25 results on '"Naidu, Ravendra"'
Search Results
2. Remediation of hexavalent chromium through adsorption by bentonite based Arquad 2HT-75 organoclays
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Sarkar, Binoy, Xi, Yunfei, Mallavarapu, Megharaj, Krishnamurti, G.S.R., Dharmarajan, Rajarathnam, Naidu, Ravendra, Sarkar, Binoy, Xi, Yunfei, Mallavarapu, Megharaj, Krishnamurti, G.S.R., Dharmarajan, Rajarathnam, and Naidu, Ravendra
- Abstract
Unlike hydrophobic organic pollutants, the potential of organoclays to adsorb inorganic ionic contaminants is relatively underexplored. The present study attempts to characterise bentonite (QB) based organoclays synthesised from a commercially available, low-cost alkyl ammonium surfactant Arquad® 2HT-75 (Aq) and test their ability to adsorb hexavalent chromium (Cr (VI)) in aqueous solution. XRD, FTIR and TGA characterisation techniques prove successful modification of the bentonite structure and reveal that higher surfactant loadings gives rise to more ordered surfactant conformation in the organoclays. The zeta potential values indicate that higher surfactant loadings also create positive charges on the organoclay surfaces. Detailed isothermal and kinetic studies show that the organoclays effectively remove hexavalent chromium (Cr (VI)) from aqueous solution by both physical and chemical adsorption processes. Higher surfactant loadings provide better adsorption efficiency. The adsorption performance is reasonably efficient under the levels of pH, temperature, electrolyte concentration and natural organic matter concentration that generally prevail in contaminated soil and water. This study shows that organoclay sorbents offer good potential for remediating Cr (VI) under real environmental conditions.
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- 2010
3. Sorption of quaternary ammonium compounds in soils: Implications to the soil microbial activities
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Sarkar, Binoy, Mallavarapu, Megharaj, Xi, Yunfei, Krishnamurti, G.S.R., Naidu, Ravendra, Sarkar, Binoy, Mallavarapu, Megharaj, Xi, Yunfei, Krishnamurti, G.S.R., and Naidu, Ravendra
- Abstract
Despite their widespread use in household activities and various industries, information on the toxicity of quaternary ammonium compounds (QACs) to microbial activities in soil is scant. This study investigated the effect of three commonly used QACs namely hexadecyltrimethyl ammonium bromide (HDTMA), octadecyltrimethyl ammonium bromide (ODTMA) and Arquad on dehydrogenase and potential nitrification activities in three different soils. The toxicity of QACs on the dehydrogenase activity and potential nitrification in these soils followed the order: HDTMA > ODTMA > Arquad and Arquad > HDTMA > ODTMA, respectively. HDTMA, ODTMA and Arquad exhibited toxicity to dehydrogenase activity at concentration of 50, 100 and 750 mg kg−1 soil, respectively, whereas potential nitrification was inhibited by HDTMA and ODTMA even at 50 mg kg−1 soil. Arquad exhibited toxicity to potential nitrification at comparatively higher concentration of 250 mg kg−1 soil, with the severity of toxicity very intense at higher concentrations. The nature of QACs and soil properties influenced the toxicity. The toxic effect of QACs on soil microbial activities was more influenced by the relative release of sorbed QACs in soils. This study provides valuable information on the toxicological properties of some widely used QACs on important soil microbial activity parameters. To our knowledge, this is the first report.
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- 2010
4. Bioavailability : definition, assessment and implications for risk assessment.
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Hartemink, A. E., McBratney, A. B., Naidu, Ravendra, Naidu, R., Semple, Kirk T., Megharaj, M., Juhasz, A. L., Bolan, N. S., Gupta, S. K., Clothier, B. E., Schulin, R., Hartemink, A. E., McBratney, A. B., Naidu, Ravendra, Naidu, R., Semple, Kirk T., Megharaj, M., Juhasz, A. L., Bolan, N. S., Gupta, S. K., Clothier, B. E., and Schulin, R.
