A newly green photocatalyst support for azo dye remediation under UV light irradiation (original) (raw)
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Journal of JSCE, 2014
The photocatalytic degradation of textile wastewater containing Reactive Black 5 (RB5) azo dye was investigated by using immobilized TiO 2 nanofiber-nanoparticle composite catalyst on glass plates. The process was studied by monitoring the change in RB5 concentration, depletion in total organic carbon (TOC) and by determining the intermediate products using UV-visible spectrophotometry and gas chromatography-mass spectrometry (GC-MS) techniques. After immobilization, the composite shows higher photocatalytic activity for degradation of RB5 than that of nanoparticle thin-film layer under UV irradia-ion. Complete decolorization was achieved in 120 min, corresponding to organic degradation with a reduction in TOC after 300 min of UV irradiation by 91%. The photocatalytic degradation mechanism of RB5 was proposed based on the identified compounds by GC-MS technique, showing the destruction of the azo dye structure, which became smaller molecular mass compounds. The degradation slightly decreased after multiple reuse of composite catalyst during photocatalytic treatment. The recovery of its photocatalytic performance was obtained through reannealing.
Molecules, 2011
The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO 2 P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO 2 used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO 2 reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the OPEN ACCESS adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.
Catalysts, 2022
A novel B-doped ZnO/TiO2 (B–ZnO/TiO2) nanocomposite photocatalyst was prepared using a mechanochemical–calcination method. For the characterization of the synthesized B–ZnO/TiO2 photocatalyst, XRD, FESEM-EDS, FTIR, UV-Vis DRS, BET, PL, and XPS techniques were used. The bandgap energy of B–ZnO/TiO2 was reduced, resulting in enhanced visible-light absorption. Significant PL quenching confirmed the reduction in the electron–hole recombination rate. Furthermore, reduced crystallite size and a larger surface area were obtained. Hence, the B–ZnO/TiO2 photocatalyst exhibited better photocatalytic activity than commercial TiO2, ZnO, B–ZnO, and ZnO/TiO2 in the removal of methylene blue (MB) dye under natural sunlight irradiation. The effects of various parameters, such as initial concentration, photocatalyst amount, solution pH, and irradiation time, were studied. Under optimal conditions (MB concentration of 15 mg/L, pH 11, B–ZnO/TiO2 amount of 30 mg, and 15 min of operation), a maximum MB ...
Polymer Nanocomposites for Photocatalytic Degradation and Photoinduced Utilizations of Azo-Dyes
Polymers, 2021
Specially designed polymer nanocomposites can photo-catalytically degrade azo dyes in wastewater and textile effluents, among which TiO2-based nanocomposites are outstanding and extensively explored. Other nanocomposites based on natural polymers (i.e., chitosan and kaolin) and the oxides of Al, Au, B, Bi, Fe, Li, and Zr are commonly used. These nanocomposites have better photocatalytic efficiency than pure TiO2 through two considerations: (i) reducing the hole/electron recombination rate by stabilizing the excited electron in the conducting band, which can be achieved in TiO2-nanocomposites with graphene, graphene oxide, hexagonal boron nitride (h-BN), metal nanoparticles, or doping; (ii) decreasing the band energy of semiconductors by forming nanocomposites between TiO2 and other oxides or conducting polymers. Increasing the absorbance efficiency by forming special nanocomposites also increases photocatalytic performance. The photo-induced isomerization is exploited in biological ...
Sprayed nanostructured TiO 2 films for efficient photocatalytic degradation of textile azo dye
Spray pyrolysis procedure for preparation of nanostructured TiO 2 films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO 2 were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO 2 is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80 ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO 2 , which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films.
DESALINATION AND WATER TREATMENT, 2018
Photocatalytic oxidation of dyes using TiO 2 is amply studied; however, there are no reports demonstrating reductive photocatalytic decolourization of dyes and underlying mechanisms. We investigated photocatalytic reduction of Reactive Black 5 (RB5) dye using TiO 2 and UV light in the presence of various hole scavengers (HSs). Around 94% of 50 mg L-1 initial RB5 was decolourized in the presence of 2 mM oxalic acid (OA) and 0.5 g L-1 TiO 2 , after 1 h irradiation at initial pH 2.8. OA yielded highest rate and extent of RB5 decolourization among all HS, probably due to superior hole-scavenging activity and capacity to produce reductive radicals. LC-MS analysis of decolourized RB5 sample revealed the presence of 2-((4-aminophenyl) sulphonyl) ethyl hydrogen sulphate, and 3,4,6-triamino-5hydroxynaphthalene-2,7-disulphonic acid as end-products; indicating cleavage of azo bonds as a main mechanism of decolourization. The contribution of reducing species for reductive RB5 decolourization was found to be in the order of e C O radical CO cb − • − • − > > 2 4 2 radical. The rates of RB5 decolourization, appearance and time point of highest accumulation of end-products, were greatly influenced by the initial pH, type and concentration of HS. TiO 2 exhibited excellent reusability and regenerability. Around 65% decolourization was obtained even after the fifth reuse. The regenerated TiO 2 exhibited photocatalytic activity almost similar to the fresh TiO 2 .
