Application of solar photocatalysis for colour removal from dye-bath wastewater (original) (raw)
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Decolouration of textile dyes in wastewaters by photocatalysis with TiO2
Solar Energy, 2005
The photocatalytic removal of colour of a synthetic textile effluent, using TiO 2 suspensions under solar radiation, has been studied at pilot plant scale. A synthetic dye solution was prepared by a mix of six commercial textile dyes. A photochemical reactor of parallel CPC reflectors with UV-transparent tubular receivers was used. The study of photodegradation was carried out using the TaguchiÕs parameter design method. Following this methodology, the reaction was conducted under different flow conditions, pH and H 2 O 2 concentrations. The results show that all dyes used in the experiences can be degraded successfully by photo-oxidation. The process shows a significant enhancement when it is carried out at high flows, alkaline media and high H 2 O 2 concentration. Colour removal from the effluent was reached at 55 min operating time.
Photocatalytic Degradation of Reactive Yellow Dye in Wastewater using H 2 O 2 /TiO 2 /UV Technique
In the present study, advanced oxidation treatment, the TiO2 /UV/H2O2 process was applied to decolourisation of the reactive yellow dyes in aqueous solution. The UV radiation was carried out with a 6 W low-pressure mercury lamp. The rate of colour removal was studied by measuring of the absorbency at characteristic wavelength. The effects of H2O2 dosage, dye initial concentration and pH on decolourisation kinetics in the batch photoreactor were investigated. The highest decolourisation rates were observed (98.8) at pH range between 3 and 7. The optimal levels of H2O2 needed for the process were examined. It appears that high levels of H2O2 could reduce decolourisation by scavenging the *OH. The colour degradation rate decreases as the dye concentration increases. The rate coefficient (k=0.0319 min-1) of degradation, follows the pseudo-first-order kinetics.
Solar photocatalytic treatment of simulated dyestuff effluents
Solar Energy, 2004
The photocatalytic organic content reduction of two selected synthetic wastewater from the textile dyeing industry, by the use of heterogeneous and homogeneous photocatalytic methods under solar irradiation, has been studied at a pilot plant scale at the Plataforma Solar de Almeria. The effect of two different TiO 2 modifications with oxidants such as H 2 O 2 and Na 2 S 2 O 8 on the decolourisation and the dissolved organic content reduction (DOC) of the wastewater was examined. The TiO 2 /H 2 O 2 system seems to be more efficient in comparison to the synergetic action that appears when using persulphate and TiO 2 in this specific wastewater. By an accumulated energy of 50 kJ l À1 the synergetic effect of TiO 2 P-25 with H 2 O 2 and Na 2 S 2 O 8 leads to a 70% and 57% DOC reduction, respectively, in the case of cotton synthetic wastewater, while the decolourisation was almost complete. The photocatalytic decolourisation, as well as the DOC reduction in the case of nylon simulated wastewater is a slower process and an accumulated energy of 50 kJ l À1 leads to almost 54% mineralisation in both cases. The photo-Fenton process in both types of wastewater was more efficient in comparison to the TiO 2 /oxidant system. An accumulated energy of 50 kJ l À1 leads to 90% reduction of the organic content.
Photocatalytic degradation of Direct Yellow 12 dye using UV/TiO2 in a shallow pond slurry reactor
Dyes and Pigments, 2006
The adsorption and photocatalytic degradation of diazo Direct Yellow 12 (Chrysophenine G), commonly used as a cotton, paper and leather dye has been investigated in aqueous suspension of semiconductor oxide TiO 2 as photocatalyst in a non-concentrating shallow pond slurry type reactor under UV light. The adsorption of dye on the semiconductor shows a strong dependence on the pH and follows a Langmuir adsorption model. The studies include dark adsorption experiments at different pH conditions and their effect on initial rate of photodegradation. The effect of initial concentration of dye, catalyst loading, pH, addition of oxidant on the reaction rate was ascertained and optimum conditions for maximum degradation was determined. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the LangmuireHinshelwood model. COD analysis of the dye under optimum conditions showed 94% reduction in COD after 2.5 h and complete decolourisation as determined by UVevis analysis was achieved in 1.5 h.
2006
The adsorption and photocatalytic degradation of diazo Direct Yellow 12 (Chrysophenine G), commonly used as a cotton, paper and leather dye has been investigated in aqueous suspension of semiconductor oxide TiO 2 as photocatalyst in a non-concentrating shallow pond slurry type reactor under UV light. The adsorption of dye on the semiconductor shows a strong dependence on the pH and follows a Langmuir adsorption model. The studies include dark adsorption experiments at different pH conditions and their effect on initial rate of photodegradation. The effect of initial concentration of dye, catalyst loading, pH, addition of oxidant on the reaction rate was ascertained and optimum conditions for maximum degradation was determined. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the LangmuireHinshelwood model. COD analysis of the dye under optimum conditions showed 94% reduction in COD after 2.5 h and complete decolourisation as determined by UVevis analysis was achieved in 1.5 h.