- Published
- 2008
5. Bioremediation approaches for organic pollutants: A critical perspective
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Kadiyala Venkateswarlu, Balasubramanian Ramakrishnan, Mallavarapu Megharaj, N. Sethunathan, Ravi Naidu, Mallavarapu, Megharaj, Balasubramanian, Ramakrishnan, Kadiyala, Venkateswarlu, Nambrattil, Sethunathan, and Naidu, Ravendra
- Subjects
organic pollutants ,Environmental remediation ,Environmental pollution ,limitations ,Bioremediation ,rhizoremediation ,electrobioremediation ,Soil Pollutants ,Organic Chemicals ,Pesticides ,GEMs ,Soil Microbiology ,lcsh:Environmental sciences ,General Environmental Science ,Pollutant ,lcsh:GE1-350 ,Waste management ,bioremediation approaches ,Aquatic ecosystem ,Biodegradation ,Contamination ,Phytoremediation ,Biodegradation, Environmental ,Petroleum ,Environmental science ,Environmental Pollution - Abstract
Due to human activities to a greater extent and natural processes to some extent, a large number of organic chemical substances such as petroleum hydrocarbons, halogenated and nitroaromatic compounds, phthalate esters, solvents and pesticides pollute the soil and aquatic environments. Remediation of these polluted sites following the conventional engineering approaches based on physicochemical methods is both technically and economically challenging. Bioremediation that involves the capabilities of microorganisms in the removal of pollutants is the most promising, relatively efficient and cost-effective technology. However, the current bioremediation approaches suffer from a number of limitations which include the poor capabilities of microbial communities in the field, lesser bioavailability of contaminants on spatial and temporal scales, and absence of bench-mark values for efficacy testing of bioremediation for their widespread application in the field. The restoration of all natural functions of some polluted soils remains impractical and, hence, the application of the principle of function-directed remediation may be sufficient to minimize the risks of persistence and spreading of pollutants. This review selectively examines and provides a critical view on the knowledge gaps and limitations in field application strategies, approaches such as composting, electrobioremediation and microbe-assisted phytoremediation, and the use of probes and assays for monitoring and testing the efficacy of bioremediation of polluted sites. Keywords: Bioremediation approaches, Organic pollutants, Electrobioremediation, GEMs, Rhizoremediation, Limitations
- Published
- 2011
6. The use of molecular techniques to characterize the microbial communities in contaminated soil and water
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Michael Beer, Seidu Malik, Mallavarapu Megharaj, Ravi Naidu, Malik, Seidu, Beer, Michael John, Mallavarapu, Megharaj, and Naidu, Ravendra
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Microorganism ,Population ,water ,microbial identification ,microbial communities ,Biology ,biodegradation ,Bioremediation ,education ,Water pollution ,Phospholipids ,Soil Microbiology ,lcsh:Environmental sciences ,General Environmental Science ,lcsh:GE1-350 ,education.field_of_study ,Ecology ,Community structure ,DNA ,Biodegradation ,Soil contamination ,Microbial population biology ,Genetic Techniques ,RNA, Ribosomal ,Environmental chemistry ,contaminated soil ,Environmental Pollution ,Water Microbiology ,molecular techniques - Abstract
Traditionally, the identification and characterization of microbial communities in contaminated soil and water has previously been limited to those microorganisms that are culturable. The application of molecular techniques to study microbial populations at contaminated sites without the need for culturing has led to the discovery of unique and previously unrecognized microorganisms as well as complex microbial diversity in contaminated soil and water which shows an exciting opportunity for bioremediation strategies. Nucleic acid extraction from contaminated sites and their subsequent amplification by polymerase chain reaction (PCR) has proved extremely useful in assessing the changes in microbial community structure by several microbial community profiling techniques. This review examines the current application of molecular techniques for the characterization of microbial communities in contaminated soil and water. Techniques that identify and quantify microbial population and catabolic genes involved in biodegradation are examined. In addition, methods that directly link microbial phylogeny to its ecological function at contaminated sites as well as high throughput methods for complex microbial community studies are discussed. Keywords: Molecular techniques, Microbial communities, Contaminated soil, Water, Microbial identification, Biodegradation
- Published
- 2008
7. One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II.
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Luo F, Yang D, Chen Z, Megharaj M, and Naidu R
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- Adsorption, Catalysis, Environmental Restoration and Remediation, Hydrogen-Ion Concentration, Kinetics, Plant Extracts chemistry, Plant Leaves chemistry, Temperature, Vitis chemistry, Azo Compounds chemistry, Benzenesulfonates chemistry, Coloring Agents chemistry, Iron chemistry, Lead chemistry, Nanoparticles chemistry
- Abstract
To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe(2+) and Pd(2+), had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography-Mass Spectrum (HPLC-MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation., (Copyright © 2015 Elsevier B.V. All rights reserved.)
