Preparation of Monolithic LaFeO3 and Catalytic Oxidation of Toluene

Porous LaFeO₃ powders were produced by high-temperature calcination of LaFeO₃ precursors obtained by hydrothermal treatment of corresponding nitrates in the presence of citric acid. Four LaFeO₃ powders calcinated at different temperatures were mixed with appropriate amounts of kaolinite, carboxymethyl cellulose, glycerol and active carbon for the preparation of monolithic LaFeO₃ by extrusion. Porous LaFeO₃ powders were characterized using powder X-ray diffraction, scanning electron microscopy, nitrogen absorption/desorption and X-ray photoelectron spectroscopy. Among the four monolithic LaFeO₃ catalysts, the catalyst calcinated at 700 °C showed the best catalytic activity for the catalytic oxidation of toluene at 36,000 mL/(g∙h), and the corresponding T_10%, T_50% and T_90% was 76 °C, 253 °C and 420 °C, respectively. The catalytic performance is attributed to the larger specific surface area (23.41 m²/g), higher surface adsorption of oxygen concentration and larger Fe²⁺/Fe³⁺ ratio associated with LaFeO₃ calcined at 700 °C.

Electrostatic interaction and surface S vacancies synergistically enhanced the photocatalytic degradation of ceftriaxone sodium

ZnIn₂S₄ ultrathin 2D nanosheets with a positive surface charge are synthesized by a hydrothermal method and different contents of surface S vacancies are induced via heat treatment of as-prepared ZnIn₂S₄ (ZIS). As the S vacancies contents increased, the photocatalytic degradation efficiency of ceftriaxone (CTRX) sodium is promoted. Especially, ZIS-300 shows the best degradation efficiency (88.8%) for an initial CTRX concentration of 10 mg L^-1 in 2 h. It is found that S vacancies cause the electron density of surface metal atoms (Zn, In) to be decreased, which makes the effective adsorption and activation of ceftriaxone anions through electrostatic adsorption interactions. Meanwhile, S vacancies also serve as active centers to promote the absorption of O₂ and gather electrons to form •O₂^- species. The photogenerated holes quickly transfer to the surface of the catalyst to directly degrade the adsorbed CTRX. Thus, the photocatalytic CTRX degradation efficiency is significantly improved. Finally, a possible mechanism for over defective ZIS is proposed. This work provides a feasible strategy for the efficient degradation of antibiotics from the perspective of electrostatic adsorption and molecule activation.

In situ recombination for durable photoelectrocatalytic degradation of organic dye in wastewater

Photoelectrocatalysis (PEC) can effectively degrade organic pollutants by using photoelectrodes without secondary pollution. However, significant mass transport resistance and decreased catalytic activity caused by the shedding of active components remain a barrier to achieving the photocatalytic system with a high degradation rate and long-term durability. Here, an in situ recombination concept is presented to overcome this challenge. The bionic coral-like electrode, obtained by in situ assembly of UIO-66 around TiO₂ nanoflowers (TNF) on Ti-foam substrate, is employed as the photoanode in PEC. Ex situ evaluation of photoelectrochemical activity demonstrates that the UIO-66@TNF/Ti-foam (U@T/T) design significantly improves the light-propagation, light-absorption and charge transfer. In Situ degradation evaluations also shows that the interesting design promotes rapid and stable degradation of organic dye (e.g. Rhodamine B (RhB)). At 2.0 V of bias potential and pH 7.0 in 5 mg L^-1 RhB, under the action of active species such as ·O₂^- and ·OH (proved by the degradation mechanism experiments), the removal rate of RhB can reach 96.1% at 120 min and almost complete removal at 200 min (99.1%).

Application of perovskite oxides and their composites for degrading organic pollutants from wastewater using advanced oxidation processes: Review of the recent progress

In the recent years, perovskite oxides are gaining an increasing amount of attention owing to their unique traits such as tunable electronic structures, flexible composition, and eco-friendly properties. In contrast, their catalytic performance is not satisfactory, which hinders real wastewater remediation. To overcome this shortcoming, various strategies are developed to design new perovskite oxide-based materials to enhance their catalytic activities in advanced oxidation process (AOPs). This review article is to provide overview of basic principle and different methods of AOPs, while the strategies to design novel perovskite oxide-based composites for enhancing the catalytic activities in AOPs have been highlighted. Moreover, the recent progress of their synthesis and applications in wastewater remediation (pertaining to the period 2016-2022) was described, and the related mechanisms were thoroughly discussed. This review article helps scientists to have a clear outlook on the selection and design of new effective perovskite oxide-based materials for the application of AOPs. At the end of the review, perspective on the challenges and future research directions are discussed.