M. Shanthi

Highly Efficient, Solar Active, and Reusable Photocatalyst: Zr-Loaded Ag–ZnO for Reactive Red 120 Dye Degradation with Synergistic Effect and Dye-Sensitized Mechanism

The different wt % of Zr-codoped Ag-ZnO catalysts were prepared by the simple precipitation-thermal decomposition method and used for degradation of anionic azo dye Reactive Red 120 (RR 120) under natural sunlight. Highly efficient 4 wt % of Zr-codoped Ag-ZnO was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM) images, field emission scanning electron microscope (FE-SEM) images, energy-dispersive spectra (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), and BET surface area measurements. Metal codopants increase the absorbance of ZnO to the entire visible region. XRD and XPS reveal that Ag is in the form of Ag(0) and Zr in the form of Zr(4+). The photocatalytic activity of 4 wt % Zr-codoped Ag-ZnO was compared with other single-metal-doped, undoped, and commercial catalysts. The quantum yields of all processes were determined and analyzed. Zr-Ag-ZnO was found to be more efficient than Ag-ZnO, Zr-ZnO, commercial ZnO, prepared ZnO, TiO(2)-P25, and TiO(2) at neutral pH for mineralization of RR 120 under solar light. To the best of our knowledge, this is the first report on the synthesis of Zr-codoped Ag-ZnO and its use in the degradation of RR 120 dye under natural sunlight illuminatioin. The influences of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on photomineralization of RR 120 have been analyzed. Mineralization of RR 120 has been confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for the higher efficiency of Zr-Ag-ZnO at neutral pH under solar light. This catalyst is found to be reusable.

Synthesis of Ce co-doped Ag–ZnO photocatalyst with excellent performance for NBB dye degradation under natural sunlight illumination

The synthesis of Ce co-doped Ag–ZnO (Ce–Ag–ZnO) has been successfully achieved by a solvothermal method. The synthesized catalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) images, diffuse reflectance spectra (DRS), photoluminescence spectra (PL), cyclic voltammetry (CV) and BET surface area measurements. The photocatalytic activity of Ce–Ag–ZnO was investigated for the degradation of Napthol Blue Black (NBB) dye in aqueous solution under solar light irradiation. Co-dopants shift the absorbance of ZnO to the visible region. Ce–Ag–ZnO is found to be more efficient than Ag–ZnO, Ce–ZnO, commercial ZnO, prepared ZnO, TiO2-P25 and TiO2 (Merck) at pH 9 for the mineralization of NBB dye under solar light irradiation. The influences of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo-mineralization of NBB have been analyzed. The mineralization of NBB dye has been confirmed by COD measurements. A degradation mechanism is proposed for the degradation of NBB under solar light. The catalyst is found to be reusable.

Synthesis, characterization and photocatalytic properties of SnO2–ZnO composite under UV-A light

The SnO2 loaded ZnO (SnO2-ZnO) was successfully synthesized by precipitation-decomposition method. The catalyst was characterized by X-ray diffraction (XRD), high resolution scanning electron microscope (HR-SEM) images, energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and BET surface area measurements. The photocatalytic activity of SnO2-ZnO was investigated for the degradation of Acid Orange 10 (AO 10) in aqueous solution using UV-A light. SnO2-ZnO is found to be more efficient than commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Merck) at pH 12 for the mineralization of AO 10 dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of AO 10 dye have been analyzed. The mineralization of AO 10 has been confirmed by chemical oxygen demand (COD) measurements. A degradation mechanism is proposed for the degradation of AO 10 with SnO2-ZnO under UV-A light. This catalyst is found to be reusable.

Photocatalytic degradation of an azo dye Sunset Yellow under UV-A light using TiO2/CAC composite catalysts.

The photocatalytic activity and the promoting effect of titania (TiO2) by commercial activated carbon (CAC) for removing the pollutant in wastewater were investigated. The TiO2/CAC composite photocatalysts with various ratios of CAC to TiO2 were prepared by sol-gel method. The catalyst was characterized by X-ray diffraction (XRD), high resolution scanning electron microscope (HR-SEM), energy dispersive spectra (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area measurement methods. The photocatalytic activity of TiO2/CAC was investigated for the degradation of Sunset Yellow (SY) in aqueous solution using UV-A light. The TiO2/CAC is found to be more efficient than prepared TiO2 and TiO2-P25 at pH 7 for the mineralization of SY. The synergism between TiO2 and CAC may increase the catalytic activity. The effects of operational parameters such as the amount of photocatalyst, dye concentration and initial pH on photo mineralization of SY have been analyzed. The mineralization of SY has been confirmed by COD measurements. The catalyst is found to be reusable.

Preparation and characterization of SeO2/TiO2 composite photocatalyst with excellent performance for sunset yellow azo dye degradation under natural sunlight illumination.

To improve the solar light induced photocatalytic application performances of TiO2, in this study, the SeO2 modified TiO2 composite photocatalysts with various ratios of SeO2 to TiO2 were prepared by sol-gel method. The catalyst was characterized by X-ray diffraction (XRD), high resolution scanning electron microscope (HR-SEM), energy dispersive spectra (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area measurement methods. The photocatalytic activity of SeO2/TiO2 was investigated for the degradation of sunset yellow (SY) in aqueous solution using solar light. The SeO2/TiO2 is found to be more efficient than prepared TiO2 and TiO2-P25 at pH 7 for the mineralization of SY. The effects of operational parameters such as the amount of photocatalyst, dye concentration and initial pH on photo mineralization of SY have been analyzed. The degradation was strongly enhanced in the presence of electron acceptors such as oxone, KIO4 and KBrO3. The kinetics of SY photodegradation was found to follow the pseudo-first order rate law and could be described in terms of Langmuir-Hinshelwood model. The mineralization of SY has been confirmed by COD measurements. The catalyst is found to be reusable.

