Doping level effect on visible-light irradiation W-doped TiO2–anatase photocatalysts for Congo red photodegradation

Enhancement of photocatalytic activity of Ba-doped CoO for degradation of Emamectin benzoate in aqueous solution

The present study was focused on the preparation of cobalt oxide (CoO) and barium-doped cobalt oxide (Ba-doped CoO) by following the co-precipitation method for the degradation of Emamectin benzoate pesticide in the aqueous medium. The prepared catalysts were characterized using SEM, EDX, and XRD to confirm the formation of catalysts and to observe the variation in the composition of catalysts during the degradation study. It can be suggested from the results of SEM, EDX, XRD, and FTIR analyses that Ba atom has successfully incorporated in the crystalline structure of CoO. The degradation of Emamectin benzoate pesticide was studied under the influence of different factors like solution pH, the dose of catalyst, contact time, temperature, and initial concentration of pesticide. It was observed that solution pH affects the degradation of the pesticide, and maximum degradation (23% and 54%) was found at pH 5.0 and 6.0 using CoO and Ba-doped CoO, respectively. The degradation of pesticides was found to be increased continuously (27-35% in case of CoO while 47-58% in case Ba-doped CoO) with the time of contact. However, the degradation was found to be decreased (23-3% in case of CoO while 47-44% in case Ba-doped CoO) with an increase in temperature. Likewise, in the beginning, degradation was observed to be increased up to some extent with the dose of catalyst and initial concentration of pesticide but started to decrease with further augmentation in the dose of catalyst and initial concentration of pesticide. It may be concluded from this study that doping of Ba considerably enhanced the photocatalytic ability of CoO for Emamectin benzoate pesticide.

Removal of the Hazardous Congo Red Dye through Degradation under Visible Light Photocatalyzed by C,N Co-Doped TiO2 Prepared from Chicken Egg White

The C,N co-doped TiO2 photocatalyst was prepared by interacting the chicken egg white having various weights (1, 2, and 4 g) with 1 g of TiO2 in an autoclave through the hydrothermal process at 150°C. The C,N co-doped TiO2 photocatalysts were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), specular reflectance UV/visible (SRUV/Vis), and transmission electron microscope (TEM) instruments. The photocatalytic activity of the co-doped TiO2 was evaluated by monitoring the photo-decolorization of Congo red dye under visible light through a batch experiment. The characterization results assigned that the C and N atoms from the chicken egg white have been successfully co-doped into TiO2 through interstitial and substitutional combination, which could notably narrow their band gap energy entering into the visible region. In line with the gap narrowing, the co-doping C,N into TiO2 could remarkably improve the photocatalytic activity under visible light in the dye photo-decolorization. The enhancement of the photocatalyst activity of TiO2-C,N was controlled by the weight of the egg white introduced, and 2 g of the egg white resulted in the highest activity. Further, the best dye photo-decolorization, which was about 98%, of 10 mg/L Congo red dye in 100 mL of the solution under visible irradiation could be reached by applying TiO2-C,N prepared from 2 g of the egg white, within 45 min, at pH 7, and 50 mg of the photocatalyst mass.

A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants

TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.

Preparation, characterization, and photocatalytic activity under UV and visible light of Co, Mn, and Ni mono-doped and (P,Mo) and (P,W) co-doped TiO2 nanoparticles: a comparative study

In this work, TiO₂-based nanomaterials have been successfully synthesized by doping TiO₂ with Co, Mn, and Ni and by co-doping it with (P,Mo) or (P,W). The structural, optical, and morphological properties of the synthesized nanomaterials have been investigated using various techniques such as XRD, FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, XPS, and SEM-EDS. The obtained results showed that the crystalline structure of the doped TiO₂-based nanomaterials depends strongly on the nature of the doping ions. The obtained band gap energy of TiO₂ co-doped with (P,Mo) changes to a level below the band gap energy of TiO₂ anatase indicating a high ability to absorb visible light. The obtained photocatalytic activity results of methyl orange degradation showed that, under visible light, the mono-doping of TiO₂ with Co and its co-doping with (P,Mo) or (P,W) improve significantly the photocatalytic activity of TiO₂ in comparison with undoped TiO₂. The activity order obtained under UV-A irradiation for the used photocatalysts is TiO₂ > > 1%Ni-TiO₂ > 1%Co-TiO₂ > 30%(P,Mo)-TiO₂ ≈ 30%(P,W)TiO₂ > 1%Mn-TiO₂ while under visible light, it is 1%Co-TiO₂ > 30%(P,Mo)-TiO₂ > 30%(P,W)TiO₂ ≈ TiO₂ > 1%Ni-TiO₂ > 1%Mn-TiO₂. The high photocatalytic activity observed for these samples could be the result of a synergetic effect of the high visible light absorption capacity and the low recombination rate of photoexcited electrons and holes.

Tuning the band gap of TiO2 by tungsten doping for efficient UV and visible photodegradation of Congo red dye

Tungsten-doped TiO₂ (W@TiO₂) nanoparticles, with different percentages of atomic tungsten dopant levels (range of 0 to 6 mol%) have been synthesized by the sol-gel method and characterized by UV-Visible spectroscopy, XRD, SEM, EDX, ICP-OES and XPS analysis. By means of UV-Vis spectroscopy, it has been observed that with 6 mol% tungsten doping the wavelength range of excitation of TiO₂ has extended to the visible portion of spectrum. Therefore, we evaluated the photocatalytic activity of W@TiO₂ catalysts for the degradation of Congo red dye under varying experimental parameters such as dopant concentration, catalyst dosage, dye concentrations and pH. Moreover, 6 mol% W@TiO₂ catalyst was deposited on a glass substrate to form thin film using spin coating technique in order to make the photocatalyst effortlessly reusable with approximately same efficiency. The results compared with standard titania, Degussa P25 both in UV- and visible light, suggest that 6 mol% W@TiO₂ can be a cost-effective choice for visible light induced photocatalytic degradation of Congo red dye.

Hydrothermally grown CdS nanoparticles for photodegradation of anionic azo dyes under UV-visible light irradiation

A CdS photocatalyst was synthesized successfully at low temperature via a catalyst-free hydrothermal technique which is simple, green and also easily controlled. The synthesized CdS photocatalyst showed hexagonal wurtzite structure with high crystallinity and excellent optical properties. The catalyst was used for degradation of two anionic azo dyes namely reactive red (RR141) and Congo red (CR) azo dyes. The catalyst showed very high efficiency of 99.8% and 99.0% toward photodegradation of RR141 and CR dye, respectively. The photodegradation reaction followed pseudo-first order kinetics. Chemical scavenger studies showed that direct photogenerated hole transfer from CdS to the azo dye was most likely the major pathway for photodegradation of the azo dye. The chemical structure of the CdS photocatalyst remained stable after photodegradation. The CdS photocatalyst retains its original efficiency even after the fifth cycle of reuse indicating the advantages of stability and reusability. The CdS nanostructures will be suitable for removal of highly toxic and hazardous organic materials in environmental protection.

A CdS photocatalyst was synthesized successfully at low temperature via a catalyst-free hydrothermal technique which is simple, green and also easily controlled.