UV or visible light induced photodegradation of AO7 on TiO2 particles: the influence of inorganic anions (original) (raw)
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Azo-dyes photocatalytic degradation in aqueous suspension of TiO2 under solar irradiation
Chemosphere, 2002
The photodegradation of two common and very stable azo-dyes, i.e. methyl-orange (C 14 H 14 N 3 SO 3 Na) and orange II (C 16 H 11 N 2 SO 4 Na), is reported. The photocatalytic oxidation was carried out in aqueous suspensions of polycrystalline TiO 2 irradiated by sunlight. Compound parabolic collectors, installed at the ''Plataforma Solar de Almer ı ıa'' (PSA, Spain) were used as the photoreactors and two identical reacting systems allowed to perform photoreactivity runs for the two dyes at the same time and under the same irradiation conditions. The disappearance of colour and substrates together with the abatement of total organic carbon content was monitored. The main sulfonate-containing intermediates were found to be in lower number in respect to those obtained under artificial irradiation. In particular there were no more evidence of the presence of hydroxylated transients. The dependence of dye photooxidation rate on: (i) substrate concentration; (ii) catalyst amount; and (iii) initial pH was investigated. The influence of the presence of strong oxidant species (H 2 O 2 , S 2 O 2À 8 ) and some ions (Cl À , SO 2À 4 ) on the process was also studied.
Effect of pH, Ions and Ionic Strength on Ti0 2 -mediated Photodegradation of Brilliant Orange
2009
The photodegradation of Brilliant Orange (BO), an anionic mono azo dye used in textile and leather industries, was investigated in aqueous TiO, suspension under UV irradiation. The effect of pH on degradation rate was investigated. The experimental results indicated that photocatalytic reaction was favoured in acidic medium. The degradation was minimum at pH 6 which is zero point charge of TiO,. The effect of different ions and ionic strength on photodegradation was also investigated. Na -, z->, AI" and Pb" ions were used to see the cationic effect and NO,', CO,'-, CI-ions were used to see the effect of anions. Pb" ion enhanced the percent degradation 25 times more than the degradation without it. The effect of ionic strength was studied using different concentrations of Pb(NO,), solution. Photodegradation was found to increase with the increase of ionic strength.
Photodegradation of aqueous solution of Mordant red17 (MR17) azo dye in UV/H 2 O 2 , advanced oxidation process was investigated in this study. Results show that MR17 dye decolorization rate was mainly effected by different parameters such as solution pH, H 2 O 2 concentration, initial dye concentrations and presence of different inorganic anions such as NO 3-, Cl-, CO 3 2-ions. The degradation percent of the dye decreased by the presence of inorganic anions in the order of CO 3 2-> Cl-> NO 3-ions. While increase the temperature of the solution medium from 283 to 318K led to increase the decolorization rate of MR17 dye from 0.048 to 0.164 min-1. The low value of the apparent activation energy E a (24.91 kJ mol-1) indicates that decoloriza-tion process of MR17 dye is achieved easily using H 2 O 2 /UV process. This results further proved by presence of 100% decolorization of MR17 dye in about 50 min and about 85.57% mineralization in a 3.0 h photoperiod.
Kinetics studies on photodegradation of methyl orange in the presence of C-N-codoped TiO2 catalyst
Egyptian Journal of Chemistry, 2019
T his work investigated the photodegradation of azo dye, methyl orange, without and with the addition of C-N-codoped TiO 2 catalyst using a visible halogen-lamp as a light source. C-Ncodoped TiO 2 was prepared by free-organic solvent peroxo sol-gel method. The effects of initial dye concentration, catalyst dosage, and pH solution on the photodegradation of methyl orange were studied. Photodegradation process for methyl orange solution at acidic condition showed high removal percentage. 5 mg L-1 methyl orange achieved color removal until 94% for 180 min irradiation in photodegradation process with the presence of C-N-codoped TiO 2 catalyst, and approximately 70% TOC removed as the results of mineralization process. The kinetics reaction rate of photodegradation of methyl orange dye with the addition of C-N-codoped TiO2 followed pseudo-first order represented by Langmuir-Hinshelwood model, the kinetics constant of photodegradation became higher by decreasing the initial concentration of methyl orange. Three organic byproducts of methyl orange formed during photodegradation process was identified by LC-MS/MS system then degradation pathway of methyl orange photodegradation in the presence of C-N-codoped TiO 2 catalyst was proposed.
