Studies on the Fluorine Generation by Fused Salt Electrolysis of KF·2HF at about 100°C

Abstract

Fluorine generation by fused salt electrolysis of KF・2HF at medium temperature of about 100°C was studied from view points of anodic polarization and anode effect. At first, equipment for manufacturing anhydrous HF and a 100 Amp fluorine cell were designed and operated. Various anodic materials (carbons with different grades of graphitization, nickel, C-Cu alloy etc.) were used and the suitable materials for the fluorine generation were selected. Some additional agents (LiF, AlF₃, NiF₂ etc.) were added to the electrolyte and their effects to anodic polarization were considered from various points. Anodic polarization (or the degree of anode effect) have been proved to have the relation with the wettability of anode by electrolyte. Wettabilities of each electrode were measured by the measurement of sizes, forms and contact angles of bubbles on the anode surface by microphotographic observation. The relation between the wettability and limiting current densities at which anode effect starts, was discussed.