Oxidation of cyanide ions

Frank SN, Bard AJ. 1977. Heterogeneous photocatalyst oxidation of cyanide ion in aqueous solutions at titanium dioxide powder. J Amer Chem Soc 99(l) 303-304. 

Figure 11.15 Voltammetric oxidation of cyanide ion at a platinum electrode. The solution contained 5 mM KCN and 0.1 M K2S04, and was adjusted to pH 10.0. The scan rate was 0.3 V min-1.

Frank, S. N. Bard, A. J. Heterogeneous photocatalytic oxidation of cyanide ion in aqueous solutions at Ti02 powder, J. Am Chem Soc. 1977, 99, 303. 

Oxidation of Cyanide Ion. In the case of CN as substrate, identification of reactants and products proved feasible. Addition of excess KCN to a 10-mM TPPFeCl solution in DMSO gives the low spin ferric bis-cyanide complex, Reaction 9. The NMR of TPPFe(CN)21 has been... 

An outer sphere oxidation of free CN1 by TPPFeIII(CN)21", which is mechanistically described by Reaction 13. The electrochemical oxidation of cyanide ion in acetonitrile occurs at potentials more positive than +0.5 volt vs. SCE (22). The electrochemical reduction of TPP-FeIII(CN)21" in acetonitrile occurs at a potential of —0.5 volt vs. SCE (25). Thus an outer sphere mechanism is considered unlikely. 

Scheme 14.4 Oxidation of cyanide ions photocatalyzed by poly(sodium styrene sulfonate-co-2-vinylnaphthalene) N denotes the naphthalene moiety contained in the copolymer as a pendant group [8].

Carbon. A stability constant for [(CN)3] has been measured there is a rapid formation of this species from [CN] + (CN)2, followed by a slower decomposition to organic products. The oxidation of cyanide ion by ozone in aqueous solution has been reported. ... 

Nowack et al. [19] used Magneli phase TiOx for the oxidation of cyanide ion to cyanate (which hydrolyzed to ammonia and carbonate) at pH 13. From initial cyanide concentrations in the range 0.5-2.0 g L the specific energy ranged from 12 to 260 kWh per kg cyanide, depending on the extent of remediation of cyanide. 

The kinetics of formation of nitrosyl complexes of iron(n) from the reaction between ferric anide and nitric and nitrous acid in strongly acidic solution have been reported. These reactions involve reduction of iron(m) to iron(n) and oxidation of cyanide ion to cyanate ion. The ferricyanide is attacked by NOj which is formed from the following rapid equilibria ... 

The cyanide is not detected by the conductivity detector of the ion chromatograph due to its low dissociation constant (pK = 9.2) [64]. An ion chromatography procedure has been used for the determination of free cyanide and metal-cyanide complexes in natural water and wastewater samples using oxidation of cyanide ion by sodium hypochlorite to the cyanate ion (pK = 3.66) and a conductivity detector. So, cyanide ions can now be measured indirectly by the conductivity detector. In this procedure, optimum operating conditions were examined. 

In most species, the element that is oxidized or reduced may not be clearly defined. For example, in the electrolytic oxidation of cyanide ion into cyanate ion,... 

Clock reactions, in which a kinetic sequence is so balanced as to lead to long induction periods followed by extremely rapid catalytic activity are well known in chemical systems. Luminol is used in two luminescent clock reactions [3,7]. In the first, the oxidation of cyanide ion by H2O2 is required before the Cu-(II) can catalyse the luminol reaction. The second is the safer, in that harmless cysteine is the inhibitor which is oxidised. 

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