Photocatalytic oxidation of cyanide on TiO2: An electrochemical approach

Pedraza-Avella, J.A.; Acevedo–Peña, Próspero; Pedraza-Rosas, J.E.

doi:10.1016/j.cattod.2007.12.063

Cited by 34 publications

(11 citation statements)

References 32 publications

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“…Furthermore, a synergistic effect between metallic salts concentration and irradiation was observed (Guerain and Leblond, 1993). To sum up, in this case two pathways can explain the EC production: firstly the catalytic ethanolysis of the EC precursors formed in the gas phase during the distillation (see Section 2.5) and secondly photochemical reactions leading to hydroxyl radical production (OH • ) by the well-known autooxidation of unsaturated compounds (Fox et al, 2007;Stodolak et al, 2007) allowing the oxidation of cyanide in cyanate (Pedraza-Avella et al, 2008) and finally EC production (see Equation (2a)). Both mechanisms are catalyzed by Cu(II) or other metallic salts, as described earlier.…”

Section: Post-distillation and Photochemical Ethyl Carbamate Productionmentioning

confidence: 99%

“…The reaction (2a) is catalyzed by metallic ions like Cu (II) or Fe (III). The non-catalytic formation of cyanate (CNO − ) or isocyanate (NCO − ) from cyanide is until now not clear since oxidation of cyanide to cyanate needs H 2 O 2 or hypochlorite ion as reactive and proceeds in basic conditions (Boulton, 1993;Sarla et al, 2004;Pedraza-Avella et al, 2008).…”

Section: Ethyl Carbamate Formation During Food Processingmentioning

confidence: 99%

See 1 more Smart Citation

Ethyl Carbamate in Foods and Beverages – A Review

Weber

Шарыпов

2009

Climate Change, Intercropping, Pest Control and Beneficial Microorganisms

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Foods and beverages contain many toxic chemicals that raise health concerns. Ethyl carbamate (EC) or urethane is the ethyl ester of carbamic acid. It occurs at low levels, from ng/L to mg/L, in many fermented foods and beverages. EC is genotoxic and carcinogenic for a number of species such as mice, rats, hamsters and monkeys. It has been classified as a group 2A carcinogen, "probably carcinogenic to humans", by the World Health Organization's International Agency for Research on Cancer (IARC) in 2007. The benchmark dose lower limit of EC is 0.3 mg/kg bw/day and the mean intake of EC from food is approximately 15 ng/kg bw/day. Those levels were calculated for relevant foods including bread, fermented milk products and soy sauce. Alcoholic beverages were not included in this calculation. However, high levels of EC can be found in distilled spirits at concentrations ranging from 0.01 mg/L to 12 mg/L depending on to the origin of spirit. Alcoholic drinks should thus be considered as a source of EC. EC is produced by several chemical mechanisms: first, from urea and various proteins like citrulline produced during the fermentation step, and second from cyanide and hydrocyanic acid, via EC precursors such as cyanate. A large panel of EC formation mechanisms is described from simple ethanolysis of urea in homogeneous liquid phase to photochemical oxidation of cyanide ion or complex heterogeneous gas/solid catalytic reactions. Determination of EC in foods and beverages involves various strategies according to the material, food or beverage, solid or liquid, and according to the concentration, from ng/L to mg/L. Usually adapted extractive techniques and pre-concentration steps are followed by analysis by gas chromatography coupled to mass spectrometry (GC-MS of GC-MS-MS). High-performance liquid chromatography (HPLC) and semi-quantitative spectroscopic methods (infra-red) are also proposed as valuable alternatives to the classical but time-consuming GC-MS. Various preventing methods are developed and used in some cases at industrial scale to lower EC levels in food. Two types of preventing methods are described. practices in all steps of the chain of food (or beverages) production lead, in general, to low EC level. Secondly, the abatement of EC precursors can be done by adapted enzymatic, physical-chemical or chemical methods according to the nature of raw materials and conditions of their production processes.

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Section: Post-distillation and Photochemical Ethyl Carbamate Productionmentioning

confidence: 99%

Section: Ethyl Carbamate Formation During Food Processingmentioning

confidence: 99%

Ethyl Carbamate in Foods and Beverages – A Review

Weber

Шарыпов

2009

Climate Change, Intercropping, Pest Control and Beneficial Microorganisms

View full text Add to dashboard Cite

show abstract

“…Furthermore, a synergistic effect between metallic salt's concentration and irradiation was observed (Guerain and Leblond 1993). To sum up, in this case two pathways can explain the EC production: first the catalytic ethanolysis of the EC precursors formed in the gas phase during the distillation (see the previous paragraph ''Production of ethyl carbamate in gas phase'') and second photochemical reactions leading to hydroxyl radical production (OH°) by the well known auto-oxidation of unsaturated compounds (Fox and Stachowiak 2007;Stodolak et al 2007) allowing the oxidation of cyanide in cyanate (Pedraza-Avella et al 2008) and finally EC production (see Eq. 2a).…”

