Potassium Tantalate K6Ta10.8O30with Tungsten Bronze Structure and Its Photocatalytic Property

Ferroelectric field enhanced tribocatalytic hydrogen production and RhB dye degradation by tungsten bronze ferroelectrics

Tribocatalysis is a method that converts mechanical energy into chemical energy. In this study, we synthesized tungsten bronze structured Ba0.75Sr0.25Nb1.9Ta0.1O6 ferroelectric ceramic submicron powder using a traditional solid-state route, and the powder exhibited excellent performance in tribocatalytic water splitting for hydrogen production. Under the friction stirring of three polytetrafluoroethylene (PTFE) magnetic stirring bars in pure water, the rate of hydrogen generation by the Ba0.75Sr0.25Nb1.9Ta0.1O6 ferroelectric submicron powder is 200 μmol h-1 g-1, and after 72 hours, the accumulated hydrogen production reaches 15 892.8 μmol g-1. Additionally, this ferroelectric tungsten bronze ferroelectric material also exhibits excellent tribocatalytic degradation ability toward RhB dyes, with degradation efficiency reaching 96% in 2 hours. The study of tribocatalysis based on tungsten bronze ferroelectric materials represents a significant step forward in versatile energy utilization for clean energy and environmental wastewater degradation.

Characterization of K6Ta10.8O30 Microrods with Tetragonal Tungsten Bronze-Like Structure Obtained from Tailings from the Penouta Sn-Ta-Nb Deposit

In this work, a deep characterization of the properties of K6Ta10.8O30 microrods has been performed. The starting material used to grow the microrods has been recovered from mining tailings coming from the Penouta Sn-Ta-Nb deposit, located in the north of Spain. The recovered material has been submitted to a thermal treatment to grow the microrods. Then, they have been characterized by scanning electron microscopy, X-ray diffraction, micro-Raman and micro-photoluminescence. The results of our study confirm that the K6Ta10.8O30 microrods have a tetragonal tungsten bronze-like crystal structure, which can be useful for ion-batteries and photocatalysis.

Recovery of niobium and tantalum by solvent extraction from Sn-Ta-Nb mining tailings

The slag from the extraction processes of metals from their ores may contain valuable components that, if adequately recovered, can be reintroduced in the technological life cycle. This is the case for the material obtained in Penouta mines in the North of Spain. These mineral sites are a main source of tin obtained from cassiterite. The mineral is submitted to a pyrometallurgical process to separate tin, however cassiterite is not the only mineral present in the veins, and large amounts of other minerals are normally discarded, constituting the slag. In the present case, besides cassiterite, one of the most abundant minerals in the ore is columbo tantalite, the source of the strategic coltan. In this work the raw material (slag) has been treated by acid leaching, using HF/H₂SO₄ as the leaching agent. Then liquid–liquid extraction of Nb and Ta was performed, with Cyanex®923 extractant, so that both metals were obtained separately. Then they were precipitated from the corresponding aqeuous solution, and calcined in order to yield Nb₂O₅ of 98.5% purity and tantalum salt, after calcination and purification, of 97.3% purity. The process described in this work opens a possibility to produce high quality materials that are considered critical by the EU from alternative sources exempt of criticality factors.

The slag from the extraction processes of metals from their ores may contain valuable components that, if adequately recovered, can be reintroduced in the technological life cycle.

In-Situ Growth of Au on KTaO3 Sub-Micron Cubes via Wet Chemical Approach for Enhanced Photodegradation of p-Nitrophenol

KTaO₃/Au hetero-nanostructures were synthesized by in-situ reduction of HAuCl₄ on the surface of hydrothermally-grown KTaO₃ sub-micron cubes. The concentration of Au source was found to be a critical factor in controlling the hetero-nucleation of Au nanoparticles on the surface of KTaO₃ sub-micron cubes. Loading of Au particles on KTaO₃ nanocrystals enriched KTaO₃ additional UV-vis absorption in the visible light region. Both KTaO₃ and KTaO₃/Au nanocrystals were shown to be active in the photo-degradation of p-nitrophenol, while the loading of Au on KTaO₃ clearly improved the photo-degradation efficiency of p-nitrophenol compared to that on bare KTaO₃ nanocrystals, probably due to the improved light absorption and charge separation.