Photocatalytic Degradation

Annually, large volumes of synthetic textile dyes are released in effluent into natural streams causing damage to human health and environment. Conventional methods have been proven inefficient due to the stability of these dyes. An alternative emerging approach is the use of nanocatalysts in photocatalytic dye degradation. In this study, the ability of citrate-stabilized silver nanoparticles (cit-AgNP) to degrade methylene blue (MB) dye was investigated. Cit-AgNP was successfully synthesized using chemical reduction method and stabilized by sodium citrate. The resulting solution was yellow in color with absorbance peak at 393 nm. The particles were spherical in shape with average diameter of 9.19 ± 4.91 nm. In the degradation study, the photocatalytic degradation of MB is visually manifested by its reduction in color when exposed to light and the eventual reduction in absorbance at peak 663 nm. The percent degradation was quantified by calculating the amount of MB that remained in the solution and showed 94.45% after 10 minutes of exposure to light. Four different setups were also compared and analyzed based on color changes, absorbance curve profiles, and percent degradation to prove the catalytic activity of cit-AgNP and it was found out that the highest and fastest degradation was the setup with MB, NaBH4, and cit-AgNP. River water samples were also utilized to evaluate the effectivity of degradation in real water applications. It has showed no significant difference compared to the setup prepared with distilled water after statistical tests. Hence, this study showed the potential of cit-AgNP for dye degradation.

Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.

We report a facile one-pot green synthesis of zinc oxide (ZnO) nanostructures using aqueous leaf extract of Dolichos Lablab L. as the reducing and capping agent. The optical properties, structure and morphology of the as-synthesized ZnO nanostructures have been characterized by UV-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) supported with energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). TEM analysis revealed that the as-synthesized ZnO nanostructures have an average particle diameter of 29 nm. XRD patterns confirmed the formation of phase-pure ZnO nanostructures with a hexagonal wurtzite structure. The synthesized ZnO nanostructures were used as a catalyst in the photodegradation of methylene blue (MB), rhodamine B (RhB) and orange II (OII) under visible and near-UV irradiation. The results showed the highest efficiency of photodegradation of ZnO nanostructures for MB (80%), RhB (95%) and OII (66%) at pH values of 11, 9 and 5, respectively, in a 210 min time interval. In addition, the antimicrobial activity of the ZnO nanostructures using the agar well diffusion method against Bacillus pumilus and Sphingomonas paucimobilis showed the highest zones of inhibition of 18 mm and 20 mm, respectively. Hence, ZnO nanostructures have the potential to be used as a photocatalyst and bactericidal component.

Ru doped titania was prepared by impregnation method and examined for the photocatalytic degradation of 2-chlorophenol at ambient conditions. Ru/TiO2 photocatalysts with metal loadings of 0.2, 0.4, 0.6 and 0.8 wt% were prepared and
characterized using TEM, XRD, FTIR, SBET and EDX analysis. The degradation of 2-chlorophenol (2-CP) in the aqueous phase was investigated under irradiation at 254 nm, employing either photodegradation in the presence of titania, Ru doped titania or photolysis, to compare the efficiency of these photoinduced advanced oxidation techniques. Photocatalysis under visible irradiation was also investigated. The removal efficiency arrived at 50% using 0.2% Ru/TiO2 catalyst.

Use of eco friendly catalysts for degradation of toxic synthetic dyes with high efficiency has always been one of the primary targets for the present day researchers. The present paper aims at giving the green synthesis of high purity carbon nano dots(CNDs from sugarcane bagasse through a mild, one-step colloidal synthesis approach . The chemical composition and semantic feature of the obtained CNDs have been characterized using UV-VIS spectroscopy. These CNDs have been explored for their photocatalytic degradation activity against four dyes belonging to two major classes of potentially toxic yet commercially useful dyes.

The photocatalytic degradation of waste water will be investigated at room temperature in a dynamic photoreactor with system UV/O2 (air) and aqueous suspension of Fe-doped ZrO2 irradiated under a variety of conditions. Fe doped Zirconia is prepared by the combustion synthesis process and characterized by XRD, BET and TGA. Phenol is degraded by the catalyst prepared. The Photocatalytic Degradation of Phenol by Fe doped ZrO2 are
measured by HPLC. Phenol is degraded very well by Fe doped Zirconia when compared to H2O2. Fe doped ZrO2 degraded almost 50% of the Phenol within 6 hrs of time.