SOLAR PHOTOLYSIS AND PHOTOCATALYTIC TREATMENT OF TEXTILE INDUSTRIAL WASTEWATER
The objective of this research was to investigate experimentally the removal the dyestuff from dyeing textile industrial wastewater by photosensitization process, for reusing it in the same industry or for domestic purpose and/ or irrigation. In this study, the photocatalytic decolorization of two collected samples of real and one prepared simulated textile industrial wastewater using titanium dioxide and zinc oxide were examined under natural weathering conditions. The effect of various operational parameters such as catalyst mass, type of catalyst, type of reactor, type of dye, dye concentration, and temperature were investigated. Photolysis and photocatalytic treatments were carried out over a suspension of titanium dioxide or zinc oxide under solar irradiation. The progress of treatment stages was followed spectrophotometrically at different wavelength. Under optimal conditions, the extent of decolorization was 100% after different periods of time ranging from 10 to 100 minutes. The decolorization percentages differ with the difference in type of dye used in textile industry. The results indicate clearly that titanium dioxide and zinc oxide could be used efficiently in photocatalytic treatments of textile industrial wastewater. However, the activity fell in the sequence: ZnO > TiO2 (Anatase) > TiO2 (Rutile) Decolorization of real and simulated textile industrial wastewater without light and without catalyst was performed to demonstrate that decolorization of the dye depends on the presence of light and catalyst, both.
Removal of synthetic and industrial effluent color by photocatalytic process
Water science and technology : a journal of the International Association on Water Pollution Research, 2018
The present work aimed at evaluating the photocatalytic process as an alternative for color removal from a synthetic solution (methylene blue dye) and of a sample of textile effluent, obtained from the various stages of the process, mainly dyeing. The parameters were evaluated using titanium dioxide (anatase, rutile, commercial and synthetized by the sol-gel method) in order to determine their structural influence in the discoloration of the samples. A synthetic methylene blue dye solution and a real effluent (Brazilian textile industry) were treated. The photocatalytic degradation was carried out over three hours in a batch reactor, under constant agitation, aeration, radiation and temperature. It was observed that the characteristics of each catalyst directly influence the photocatalytic activity. As a result, for the variables used in this work, the photocatalyst TiO anatase phase with a concentration of 1 kg/m³ was the most efficient condition, presenting full color removal for ...
The Comparison of Photocatalytic Degradation and Decolorization Processes of Dyeing Effluents
International Journal of Photoenergy, 2013
Treatment of dye effluents resulting from the industrial scale dyeing of cotton, polyacrylic fibres, leather, and flax fabrics by photocatalytic methods was investigated. Photocatalytic processes were initiated by UV-a light ( max 366 nm) and were conducted in the presence of TiO 2 , TiO 2 /FeCl 3 , or FeCl 3 as photocatalysts. It was found that the photocatalytic process carried out with TiO 2 and TiO 2 /FeCl 3 was the most effective method for decolorization of textile dyeing effluents and degradation of dyes, except for effluents containing very high concentrations of stable azo dyes. During the photocatalytic degradation of anionic dyes, a mixture of TiO 2 /FeCl 3 was more effective, while in the case of cationic dyes, more suitable seems to be TiO 2 alone. d Absorption band without any clear maximum.
The photocatalytic decolorization of industrial wastewater was investigated by using TiO2 and ZnO photocatalysts. Heterogeneous photocatalytic processes applied under natural weathering conditions, in the presence of solar radiation show a promising degradation capability. The complete removal of color could be achieved in a relatively short time of about 20 minutes, when ZnO was used and about 100 minutes when TiO2 was used under solar irradiation. However, in the presence of artificial UV-light, complete decolorization of textile industrial wastewater was obtained after less than one hour of irradiation when ZnO was used and in less than two hours, when TiO2 was used at the same temperature. The results indicate that the degree of photocatalytic decolorization of textile industrial wastewater was obviously affected by different parameters. These parameters include catalyst mass, type of catalyst, type of reactor, type of dye, dye concentration, and temperature. The procedure used in this research can be used as an efficient technology for solar photocatalytic decolorization of the colored wastewater discharged from the textile industry under the climatic conditions of most countries.
Decolorization of Textile Dyes by Immobilized Photocatalytic Degradation Process
irphouse.com
The photocatalytic degradation of various dyes (Reactive Black-5 (RB-5), Red (ME4BL), Golden yellow (MERL), Blue-222, Methylene Blue, and Malachite Green) has been studied, using TiO 2 (P25) as a photocatalyst. Experiments were conducted in continuous immobilized photocatalytic reactor and show effective decolorization of all textile dye solutions. The thin film immobilized surface photo-reactor was able to give nearly 90-98% color removal depending on the initial concentration and exposure time. Flow rate has noticeable effect on color removal particularly at higher concentration. This process was found to be effective for the decolorization of textile wastewater.