KBiO3 as an Effective Visible-Light-Driven Photocatalyst: Degradation Mechanism for Different Organic Pollutants

A highly efficient in situ redox stabilization strategy for Am-Cm separation using AgBiO3

AgBiO3 is reported for the exclusive oxidation of Am3+ → AmO2+ at near-neutral pH conditions. Literature methods of AmO2+ generation are generally two-step processes; i.e., Am3+ → AmO22+ oxidation followed by AmO22+ → AmO2+ reduction. These methods for Am3+ → AmO2+ oxidation use high temperatures (80-100 °C) and/or several reagents, causing the in situ presence of the AmO2+-complex rather than the AmO2+aq ions. This not only interferes with the much-needed Am-Cm selectivity but also limits the use of AmO2+aq in any other experimental study. The single-step Am3+ → AmO2+ oxidation in the present work using AgBiO3 is done at 25 °C in a non-complexing medium at pH ∼4, making it a first-of-its-kind report. Am-Eu and Am-Cm separation in a single contact, with a separation factor >104, was achieved using the present method, which is unprecedented among aqueous feed solutions. The AmO2+ generated using the present method under non-complexing pH conditions makes it also suitable for exploring the fundamental chemistry of the higher valent americyl ion. A complexation study using the thus-generated AmO2+ ion with acetate ion supports the concept.

Theoretical study on the stability, ferroelectricity and photocatalytic properties of CaBiO3

Materials with high ferroelectric polarization strength and sufficient absorption of visible light have unique advantages in photocatalysis. Based on the results of structure search, phonon frequency, and elasticity coefficient calculations, CaBiO₃ has a stable R3 polar structure. First-principles calculations indicate that R3-CaBiO₃ is a potentially efficient ferroelectric visible-light photocatalytic material for hydrogen production. CaBiO₃ under slight strain can maintain high ferroelectric polarization strength, strong visible light absorption capacity and small effective mass. CaBiO₃ under tensile strain has potentially ferroelectric photogeneration of hydrogen with a band edge position that crosses the redox potential of water. These results can expand the application of Bi-based materials in photocatalytic hydrogen production.

A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h⁺ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

Promoting superoxide generation in Bi2WO6 by less electronegative substitution for enhanced photocatalytic performance: an example of Te doping

Doping with elements with lower electronegativity, like Te, shifts the band potentials of Bi2WO6 to the point that superoxide radical generation is feasible. As a result, an optimum of 2.5 at% Te doping improves the activity of Bi2WO6 by 48 times.

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O-AgBiO3 towards Enhanced Selective Photoelectrochemical Detection

Due to integrated advances in photoelectrochemical (PEC) functionalities for environment detection applications, one-dimensional (1D) TiO2 nanostructures provide a new strategy (PEC sensors) towards organics detection in wastewater. However, the unidealized selectivity to the oxidation of water and organics limits the PEC detection performance. Herein, we designed a ternary photoanode consisting of Ag2O-AgBiO3/TiO2 nanotube arrays (NTAs) to solve this issue by using a facile one-step precipitation reaction. High oxidation capacity for organics is achieved by regulating the surface free radicals properly through the heterostructure formed between the interface of TiO2 and AgBiO3. More importantly, as a trap for electron capture, Ag2O in this ternary system could not only further improve the separation efficiency of charge carriers, but also capture electrons transferred to the TiO2 conduction band, thus reducing the electrons transferred to the external circuit and the corresponding background photocurrent when detecting organics. As a result, the reconstructed TiO2 NTAs decrease their photocurrent response to water and enhance their response to organics, thus presenting lower oxidation activity to water and higher activity to organics, that is, highly selective oxidation characteristics. This work provides more insights into the impact of charge transfer and surface free radicals on developing promising and efficient PEC sensors for organics.

Perovskites as Catalysts in Advanced Oxidation Processes for Wastewater Treatment

Advanced oxidation processes (AOPs), based on the formation of highly reactive radicals are able to degrade many organic contaminants present in effluent water. In the heterogeneous AOPS the presence of a solid which acts as catalyst in combination with other systems (O3, H2O2, light) is required. Among the different materials that can catalyse these processes, perovskites are found to be very promising, because they are highly stable and exhibit a high mobility of network oxygen with the possibility of forming vacancies and to stabilize unusual oxidation states of metals. In this review, we show the fundaments of different kinds of AOPs and the application of perovskite type oxides in them, classified attending to the oxidant used, ozone, H2O2 or peroxymonosulfate, alone or in combination with other systems. The photocatalytic oxidation, consisting in the activation of the perovskite by irradiation with ultraviolet or visible light is also revised.