Advanced oxidation procedures (AOPs) refer to a variety of technical procedures that produce OH radicals to sufficiently oxidize wastewater, organic pollutant streams, and toxic effluents from industrial, hospital, pharmaceutical and municipal wastes. Through the implementation of such procedures, the (post) treatment of such waste effluents leads to products that are more susceptible to bioremediation, are less toxic and possess less pollutant load. The basic mechanism produces free OH radicals and other reactive species such as superoxide anions, hydrogen peroxide, etc. A basic classification of AOPs is presented in this short review, analyzing the processes of UV/H₂O₂, Fenton and photo-Fenton, ozone-based (O₃) processes, photocatalysis and sonolysis from chemical and equipment points of view to clarify the nature of the reactive species in each AOP and their advantages. Finally, combined AOP implementations are favored through the literature as an efficient solution in addressing the issue of global environmental waste management.

Metal-organic frameworks (MOFs) have received a lot of attention due to their unique properties and abundant functionalities. Permanent porosity and high surface area are just a few traits that have made them attractive to researchers. They can be prepared as task-specific materials by exploiting the functional group variety and tuning their size and geometry. The main purpose of this review is to present an alternative method of preparing MOF crystals and underline the advantages of ultrasound assisted (sonochemical) synthesis. State of the art ultrasound assisted techniques for the preparation of MOFs in nanoscale are presented. Optimization of morphology and particle size is highlighted throughout this work, as we discuss the effects of various factors, such as energy input, reagent concentration, adequate solvents, reaction time and more.

Bulk oxygen self-diffusion in yttria-stabilised zirconia (YSZ) was investigated using tracer diffusion experiments and molecular dynamics (MD) simulation as a function of the yttria content. Experimentally, ¹⁸O tracer diffusion was measured as a function of temperature (650–1200 K) and yttria content (8–24 mol% Y₂O₃) using gas-phase exchange of the stable isotope ¹⁸O and SIMS analysis. For a given temperature, the diffusivity was highest for YSZ containing 10 mol% yttria. The activation enthalpy of diffusion was 0.8 to 1.0 eV, independent of the yttria content. The diffusion process was simulated with molecular dynamics using the program DL_POLY and comparing different potential sets. The oxygen diffusion coefficient was found to be of similar magnitude to the experimental value, and also showed similar concentration dependence with a maximum for YSZ containing 10 mol% yttria. The calculated activation enthalpies of oxygen transport are close to the values observed experimentally.

Composite materials constitute an appealing choice in many industrial sectors, due to their unique composition and characteristics, such as low maintenance requirements, light weight, corrosion resistance, and durability. However, the sustainable management of end-of-life composite materials remains a challenge. Recovery strategies, design aspects, and their interconnection are currently largely unexplored, while technologies involved in the circular economy (reuse, reduce, recycle, refurbish, etc.) could be improved. The current paper provides an overview of the existing methods of composite material waste management, while presenting new circular economy prospects for end-of-life strategies and providing a brief roadmap towards circularity for industries. Finally, existing circular economy practices in regard to composites are presented in different European countries to present the applicability of composite material end-of-life waste management.

Self-diffusion of calcium, yttrium, and zirconium in single-crystalline YSZ and CSZ (YSZ: yttria-stabilized zirconia; containing 10 to 32 mol % ${\mathrm{Y}}_2{\mathrm{O}}_3;$ CSZ: calcia-stabilized zirconia; containing 11 and 17 mol % CaO) was measured at temperatures between 960 and 1700 °C. For zirconium and calcium diffusion, the stable isotopes ${}^{44}\mathrm{Ca}$ and ${}^{96}\mathrm{Zr}$ were used as tracers and the samples were analyzed with secondary ion mass spectrometry. In the case of yttrium diffusion, the radioactive tracer ${}^{88}\mathrm{Y}$ was used and an abrasive sectioning technique was applied. Zirconium bulk diffusion is slower than yttrium and calcium bulk diffusion, and there is a nearly linear correlation of diffusion coefficient with cation radius. In YSZ, zirconium and yttrium bulk diffusivity are maximum for a stabilizer content of 10–11 mol %, while in CSZ both calcium and zirconium tracer diffusion are independent of the calcium content. The activation enthalpy of yttrium stabilizer bulk diffusion (4.2 eV) is, as in CSZ, slightly smaller than for zirconium bulk diffusion (4.5 eV). The yttrium dislocation pipe diffusivity is five to six orders of magnitude faster than the bulk diffusivity, and its activation enthalpy (3.5 eV) is also smaller than that of the bulk diffusion. From the activation enthalpy and from the concentration dependence of the cation bulk diffusion, it is concluded that the cation diffusion occurs either via free vacancies $({\mathrm{V}}_{\mathrm{Zr}}^{\text{4′}}$ in YSZ) or via bound vacancies $\mathrm{([}{\mathrm{V}}_{\mathrm{Zr}}^{\text{4′}}\text{−2}{\mathrm{V}}_{\mathrm{O}}^{\text{2•}}{]}^x$ in CSZ).