Photocatalytic degradation of CI Acid Green 25 and CI Acid Red 88 in aqueous suspensions of titanium dioxide (original) (raw)
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Journal of Photochemistry and Photobiology C-photochemistry Reviews, 2008
The degradation pathways for citric acid (Cit, 5 mM, pH 2.8) degradation by TiO 2 -heterogeneous photocatalysis were studied through the analysis of its degradation intermediate products. The most important product formed was 3-oxoglutaric acid, but several other compounds, like acetoacetic, lactic, pyruvic, malic, glyoxylic, acetic and formic acids plus acetone were found. While citric acid is present, the intermediates cannot be photocatalytically degraded.
Catalysis Today, 2007
The photocatalytic degradation of maleic hydrazide (1), propham (2), tebuthiuron (3), propachlor (4), chlortoluron (5), thiram (6), phenoxyacetic acid (7), 2,4,5-trichlorophenoxy acetic acid (8), 4-chlorophenoxy acetic acid (9), uracil (10), 5-bromouracil (11) and bromothymol blue (12) have been investigated in aqueous suspensions of titanium dioxide (TiO 2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the compounds were investigated under different conditions, such as types of TiO 2 , pH, catalyst concentration, substrate concentration, temperature and in the presence of different electron acceptors, such as hydrogen peroxide (H 2 O 2), potassium persulphate (K 2 S 2 O 8), ammonium persulphate (NH 4) 2 S 2 O 8 and potassium bromate (KBrO 3) besides molecular oxygen. TiO 2 Degussa P25 was found to be more efficient photocatalyst for the degradation of the model compounds as compared with other photocatalysts. The degradation products were analysed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed.
Journal of Molecular …, 2007
The photocatalytic degradation of maleic hydrazide (1), propham (2), tebuthiuron (3), propachlor (4), chlortoluron (5), thiram (6), phenoxyacetic acid (7), 2,4,5-trichlorophenoxy acetic acid (8), 4-chlorophenoxy acetic acid (9), uracil (10), 5-bromouracil (11) and bromothymol blue (12) have been investigated in aqueous suspensions of titanium dioxide (TiO 2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the compounds were investigated under different conditions, such as types of TiO 2 , pH, catalyst concentration, substrate concentration, temperature and in the presence of different electron acceptors, such as hydrogen peroxide (H 2 O 2), potassium persulphate (K 2 S 2 O 8), ammonium persulphate (NH 4) 2 S 2 O 8 and potassium bromate (KBrO 3) besides molecular oxygen. TiO 2 Degussa P25 was found to be more efficient photocatalyst for the degradation of the model compounds as compared with other photocatalysts. The degradation products were analysed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed.
2011
As part of the study on TiO 2 -heterogeneous photocatalytic degradation of citric acid (Cit), degradation of 3-oxoglutaric acid (OGA, 5 mM, pH 2.8), one of the main intermediates of Cit, was analyzed. As reactive -ketodicarboxylic acid, OGA decays rapidly in ambient dark conditions to acetoacetic acid and acetone. The photocatalytic reaction over TiO 2 under UV light is thus affected by this thermal pathway and, in addition to the products found in dark conditions, other carboxylic acids like lactic, pyruvic, glyoxylic and acetic acid were detected and quantified. TOC decrease is proven due mostly by the thermal reaction. Kinetic parameters for both thermal and photochemical reactions were obtained from the experimental data, and mechanisms for the TiO 2 -photocatalytic degradation were proposed for OGA and its intermediates. The interplay between OGA thermal and photocatalytic decay is verified, a subject not very much described in the literature.
