Innovative surfactant-based mechanical separation processes for recycling of ultrafine active materials in High-Temperature Water Electrolyzers (HTEL)
For circular economy driven recycling, the selective separation of NiO and solid electrolyte materials (ZrO₂ and YSZ) is demonstrated, as a sustainable component of the emerging hydrogen economy
image: Schematic representation of selective separation of Organic Phase (NiO) and Aqueous phase (YSZ and ZrO2)
Credit: Sohyun Ahn, Helmholtz Institute Freiberg for Resource Technology, Germany
A latest study introduces a surfactant-based method for the selective recovery of fine active materials from high-temperature water electrolyzers. By employing cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), researchers modified the surface characteristics of materials such as NiO, YSZ, and ZrO₂, enabling the efficient separation of these components. The findings demonstrate that NiO can be selectively recovered in the organic phase, while the other particles remain in the aqueous phase. In contrast to traditional, energy-intensive metallurgical methods, this approach minimizes chemical consumption and promotes a more sustainable circular economy. The study also suggests potential optimizations, such as increasing the number of phase separation stages for enhanced recovery. Additionally, magnetic separation techniques are proposed for materials like perovskite LSM. This work was published in Industrial Chemistry & Materials on 9th July 2024.
Mechanical separation processes are very important for recycling owing to their several key benefits, especially in terms of cost efficiency, energy savings and less environmental impacts. However, due to the advantage of high efficiency of chemical processes, most research in recycling of critical raw materials is focused on them. This also applies to fine active materials used in electrolysis, which is considered a key technology for green hydrogen production. The functional layer of HTELs relies on the use of critical raw materials with analogous physical surface properties, likely defined by their wettability. This presents a challenge for further development of mechanical separation processes for recycling. “We aimed to explore the influence of surfactants in the mechanical separation process of fine active materials used in high-temperature electrolyzers,” said Dr. Sohyun Ahn, a PhD student at Helmholtz Institute Freiberg for Resource Technology, “The goal was to understand how surfactants affect the wettability of the materials and towards the selective separation.”
The key point is that surfactants can significantly enhance the selective mechanical separation of ultrafine particles, which can improve material recovery and reduce energy consumption in HTEL cells. Although the recovery is relatively low compared to chemical processes, this approach contributes to more sustainable recycling within the circular economy. “We are looking forward to even higher recoveries with the further process optimization,” said Dr. Ahn, “In addition, we discovered the unexpected wettability of NiO, which was dispersed stable in the organic phase at a certain pH range, which plays a key role in designing the mechanical separation process.”
The materials used in HTEL cells are not standardized yet, and various composites are still under development. As a result, the recycling process design may vary, so the next step is to investigate and optimize the effect of various surfactants for different materials and improve separation techniques for large-scale applications. “The ultimate goal is to integrate and extend this approach into industrial processes, especially energy systems and material recovery technologies, towards promoting the resource efficiency and sustainability in the circular economy,” said Dr. Ahn. Potential applications include improved recycling methods for materials important in energy storage and conversion devices.
The research team includes Sohyun Ahn, Suvarna Patil, Martin Rudolph from Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Germany.
This research is funded by the German Federal Ministry for Education and Research (BMBF) as part of the project H2Giga- ReNaRe – Recycling – Nachhaltige Ressourcennutzung, Grant No.: 03HY111D).
Industrial Chemistry & Materials is a peer-reviewed interdisciplinary academic journal published by Royal Society of Chemistry (RSC) with APCs currently waived. Icm publishes significant innovative research and major technological breakthroughs in all aspects of industrial chemistry and materials, especially the important innovation of the low-carbon chemical industry, energy, and functional materials.