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- 2016
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8. Novel methodologies for automatically and simultaneously determining BTEX components using FTIR spectra.
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Wang L, Liu E, Cheng Y, Bekele DN, Lamb D, Chen Z, Megharaj M, and Naidu R
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- Automation, Benzene Derivatives chemistry, Filtration, Neural Networks, Computer, Petroleum analysis, Time Factors, Volatilization, Benzene Derivatives analysis, Spectroscopy, Fourier Transform Infrared methods
- Abstract
This study introduced a patented novel methodological system for automatically analysis of Fourier Transform Infrared Spectrometer (FTIR) spectrum data located at 'fingerprint' region (wavenumber 670-800 cm(-1)), to simultaneously determinate multiple petroleum hydrocarbons (PHs) in real mixture samples. This system includes: an object oriented baseline correction; Band decomposition (curve fitting) method with mathematical optimization; and Artificial Neural Network (ANN) for determination, which is suitable for the characteristics of this IR regions, where the spectra are normally with low signal to noise ratio and high density of peaks. BTEX components are potentially lethal carcinogens and contained in many petroleum products. As a case study, six BTEX components were determinate automatically and simultaneously in mixture vapor samples. The robustness of the BTEX determination was validated using real petroleum samples, and the prediction results were compared with gas chromatography-mass spectrometry (GC-MS)., (Copyright © 2015 Elsevier B.V. All rights reserved.)
- Published
- 2015
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9. The mechanism for degrading Orange II based on adsorption and reduction by ion-based nanoparticles synthesized by grape leaf extract.
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Luo F, Yang D, Chen Z, Megharaj M, and Naidu R
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- Adsorption, Green Chemistry Technology, Models, Theoretical, Plant Leaves chemistry, Azo Compounds isolation & purification, Benzenesulfonates isolation & purification, Environmental Pollutants isolation & purification, Environmental Restoration and Remediation methods, Nanoparticles chemistry, Plant Extracts chemistry, Vitis chemistry
- Abstract
Biomolecules taken from plant extracts have often been used in the single-step synthesis of iron-based nanoparticles (Fe NPs) due to their low cost, environmental safety and sustainable properties. However, the composition of Fe NPs and the degradation mechanism of organic contaminants by them are limited because these are linked to the reactivity of Fe NPs. In this study, Fe NPs synthesized by grape leaf extract served to remove Orange II. Batch experiments showed that more than 92% of Orange II was removed by Fe NPs at high temperature based on adsorption and reduction and confirmed by kinetic studies. To understand the role of Fe NPs in the removal process of azo dye, surface analysis via X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were employed, showing that the Fe NPs were composed of biomolecules, hydrous iron oxides and Fe(0), thus providing evidence for the adsorption of Orange II onto hydrous iron oxides and its reduction by Fe(0). Degraded products such as 2-naphthol were identified using LC-MS analysis. A degradation mechanism based on asymmetrical azo bond cleavage for the removal of Orange II was proposed., (Copyright © 2015 Elsevier B.V. All rights reserved.)
- Published
- 2015
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10. Inhibition or promotion of biodegradation of nitrate by Paracoccus sp. in the presence of nanoscale zero-valent iron.
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Jiang C, Xu X, Megharaj M, Naidu R, and Chen Z
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- Biodegradation, Environmental, Nitrates chemistry, Soil Pollutants metabolism, Iron chemistry, Metal Nanoparticles chemistry, Nitrates metabolism, Paracoccus physiology, Soil Pollutants chemistry
- Abstract
To investigate the effect of nanoscale zero-valent iron (nZVI) on the growth of Paracoccus sp. strain and biodenitrification under aerobic conditions, specific factors were studied, pH, concentration of nitrate, Fe (II) and carbon dioxide. Low concentration of nZVI (50mg/L) promoted both cell growth and biodegradation of nitrate which rose from 69.91% to 76.16%, while nitrate removal fell to 67.10% in the presence of high nZVI concentration (1000 mg/L). This may be attributed to the ions produced in nZVI corrosion being used as an electron source for the biodegradation of nitrate. However, the excess uptake of Fe (II) causes oxidative damage to the cells. To confirm this, nitrate was completely removed after 20 h when 100mg/L Fe (II) was added to the solution, which is much faster than the control (86.05%, without adding Fe (II)). However, nitrate removal reached only 45.64% after 20 h, with low cell density (OD 600=0.62) in the presence of 300 mg/L Fe (II). Characterization techniques indicated that nZVI adhered to microorganism cell membranes. These findings confirmed that nZVI could affect the activity of the strain and consequently change the biodenitrification., (Copyright © 2015 Elsevier B.V. All rights reserved.)
