Photocatalytic Decoloration Efficiencies of ZnO and TiO 2 : A Comparative Study (original) (raw)
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Drinking Water Engineering and Science, 2017
In this study, we evaluated the photocatalytic activities of analytical reagent (AR) grade ZnO, TiO 2 , and SnO 2 to identify a low-cost photocatalyst for dye degradation. The obtained samples of ZnO, TiO 2 , and SnO 2 were characterised by X-ray diffractogram (XRD), scanning electron microscope imaging, and UV-VIS diffuse reflectance spectroscopy. The decolourisation of three structurally diverse dyes, namely crystal violet, basic blue, and methyl red under solar irradiation, was used to evaluate the photocatalytic activities of three metal oxides. The photocatalytic activities of the received three metal oxides were tested with the photocatalytic degradation of dyes and compared with Degussa P-25. Dye solutions with each metal oxide at initial pH 9 were subjected to irradiation under sunlight and monitored for up to the stage of complete decolourisation. The results indicate that ZnO exhibited the highest photocatalytic activity as compared to TiO 2 and SnO 2 as well as that of Degussa P-25 (TiO 2). The photocatalytic dye decolourisation rates with ZnO were 1.14-1.35, 1.70-3.1, and 4-8.5 times higher than those of the Degussa P-25, TiO 2 , and SnO 2 , respectively. The percentage COD removal was studied for ZnO and partial removal was observed at the decolourisation stage. To enhance photocatalytic activity of AR grade ZnO, it was loaded with Ag metal and about 20 % enhancement in the activity was observed.
2017
Decolorization of blue azo dye (Cibacron Blue FN-R) from simulated wastewater has been investigated as a function of solar photocatalysis process. The photocatalysis activity using different catalysis was compared. Different parameters affected the removal efficiency, including initial concentration of dye, pH of the solution, catalysis dosage, and H2O2 concentration, were evaluated to find out the optimum operation conditions. The results proved that, the optimal pH value for TiO2, V2O5 and ZnO were 2, 2, and 8 respectively and the best catalysis dosage was 500mg/L for TiO2, V2O5 and ZnO. In addition, the most efficient H2O2 concentration was 300,100, 100 mg/L for TiO2, V2O5 and ZnO respectively. The theoretical relationships described the photocatalysis process have been predicted for the three catalysis. It can be concluded, from these experiments, that the using of ZnO as a photocatalysis was found to be more efficient than TiO2 and V2O5 to remove blue azo dye from aqueous solut...
Photo Degradation of Industrial Dye Using ZnO as Photo Catalyst
2015
In this study, the potential of a common semiconductor, ZnO, has been explored as an effective photocatalyst for the photodegradation of model dye: Methylene Blue, a commonly used textile dye. Using advanced oxidation processes (AOPs), ZnO appears to be a suitable alternative to TiO2 for water treatment. The experiments were carried out by irradiating the aqueous solution of dye containing photocatalysts with UV light. Here, a detailed investigation of the effects of process parameters like catalyst loading, initial dye concentration, presence of hydrogen peroxide and pH on the extent of photodegradation have been presented. Hence, it may be a viable technique for the safe disposal of textile wastewater into the water streams.
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.
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...
Nanochemistry Research, 2016
Nanoparticles of the ZnO and TiO2 were synthesized and the physicochemical properties of the compounds were characterized by IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns of the ZnO and TiO2 nanoparticles could be indexed to hexagonal and rutile phase, respectively. Aggregated nanoparticles of ZnO and TiO2 with spherical-like shapes were observed with particle diameter in the range of 80-100 nm. These nanoparticles were used for photocatalytic degradation of various dyes, Rhodamine B (RhB), Methylene blue (MB) and Acridine orange (AO) under solar light irradiation at room temperature. Effect of the amount of catalyst on the rate of photodegradation was investigated. In general, because ZnO is unstable, due to incongruous dissolution to yield Zn(OH)2 on the ZnO particle surfaces and thus leading to catalyst inactivation,the catalytic activity of the system for photodegradation of dyes decreased dramatically when TiO2 was replaced by ZnO.