The heterogeneous photocatalytic degradation of dyes reactive red 120 and reactive blue 4 under ideal solutions and hydrolysates dyes simulating a staining process with an initial concentration of 50 mg • L-1 was studied, using 200 mg • L-1 of TiO2 doped with Fe or N. Total degradation of both dyes was achieved with the addition of an auxiliary oxidizing agent such as hydrogen peroxide (H2O2) at a concentration of 12.0 mM. Such degradation was achieved after one hour of reaction for doped catalysts (N-TiO2 and Fe-TiO2). For solutions of hydrolysed dye that simulated waste water from the textile industry was found that the pH adversely affects dye degradation due to repulsion between the photocatalysts and dyes. In all the studied cases further degradation of reactive red dye 120 was observed relative to reactive blue 4, which can be associated with the complex molecular structure of the second dye.

We herein have reported on tuning of the morphology and crystallite size of the hydrothermally prepared zeolite nanostructures by using different aluminum sources. The investigation revealed that aluminum sulfate and aluminum chloride precursors produced non-crystalline forms, while aluminum isopropoxide, alumina, and aluminum metal precursors generated analcime nanoparticles with crystallite size of ca. 94.79, 112.57, and 105.87 nm, respectively. However, sodium aluminate precursor gave a mixture of analcime and nacrite phases with a crys-tallite size of ca. 77.95 nm. The as-prepared nanostructures were identified using XRD, FT-IR, FE-SEM, EDS, UV–Vis spectroscopy and BET surface area. The results exhibited that the direct optical energy gaps (E g) and BET surface area were found to be (3.29 eV and 20.18 m 2 /g), (3.15 eV and 16.28 m 2 /g), (3.21 eV and 18.67 m 2 /g), and (2.69 eV and 17.82 m 2 /g) for the zeolite products prepared using aluminum isopropoxide, sodium aluminate, alumina, and aluminum metal precursors, respectively. The results also showed that the as-prepared zeolite nanostructures could be simultaneously used as adsorbents and photocatalysts for the removal of methylene blue (MB) dye from aqueous solutions. The adsorption of methylene blue dye over the zeolite adsor-bents obeys pseudo-second-order model and intra-particle diffusion model. Interestingly, zeolite photocatalyst prepared using aluminum isopropoxide degraded the MB dye with percentage of 85% and 100% within 180 and 110 min in the presence of UV and (UV + H 2 O 2), respectively. The degradation processes followed the pseudo first order model. The prepared zeolites are proposed as promising candidates for the removal of MB from aqueous media.

In this study, pure ZnO, CeO2 and ZnO/CeO2 nanocomposites were synthesized using a thermal decomposition method and subsequently characterized using different standard techniques. High-resolution X-ray photoelectron spectroscopy measurements confirmed the oxidation states and presence of Zn2+ , Ce4+ , Ce3+ and different bonded oxygen species in the nanocomposites. The prepared pure ZnO and CeO2 as well as the ZnO/CeO2 nanocomposites with various proportions of ZnO and CeO2 were tested for photocatalytic degradation of methyl orange, methylene blue and phenol under visible-light irradiation. The optimized and highly efficient ZnO/CeO2 (90:10) nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methyl orange, methylene blue, and phenol as well as industrial textile effluent compared to ZnO, CeO2 and the other investigated nanocomposites. Moreover, the recycling results demonstrate that the ZnO/CeO2 (90:10) nanocomposite exhibited good stabili...

Zinc oxide (ZnO) Nanoparticles were synthesized with Ni/Co, Gd3+, and Tb3+ doping using co-precipitation method under normal suitable conditions. These prepared pure and doped ZnO nanoparticles were characterized for size, surface, structural and optical properties with the help of scanning electron microscopy (SEM), particle size analyser, fluorescence microscopy, energy dispersive X-ray spectroscopy (EDX), fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectroscopy. Due to doping effect, the band gap varies from 3.20 eV to 3.35 eV and shows the blue shift. Further, the as-characterized pure and doped ZnO NPs are used for photocatalytic degradation and antibacterial activities. The results show that there is presence of antibacterial activities from these characterized ZnO NPs. The Tb3+ and Gd3+-doped ZnO NPs show high photocatalytic degradation for Victoria blue B dye and also suppress the bacterial activities of Staphylococcus Aureus bacteria. Therefore, we can conclude that by reducing the band gap of ZnO NPs through doping with Tb3+ and Gd3+ can be further used in making Nanoelectronics devices, sensing applications, photovoltaic, food, cosmetics and medicine industry.