Electroprecipitation of Metal Ions from Aqueous Electrolytes: Kinetic Study and Process Performance

GDEx (Gas-diffusion electrocrystallization) is defined as the reactive precipitation of intermediaries issued from an electrochemical reaction at a gas-diffusion electrode (GDE), with metal precursors provided in the electrolyte. It can be used as a synthesis method to prepare (nano)particles or as a metal removal and recovery process. An exploratory study of the GDEx process was carried out to demonstrate the similarities and differences of GDEx with alkaline titration, a well-known precipitation method. This work focused on understanding the GDEx process with regards to how metal ions are recovered, and how and why they precipitate as nanoparticles. The focus was on air-fed GDEs for the formation of metal (oxy)(hydr)oxide nanoparticles. In summary, the key contributions of this PhD were: (1) demonstrating that although it is an electrochemical process and therefore inherently heterogeneous, GDEx can have the appearance of a homogeneous process, (2) the comparison of GDEx to alkaline titration, (3) the discovery of oxidation-assisted alkaline precipitation and its role in GDEx as a process to synthesize metal (oxy)(hydr)oxide nanoparticles, and (4) the investigation of the accumulation of species in the porous GDE, a phenomenon observable during the GDEx process in batch mode. Future work includes the development of an all-encompassing model to reach the goal of GDEx as a process for synthesis-by-design.

Publication year:2020

Accessibility:Open