- Published
- 2015
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11. Green synthesized conditions impacting on the reactivity of Fe NPs for the degradation of malachite green.
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Huang L, Luo F, Chen Z, Megharaj M, and Naidu R
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- Hydrogen-Ion Concentration, Metal Nanoparticles ultrastructure, Plant Extracts chemistry, Solutions, Spectrophotometry, Ultraviolet, Spectroscopy, Fourier Transform Infrared, Tea chemistry, Temperature, X-Ray Diffraction, Green Chemistry Technology methods, Iron chemistry, Metal Nanoparticles chemistry, Rosaniline Dyes chemistry
- Abstract
This study investigates green tea extract synthesized conditions impacting on the reactivity of iron nanoparticles (Fe NPs) used for the degradation of malachite green (MG), including the volume ratio of Fe(2+) and tea extract, the solution pH and temperature. Results indicated that the reactivity of Fe NPs increased with higher temperature, but fell with increasing pH and the volume ratio of Fe(2+) and tea extract. Scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), Fourier transform infrared spectroscope (FTIR) and X-ray diffraction (XRD) indicated that Fe NPs were spherical in shape, their diameter was 70-80 nm and they were mainly composed of iron oxide nanoparticles. UV-visible (UV-vis) indicated that reactivity of Fe NPs used in degradation of MG significantly depended on the synthesized conditions of Fe NPs. This was due to their impact on the reactivity and morphology of Fe NPs. Finally, degradation of MG showed that 90.56% of MG was removed using Fe NPs., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2015
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12. Application of neural networks with novel independent component analysis methodologies to a Prussian blue modified glassy carbon electrode array.
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Wang L, Yang D, Fang C, Chen Z, Lesniewski PJ, Mallavarapu M, and Naidu R
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- Agricultural Irrigation, Biosensing Techniques, Calibration, Coloring Agents chemistry, Electrochemical Techniques, Molecular Imprinting, Principal Component Analysis, Algorithms, Carbon chemistry, Electrodes, Ferrocyanides chemistry, Glass chemistry, Neural Networks, Computer, Water Pollutants, Chemical analysis
- Abstract
Sodium potassium absorption ratio (SPAR) is an important measure of agricultural water quality, wherein four exchangeable cations (K(+), Na(+), Ca(2+) and Mg(2+)) should be simultaneously determined. An ISE-array is suitable for this application because its simplicity, rapid response characteristics and lower cost. However, cross-interferences caused by the poor selectivity of ISEs need to be overcome using multivariate chemometric methods. In this paper, a solid contact ISE array, based on a Prussian blue modified glassy carbon electrode (PB-GCE), was applied with a novel chemometric strategy. One of the most popular independent component analysis (ICA) methods, the fast fixed-point algorithm for ICA (fastICA), was implemented by the genetic algorithm (geneticICA) to avoid the local maxima problem commonly observed with fastICA. This geneticICA can be implemented as a data preprocessing method to improve the prediction accuracy of the Back-propagation neural network (BPNN). The ISE array system was validated using 20 real irrigation water samples from South Australia, and acceptable prediction accuracies were obtained., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2015
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13. Green synthesis of iron nanoparticles by various tea extracts: comparative study of the reactivity.
