Application of particle-fluid interactions for selective separation of fine particles for the recycling of HTEL electrolyzer

For efficient renewable energy circulation, hydrogen production via water electrolysis technology has been developed over past decades. Amongst three technologies, high temperature water electrolysis (HTEL) is considered as a promising technology because of its high efficiency. Rare earth elements are the best candidates to make the cell more promising. However, reaching a long-term operation is an unsolved challenge because the durability of used ceramic materials is still an issue. Hence, development of the recycling processes for these critical raw materials is an important topic.
Ceramic materials used in HTEL cell have a similar surface property in terms of wettability. For this reason, fine particles cannot be separated without help from surfactants. In this study, representative materials such as Nickel oxide (NiO), Lanthanum strontium manganite (LSM), Yttria stabilized zirconia (YSZ), and Zirconium (ZrO2) oxide are used and their surface charge are investigated. Depending on the pH value, materials show change of their surface charge. Considering their electric charge, different surfactants applied to drive the particle surface hydrophobic. Since NiO and LSM have positive surface charge in base dispersion, particles may be hydrophobized with anion surfactant. Wettability of the YSZ and ZrO2, materials with opposite surface charge, changed by addition of cation surfactant. Their changed wettability can be described by using particle attachment on single air bubbles. Additional approach by using liquid-liquid phase transfer explain their behavior at the oil-water interfaces. This approach provides a contribution to scale-up the recycling processes of HTEL cells.