Development of Fine Particle Mechanical Separation Processes with Representative Catalyst Materials for Recycling PEM Water Electrolyzers Exploiting their Wetting Characteristics

Demand for technologies using water electrolysis to produce green hydrogen is increasing, although recycling research on membrane electrode assemblies, which contain various precious and highly critical metals, is still limited. This study therefore aims at exploiting the feasibility of fine particle separation processes based on the difference in hydrophobicity of the ultrafine materials used as catalysts in polymer electrolyte membrane electrolyzers and at providing a fundamental study with representative materials of carbon black and TiO2. Since the cathode materials including carbon black are hydrophobic and the anode materials as well as TiO2 are hydrophilic, the characterizations of their various surface properties such as zeta potentials, dispersion characteristics, and bubble coverage angle tests have been investigated. In addition, using liquid-liquid particle extraction in a mixture model, 99 % of carbon black is recovered in the organic phase and 97 % of TiO2 is selectively separated in the aqueous phase with the help of the dispersant, sodium hexametaphosphate.