Designing a New Efficient Photocatalyst Based on Functionalization of Zn-Infinite Coordination Polymer with Ru(acac)3 Complex for Dye Degradation in Aqueous Solutions: Charge Separation Effect

A new Zn-containing infinite coordination polymer, Zn-ICP, functionalized with Ru(acac)₃ complex was designed and utilized as an efficient visible light photocatalyst for dye degradation in aqueous solutions. Incorporation of Ru(acac)₃ not only extended the light absorption of the Zn-ICP to the visible region but also led to electron-hole separation. Upon visible light illumination, photoinduced electron transfer from excited state of Zn-ICP to Ru(acac)₃ occurred, resulting in electron-hole separation as indicated by photoluminescence and electrochemical impedance spectroscopy. The obtained Ru-Zn-ICP revealed enhanced visible light photocatalytic activity in degradation of organic pollutants compared to pristine Zn-ICP owing to photoinduced electron transfer in the Ru-Zn-ICP system and efficient separation of photogenerated electron-hole pairs. The prepared Ru-Zn-ICP photocatalyst was readily recycled without major loss of activity in the successive cycles.

A review on heterogeneous sonocatalyst for treatment of organic pollutants in aqueous phase based on catalytic mechanism

Heterogeneous sonocatalysis, as an emerging advanced oxidation process (AOP), has shown immense potential in water treatment and been widely demonstrated to remove persistent organic compounds in the past decade. The present article aims to provide a comprehensive review on the development of a heterogeneous catalyst for enhancing the ultrasonic degradation rate of organic pollutants from a viewpoint of sonocatalytic mechanism. The rational design and fundamentals for preparing sonocatalysts are presented in the context of facilitating the heterogeneous nucleation and photo-thermal-catalytic effects as well as considering the mechanical stability and separation capacity of the heterogeneous catalyst. In addition, some new trends, ongoing challenges and possible methods to overcome these challenges are also highlighted and proposed.

Synthesis, characterization and sonocatalytic applications of nano-structured carbon based TiO2 catalysts

In order to enhance sonocatalytic oxidation of a recalcitrant organic pollutant, rhodamine B (RhB), it is necessary to study the fundamental aspects of sonocatalysis. In this study, TiO₂-incorporated nano-structured carbon (i.e., carbon nanotubes (CNTs) or graphene (GR)) composites were synthesized by coating TiO₂ on CNTs or GR of different mass percentages (0.5, 1, 5, and 10 wt%) by a facile hydrothermal method. The sonocatalytic degradation rates of RhB were examined for the effect of ultrasound (US) frequency and calcination temperature by using the prepared TiO₂-NSC composites. Since US frequency affected the sonoluminescence (SL) intensities, it was proposed that there exists a correlation between the surface area or band-gap of the sonocatalysts and the degradation kinetic constants of RhB. In addition, the reusability of TiO₂-GR composites was also investigated. Overall, the performance of TiO₂-GRs prepared by the hydrothermal method was better than that of calcined TiO₂-CNTs. Among TiO₂-GRs, 5% GR incorporated media (TiO₂-GR-5) showed the best performance. Interestingly, the kinetic constants of sonocatalysts prepared under hydrothermal conditions had a negative linear relationship with the band-gap energy for the corresponding media. Furthermore, the strongest SL intensity and highest degradation rates of RhB for both carbonaceous composites were observed at 500 kHz. The kinetic constants of calcined media decreased linearly as the specific area of the media decreased, while the band-gap energy could not be correlated with the kinetic constants. The GR combined TiO₂ composite might be a good sonocatalyst in wastewater treatment using ultrasound-based oxidation because of its high stability.

Heterogeneous sonocatalytic degradation of anazolene sodium by synthesized dysprosium doped CdSe nanostructures

Undoped and Dy-doped CdSe nanoparticles are synthesized and then characterized by the SEM, XRD, FT-IR, XPS and BET methods, which verify successful preparation of the doped catalyst. The sonocatalytic degradation of anazolene sodium as a model azo dye is higher than sonolysis process and the 2% Dy-doped CdSe with band gap of 1.42eV exhibits the greatest sonocatalytic performance. The decolorization efficiency (DE%) of sonocatalysis with 2% Dy-doped CdSe, undoped CdSe and sonolysis after 90min of the process is 91.32%, 56.13% and 39.14%, respectively. In addition, the sonocatalytic degradation of anazolene sodium increases with enhancement of the dopant, catalyst dosage, ultrasonic power, dissolved gasses and decreasing of initial anazolene sodium concentration. Furthermore, with addition of chloroform, sulfate, chloride and ethanol as the radical scavengers, the DE% decreases indicating the controlling mechanism of free radicals for the dye degradation. Besides, the results reveal the appropriate reusability of the catalyst and various degradation by-products are identified using the GC-MS technique. Eventually, the empirical kinetic model is expanded by nonlinear regression analysis for prediction of pseudo first-order constants in various operational conditions.