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Huang L, Weng X, Chen Z, Megharaj M, and Naidu R
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- Adsorption, Benzene chemistry, Caffeine chemistry, Kinetics, Microscopy, Electron, Scanning, Oxygen chemistry, Polyphenols chemistry, Rosaniline Dyes chemistry, Spectrophotometry, Ultraviolet, X-Ray Diffraction, Green Chemistry Technology, Iron chemistry, Metal Nanoparticles chemistry, Nanotechnology, Tea chemistry
- Abstract
Iron nanoparticles (Fe NPs) are often synthesized using sodium borohydride with aggregation, which is a high cost process and environmentally toxic. To address these issues, Fe NPs were synthesized using green methods based on tea extracts, including green, oolong and black teas. The best method for degrading malachite green (MG) was Fe NPs synthesized by green tea extracts because it contains a high concentration of caffeine/polyphenols which act as both reducing and capping agents in the synthesis of Fe NPs. These characteristics were confirmed by a scanning electron microscope (SEM), UV-visible (UV-vis) and specific surface area (BET). To understand the formation of Fe NPs using various tea extracts, the synthesized Fe NPs were characterized by SEM, X-ray energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). What emerged were different sizes and concentrations of Fe NPs being synthesized by tea extracts, leading to various degradations of MG. Furthermore, kinetics for the degradation of MG using these Fe NPs fitted well to the pseudo first-order reaction kinetics model with more than 20 kJ/mol activation energy, suggesting a chemically diffusion-controlled reaction. The degradation mechanism using these Fe NPs included adsorption of MG to Fe NPs, oxidation of iron, and cleaving the bond that was connected to the benzene ring., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2014
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14. Burkholderia vietnamiensis C09V as the functional biomaterial used to remove crystal violet and Cu(II).
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Zhou F, Cheng Y, Gan L, Chen Z, Megharaj M, and Naidu R
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- Biodegradation, Environmental, Industrial Waste, Water Pollutants, Chemical, Burkholderia metabolism, Copper metabolism, Gentian Violet metabolism, Water Purification methods
- Abstract
Burkholderia vietnamiensis C09V (B.V. C09V) was used to remove both crystal violet (CV) and Cu(II) because dye effluents often contain dyes and metal ions. Inhibiting the strain׳s growth through the biosorption of Cu(II) on B.V. C09V and promoting its growth by using CV as a carbon source led to the degradation of CV (30mg/L). It fell to 36.9 percent and the amount of Cu(II) (50mg/L) removed rose to 34.9 percent in the presence of both CV and Cu(II). This outcome is comparable to the single presence of CV and Cu(II). EDS analysis showed that Cu(II) was adsorbed onto the strain (the atomic percentage of Cu(II) was 1.9 percent), while kinetic studies indicated that firstly, the decolorization of CV fitted well to the pseudo first-order degradation kinetic model and secondly, the biosorption of Cu(II) fitted well to the pseudo second-order kinetic model. The degradation rate constants of CV were stable in the 0.101-0.0068/h range and R(2) was both higher than 0.981 when Cu(II) concentrations were present. Furthermore, the biosorption capacity of Cu(II) ranged from 38.8 to 20.3mg/g at the CV concentration of 30mg/L (both R(2)>0.96). This suggests that the strain has the potential to degrade CV and facilitate the biosorption of Cu(II) in dye effluent., (Copyright © 2014 Elsevier Inc. All rights reserved.)
- Published
- 2014
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15. Synthesis of iron-based nanoparticles using oolong tea extract for the degradation of malachite green.
- Author
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Huang L, Weng X, Chen Z, Megharaj M, and Naidu R
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- Microscopy, Electron, Scanning, Spectrometry, X-Ray Emission, Spectrophotometry, Ultraviolet, Spectroscopy, Fourier Transform Infrared, X-Ray Diffraction, Coloring Agents metabolism, Iron chemistry, Metal Nanoparticles chemistry, Plant Extracts chemistry, Plant Leaves chemistry, Rosaniline Dyes metabolism, Tea chemistry
- Abstract
Iron-based nanoparticles (OT-FeNP) were synthesized using oolong tea extracts. Their morphology, structure and size were confirmed by scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-visible (UV-vis) and Fourier Transform Infrared spectroscopy (FTIR). Formation of FeNP results in mostly spherical particles with diameters ranging from 40 to 50 nm. Degradation of malachite green (MG) using OT-FeNP demonstrated that kinetics fitted well to the pseudo first-order reaction by removing 75.5% of MG (50 mg/L). This indicated that OT-FeNP has the potential to serve as a green nanomaterial for environmental remediation., (Copyright © 2013 Elsevier B.V. All rights reserved.)
- Published
- 2014
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16. Green synthesis of Fe nanoparticles using eucalyptus leaf extracts for treatment of eutrophic wastewater.