Section: Production Of Ethyl Carbamate In Gas Phasementioning

confidence: 99%

“…The reaction (2a) is catalysed by metallic ions like Cu (II) or Fe (III). The noncatalytic formation of cyanate (CNO -) or isocyanate (NCO -) from cyanide is until now not clear since oxidation of cyanide to cyanate needs H 2 O 2 or hypochlorite ion as reactive and proceeds in basic conditions (Boulton 1993;Sarla et al 2004;Pedraza-Avella et al 2008). …”

Section: Ethyl Carbamate In Foods and Beverages: Formation And Mechanmentioning

confidence: 99%

Ethyl carbamate in foods and beverages: a review

2008

View full text Add to dashboard Cite

Food and beverages contain many toxic chemicals that raise health concerns. Ethyl carbamate (EC) or urethane is the ethyl ester of carbamic acid. It occurs at low level, from ng/L to mg/L, in many fermented foods and beverages. Ethyl carbamate is genotoxic and carcinogenic for a number of species such as mice, rats, hamsters and monkeys. It has been classified as a group 2A carcinogen, ''probably carcinogenic to humans'', by the World Health Organization's International Agency for Research on Cancer (IARC) in 2007. The benchmark dose lower limit of ethyl carbamate is 0.3 mg/kg bw per day and the mean intake of ethyl carbamate from food is approximately 15 ng/kg bw per day. Those levels were calculated for relevant foods including bread, fermented milk products and soy sauce. Alcoholic beverages were not included in this calculation. However, high levels of ethyl carbamate can be found in distillated spirits at concentrations ranging from 0.01 to 12 mg/L depending on to the origin of spirit. Alcoholic drinks should thus be considered as a source of ethyl carbamate. Ethyl carbamate is produced by several chemical mechanisms: first, from urea and various proteins like citrulline produced during the fermentation step and second from cyanide, and hydrocyanic acid, via ethyl carbamate precursors such as cyanate. A large panel of ethyl carbamate formation mechanisms is described from simple ethanolysis of urea in homogeneous liquid phase to photochemical oxidation of cyanide ion or complex heterogeneous gas/solid catalytic reactions. Determination of ethyl carbamate in foods and beverages involves various strategies according to the material, food or beverage, solid or liquid, and according to the concentration, from ng/L to mg/L. Usually, adapted extractive techniques and preconcentration step are followed by analysis by gas chromatography coupled to mass spectrometry (GC-MS of GC-MS-MS). High performance liquid chromatography (HPLC) and semi-quantitative spectroscopic methods (infra-red) are also proposed as valuable alternatives to the classical but time-consuming GC-MS. Various preventing methods are developed and used in some cases at industrial scale to lower ethyl carbamate levels in food. Two types of preventing methods are described. First, adapted and optimised practices in all step of the chain of foods' (or beverages) production lead in general to low ethyl carbamate level. Second, the abatement of ethyl carbamate precursors can be done by adapted enzymatic, physical chemical or chemical methods according to the natures of raw materials and conditions of their production processes.

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“…Furthermore, it is also important to point out that the potentials of both conduction and valence bands of TiO 2 follow a Nernstian pH dependence, decreasing 59 mV per pH unit according to Eqs. (10) and (11), and consequently, the ability of electrons and holes to participate in redox processes is determined by the pH of the solution [29].…”

Section: Effect Of Ph On the Photocatalytic Behaviormentioning

confidence: 99%

Effect of different type of scavengers on the photocatalytic removal of copper and cyanide in the presence of TiO2@yeast hybrids

Zheng

Pan

et al. 2015

J Mater Sci: Mater Electron

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Effect of different type of organic or inorganic additions (formic acid, AgNO 3 , NaCl) on the photocatalytic reduction of copper and photooxidation of cyanide with illuminated TiO 2 @yeast was studied in this work together with the impact of solution pH values and contact time. The results indicated that pH values exhibited a great effect on the adsorption and photocatalytic performance of cyanide and copper because the surface charge of the TiO 2 @yeast and the existence form of cyanide and copper are highly pH dependent. The optimal adsorption and photo-oxidation of cyanide was observed at pH 2.0 while the best adsorptive and photocatalytic efficiency for copper was achieved at pH 5.0 within the studied range. The addition of formic acid increased the photo-reduction rate of copper and inhibited the photo-oxidation of cyanide. AgNO 3 , as electron acceptor, restrained the Cu(II) reduction from 75.0 to 30.5 %, whereas accelerate the photooxidation of cyanide. Besides, the presence of chloride ions retarded the removal efficiency of both cyanide and copper. The first-order kinetic model well described the experimental data. One possible mechanism of the effect of additives on copper and cyanide degradation was discussed.

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Photocatalytic oxidation of cyanide on TiO2: An electrochemical approach

Cited by 34 publications

References 32 publications

Ethyl Carbamate in Foods and Beverages – A Review

Ethyl Carbamate in Foods and Beverages – A Review

Ethyl carbamate in foods and beverages: a review

Effect of different type of scavengers on the photocatalytic removal of copper and cyanide in the presence of TiO2@yeast hybrids

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