Photocatalytic detoxification of Acid Red 18 by modified ZnO catalyst under sunlight irradiation.

In this work, hybrid structured Bi-Au-ZnO composite was prepared by precipitation-decomposition method. This method is mild, economical and efficient. Bi-Au-ZnO was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and BET surface area measurements. Photocatalytic activity of Bi-Au-ZnO was evaluated by irradiating the Acid Red 18 (AR 18) dye solution under sun light. Heterostructured Bi-Au-ZnO photocatalyst showed higher photocatalytic activity than those of individual Bi-ZnO, Au-ZnO, bare ZnO, and TiO2-P25 at pH 11. The effects of operational parameters such as the amount of catalyst dosage, dye concentration, initial pH on photo mineralization of AR 18 dye have been analyzed. The mineralization of AR 18 has been confirmed by chemical oxygen demand (COD) measurements. A possible mechanism is proposed for the degradation of AR 18 under sun light. Finally, Bi-Au-ZnO heterojunction photocatalyst was more stable and could be easily recycled several times opening a new avenue for potential industrial applications.

Solar active photocatalyst for effective degradation of RR 120 with dye sensitized mechanism.

Solar active WO3 loaded Ag-ZnO (WO3-Ag-ZnO) was successfully synthesized by precipitation-decomposition method. XPS reveals that the presence of metallic silver in the catalyst. The photocatalytic activity of WO3-Ag-ZnO was investigated for the degradation of Reactive Red 120 (RR 120) in aqueous solution using solar light. WO3-Ag-ZnO is found to be more efficient than Ag-ZnO, WO3-ZnO, Ag-WO3, commercial ZnO, prepared ZnO, Degussa TiO2-P25, pure WO3 and TiO2 (Merck) at pH 7 for the mineralization of RR 120. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of RR 120 have been analyzed. The mineralization of RR 120 has been confirmed by COD measurements. A dual mechanism has been proposed for efficient degradation of RR 120 dye with WO3-Ag-ZnO under solar light at neutral pH. This catalyst is found to be reusable.

Ag2S-ZnO--an efficient photocatalyst for the mineralization of Acid Black 1 with UV light.

The Ag(2)S loaded ZnO (Ag(2)S-ZnO) was successfully synthesized by precipitation of zinc oxalate and Ag(2)S and calcination of the mixed precipitate at 400 °C for 12 h. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) images, energy dispersive spectra (EDS), diffuse reflectance spectra (DRS) photoluminescence spectra (PL) and BET surface area measurements. The photocatalytic activity of Ag(2)S-ZnO was investigated for the degradation of Acid Black (AB 1) in aqueous solution using UV light. Ag(2)S-ZnO is found to be more efficient than commercial ZnO, prepared ZnO and TiO(2)-P25 at pH 9 for the mineralization of Acid Black 1. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization have been analyzed. Mechanism of degradation by Ag(2)S-ZnO is proposed. The mineralization of Acid Black 1 has also been confirmed by COD measurements. The catalyst is found to be reusable.

Hydrothermal fabrication of natural sun light active Dy2WO6 doped ZnO and its enhanced photo-electrocatalytic activity and self-cleaning properties

In this article we report the fabrication of 3 wt% Dy2WO6 doped ZnO via a template-free hydrothermal process and its photocatalytic activity against azo dyes Rhodamine-B (Rh-B) and Trypan Blue (TB) in solar light irradiation. The as prepared Dy2WO6 doped ZnO was characterised by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution scanning electron microscopy (HR-SEM) field emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS), diffused reflectance (DRS) and photoluminescence (PL) spectroscopy. The results suggested that rare earth tungstate doping, with Dy2WO6, on ZnO has a great influence on the photocatalytic activity. Dy2WO6-ZnO possesses high reusability without appreciable loss of catalytic activity up to four runs and exhibits higher electrocatalytic activity than the prepared ZnO for methanol electrooxidation in alkaline medium, revealing its promising potential as the anode catalyst in direct methanol fuel cells. Hydrophobicity of ZnO increases on doping with Dy2WO6.

Photocatalytic mineralization of a water pollutant, Sunset Yellow dye by an advanced oxidation process using a modified catalyst

ZnS-loaded TiO2 (ZnS–TiO2) was synthesized by a sol–gel method. The catalyst was characterized by using different techniques (XRD, HR-SEM, EDS, DRS, PL, XPS, and BET methods). The photocatalytic activity of ZnS–TiO2 was investigated for the degradation of Sunset Yellow FCF (SY) dye in an aqueous solution using ultraviolet light. ZnS–TiO2 is found to be more efficient than prepared TiO2, TiO2–P25, TiO2 (Merck), and ZnS at pH 7 for the mineralization of SY. The effects of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on photo mineralization of SY have been analyzed. The mineralization of SY has been confirmed by chemical oxygen demand measurements. The catalyst is found to be reusable.