- Author
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Wang T, Jin X, Chen Z, Megharaj M, and Naidu R
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- Animals, China, Microscopy, Electron, Scanning, Plant Leaves chemistry, Spectrometry, X-Ray Emission, Spectroscopy, Fourier Transform Infrared, Swine, Wastewater analysis, X-Ray Diffraction, Eucalyptus chemistry, Iron chemistry, Metal Nanoparticles chemistry, Plant Extracts chemistry, Waste Disposal, Fluid methods
- Abstract
Iron nanoparticles were firstly synthesized through a one-step room-temperature biosynthetic route using eucalyptus leaf extracts (EL-Fe NPs). Scanning electron microscopy (SEM) and X-ray energy-dispersive spectrometer (EDS) confirmed the successful synthesis of the spheroidal iron nanoparticles. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared spectrometer (FTIR) indicated that some polyphenols are bound to the surfaces of EL-Fe NPs as a capping/stabilizing agent. Reactivity of EL-Fe NPs was evaluated for the treatment of swine wastewater and results indicated that 71.7% of total N and 84.5% of COD were removed, respectively. This demonstrated the tremendous potential of EL-Fe NPs for in situ remediation of eutrophic wastewater., (© 2013.)
- Published
- 2014
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17. Functional clay supported bimetallic nZVI/Pd nanoparticles used for removal of methyl orange from aqueous solution.
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Wang T, Su J, Jin X, Chen Z, Megharaj M, and Naidu R
- Subjects
- Color, Metal Nanoparticles chemistry, Waste Disposal, Fluid methods, Azo Compounds chemistry, Bentonite chemistry, Coloring Agents chemistry, Iron chemistry, Palladium chemistry, Water Pollutants, Chemical chemistry
- Abstract
Bentonite supported Fe/Pd nanoparticles (B/nZVI/Pd) were synthesized as composites that exhibit functionalities assisting in the removal of methyl orange (MO) from aqueous solution. The results showed that 91.87% of MO was removed using B/nZVI/Pd, while only 85% and 1.41% of MO were removed using nZVI/Pd and bentonite after 10 min, respectively. The new findings include that the presence of bentonite decreased the aggregation of nZVI/Pd and nZVI in the composite played its role as a reductant, while Pd(0) acted as the catalyst to enhance the degradation of MO, which were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis analysis and the batch experiments. The increase in B/nZVI/Pd loading led to greater removal efficiency, while decolorization efficiency declined in the presence of anions such as nitrate, sulfite and carbonate, especially nitrate, which decreased the apparent rate constant k(obs) almost 17.06-fold. The kinetics study indicated that the degradation of MO fitted well to the pseudo-first-order model, where the k(obs) was 0.0721 min(-1). Finally, the reactivity of aged B/nZVI/Pd was investigated, and the application of B/nZVI/Pd in wastewater indicated a removal efficiency higher than 93.75%. This provided a new environmental pollution management option for dyes-contaminated sites., (Copyright © 2013 Elsevier B.V. All rights reserved.)
- Published
- 2013
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18. Speciation of glyphosate, phosphate and aminomethylphosphonic acid in soil extracts by ion chromatography with inductively coupled plasma mass spectrometry with an octopole reaction system.
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Chen Z, He W, Beer M, Megharaj M, and Naidu R
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- Chromatography methods, Glycine analysis, Helium, Ions, Isoxazoles, Mass Spectrometry methods, Tetrazoles, Glyphosate, Glycine analogs & derivatives, Organophosphonates analysis, Phosphates analysis, Soil analysis
- Abstract
Ion-pairing chromatography coupled with inductively coupled plasma mass spectrometry (ICP-MS) used for the speciation of phosphorus is limited as the mobile phase containing organic solvents changes in detection sensitivity and the carbon precipitates on torch and cones. To address this issue, anion-exchange chromatography with ICP-MS has been used for the speciation of glyphosate, phosphate and aminomethylphosphonic acid in soil extracts. The separation of the targets on a new column was achieved within 5 min using an eluent containing 20 mM NH(4)NO(3) at pH 5.1. Furthermore, since the polyatomic ions such as (14)N(16)O(1)H(+) and (15)N(16)O(+) from a nitrogen-based ion-pairing reagent interfered with ICP-MS detection of (31)P, an octopole reaction system was investigated to determine whether the polyatomic interferences could be reduced. The results show that addition of He to the cell can benefit analyses by reducing such interferences, but at the expense of reduced sensitivity. The detection limits in the range of 1.0-1.5 microg L(-1) (expressed as P) was achieved when 50 microL was injected using He as the collusion gas.
