ELIMINATION OF DIRECT AZO DYE RED 80 IN AQUEOUS SOLUTION BY HETEROGENEOUS PHOTOCATALYSIS (original) (raw)
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Photochemical and photocatalytic degradation of an azo dye in aqueous solution by UV irradiation
Journal of Photochemistry and Photobiology A: Chemistry, 2003
The photochemical and photocatalytic degradation of aqueous solutions of Solophenyl Green (SG) BLE 155%, an azo dye preparation very persistent in heavy colored textile waters, has been investigated by means of ultraviolet (UV) irradiation. The pure photochemical process demonstrated to be very efficient for low initial concentrations of the dyestuff. For higher concentrations the photocatalyitic degradation was carried on using commercial titanium dioxide, and mixtures of this semiconductor with different activated carbons (AC) suspended in the solution. The kinetics of photocatalytic dyestuff degradation were found to follow a first-order rate law. It was observed that the presence of the activated carbon enhanced the photoefficiency of the titanium dioxide catalyst. Differently activated carbon materials induced different increases in the apparent first-order rate constant of the process. The effect was quantified in terms of a synergy factor (R) already described in the literature. The kinetic behavior could be described in terms of a modified Langmuir-Hinshelwood model. The values of the adsorption equilibrium constants for the organic molecules, K C , and for the reaction rate constants, k C , were 0.0923 l mg −1 and 1.58 mg l −1 min −1 for the TiO 2 /UV process and 0.0928 l mg −1 and 2.64 mg l −1 min −1 for the TiO 2 + AC/UV system with highest synergy factor, respectively. The mechanism of degradation was discussed in terms of the titanium dioxide photosensitization by the activated carbon.
Journal of Photochemistry and Photobiology A: Chemistry, 2006
The degradation of three commercially available textile azo dyes, Solophenyl Green BLE 155% (SG), Erionyl Red B (ER) and Chromotrope 2R (C2R), has been studied by using photochemical and photocatalytic processes under UV irradiation. The adequacy of each process depends on the concentration of dye. At low dye concentration, the neat photochemical degradation is very efficient. The photocatalytic process, using either slurry of Degussa P-25 TiO 2 or a biphasic mixture of TiO 2 and activated carbon (AC), more effectively bleaches heavier colored solutions. The heterogeneous photocatalytic regime was characterized in terms of catalyst load, TiO 2 to AC mass ratio, initial dye concentration and oxygen partial pressure. Catalyst recovery and reuse was also analyzed. Based on the Langmuir-Hinshelwood approach, reaction rates and adsorption equilibrium constants were calculated. A positive effect on the photocatalytic degradation was observed by the addition of AC to TiO 2 catalyst, which was quantified in terms of a synergy factor (R). The efficiencies of different photo-induced degradation processes were compared based on the experimentally determined apparent rate constants, mineralization degrees and initial quantum yields.
Optimised photocatalytic degradation of a mixture of azo dyes using a TiO 2 /H 2 O 2 /UV process
Water Science & Technology, 2012
The aim of the present study was to optimise the photocatalytic degradation of a mixture of six commercial azo dyes, by exposure to UV radiation in an aqueous solution containing TiO2-P25. Response surface methodology, based on a 32 full factorial experimental design with three replicates was employed for process optimisation with respect to two parameters: TiO2 (0.1–0.9 g/L) and H2O2 (1–100 mmol/L). The optimum conditions for photocatalytic degradation were achieved at concentrations of 0.5 g TiO2/L and 50 mmol H2O2/L, respectively. Dye mineralisation was confirmed by monitoring TOC, conductivity, sulfate and nitrate ions, with a sulfate ion yield of 96% under optimal reactor conditions. Complete decolorisation was attained after 240 min irradiation time for all tested azo-dyes, in a process which followed a pseudo-first kinetic order model, with a kinetic rate constant of approximately 0.018 min−1. Based on these results, this photocatalytic process has promise as an alternative f...
Journal of Photochemistry and Photobiology A-chemistry, 2003
Acid Red 14 (AR14), commonly used as a textile dye, could be photocatalytically degraded using TiO 2 suspensions irradiated by a UV-C lamp (30 W). The experiments showed that TiO 2 and UV light had a negligible effect when they were used on their own. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction (K = 1.41 × 10 −2 min −1 ). The effects of some parameters such as pH, the amount of TiO 2 and initial dye concentration were also examined.
