Model and Mechanism of Anode Effect of an Electrochemical Cell for Nd or (Nd, Pr) Reduction
Andre Luiz Nunis da Silva,
Celia Aparecida Lino dos Santos,
Rogério de Melo Riberio de Araújo,
Dominic Feldhaus,
Bernd Friedrich,
Fernando José Gomes Landgraf,
Roberto Guardani
Affiliations
Andre Luiz Nunis da Silva
Laboratory of Metallurgical Processes, IPT—Institute for Technological Research of Sao Paulo State, Av. Prof. Almeida Prado, Sao Paulo 05508-901, SP, Brazil
Celia Aparecida Lino dos Santos
Laboratory for Corrosion and Protection, IPT—Institute for Technological Research of Sao Paulo State, Av. Prof. Almeida Prado, Sao Paulo 05508-901, SP, Brazil
Rogério de Melo Riberio de Araújo
Laboratory of Metallurgical Processes, IPT—Institute for Technological Research of Sao Paulo State, Av. Prof. Almeida Prado, Sao Paulo 05508-901, SP, Brazil
Dominic Feldhaus
IME Process Metallurgy and Metal Recycling, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany
Bernd Friedrich
IME Process Metallurgy and Metal Recycling, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany
Fernando José Gomes Landgraf
Department of Metallurgical and Materials Engineering, University of Sao Paulo, Av. Prof. Mello Moraes, Sao Paulo 05508-030, SP, Brazil
Roberto Guardani
Department of Chemical Engineering, University of Sao Paulo, Av. Luciano Gualberto, Sao Paulo 05508-010, SP, Brazil
The anode effect can occur during neodymium and didymium oxide electrowinning, causing a surge in the electrochemical cell voltage, interrupting the process, and increasing the greenhouse gas emissions. In this work, we develop a mathematical model, based on the mass balance of gas bubbles evolving from the anode, to understand the influence of some process parameters on the anode effect. The anode effect occurs due to bubble coverage and limitations on the mass transfer of the oxide species. Variables such as current density, oxide content, viscosity, and electrolyte composition play an important role in the anodic process. Finally, we propose a mechanism for the occurrence of the anode effect during Nd or Di (Nd–Pr) oxide electrolytic reduction based on models used in aluminum electrolysis.