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- 2009
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19. Removal of interferences in the speciation of chromium using an octopole reaction system in ion chromatography with inductively coupled plasma mass spectrometry.
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Chen Z, Megharaj M, and Naidu R
- Abstract
When inductively coupled plasma mass spectrometry (ICP-MS) is used for the detection of (52)Cr (83.8%) species in ion chromatography (IC), interference from polyatomic ions such as (40)Ar(12)C(+) and (35)Cl(16)O(1)H(+), often occurs due to their mass at m/z 52. To address the issue, an octopole reaction system (ORS) in ICP-MS, including He and H(2) modes, was used to determine whether the background and interference from polyatomic ions could be reduced in the detection of (52)Cr. Compared to standard mode, the polyatomic ions were reduced by either He or H(2); for example, more than 97 and 98% of (35)Cl was removed using a He and H(2) tune, respectively. However, the detection sensitivity for (52)Cr was decreased, for example, the sensitivity was 27.95 and 67.02% of the standard mode for Cr(EDTA)(2)(-)using a He and H(2) tune, respectively. The H(2) tune is recommended for the detection of (52)Cr at a flow rate of 2.0mL/min with detection limits in the range of 0.2-0.4mug/L. The developed method was used to measure chromium speciation in waters containing high concentration of chloride.
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- 2007
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20. Confirmation of lead aminocarboxylic complex formation using electrospray ionization mass spectrometry and speciation by anion-exchange chromatography coupled with ICP-MS.
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Chen Z, Owens G, Kim KR, and Naidu R
- Abstract
Inductively coupled plasma mass spectrometry (ICP-MS) and electrospray ionization mass spectrometry (ESI-MS) were used as complementary techniques to provide element and molecular information for aminocarboxylic lead species including [Pb(NTA)]1-, [Pb(HEDTA)]1-, [Pb(EDTA)]2- and [Pb(DTPA)]3-. ESI-MS was used to initially confirm the formation of lead aminocarboxylic complexes in solution and subsequently anion-change chromatography coupled with ICP-MS was used to speciate these complexes using a mobile phase containing 30 mM NH4H2PO4 at pH of 8.0. However, [Pb(NTA)]1- was not observed during chromatographic separation due to its poor stability. The species [Pb(HEDTA)]1-, [Pb(EDTA)]2- and [Pb(DTPA)]3- were separated within 15 min with reasonable resolution and detection limits ranging from 0.05 to 0.2 microg L(-1) with simple direct injection of sample. The proposed method was used to speciate aminocarboxylic lead complexes in soil solution.
- Published
- 2007
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21. Speciation of iodate and iodide in seawater by non-suppressed ion chromatography with inductively coupled plasma mass spectrometry.
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Chen Z, Megharaj M, and Naidu R
- Abstract
A non-suppressed ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for simultaneous determination of trace iodate and iodide in seawater. An anion-exchange column (G3154A/101, provided by Agilent) was used for the separation of iodate and iodide with an eluent containing 20mM NH(4)NO(3) at pH 5.6, which reduced the build-up of salts on the sampler and skimmer cones. The influences of competing ion (NO(3)(-)) in the eluent on the retention time and detection sensitivity were investigated to give reasonable resolution and detection limits. Linear plots were obtained in a concentration range of 5.0-500 microg/L and the detection limit was 1.5 microg/L for iodate and 2.0 microg/L for iodide. The proposed method was used to determinate iodate and iodide in seawaters without sample pre-treatment with exception of dilution.
- Published
- 2007
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22. Speciation of chromium in waste water using ion chromatography inductively coupled plasma mass spectrometry.
- Author
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Chen Z, Megharaj M, and Naidu R
- Abstract
Ion chromatography (IC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was systematically investigated for determining the speciation of chromium in environmental samples. Firstly, the stability of complexes formed by Cr(III) with various aminopolycarboxylic acids was studied by electrospray ionization mass spectrometry (ESI-MS). The results showed that [Cr(EDTA)](-) was stable in solution. Secondly, various mobile phases were examined to separate Cl(-) from chromium species by IC to avoid Cl(-) interference. The separation of [Cr(EDTA)](-) and Cr(VI) was achieved on a new anion-exchange column (G3154A/102) using a mobile phase containing 20mM NH(4)NO(3) and 10mM NH(4)H(2)PO(4) at pH 7.0 without Cl(-) interference. Detection limits for chromium species were below 0.2 microg/L with a direct injection of sample and without prior removal of interferences from the matrix. Finally, the proposed method was used for the determination of chromium species in contaminated waters.
