Photocatalytic oxidation of cyanide in aqueous TiO2 suspensions irradiated by sunlight in mild and strong oxidant conditions

Augugliaro, Vincenzo; Gálvez, Julian Blanco; Vázquez, Julián; López, Elisa García; Loddo, Vittorio; López-Muñoz, Marı́a José; Rodríguez, Sergio; Marcı̀, Giuseppe; Palmisano, Leonardo; Schiavello, M.; Ruiz, J.Soria

doi:10.1016/s0920-5861(99)00186-8

Cited by 69 publications

(25 citation statements)

References 14 publications

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“…A number of methods are currently available for cyanide remediation with varying degrees of effectiveness, namely biological treatment [3,4], chemical oxidation [5,6], electrochemical decomposition [7][8][9][10], photocatalytic [11][12][13][14][15] and catalytic oxidation [16][17]. The most common method for treating cyanides is alkaline chlorination which results in the formation of a highly toxic cyanogen chloride intermediate and, if organic material is present, chlorinated VOC's.…”

Section: Introductionmentioning

confidence: 99%

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Stoyanova

Christoskova

2005

Open Chemistry

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Catalytic activity of mixed Ni-Fe oxide systems with respect to air oxidation of aqueous cyanide solution at 308 K was investigated. The catalysts employed were prepared by an oxidation-precipitation method at room temperature and were characterized by powder Xray diffraction (XRD), Mössbauer spectroscopy, and chemical analysis. The cyanide oxidation rate was found to be dependent on the catalyst's calcination temperature, pH of the medium, and catalyst loading. Results revealed that the catalyst calcined at 120 • C is the most active where up to 90 % of free cyanide (4 mM) was removed after oxidation for 30 minutes in the presence of 2.5 g/L catalyst at pH 9.5. The cyanide conversion becomes less favorable as the pH of the solution increases (with other constant parameters). The selectivity data showed that carbon dioxide is the main oxidation product, regardless of pH of the solution.

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Section: Introductionmentioning

confidence: 99%

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Stoyanova

Christoskova

2005

Open Chemistry

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“…It is therefore important to convert the cyanate into other stable inert end products. The photocatalytic oxidation of cyanate on TiO 2 surfaces may be a viable method for decontamination of cyanate into nitrate [48][49][50]. The enhancement of the photocatalytic reduction of Fe(VI) in the presence of cyanate was observed in preliminary experiments ( Figure 6).…”

Section: Cyanatementioning

confidence: 89%

Heterogeneous photocatalytic reduction of ferrate(VI) in UV‐irradiated titania suspensions: Role in enhancing destruction of nitrogen‐containing pollutants

Sharma

Winkelmann

Krasnova

et al. 2003

International Journal of Photoenergy

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Abstract. The results of the heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated TiO 2 suspensions are presented and suggest indirect observation of the formation of Fe(V) by the photoreduction of Fe(VI) with e cb − at TiO 2 surfaces. Because Fe(V) selectively and rapidly oxidizes low reactivity pollutants with the production of the non-toxic by-product, Fe(III), the photocatalytic reduction of Fe(VI) has a role in pollution remediation processes. The experiments were conducted as a function of TiO 2 suspension concentrations, Fe(VI) concentrations, and pH in basic media. The initial rate of Fe(VI) reduction gave a fractional order with respect to initial Fe(VI) concentrations and adheres to simple Langmuir-Hinshelwood kinetics.Results suggest that the surface reaction (Fe(VI) + e cb − → Fe(V)) is the rate-controlling step. The photocatalytic reduction of Fe(VI) in the presence of less reactive nitrogen-containing species (ammonia, cyanate, and fulvic acid) were also investigated. Enhancement in the rate of Fe(VI) reduction was observed. A reaction scheme involving Fe(V) as an intermediate is presented which explains the faster photocatalytic oxidation of pollutants in the presence of Fe(VI).

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“…In an aqueous medium with cyanide, the first product of the photocatalytic oxidation using nanocrystals of TiO 2 is CNO - (Augugliaro, 1999). The chemical reactions that represent this oxidation process are as follows:…”

Section: Tio 2 Photocatalystmentioning

confidence: 99%

Detoxification of cyanide using titanium dioxide and hydrocyclone sparger with chlorine dioxide

Parga

Vázquez

Valenzuelab

et al. 2012

Chemical Speciation & Bioavailability

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The extraction of gold and silver from minerals and concentrates with cyanide is an important hydrometallurgy process that has been studied for more than 120 years. This technology, which consists of the dissolutions of the precious metals in cyanide solutions, followed by the recovery of the values by cementation, activated carbon or ion exchange resin. Most of the wastes in the industrial effluents' milling are known to contain high contents of free cyanide as well as metallic cyanide complexes, which give them a high degree of toxicity. Appropriate methods for the treatment of cyanide solutions include cyanide destruction by oxidation using a photoelectrocatalytic detoxification technique with titanium dioxide microelectrodes. This is one of the most innovative ways for the treatment of wastewater containing cyanide. Another is the use of chlorine dioxide (ClO 2 ) with a gas-sparged hydrocyclone as the reactor. The results show that photodegradation of cyanide was 93% in 30 minutes using a 450 W halogen lamp, and in the case of ClO 2, the destruction of cyanides was 99% in 1 minute. In both cases, excellent performances can be achieved with the high capacity of these technologies.

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Photocatalytic oxidation of cyanide in aqueous TiO2 suspensions irradiated by sunlight in mild and strong oxidant conditions

Cited by 69 publications

References 14 publications

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Heterogeneous photocatalytic reduction of ferrate(VI) in UV‐irradiated titania suspensions: Role in enhancing destruction of nitrogen‐containing pollutants

Detoxification of cyanide using titanium dioxide and hydrocyclone sparger with chlorine dioxide

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