineering Chemistry Research

The present work deals with the photocatalytic removal of Cr(VI) by zinc oxide particles. Cr(VI) removal capacity of 494.4mg/g, 369.27mg/g, and 355.59mg/g was noted in sunlight, fluorescent, and dark conditions respectively at optimized parameters (pH: 5.0, initial Cr(VI) concentration: 50mg/L, particle dosage: 10mg/L, contact time: 60min). A Langmuir isotherm model and pseudo first order kinetics were observed. The aggregation of Cr(VI) interacted ZnO particles was observed by dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results suggest the photon-assisted reduction of Cr(VI) to Cr(III) on the ZnO particle. The EDX, FTIR, and EELS indicated Cr(VI) removal by an adsorption-coupled reduction mechanism. Lower aggregation observed in the sunlight condition favoured enhanced Cr(VI) sorption compared to that in fluorescent light. Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX) confirmed the interaction of Cr(VI) on the particle surface and the electron energy loss spectroscopy (EELS) confirmed its subsequent reduction to Cr(III). The applicability of the process was studied with Cr(VI)-Cr(III) binary mixture and the multi-metal solutions. © 2015 Canadian Society for Chemical Engineering.

The Canadian Journal of Chemical Engineering

Studies on photo-assisted removal of Cr(VI) by ZnO particles

The current study deals with Cr(VI) removal using a polymer-nano metal oxide based composite film under fluorescent light condition. This was prepared by the layer-by-layer coating of chitosan/polyethylene glycol (PEG) blend, polystyrene sulphate (PSS) and nanotitania/nanoalumina mixture respectively on the glass slide. The Taguchi's orthogonal array (L25) design was employed for determining the optimal process factors (pH: 6, reaction time: 10 min and initial Cr(VI) concentration: 20 mg L-1) and the film preparation factors (dosage of PEG: 0.5v/v%, dosage of PSS: 0.25v/v%, dosage of nanotitania-nanoalumina mixture: 95:5 mg L-1). The maximum removal capacity observed at the optimal conditions was 278.9 ± 4.3 mg g -1. The SEM-EDX, XPS, FTIR-ATR spectra confirmed the photocatalytic reduction of Cr(VI) and binding of Cr(III) species on the PSS layer. A 97% regeneration of the film and a cumulative removal capacity of 2467.6 mg g -1 were observed after nine cycles of reuse. This removal capacity for chromium is about twenty fold higher than that reported by any single nanoparticle so far. © 2014 Elsevier Ltd.

Journal of Environmental Chemical Engineering

Preparation and characterization of layer-by-layer coated nano metal oxides-polymer composite film using Taguchi design method for Cr(VI) removal

Chrome mining activity has contributed intensively towards pollution of hexavalent chromium around Sukinda Valley, Orissa, India. In an attempt to study the specific contribution of exopolysaccharides (EPS) extracted from indigenous isolates towards Cr(VI) reduction, three chromium (VI) tolerant strains were isolated from the effluent mining sludge. Based on the tolerance towards Cr(VI) and EPS production capacity, one of them was selected for further work. The taxonomic identity of the selected strain was confirmed to be Enterobactercloacae (showing 98% similarity in BLAST search to E. cloacae) through 16S rRNA analysis. The EPS production was observed to increase with increasing Cr(VI) concentration in the growth medium, highest being 0. 078 at 100 mg/l Cr(VI). The extracted EPS from Enterobactercloacae SUKCr1D was able to reduce 31. 7% of Cr(VI) at 10 mg/l concentration, which was relevant to the prevailing natural concentrations at Sukinda mine effluent sludge. The FT-IR spectral studies confirmed the surface chemical interactions of hexavalent chromium with EPS. © 2011 Springer Science+Business Media B.V.