- Published
- 2007
- Full Text
- View/download PDF
23. Confirmation of vanadium complex formation using electrospray mass spectrometry and determination of vanadium speciation by sample stacking capillary electrophoresis.
- Author
-
Chen Z, Owens G, and Naidu R
- Subjects
- Acetic Acid chemistry, Edetic Acid chemistry, Egtazic Acid chemistry, Electrochemistry methods, Ethylenediamines chemistry, Hydrogen-Ion Concentration, Ions, Ligands, Nitrilotriacetic Acid chemistry, Pentetic Acid chemistry, Sensitivity and Specificity, Temperature, Vanadium chemistry, Electrophoresis, Capillary methods, Spectrometry, Mass, Electrospray Ionization methods, Vanadium analysis
- Abstract
Capillary zone electrophoresis (CZE) with UV detection was used to determine vanadium species. Nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA) and 2,6-pyridinedicarboxylic acid (PDCA) were investigated to determine whether these ligands formed stable anionic complexes with vanadium. Of all the ligands studied HEDTA was the most suitable ligand because it gave the largest UV response with reasonable migration time. Electrospray mass spectrometry (ES-MS) was used to confirm the formation of [VO(2)(HEDTA)](2-) and [VO(HEDTA)](1-) in solution. An electrolyte containing 25 mM phosphate, 0.25 mM tetradecyltrimethylammonium bromide (TTAB) at pH 5.5 was optimum for the separation of these anionic vanadium complexes. Sample stacking techniques, including large-volume sample stacking (LVSS) and field-amplified sample injection (FASI), were tested to improve the sensitivity. Best sensitivity was obtained using FASI, with detection limits of 0.001 microM, equivalent to 0.4 microg L(-1), for [VO(2)(HEDTA)](2-) and 0.01 microM, equivalent to 3.4 microg L(-1) for [VO(HEDTA)](1-). The utility of the method for the speciation of V(IV) and V(V) was demonstrated using ground water samples.
- Published
- 2007
- Full Text
- View/download PDF
24. On-column complexation capillary electrophoretic separation of Fe2+ and Fe3+ using 2,6-pyridinedicarboxylic acid coupled with large-volume sample stacking.
- Author
-
Chen Z and Naidu R
- Subjects
- Hydrogen-Ion Concentration, Picolinic Acids, Reproducibility of Results, Sensitivity and Specificity, Spectrophotometry, Ultraviolet, Electrophoresis, Capillary methods, Ferric Compounds isolation & purification, Ferrous Compounds isolation & purification, Pyridines chemistry
- Abstract
On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.
- Published
- 2004
- Full Text
- View/download PDF
25. On-column complexation of metal ions using 2,6-pyridinedicarboxylic acid and separation of their anionic complexes by capillary electrophoresis with direct UV detection.
- Author
-
Chen Z and Naidu R
- Subjects
- Reproducibility of Results, Sensitivity and Specificity, Electrophoresis, Capillary methods, Metals chemistry, Picolinic Acids chemistry, Spectrophotometry, Ultraviolet methods
- Abstract
On-column complexation of metal ions with 2,6-pyridinedicarboxylate (2,6-PDC) to form anionic complexes enabled their separation by capillary zone electrophoresis with direct UV detection at 214 nm. Nine metal ions, Cu2+, Zn2+, Ni2+, Cd2+ Mn2+, Pb2+, Fe3+, Al3+ and Ca2+, were determined in less than 7 min using 10 mM 2.6-PDC solution containing 0.75 mM tetradecyltrimethylammonium bromide at pH 4.0. Satisfactory working ranges (20-300 microM), detection limits (3-10 microM) and good repeatability of the peak areas (RSD 2.1-4.2%, n=5) were obtained using hydrodynamic injection (30 s). The proposed method was used successfully for the determination of Mn2+, Fe3+, Al3+ and Ca2+ in groundwaters.
- Published
- 2002
- Full Text
- View/download PDF
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