Highly efficient visible light TiO2 photocatalyst prepared by sol-gel method at temperatures lower than 300°C

TiO2 Phase Ratio's Contribution to the Photocatalytic Activity

Photocatalysis is one of the approaches for solving environmental issues derived from extremely harmful pollution caused by industrial dyes, medicine, and heavy metals. Titanium dioxide is among the most promising photocatalytic semiconductors; thus, in this work, TiO2 powders were prepared by a hydrothermal synthesis using titanium tetrachloride TiCl4 as a Ti source. The effect of the hydrochloric acid (HCl) concentration on TiO2 formation was analyzed, in which a thorough morpho-structural analysis was performed employing different analysis methods like XRD, Raman spectroscopy, SEM/TEM, and N2 physisorption. EPR spectroscopy was employed to characterize the paramagnetic defect centers and the photogeneration of reactive oxygen species. Photocatalytic properties were tested by photocatalytic degradation of the rhodamine B (RhB) dye under UV light irradiation and using a solar simulator. The pH value directly influenced the formation of the TiO2 phases; for less acidic conditions, the anatase phase of TiO2 crystallized, with a crystallite size of ≈9 nm. Promising results were observed for TiO2, which contained 76% rutile, showing a 96% degradation of RhB under the solar simulator and 91% under UV light after 90 min irradiation, and the best result showed that the sample with 67% of the anatase phase after 60 min irradiation under the solar simulator had a 99% degradation efficiency.

Photocatalytic degradation of ammonia with titania nanoparticles under UV light irradiation

Ammonia is one of the major pollutants of water resources, posing a serious threat to human health and the environment. Titania nanoparticles were used to examine the photocatalytic degradation of ammonia from an aqueous solution in this study. Titania nanoparticles (NPs) were first synthesized via the sol-gel method, then characterized using XRD, FTIR, DLS, EDX, FE-SEM, and TEM analyses. Four effective parameters (pH, initial concentration of pollutant, catalyst dosage, and irradiation time) for photocatalytic degradation were explored using Design-Expert Software. The greatest photocatalytic activity of titania NPs was found in optimal conditions, according to the findings (97%). The optimum amounts of catalyst dosage, initial pollutant concentration, irradiation time, and pH were obtained at 0.3 g/l, 1500 mg/l, 120 min, and 12, respectively. Furthermore, studies revealed that pH was the most efficient variable in comparison with others and that increasing the pH value from 8 to 12 boosted ammonia removal from 40 to 97%. NPs showed high stability as the ammonia removal decreased from 96.96% to 65% after four cycles. Generally, this research has created a precedent for the development of morphology-dependent photocatalysts for the degradation of organic contaminants.

Facile Construction of All-Solid-State Z-Scheme g-C3N4/TiO2 Thin Film for the Efficient Visible-Light Degradation of Organic Pollutant

The increasing discharge of dyes and antibiotic pollutants in water has brought serious environmental problems. However, it is difficult to remove such pollutants effectively by traditional sewage treatment technologies. Semiconductor photocatalysis is a new environment-friendly technique and is widely used in aqueous pollution control. TiO₂ is one of the most investigated photocatalysts; however, it still faces the main drawbacks of a poor visible-light response and a low charge-separation efficiency. Moreover, powder photocatalyst is difficult to be recovered, which is another obstacle limiting the practical application. In this article, g-C₃N₄/TiO₂ heterojunction is simply immobilized on a glass substrate to form an all-solid-state Z-scheme heterojunction. The obtained thin-film photocatalyst was characterized and applied in the visible-light photodegradation of colored rhodamine B and tetracycline hydrochloride. The photocatalytic performance is related to the deposited layers, and the sample with five layers shows the best photocatalytic efficiency. The thin-film photocatalyst is easy to be recovered with stability. The active component responsible for the photodegradation is identified and a Z-scheme mechanism is proposed.

Effects of doping amounts of potassium ferricyanide with titanium dioxide and calcination durations on visible-light degradation of pharmaceuticals

Acetaminophen (ACT) is one of the most frequently detected pharmaceuticals in aqueous environments, and treatment of ACT were generally carried out by photocatalytic degradations under high energy UV irradiation. In this study, potassium ferricyanide was utilized as a quadruple-elemental dopant in a TiO₂ photocatalyst in order to enhance its visible-light activity. Two critical parameters (amounts of dopants and durations of calcination) of the synthesis of the photocatalyst by a sol-gel method were systematically evaluated. Crystal structure of the doping TiO₂ was examined by X-ray diffraction while the effects of the two parameters on the photocatalytic activity were elucidated by various characterizations. Increasing the amount of dopant or the duration of calcination red-shifted the UV-vis DRS of the doped TiO₂. The estimated band gap energy of the doped TiO₂ decreased slightly as the amount of dopant increased, but it increased as the duration of calcination increased. The FT-IR yielded characteristic peaks that revealed the effects of the two parameters, whereas the SEM images revealed the morphological evolutions of each effect. The photocatalyst, synthesized at optimum conditions was able to remove 99.1 % acetaminophen with rate constant of 7.9 × 10^-3 min^-1, which was 4.88 times greater than virgin TiO₂. In general, this study not only optimized synthetic conditions of the new visible-light active photocatalyst for ACT degradation but also presented characterizations conducted by SEM, XRD, UV-vis DRS, and FTIR to elucidate the relationship between modified structure and the photocatalytic activity. Graphical abstract Effects of doping amounts of K₃[Fe(CN)₆] and calcunation duration on visible light absorbance of TiO₂ photocatalysts.

Photodegradation of Reactive Red 141 and Reactive Yellow 105 Dyes Using Prepared TiO2 Nanoparticles

The photodegradation of Reactive Red 141 (RR-141) and Reactive Yellow 105 (RY-105) dyes using TiO2 nanoparticles was investigated under UV light irradiation. TiO2 was prepared by sol-gel process and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with Energy Dispersive X-ray analysis (EDAX) and FTIR. The effects of operational parameters such as illumination time, catalyst dose, initial concentration and pH of dye solutions on photodegradation by TiO2 have been analyzed. The degradation of the selected dyes followed pseudo-first order reaction according to the Langmuir-Hinshelwood kinetic model.