ROASTING, FLUIDIZED-BED SEPARATION, AND HYDROMETALLURGICAL TREATMENT OF WASTE TANTALUM CAPACITOR TO RECOVER PURIFIED TANTALUM

摘要

A physical separation technique of tantalum capacitors from waste print circuit boards is in a development phase in Japan. A tantalum capacitor consists of an exterior coating of resin (epoxy resin) mixed with silica fillers and a sintered tantalum compact, the latter of which is impregnated with manganese dioxide (MnO_2). In this study, we developed a process to recover tantalum oxide from tantalum capacitors by roasting, fluidized-bed separation, and hydrometallurgical treatments. Our aim was to recover tantalum oxide with high purity from waste tantalum capacitors. In this process, the exterior resin was selectively decomposed by roasting without oxidation and pulverization of the sintered tantalum compact at a proper temperature. Furthermore, the decomposed resin with silica filler on the surface of the sintered tantalum compact was mostly removed by fluidized-bed separation. The surface of the sintered tantalum compact was cleaned by ultrasonic irradiation in an acid solution to remove the MnO_2 paste as well as residual Ag paste and silica filler. The impregnated MnO_2 in the sintered tantalum compact was leached as Mn(II) ions using acid solutions via the reducing effect of tantalum metal to recover purified tantalum oxide.