Leaching reaction of manganese dioxide from tantalum capacitor scrap. A study on the recycling of high quality rare metal secondary resource

A process is proposed for the recycling of Ta capacitor scrap containing 4-7% MnO₂ as solid electrolyte. This paper describes the removal leaching of MnO₂ with various agents and disscusses the dissolution reaction of MnO₂ in FeSO₄-H₂SO₄ aqueous solution from thermodynamic and kinetic aspects. In leaching of block Ta anode scrap, H₂O₂ and Na₂SO₃ solution were the most effective leaching agents, with more than 90% of Mn extraction at room temperature after 24 hours. When the sample was ground to -200 mesh, MnO₂ was almost completely removed in a short time by use of H₂O₂ solution. FeSO₄ solution also showed a satisfactory result. The overall reaction of the primary per was controlled by mass transfer of Fe²⁺ ions through the boundary layer between the solution and the surface of MnO₂ inside the capacitor. Dissolution of Fe(OH)₃ and other reaction products was the rate determining step in the secondary per Hermetic seal type Ta capacitor scrap was upgraded by applying the Fe³⁺/Fe²⁺ oxidative-reductive leaching method.