Photocatalytic degradation of azo dyes using Zn-doped and undoped TiO2 nanoparticles
Applied Physics A, 2013
Mn (0.5%, 1%, 1.5% and 2%) doped and undoped ZnO nanoparticles (NPs) capped with PVP (1.0%) were successfully synthesized via co-precipitation approach using zinc acetate, sodium hydroxide and manganese acetate as precursors. Structural analysis was performed by XRD confirming phase purity and crystalline wurtzite structure. TEM results show average particle size 15-20 nm and 22-25 nm for Mn (1%) and Mn (2%) doped ZnO NPs respectively. Manganese (Mn) doping has led to reduction in band gap which facilitate the absorption of radiation in visible region. The Photocatalytic activity of undoped and Mn (0.5%,1%,1.5% and 2%) doped NPs was analyzed via degradation of crystal violet (CV) dye. The crystal violet decomposition rate of undoped and Mn doped NPs were studied under UV-visible region. It is observed from degradation studies that the doping has a pronounced effect on the photocatalytic activity of ZnO NPs. Kinetic studies shows that photo degradation of CV follow a pseudo first-order kinetic law. Experiments for reusability of Mn (1%) doped with PVP (1%) capped ZnO were also performed to determine the stability of as prepared sample. It shows an increase in catalytic activity of NPs by small amount when exposed to UV irradiation for 3 h. Photoluminescence and UV-Visible absorption spectroscopy studies were also performed for studying the effect of UV irradiation on the surface of ZnO NPs.
Zinc oxide assisted photocatalytic decoloriztion of reactive red 2 dye
The photocatalytic decolorizations of aqueous solutions of Reactive Red 2 dye in the presence of ZnO suspension has been investigated with the use of artificial UV-A light sources. The effects of various parameters, such as time of irradiation, photocatalyst amount, pH, addition of H 2 O 2 and temperature on photocatalytic degradation were investigated.
Journal of Physics and Chemistry of Solids, 2011
Polydispersed ZnO nanoparticles (ZnO1000 and ZnO600) with two different windows of particle size distributions ( $ 120 and 30 nm) were synthesized using citrate gel route and different annealing treatments (1000 and 600 1C, respectively). Photocatalytic efficiency of these samples was compared with TiO 2 in its commercial form-P25, on two dyes, Methylene blue (MB) and Methyl orange (MO). The X-ray diffraction data showed wrutzite ZnO and anatase and rutile phases of P25. UV-visible absorbance spectra of ZnO1000 showed broad absorption range from UV-to-visible (from 382 to 700 nm), as against sharp absorption peaks in UV range for both ZnO600 and P25. The microstructural morphology as seen through scanning electron micrographs showed ZnO1000 with tetrapod-like structures while the ZnO600 showed almost spherical morphologies. Upon subjecting these catalysts to dye solutions in sunlight it was found that both the dyes were completely decolorised within 20 min by ZnO1000, as against partial decolorisation by ZnO600 and P25 ( 53% and 78% for MO and 77% and 88% for MB samples). The effect of catalyst loading (from 125 mg to 1 g) on decolorisation showed that ZnO1000 had good efficiency for all concentrations which was followed by P25 and then by ZnO600. Small perturbations are attributed to the competition between sunlight scattering-induced, reduced irradiation field and the exposed surface area offered by catalyst, which work as active sites for decolorisation. The reusability of the catalysts when studied on fresh dye samples (4 trials), the decolorisation efficiency decreased merely from 99.2% to 99.12% for ZnO1000 as compared to ZnO600 (53.3% to 19.94%) and P25 (78.3% to 31.42%), indicating the efficient reusability of ZnO1000. The effective half life of the catalysts, in terms of number of reuses, were calculated and found to be $ 3 for both ZnO600 and P25 and was 4 3000 for ZnO1000, which justifies its extremely high reuse. The byproduct analysis (compared with standards prescribed by World Health Organisation (WHO) and Central Pollution Control Board of India (CPCB)) showed cleavage of the chromophore and of other bonds with opening of benzene rings, indicating degradation of the dyes in concurrence with decolorisation, in the stipulated time. Further, cytotoxicity studies performed on SiHa cell lines showed non-toxicity of the byproducts with ZnO1000 as compared to ZnO600 and P25.
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%).