Heterogeneous catalysis in solution. Part 18. The catalysis by carbons of oxidation–reduction reactions

Austin, J. M.; Groenewald, T.; Spiro, M.

doi:10.1039/dt9800000854

Cited by 18 publications

(6 citation statements)

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“…An important aspect in the treatment of aqueous systems using active carbons is that it can be used to remove both inorganic and organic species, and this is very important in the purification of water. Applications of the adsorption of metal species from aqueous solution are for the recovery of noble metals, − treatment of potable and wastewater containing trace amounts of toxic metals, − and preparation of metal catalysts supported on carbon. − The adsorption of inorganic or ionic species from solution are mainly controlled by electrostatic forces, and this needs to be discussed in terms of the speciation of the adsorbate and the amphoteric nature of the carbon adsorbent, which is related to the various types of functional groups present on the surface . There is also the role of specific interactions between the adsorbate and adsorbent to consider.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Metal Ions on Nitrogen Surface Functional Groups in Activated Carbons

Xiao²,

2001

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A commercially available coconut-shell-derived active carbon was oxidized with nitric acid, and both the original and oxidized active carbons were treated with ammonia at 1073 K to incorporate nitrogen functional groups into the carbon. An active carbon with very high nitrogen content (∼9.4 wt % daf) was also prepared from a nitrogen-rich precursor, polyacrylonitrile (PAN). These nitrogen-rich carbons had points of zero charge (pHpzc) similar to H-type active carbons. X-ray absorption near-edge structure (XANES) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) were used to characterize the nitrogen functional groups in the carbons. The nitrogen functional groups present on the carbon surface were pyridinic, pyrrolic (or indolic), and pyridonic structures. The adsorption of transition metal cations Cd2+, Ni2+, and Cu2+ from aqueous solution on the suite of active carbons showed that adsorption was markedly higher for carbons with nitrogen functional groups present on the surface than for carbons with similar pHpzc values. In contrast, the adsorption characteristics of Ca2+ from aqueous solution were similar for all the carbons studied. Flow microcalorimetry (FMC) studies showed that the enthalpies of adsorption of Cd2+(aq) on the active carbons with high nitrogen contents were much higher than for nitric acid oxidized carbons studied previously, which also had enhanced adsorption characteristics for metal ion species. The enthalpies of adsorption of Cu2+ were similar to those obtained for Cd2+ for specific active carbons. The nitrogen functional groups in the carbons act as surface coordination sites for the adsorption of transition metal ions from aqueous solution. The adsorption characteristics of these carbons are compared with those of oxidized carbons.

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Section: Introductionmentioning

confidence: 99%

Adsorption of Metal Ions on Nitrogen Surface Functional Groups in Activated Carbons

Xiao²,

2001

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“…Heating 21 with activated charcoal in CHCl 3 at reflux for 30 min apparently effected reduction to give 22 , which underwent an intramolecular substitution to give 23 , in which the original anthracenes are now linked by four carbon−carbon bonds. No reaction occurs in the absence of activated charcoal, indicating that it is necessary for the reduction . Oxidation of rugulosin ( 1) with MnO 2 gave dehydrorugulosin with the same ring system as 23 in unspecified yield 1c.…”

Section: Resultsmentioning

confidence: 99%

Efficient Syntheses of Rugulosin Analogues

Snider

Gao

2005

J. Org. Chem.

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Oxidation of 3b or 14c,d with Pb(OAc)4 in AcOH for 20 min at 25 degrees C and 1 h at 75 degrees C gave flavoskyrin-type dimers 6b and 15c,d in 53-86% yield. Heating a solution of 6b or 15c,d in pyridine under air for 1 h at 75-80 degrees C and then for 1-2 h at 110 degrees C afforded rugulosin-type dimers 10b and 17c,d in 61-88% yield. This two-step sequence provides a practical route to this unusual natural product skeleton.

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“…time plots could be used to predict the [Ox,] us. t decay curves due to reaction (3) for a wide range of initial concentrations of Ox, and Red, which are also very different to those used to generate the Tafel data. Indeed, provided that k,, (1 -a 2 ) z , F/RT and ioq , remain unchanged, it is possible to simulate the kinetics even for reaction conditions such that i, z il.c, i.e.…”

Section: ( D )mentioning

confidence: 86%

“…In general, redox reactions such as (3) will require a catalyst if one of the couples is irreversible. In order to catalyse reaction (3) with maximum efficiency the second redox 2048 Redox Catalysis couple should be reversible. The combination of a totally irreversible redox couple with a totally reversible redox couple represents, therefore, an important, optimum case in redox catalysis.…”

Section: Introductionmentioning

confidence: 99%

Redox catalysis. Theory for a Nernstian reaction coupled to an irreversible reaction

Mills¹,

McMurray²

1989

J. Chem. Soc., Faraday Trans. 1

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Heterogeneous catalysis in solution. Part 18. The catalysis by carbons of oxidation–reduction reactions

Cited by 18 publications

References 0 publications

Adsorption of Metal Ions on Nitrogen Surface Functional Groups in Activated Carbons

Adsorption of Metal Ions on Nitrogen Surface Functional Groups in Activated Carbons

Efficient Syntheses of Rugulosin Analogues

Redox catalysis. Theory for a Nernstian reaction coupled to an irreversible reaction

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