Influence of chemical structure of dyes, of pH and of inorganic salts on their photocatalytic degradation by TiO2 comparison of the efficiency of powder and supported TiO2 (original) (raw)
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This paper presents the review of the effects of operating parameters on the photocatalytic degradation of textile dyes using TiO 2-based photocatalysts. It further examines various methods used in the preparations of the considered photocatalysts. The findings revealed that various parameters, such as the initial pH of the solution to be degraded, oxidizing agents, temperature at which the catalysts must be calcined, dopant(s) content and catalyst loading exert their individual influence on the photocatalytic degradation of any dye in wastewaters. It was also found out that sol–gel method is widely used in the production of TiO 2-based photocatalysts because of the advantage derived from its ability to synthesize nanosized crystallized powder of the photocatalysts of high purity at relatively low temperature.
Journal of Materials Science & Technology, 2017
TiO 2 particles with desirable properties were produced by undergoing specific durations of ball milling. Characterizations of the TiO 2 particles before and after ball milling were investigated via X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), particle size analysis, zeta potential, and scanning electron microscope (SEM). The equilibrium adsorption data were well fitted to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. Compared to the as-received TiO 2 (mean particle size d 50 =0.78 µm, specific surface area=88.17 m 2 g-1 , pore volume=0.41 cm 3 g-1), the 60 min ball-milled TiO 2 (d 50 =0.55 µm, specific surface area=99.48 m 2 g-1 , pore volume=0.48 cm 3 g-1) enhanced the adsorption quantity of congo red and methylene blue from 10.4 mg g-1 to 13.6 mg g-1 , and from 17.0 mg g-1 to 22.2 mg g-1 , respectively; and also improved the kinetic rates from k=0.1325 to 0.2193, and k=0.0944 to 0.1553, respectively. Dye adsorption and degradation efficiency of congo red was enhanced in acidic pH range (2-5.14), and methylene blue was enhanced in alkaline pH range (7.58-12).
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.
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.
Contemporary Engineering Sciences, 2015
Synthetic dyes are difficult to degrade in nature and contain hazardous material which can generate skin cancer and if not well treat, the synthetic dyes wastewater also can kill the organism live in the environment. One of alternative methods for handling the synthetic dyes wastewater is by using photocatalytic process as one of Advanced Oxidation Processes (AOPs). Semiconductor photocatalyst of TiO2 under solar irradiation was chose in this process. The objective of this work is to study the application of Titanium dioxide (TiO2) nano-particles photocatalyst to degrade the sample of synthetic dye wastewater with solar irradiation assistance. The anatase-powder and anatase-nano powder of TiO2 used in this research was coated on the plastic media to prevent the cost of separation. The synthetic dye wastewater was made from Procion Redas a model of organic pollutant. The concentration of Procion Red was 100 mg/L. The TiO2 concentration of the 1626 Tuty Emilia Agustina et al. coating solution immobilized on the plastic material was varied between5-40% (w/v).The photocatalytic degradation of Procion Red synthetic dye was studied under solar irradiation within 3-12 hours, from 9 am until 3 pm for 2 days. The results show that the highest color degradation of 98% and COD degradation of 56% were achieved when using 40% anatase-nanopowder TiO2concentration of coating solution under sunlight of 12 hrs. The nano-particles have a high interaction surface. As the interaction of particles increase, the catalyst activity will increases and inhibit the recombination reaction. In the nano-particle size, the TiO2photocatalyst can absorb the UV vis from the sunlight to excite the electron and furthermore generate the hydroxyl radical as a strong oxidiser. The hydroxyl radicals oxidize the organic pollutant to be the less harmful compound and finally to carbon dioxide and water. As the generation of hydroxyl radical rise, the degradation of organic pollutant will increase. As the conclusion, it is feasible to apply the TiO2nano-particles photocatalyst to degrade the sample of synthetic dye wastewater with solar irradiation assistance. In this research, the degradation of colour and COD increase as the nano-particles TiO2photocatalyst concentration of coating solution and the exposure time increase. The colour degradation and COD degradation of 98% and 56%, respectively, was obtained under solar irradiation of 12 hours.
Water Science and Technology, 2020
Recently, the utilization of wastes, recovery of high value-added products from waste, and their use as raw materials in other industries with the logic of industrial symbiosis has become an important issue. In this study, removal efficiency of Reactive Orange 16 (RO16) dye from aqueous solution was studied using TiO2 catalyst recycled from an industrial waste effluent. The recycling of TiO2 waste from a paints manufacturing industry was carried out by sintering the TiO2-containing waste. The catalyst usability of TiO2-containing powder was then investigated in the removal of RO16 dye by photocatalytic oxidation process. In photocatalytic oxidation studies, TiO2/UV and TiO2/UV/H2O2 processes were investigated, where the effect of annealing temperature, the effect of H2O2 concentration, and the adsorption and photocatalytic effects on RO16 dye removal were studied. The results showed that 100% RO16 removal was obtained for the 10 mg/L initial RO16 concentration using the TiO2 (1 g/L)...
The influence of titanium dioxide phase composition on dyes photocatalysis
Journal of Sol-Gel Science and Technology, 2011
A comparative study of TiO 2 powders prepared by sol-gel methods is presented. Titanium tetraisopropoxide was used as the precursor for the sol-gel processes. The effects of the annealing treatment on phase, crystallite size, porosity and photodegradation of dyes (methyl orange and methylene blue) were studied. The phase structure, microstructure and surface properties of the films were characterized by using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The X-ray diffraction was used for crystal phase identification, for the accurate estimation of the anatase-rutile ratio and for the crystallite size evaluation of each polymorph in the samples. It was found that the only TiO 2 anatase phase of the synthesized TiO 2 develops below 500°C, between 600 and 800°C the anatase coexist with rutile and above 800°C only the rutile phase was found in the samples. Attention has been paid not only to crystal structures, but also to the porosity, the particle size and the photocatalytic properties. However, the annealing temperature was found to have significant influence on the photocatalytic properties. Different TiO 2 doctor blade thin films were obtained mixing the sol gel powder (100% anatase) and TiO 2 Aldrich with TiO 2 Degussa P25. The surfactant (Triton X100 or sodium dodecyl sulfate) affects the packing density of the particles during deposition and the photocatalytic degradation efficiency of the dyes. The photocatalytic degradation kinetics of methyl orange and methylene blue using TiO 2 thin film were investigated.
Environmental Progress, 2005
The photocatalytic degradation of methylene blue and methyl orange have been studied in the presence of titanium dioxide powder illuminated with a 300-W UV lamp. The effect of hydrogen peroxide on the degradation process was also determined. It was found that the color removal efficiency was affected by the concentration of dye, amount of TiO 2 added, and the pH of the solution. The degradation of dyes obeys first-order kinetics, with the apparent first-order rate constant increasing with decreasing dye concentration. The rate constants were evaluated as a function of the concentration of dye, amount of TiO 2 , and pH.
The total annual production of synthetic dye is more than 7 Â 10 5 tons. Annually, through only textile waste effluents, around one thousand tons of non-biodegradable textile dyes are discharged into natural streams and water bodies. Therefore, with growing environmental concerns and environmental awareness there is a need for the removal of dyes from local and industrial water effluents with a cost effective technology. In general, these dyes have been found to be resistant to biological as well as physical treatment technologies.