Chromium 1994

Geiger, David K.

doi:10.1016/0010-8545(96)01276-3

Cited by 5 publications

(3 citation statements)

References 99 publications

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“…This can be explained in terms of the partial oxidation and deprotonation of the carboxylate and phosphate groups in the outer membrane lipopolysaccharide by the K 2 Cr 2 O 7 which then increases the net of negatively charged functional groups that enhances the biosorption of Cu(II) to the biomass (Geiger 1996;He and Tebo, 1998).Whereas the presence of the other metal ions with or without Cr in the Cu (II) biosorption mixture have a significant antagonistic effect in the Cu (II) biosorption.…”

Section: Resultsmentioning

confidence: 99%

Biosorption of heavy metals from waste water using Pseudomonas sp.

Hussein¹,

Ibrahim²,

Kandeel³

et al. 2004

Electron. J. Biotechnol.

164

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Biosorption experiments for Cr(VI), Cu(II), Cd(II) and Ni(II) were investigated in this study using nonliving biomass of different Pseudomonas species. The applicability of the Langmuir and Freundlich models for the different biosorbent was tested. The coefficient of determination (R 2 ) of both models were mostly greater than 0.9. In case of Ni(II) and Cu(II), their coefficients were found to be close to one. This indicates that both models adequately describe the experimental data of the biosorption of these metals. The maximum adsorption capacity was found to be the highest for Ni followed by Cd(II), Cu(II) and Cr(VI). Whereas the Freundlich constant k in case of Cd(II) was found to be greater than the other metals. Maximum Cr(VI) removal reached around 38% and its removal increased with the increase of Cr(VI) influent. Cu(II) removal was at its maximum value in presence of Cr(VI) as a binary metal, which reached 93% of its influent concentration. Concerning to Cd(II) and Ni(II) similar removal ratios were obtained, since it was ranged between 35 to 88% and their maximum removal were obtained in the case of individual Cd(II) and Ni(II). *Corresponding authorThe presence of heavy metals in aquatic environments is known to cause severe damage to aquatic life, beside the fact that these metals kill microorganisms during biological treatment of wastewater with a consequent delay of the process of water purification. Most of the heavy metal salts are soluble in water and form aqueous solutions and consequently cannot be separated by ordinary physical means of separation.Physico-chemical methods, such as chemical precipitation, chemical oxidation or reduction, electrochemical treatment, evaporative recovery, filtration, ion exchange, and membrane technologies have been widely used to remove heavy metal ions from industrial wastewater. These processes may be ineffective or expensive, especially when the heavy metal ions are in solutions containing in the order of 1-100 mg dissolved heavy metal ions/L (Volesky, 1990a; Volesky, 1990b). Biological methods such as biosorption/ bioaccumulation for the removal of heavy metal ions may provide an attractive alternative to physico-chemical methods (Kapoor and Viraraghavan, 1995).

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Section: Resultsmentioning

confidence: 99%

Biosorption of heavy metals from waste water using Pseudomonas sp.

Hussein¹,

Ibrahim²,

Kandeel³

et al. 2004

Electron. J. Biotechnol.

164

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“…[8,[10][11][12][13], (ii) intermolecular oxidation of some chromium(III) species, e.g. [14][15][16], (iii) intramolecular photoredox chromium(III) transformation into chromium(V), e.g. [17][18], and (iv) oxidation of chromium(0) species in the presence of chromium(V) stabilizing ligands, e.g.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of a macrocyclic chromium(III) complex oxidation to chromium(IV) by hexacyanoferrate(III) in strongly alkaline media

Chatłas

Impert

Katafias

et al. 2004

Transition Metal Chemistry

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Oxidation of the macrocyclic Cr(III) complex cis-[Cr(cycb)(OH)(2)](+), where cycb = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by an excess of the hexacyanoferrate( III) in basic solution, slowly produces Cr(V) species. These species, detected using e.p.r. spectroscopy, are stable under ambient conditions for many hours, and the hyperfine structure of the e.p.r. spectrum is consistent with the interaction of the d-electron with four equivalent nitrogen nuclei. Electro-spray ionization mass spectrometry suggests a concomitant oxidation of the macrocyclic ligand, in which double bonds and double bonded oxygen atoms have been introduced. By comparison basic chromate(III) solutions are oxidized rapidly to chromate(VI) by hexacyanoferrate(III) without any detectable generation of stable Cr(V) intermediates. Kinetics of oxidation of the macrocyclic Cr(III) complex in alkaline solution has been studied under excess of the reductant. Rate determining formation of Cr(IV) by a second order process involving the Cr(III) and the Fe(III) reactants is seen. This reaction also involves a characteristic higher order than linear dependence on the hydroxide concentration. Reaction mechanisms for the processes, including oxidation of the coordinated macrocyclic ligand under excess of the oxidant- are proposed

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“…[1][2][3][4][5][6] Despite the fact that the main spectroscopic features have been described for a wide range of Cr (III) complexes, the nature of reactive states and photochemical relaxation mechanisms is still not known for many of them. Often with transition metal complexes electronic transitions from the ground electronic state proceed to a manifold of many electronic states that are very close in energy.…”

Section: Introductionmentioning

confidence: 98%

Photoracemization and excited state relaxation through non-adiabatic pathways in chromium (III) oxalate ions

Żurek

Paterson

2012

The Journal of Chemical Physics

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Computational studies on the photochemistry of the open-shell chromium oxalate [Cr(C(2)O(4))(3)](3-) ion, including its non-adiabatic relaxation pathways, have been performed. The presence of the peaked conical intersection of a quasi-Jahn-Teller type, connecting the (4)T state with (4)A(2) ground state, accounts for the observed photoinduced racemization. This involves the rupture of one of the Cr-O bonds and the complex forms an unstable trigonal bipyramid form that connects both ground state stereoisomers with the excited quartet manifold. Intersystem crossing seams have been located between the (4)T and lower lying (2)E state which can quench the quartet reaction and lead to (2)E → (4)A(2) emission.

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Chromium 1994

Cited by 5 publications

References 99 publications

Biosorption of heavy metals from waste water using Pseudomonas sp.

Biosorption of heavy metals from waste water using Pseudomonas sp.

Kinetics and mechanism of a macrocyclic chromium(III) complex oxidation to chromium(IV) by hexacyanoferrate(III) in strongly alkaline media

Photoracemization and excited state relaxation through non-adiabatic pathways in chromium (III) oxalate ions

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