Journal of the Chilean Chemical Society, 2009
The photocatalytic degradation of aqueous solution of commercial azo textile dye, direct red 23 (DR23), was carried out in TiO 2 suspension at 30ºC with the use of artificial and solar light sources. The photoreaction followed the first-order behavior with respect to the azo dye as a function of irradiation time. A 2 3 factorial design was carried out, in order to obtain the best experimental conditions, using the rate constant of DR23 degradation as the analytical response. Seven chemical species were determined from the normalized UV-Vis spectra during the DR23 degradation through Imbrie Q mode factor analysis followed by varimax and Imbrie oblique rotations. The addition of electron acceptors, such as H 2 O 2 , S 2 O 8 2-, and ClO 3 on the optimized conditions, was carried out to increase the DR23 degradation rate. Comparison of degradation efficiencies under artificial and solar radiation was examined in the presence of oxidants.
Process Development for Photocatalytic Degradation of Reactive Dyes in Wastewater
Advanced oxidation processes (AOPs) are widely used for the removal of recalcitrant organic constituents from industrial and municipal wastewater. This study mainly focused the use of TiO 2 and ZnO catalysts for removal of textile dyes. Synthesis of TiO 2 and ZnO photo catalysts was done by sol-gel method. These catalysts were used to obtain enhanced photo catalytic action and were coated on glass beads to improve the photo catalytic activity. The synthesized beads were examined using SEM, FTIR and XRD. Synthesized photocatalysts were examined extensively for their photocatalytic activities with Reactive Orange(RO), Reactive Blue(RB), Textile industry Effluent (TIE) and mixture of dyes (RO+RB, RO+RB +TIE) at various concentrations (50ppm, 100ppm). The photocatalytic degradation of RO, RB, TIE, RO+RB and RO+RB +TIE dyes solution (100mg/L and 50mg/L) using TiO 2 and ZnO were investigated under UV light irradiation (λ=254nm). Photocatalytic studies revealed that the TiO 2 has shown much higher photocatalytic activity than the ZnO catalyst. The photocatalytic activity of the TiO 2 catalyst follows the order: Reactive Orange of 50 ppm (80.98%) > Reactive Blue dye of 50 ppm (77.17%)> Reactive Orange dye of 100 ppm (74.98)>Reactive blue of 100 ppm (72%). The photocatalytic activity of the ZnO catalyst follows the order: Reactive Orange of 50 ppm (75.12%) > Reactive Blue dye of 50 ppm (73.98%)> Reactive Blue dye of 100 ppm (71%)>Reactive Orange of 100 ppm (70%).
Chemistry & Chemical Technology, 2010
In this work a detailed investigation of heterogeneous photocatalytic degradation of Navy blue HE2R 1 (NB), azo dye of the reactive class is presented using UV/TiO2/H2O2 process in the aqueous suspension under 8W low-pressure mercury vapor lamp irradiation. Here we also report about optimization of various experimental parameters such as effect of catalyst concentration, effect of substrate concentration, effect of H2O2 addition. The effect of the UV/TiO2/H2O2 process employment and selection of optional operational parameters on complete decolorization and substantial decrease of Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) of dye solution has been established.
