Effect of Fluoride Addition on the Electrolysis of DyCl_3, NdCl_3 and SmCl_3 in Molten Chloride Bath

摘要

A disproportionation reaction and a shuttle reaction, such as Ln + 2Ln~(3+) = 3Ln~(2+) /Ln~(2+) = Ln~(3+) + e, accompany the electrodeposition of rare earths. Under these conditions, current efficiency is very low and dendritic growth may cause short-circuits between the electrodes. This will disturb the industrial production of rare earth metals. Using the pulse potential technique in combination with a mixed fluoride/chloride salt, the dendritic growth might be suppressed. In our study, we investigated the effect of the addition of fluoride into the chloride bath by means of both the cyclic voltammetry and the differential pulse voltammetry techniques. Results showed obvious improvement, in the current efficiency and the morphology of cathode deposition, when the fluoride was added to the bath by about 5mol%.