Environmental Science & Technology, 1996
Photosensitized degradation of a textile azo dye, Acid Orange 7, has been carried out on TiO 2 particles using visible light. Mechanistic details of the dye degradation have been elucidated using diffuse reflectance absorption and FTIR techniques. Degradation does not occur on Al 2 O 3 surface or in the absence of oxygen. The dependence of the dye degradation rate on the surface coverage shows the participation of excited dye and TiO 2 semiconductor in the surface photochemical process. Diffuse reflectance laser flash photolysis confirms the charge injection from the excited dye molecule into the conduction band of the semiconductor as the primary mechanism for producing oxidized dye radical. The surfaceadsorbed oxygen plays an important role in scavenging photogenerated electrons, thus preventing the recombination between the oxidized dye radical and the photoinjected electrons. Diffuse reflectance FTIR was used to make a tentative identification of reaction intermediates and end products of dye degradation. The intermediates, 1,2-naphthoquinone and phthalic acid, have been identified during the course of degradation. Though less explored in photocatalysis, the photosensitization approach could be an excellent choice for the degradation of colored pollutants using visible light.
Photodegradation of aqueous solution of Mordant red17 (MR17) azo dye in UV/H 2 O 2 , advanced oxidation process was investigated in this study. Results show that MR17 dye decolorization rate was mainly effected by different parameters such as solution pH, H 2 O 2 concentration, initial dye concentrations and presence of different inorganic anions such as NO 3 -, Cl -, CO 3 2ions. The degradation percent of the dye decreased by the presence of inorganic anions in the order of CO 3 2-> Cl -> NO 3 ions. While increase the temperature of the solution medium from 283 to 318K led to increase the decolorization rate of MR17 dye from 0.048 to 0.164 min -1 . The low value of the apparent activation energy E a (24.91 kJ mol -1 ) indicates that decolorization process of MR17 dye is achieved easily using H 2 O 2 /UV process. This results further proved by presence of 100% decolorization of MR17 dye in about 50 min and about 85.57% mineralization in a 3.0 h photoperiod.
Journal of Photochemistry and Photobiology A: Chemistry, 2004
The aqueous phase photocatalytic degradation of Sirius Gelb GC used in the textile industry, was investigated. In order to optimize the working pH, three different dye solutions were prepared at pH 3.5; 7.0 and 11.0. One hundred cubic centimeter portions of the solution were irradiated with a low pressure UV lamb in the absence and presence of catalysts TiO 2 or Ag loaded-TiO 2. In all conditions, the samples withdrawn from the reactor were centrifuged and separated from the catalyst and degradation percentages were calculated from the measurement of the residual dye concentrations, spectrophotometrically. The optimum pH, which provides the best degradation ratio was found to be 3.5 for the dye. At the same pH, it was found that silver loaded catalyst is more effective than neat TiO 2 catalyst. The silver loading dramatically reduced the irradiation time from 20 min to 8 min for Sirius Gelb GC. However, the catalytical behavior of the both the catalysts was also investigated in heavy salt media such as simulated wastewater and in a river fluent. Pooled standard deviation (S pooled) of the repeated measurements in all conditions is 0.615 for N = 47 and 38 degrees of freedom. Confidence limit of the method is 98.8 ± 0.2 in 95% confidence level.
Effect of Tio 2 Concentration on Photocatalytic Degradation of Reactive Orange 16 Dye ( Ro 16 ) 1
2014
Organic contaminants from industrial and/or domestic effluents may be harmful to humans directly or indirectly by degrading the quality of the environment. Consequently these contaminants must be reduced to levels that are not harmful to humans and the environment before disposal. Among the available chemical methods heterogeneous photocatalytic oxidation has been found particularly to be effective in removal of large number of persistent organics in water. Degradation of the organics was achieved by exposing synthetic effluents to UV light in a photocatalytic reactor in a dark compartment in the presence of catalyst. The degradation of RO16 was conducted at pH 5.5, 24 hr, 294 K and lamp power of 200 W. RO16 was prepared in 200 ml dye solution with concentrations of 20, 40 and 60 mg/L and the degradation took place in presence of TiO2 at concentrations of (0.5-4.0) g/L. While photolysis (in absence of TiO2) was found to have no effect on the degradation of RO16, photocatalysis (in presence of TiO2 catalyst) degraded the dye to 0.4 mg/L.
Photocatalytic Degradation of Methyl Orange in Aqueous TiO2 Suspensions
Asian Journal of Chemistry, 2013
The degradation of methyl orange was studied using advanced oxidation process by exposed to UV irradiation in the presence of TiO2. TiO2 or UV light has a negligible effect when used alone. The effect of TiO2 dosage, initial pH of dye solution and the solution area exposed to UV light were studied. It is found that in the investigated range, degradation rate of methyl orange increases with the increase in TiO2 concentration and exposure area of solution. Acidic media is fvaourable to methyl orange degradation. The photodestruction of methyl orange is significantly inhibited by addition of KI as active holes scavenger at pH 2. However, the roles of •OH and H2O2 are increased gradually as the increase of initial pH value of dye solution.