Optimization of the photocatalytic degradation of commercial azo dyes in aqueous TiO2 suspensions
Reaction Kinetics, Mechanisms and Catalysis, 2014
The photocatalytic degradation of three textile azo dyes, Remazol Yellow Gold RGB, Remazol Blue RGB and Remazol Carbon RGB has been studied in model effluents regarding the variation of parameters as concentration of titanium dioxide (TiO 2 ), concentration of the dyes, effect of hydrogen peroxide (H 2 O 2 ), effect of pH, recycling of TiO 2 . The concentration of 1 g L -1 of TiO 2 degraded around 100 % of Remazol Blue RGB and Remazol Carbon RGB and around 90 % for the Remazol Yellow Gold RGB after 120 min of photodegradation. The remaining concentrations of added TiO 2 were found to be less efficient, except for Remazol Blue RGB, which still reaches about 80 % photodegradation, for 0.1 g L -1 of TiO 2 . The efficiency of photodegradation of all dyes decreased with an increase of the initial dye concentration. For a concentration of 30 mg L -1 , all dyes showed around 100 %. However, upon increasing the concentration of the dye until 150 mg L -1 , the photodegradation becomes very slow, with photodegradation rates off only 11 % for Remazol Yellow Gold RGB and Remazol Blue RGB and 9.7 % for the Remazol Carbon RGB. Photodegradation of the three dyes was found to be pH dependent. The maximum reaction rate was observed with 0.3 9 10 -3 mol L -1 120 min). At higher concentrations of H 2 O 2 , the degradation efficiency decreased significantly for all dyes. In what regards the reuse of the photocatalyst, the first cycle degraded 100 % of the Remazol Carbon RGB after 60 min of irradiation and the second and third cycles degraded 44 and 36 % of the dye. The effect of the simultaneous photodegradation of the three azo dyes in water was further investigated for distilled and natural lake water. It was observed that the degradation rates achieved in mono and three-component system were identical. The degradation yield in lake water observed to be smaller than in distillated water with 75, 72 and 53 % (99, 98 and 88 % in distilled water) of degradation for Remazol Blue RGB, Remazol Carbon RGB and Remazol Yellow Gold RGB, respectively.
Research Article, 2019
Industrial wastewaters are the major source polluting the surface and ground water resources. Pollutants released along with the untreated textile industry wastewaters are responsible for the great damage to the natural resources like water. Considering the hazardous effects of the azo dyes (textile coloring agents) and their byproducts, there is a need to develop cost-effective and efficient treatment method for the textile wastewaters as such dyes have been reported as toxic, mutagenic, and carcinogenic and can cause direct demolition of aquatic communities. One of the possible and effective treatment methods is the use of TiO 2 photocatalysis due to its chemical stability, low cost, and non-toxic nature. The present study explored the photocatalytic potential of anatase-type of bimetallic Cu-Ni/TiO 2 photocatalysts under visible light irradiation for possible photocatalytic degradation and mineralization of Methyl Orange (MO), as model azo dye. The focus was to correlate the synthesis (different calcination temperatures, phase composition of TiO 2 either anatase or rutile, and metal ion loading in terms of concentration and composition (Cu:Ni)) and operational parameters (photocatalyst loading, pollutant concentration, and irradiation time) that were believed responsible for the enhanced photocatalytic performance. Blank experiments were carried out to check the effect of metal loading in comparison to bare TiO 2 and effect of absence or presence of light and photocatalysts on MO photodegradation. Results obtained using bimetallic photocatalysts are promising as compared to bare TiO 2 as 100% MO removal and ~ 90% %COD removal were obtained in 90 min of irradiation, obeying a pseudo-first-order kinetics with photocatalytic reaction via the Langmuir-Hinshelwood mechanism with a good linear fit. Photocatalysts synthesized using anatase TiO 2 were reported with improved performance compared to rutile phase. It is evident that synthesis parameters influence photocatalyst performance directly. The higher rate constant (> 1) that proves the excellent adsorption capacity of the tested photocatalysts for tested pollutants on the surface may have a great prospective for photocatalytic water purification at neutral pH.
A review on Parameters Affecting the Photocatalytic Degradation of Dyes using Photocatalysts
2013
Production of clean hydrogen energy and removal of environmental pollutants using photocatalysis technique have received a great deal of interest in recent few decades. Photocatalytic reaction catalyzed by semiconductors has been approved as a promising process for solving energy and environmental issues. This paper presents an overview of photocatalytic degradation of dyes in presence of UV light. We highlight here the effects of various parameters, such as the amount of the catalyst loading, initial concentrations of dye and pH along with the study of reaction mechanism of photocatalysis. A case study is examined which gives an overview of different operating parameters affecting the photocatalytic degradation of Rhodamine-B in aqueous solution with titanium dioxide (TiO 2 ) and niobium pentaoxide (Nb 2 O 5 ) as photocatalyst in slurry form has been carried out using UV-A light (254 nm). The effect of various parameters such as catalyst loading, pH and initial concentration of the RB dye on degradation is determined. The maximum rate of degradation was observed in acidic medium at pH 3 for catalyst TiO 2 and Nb 2 O 5 respectively. It was observed that the photocatalytic activity of TiO 2 is greater than Nb 2 O 5 .