Introduction: The photocatalytic degradation of dyes has been investigated throughout the world irrespective of the level of science in that country. The normal variables considered are the concentration of oxidising species, the concentration of the dye employed, the catalyst used and intensity and source of photons applied for degradation studies. The kinetic data obtained on the decolorization have usually been treated with pseudo first order kinetic expression even there are some exceptions. Conclusion: This presentation addresses the limitations of the consideration of this topic under these experimental parameters and shows how the study can be directed in future. A R T I C L E H I S T O R Y Received: September 15, 2017 Revised: Decemebr 05, 2017 Accepted: December 06, 2017 DOI: 10.2174/2211544707666171219161846

Photocatalytic Degradation of Dyes: An Overview

Synthesis and characterization of TiO2 nanorods by hydrothermal method with different pH conditions and their photocatalytic activity

Preparation and characterization of graphene – TiO2 nanocomposite for enhanced photodegradation of Rhodamine-B dye

In this paper, a comparative study on the photocatalytic degradation of the Rhodamine B (RhB) dye as a model compound using N-Fe codoped TiO2 nanorods under UV and visible-light (λ ≥420 nm) irradiations has been performed. TiO2 photocatalysts were fabricated as aligned nanorod arrays by liquid-phase deposition process, annealed at different temperatures from 400 to 800 °C. The effects of annealing temperature on the phase structure, crystallinity, BET surface area, and resulting photocatalytic activity of N-Fe codoped TiO2 nanorods were also investigated. The degradation studies confirmed that the nanorods annealed at 600 °C composed of both anatase (79%) and rutile phases (21%) and offered the highest activity and stability among the series of nanorods, as it degraded 94.8% and 87.2% RhB in 120 min irradiation under UV and visible-light, respectively. Above 600 °C, the photocatalytic performance of nanorods decreased owning to a phase change, decreased surface area and bandgap, and growth of TiO2 crystallites induced by the annealing temperature. It is hoped that this work could provide precious information on the design of ID catalyst materials with more superior photodegradation properties especially under visible-light for the further industrial applications.

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Photocatalytic degradation evaluation of N-Fe codoped aligned TiO2 nanorods based on the effect of annealing temperature

A novel (Nb4O5–TiO2)@rGO nanocomposite was synthesized using a Na+ ion intercalation-assisted hydrothermal technique and examined its photocatalyst dye degradation and supercapacitor applications. The synthesized (Nb4O5–TiO2) nanorods were segregated by well dispersed reduced graphene oxide with different weight ratios. A strong interaction was observed between the (Nb4O5–TiO2) to rGO nanosheets, even with high rGO content (5 wt. %). Experiments examining the photocatalytic degradation of methylene blue suggested that the (Nb4O5–TiO2)@ 5rGO nanocomposites exhibit excellent charge carrier mobility with a higher methylene blue degradation rate (92%) than Nb4O5–TiO2 nanorods and other (Nb4O5–TiO2)@rGO nanocomposites under ultraviolet and visible light irradiation. On the other hand, the (Nb4O5–TiO2)@ 5rGO nanocomposite exhibited excellent electrochemical performance with high specific capacitance (365 F g−1), long cycling stability (∼100% capacitance retention after 1000 cycles), and good rate capability (70% capacitance retention at 25 A g−1). In addition, the photocatalytic and supercapacitor efficiency of the (Nb4O5–TiO2)@rGO nanocomposite increased gradually with increasing amount of rGO in the composite. These features collectively demonstrated the high rate of photocatalytic degradation efficiency and good energy storage performance of the (Nb4O5–TiO2)@ 5rGO nanocomposite, which suggests a new route for large scale applications in energy and environmental fields.

Synthesis of rGO-doped Nb4O5–TiO2 nanorods for photocatalytic and electrochemical energy storage applications

The Photocatalytic degradation of methylene blue dye (MB) was studied using Titanate nanoparticles catalyst under UV light in a tubular reactor. Titanate nanoparticles were synthesized by hydrothermal reaction using TiO2 and NaOH as the precursors and calcinations at 500°C for 4 hr. The products were characterized with TEM and XRD. The parameters studied are Titanate nanoparticles catalyst dosage, initial concentration of dye and pH of the reaction mixture. The degradation of dye was found to be effective in the range: catalyst dose 0.10, 0.15, 0.20 g catalyst/ 400 mL of dye solution, initial dye concentration 5, 10, 15 ppm and pH of reaction mixture 1.4, 7, 12.6. Experimentation on different concentrations of TiO2 nanoparticles showed that 0.2 g TiO2/ 400 ml of effluent is the most suitable catalyst concentration. Photocatalytic processes were found to work better in basic medium and the present study showed that the best pH value was 12.6. The effect of the initial methylene blue concentration on the percentage degradation was also studied, demonstrating that the degradation of methylene blue generally increased when decreasing its concentration. The results showed that a percentage methylene blue degradation of 97.6% could be obtained when treating an effluent with 5 ppm of methylene blue for 90 minutes at 0.2 g TiO2/ 400 ml of effluent and pH 12.6. This corresponds to 97.2% degradation when working on an effluent with 10 ppm methylene blue and 93%, when treating an effluent with 15 ppm of methylene blue for 90 minutes.

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Synthesis of TiO 2 Nanoparticles and Their Photocatalytic Activity for Methylene Blue

Green synthesis of gold nanoparticles using Jatropha integerrima Jacq. flower extract and their antibacterial activity

Quercetin's potential to protect adult male albino rats from the health hazards of a high-fat diet on pancreatic and renal tissues

Biogenic nanoscale silver particles synthesis using butter fruit pulp extract and study of antibacterial efficacy against Providencia vermicola in rohu fish

Titanate nanotubes were evaluated for photocatalytic depletion of methylene blue (MB) dye under UV radiation in a cylindrical reactor. Titanate has been prepared using the method of hydrothermal treatment where the precursors are TiO2 and NaOH. Transmitting electron microscopy (TEM) and x-ray diffraction (XRD) were used to characterize the prepared nanotubes. The effect of some parameters was examined. It was shown that removing the dye is effective: dye initial concentration 5 to 10 ppm, dosage of catalyst 0.25 to 0.50 g catalyst/l of the solution, and mixture pH 1.4 to 12.6. A total of 17 runs have been designed to take into account the effective ranges of the effective variables using the experimental Box–Behnken technique. Two polynomial models were tailored to the experimental outputs created by the response surface methodology, demonstrating a functional correlation between MB’s percent degradation and experimental parameters. Design Expert program V.6.0.7 was utilized to maximize the reaction rate of the experimental parameters. The optimum parameter values were initial concentration of MB 5.45 ppm, a dose of TiO2 0.50  g  /  l, and pH of the mixture 11.89. Under these conditions, the percentage of degradation of MB was 99.0995%.

Dina S. Hussein

Papers

Synthesis of TiO 2 Nanoparticles and Their Photocatalytic Activity for Methylene Blue

Green synthesis of gold nanoparticles using Jatropha integerrima Jacq. flower extract and their antibacterial activity

Quercetin's potential to protect adult male albino rats from the health hazards of a high-fat diet on pancreatic and renal tissues

Biogenic nanoscale silver particles synthesis using butter fruit pulp extract and study of antibacterial efficacy against Providencia vermicola in rohu fish

Optimization of photocatalytic degradation of methylene blue dye using titanate nanotube