Photocatalytic degradation of textile dyes by hydrogel supported titanium dioxide nanoparticles
Background: Textile industry has been condemned as one of the world's worst offenders in terms of pollution because 10-15% of all the dyes used in the industry are lost within wastewater during processing. The presence of even very low concentrations of dyes in effluent is highly visible and degradation products of these textile dyes are often carcinogenic. Owing to the complex nature of synthetic dyes, conventional biological treatment methods are ineffective. Hence there exist needs for developing treatment techniques that can lead to the complete destruction of the dye molecules from waste stream. The current study focused to develop a new photocatalytic reactor using immobilized TiO2 capacity to decolourise and degrade textile industry effluent in an effective way. Methods: TiO2 nanoparticles synthesized by simple precipitation method at pH 5 was successfully entrapped in biopolymer calcium (Ca)-alginate and used as heterogeneous photocatalyst for the degradation of various textile dyes using UV radiations. Photocatalyst was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of previous operational parameters on the photodegradation has been studied by setting up a laboratory scale photocatalytic reactor. Results: The scanning electron microscopic images indicate that, the alginate gel acts as a bridge that binds the nanoparticles together. The experimental results showed that the rate of degradation depends on the chemical structure of different dyes as well as adsorption of dyes by TiO2 which is directly proportional to the surface area and dispersion of the catalyst, the adsorption of light by the dye. The kinetics of COD disappearance was slower than the discoloration of the solution. The supported TiO2 can be used several times without lose of efficiency Conclusions: The results of this study have shown that the degradation of different textile dyes was successfully carried out in laboratory scale photoreactor containing coated TiO2 as photo catalyst. Calcium alginate can be used as a green support for immobilizing TiO2 nanoparticles and can be used for developing a new environment friendly immobilization system for large scale water treatment. Keywords: Immobilized TiO2 nanoparticles, photocatalytic degradation, textile dyes
Journals of Community Health Research, 2015
Introduction: In this research mixed ZnO and TiO2 was used for degradation of an azo dye (Direct Blue 71). Material and Methods: In comparison with just TiO2 or ZnO as photocatalyst, mixed photocatalyst (ZnO/TiO2) is more efficient catalyst for degradation of dye under UV irrad iation. The progress of the reactions was monitored spectrophotometrically by measuring the absorbance of dye at special wavelengths. The effects of various parameters such as ZnO/TiO2 ratio, amount of photocatalyst, pH, init ial dye concentration and irradiation time on decolorization rate were systematically investigated. Results: Results show that approximately 90 % of Direct Blue 71 has been eliminated after 70 minutes and optimized condition.
DESALINATION AND WATER TREATMENT, 2019
Dyes used in the textile industry have varied and complex structures are designed to resist degradation by external agents. Most are water soluble, resistant to chemical agents and not biodegradable, so they cannot be easily removed by wastewater treatment plants. Remazol Brilliant Blue R (RBBR) is one of the most important colorants in the textile industry, and it is frequently used as a starting material in the production of polymer dyes. This work studied the degradation of a textile dye by a heterogeneous photocatalysis process, using a titanium dioxide catalyst doped with nitrogen from urea, in the presence of visible light irradiation. For the optimization of the process a Box-Benhken experimental design was performed. Where, the TiO 2 was varied from 0.1 gL-1 (-1) to 1.0 gL-1 (+1), and the pH between 2.0 (-1) to 11(+1). With the optimal response it was possible to remove 86.3% of the dye (R 2 = 0.987 and Q 2 = 0.873, p ≤ 0.001). The mineralization grade was determined through TOC analysis, which reached 50%, and the toxicity was evaluated with Daphnia magna nematodes, which was reduced considerably after photocatalytic treatment.