Heterogeneous photocatalytic degradation of citric acid over TiO2
Applied Catalysis B: Environmental, 2011
As part of the study on TiO 2 -heterogeneous photocatalytic degradation of citric acid (Cit), degradation of 3-oxoglutaric acid (OGA, 5 mM, pH 2.8), one of the main intermediates of Cit, was analyzed. As reactive -ketodicarboxylic acid, OGA decays rapidly in ambient dark conditions to acetoacetic acid and acetone. The photocatalytic reaction over TiO 2 under UV light is thus affected by this thermal pathway and, in addition to the products found in dark conditions, other carboxylic acids like lactic, pyruvic, glyoxylic and acetic acid were detected and quantified. TOC decrease is proven due mostly by the thermal reaction. Kinetic parameters for both thermal and photochemical reactions were obtained from the experimental data, and mechanisms for the TiO 2 -photocatalytic degradation were proposed for OGA and its intermediates. The interplay between OGA thermal and photocatalytic decay is verified, a subject not very much described in the literature.
2011
As part of the study on TiO 2 -heterogeneous photocatalytic degradation of citric acid (Cit), degradation of 3-oxoglutaric acid (OGA, 5 mM, pH 2.8), one of the main intermediates of Cit, was analyzed. As reactive -ketodicarboxylic acid, OGA decays rapidly in ambient dark conditions to acetoacetic acid and acetone. The photocatalytic reaction over TiO 2 under UV light is thus affected by this thermal pathway and, in addition to the products found in dark conditions, other carboxylic acids like lactic, pyruvic, glyoxylic and acetic acid were detected and quantified. TOC decrease is proven due mostly by the thermal reaction. Kinetic parameters for both thermal and photochemical reactions were obtained from the experimental data, and mechanisms for the TiO 2 -photocatalytic degradation were proposed for OGA and its intermediates. The interplay between OGA thermal and photocatalytic decay is verified, a subject not very much described in the literature.
Dyes and Pigments, 2005
The photocatalytic degradation of two selected dye derivatives, chromotrope 2B (1) and amido black 10B (2), has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions which is essential from an application point of view. The degradation was monitored by measuring the change in substrate concentration as a function of irradiation time employing UV spectroscopic analysis. In these studies, a number of byproducts are formed during the photooxidation process which can potentially be harmful to the environment, therefore, we have studied the mineralization of the pollutants by measuring the total organic carbon (TOC) as a function of irradiation time. The degradation of dyes were studied using different parameters such as types of TiO 2 , reaction pH, catalyst concentration, substrate concentration and in the presence of different electron acceptors such as hydrogen peroxide (H 2 O 2 ), potassium bromate (KBrO 3 ) and ammonium persulphate (NH 4 ) 2 S 2 O 8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The dye derivative (1) was found to degrade faster as compared to the dye derivative (2).
Journal of Photochemistry and Photobiology A: Chemistry, 1994
The photocatalytic decomposition of p-tohrenesulphonic acid (PTSA), in aqueous titanium dioxide suspensions and in systems containing TiOa particles immobilized using a polymer on the inner wall of the reaction vessel, was investigated. p-Cresol was identified by gas chromatography-mass spectrometry (GC-MS) as the main intermediate at the initial stage of photocatalytic PTSA decomposition. The initial PTSA decomposition rates were evaluated from the dependence of the PTSA concentrations on the irradiation time and the values obtained were used for photocatalytic activity comparisons. The initial PTSA concentration, temperature and addition of ferric ions strongly influence the initial PTSA decomposition rate in systems containing powdered and immobilized TiOr. Suitable modification of the experimental conditions guarantees fast photocatalytic decomposition of PTSA in systems containing immobilized titanium dioxide particles.
Applied Catalysis B: Environmental, 2007
Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO 2 under air bubbling and near UV-light was tested under different conditions. The reaction was improved by addition of H 2 O 2 , Fe(III) or both. Minor amounts of H 2 O 2 were effective to enhance the oxidation and the mineralization. H 2 O 2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolonged irradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H 2 O 2 /Cit/Fe molar ratio). However, a lower amount of Fe (1:1:0.2 H 2 O 2 /Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO 2 were performed for comparison. When both H 2 O 2 and Fe(III) were present, the behavior with and without TiO 2 was very similar. So far, 3-oxoglutaric acid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems. #