Biodegradation

Bio-reduction of Cr(VI) by exopolysaccharides (EPS) from indigenous bacterial species of Sukinda chromite mine, India

The current study focuses on the quantification and mechanistics of Cr(VI) biosorption with Acinetobacter junii, indigenous bacteria isolated from chromite mine sites of Sukinda valley, Orissa, India. The equilibrium sorption capacity 22.22, 13.88, 6.94mg of Cr(VI)g -1 of biomass was obtained for logarithmic phase, stationary phase and heat killed biomass respectively at optimum sorption conditions (pH: 2.0, contact time: 120min, temperature: 27°C, initial Cr(VI) concentration: 100mgL -1, biosorbent dosage: 2gL -1). The Langmuir isotherm model and pseudo first order (Lagergren kinetic model) were observed to hold good for the bio-sorbents. Three subsequent sorption/desorption cycles yielded 54.9, 38.4 and 34.5% regeneration of the biosorbent indicating an irreversible chromium(VI) binding property of the sorbent system. The mechanistic aspects of sorption by heat killed and log phase biomass were compared using FTIR and SEM techniques. The number of binding sites on biomass surface measured by acid/base titration (215μmolg -1 and 99μmolg -1 for logarithmic phase and heat killed biomass respectively) corroborated with the observations made by batch sorption studies. Detailed surface characterization studied through FT-IR, SEM, EDX and zeta potential measurement provided evidence for sorption through oxyanionic binding to the cell surface. The EPR spectroscopy revealed the reduction of Cr(VI) to Cr(V) on the biomass surface upon Cr(VI) sorption. © 2012 Elsevier B.V.

Chemical Engineering Journal

Comparative kinetics, equilibrium, thermodynamic and mechanistic studies on biosorption of hexavalent chromium by live and heat killed biomass of Acinetobacter junii VITSUKMW2, an indigenous chromite mine isolate

In view of increasing commercial applications of metal oxide nanoparticles their toxicity assessment becomes important. Alumina (Al2O 3) nanoparticles have wide range of applications in industrial as well as personal care products. In the absence of prior report on toxicological impact of alumina nanoparticles to microalgae, the principal objective of this study was to demonstrate the effect of the nanoparticles on microalgae isolated from aquatic environment (Scenedesmus sp. and Chlorella sp.). The growth inhibitory effect of alumina nanoparticles was observed for both the species (72 h EC50 value, 45.4 mg/L for Chlorella sp.; 39.35 mg/L for Scenedesmus sp.). Bulk alumina also showed toxicity though to a lesser extent (72 h EC50 value, 110.2 mg/L for Chlorella sp.; 100.4 mg/L for Scenedesmus sp.). A clear decrease in chlorophyll content was observed in the treated cells compared to the untreated ones, more effect being notable in the case of nanoparticles. Preliminary results based on FT-IR studies, optical and scanning electron microscopic images suggest interaction of the nanoparticles with the cell surface. © 2011 Springer Science+Business Media B.V.

Journal of Nanoparticle Research

Studies on toxicity of aluminum oxide (Al2O3) nanoparticles to microalgae species: Scenedesmus sp. and Chlorella sp.

Metal oxide nanoparticles (NPs) are known to possess strong antimicrobial properties. Aluminum oxide NPs have wide-range applications in industrial as well as personal care products. In the absence of prior reports on the antimicrobial properties of alumina NPs for a wide concentration range, the principal objective of the present work was to study the growth-inhibitory effect of alumina NPs over a wide concentration range (10-1000 μg/mL) on an environmentally relevant gram-negative model microorganism, Escherichia coli. The mean diameter of the NPs was determined to be 179 nm in aqueous dispersion used for this study, and surface area was determined to be 21.23 m2/g. The concentration of 1000 μg/mL was found to be moderately inhibitory for bacteria. Almost negligible dependence of growth rate on the concentration of the NPs was observed. The extracellular protein content was found to be slightly lower in case of cells interacting with 1000 μg/mL alumina than the uninteracted control cells. Fourier transform-infrared studies established differences in structure between interacted and uninteracted cells. Alumina NPs showed a mild growth-inhibitory effect, only at very high concentrations, which might be due to surface charge interactions between the particles and cells. Free-radical scavenging properties of the particles might have prevented cell wall disruption and drastic antimicrobial action. This laboratory-scale study suggests that alumina NPs may only exhibit mild toxicity toward microorganisms in the environment. From the Clinical Editor: Metal oxide NPs, inluding aluminum oxide NPs, are known to possess strong antimicrobial properties. The study demonstrated a mild to moderate growth-inhibitory effect of alumina NPs over a wide concentration range (10-1000 μg/mL) on Escherichia coli. Almost negligible dependence on the concentration was observed. © 2009 Elsevier Inc. All rights reserved.

Journal	Data powered by TypesetIndustrial & Engineering Chemistry Research
Publisher	Data powered by TypesetAmerican Chemical Society (ACS)
ISSN	0888-5885
Open Access	0