Tatsuya Oki

Chapter 255 - Recycling of Rare Earths from Scrap

Abstract With the increased concern about the rare-earth supply chain risk, recycling rare-earths from scrap is receiving significant attention. In this monograph, the studies of the rare-earth recycling technologies have been reviewed with respect to magnets, phosphors, batteries, polishing powders and others from the viewpoints of physical separation, hydrometallurgy, and pyrometallurgy. The important issues inherent in each scrap were pointed out. Particularly-important issues are dismantling, demagnetization, the separation from iron for the magnets, and the fine particle separation and the terbium dissolution for the phosphors. Emerging technologies, such as the automated dismantling methods for the magneta and the application of high gradient magnetic separation for the phosphors, together with a new extractant have been noted. A cost barrier before the actual implementation of the developed process should be overcome not only by the technologies, but also by the integration with a social system establishment.

Selective recovery of catalyst layer from supporting matrix of ceramic-honeycomb-type automobile catalyst

Natural resources of platinum group metals (PGMs) are limited and their demand is increasing because of their extensive uses in industrial applications. The low rate of production of PGMs due to low concentration in the related natural ores and high cost of production have made the recovery of PGMs from previously discarded catalytic converters a viable proposition. The ceramic-honeycomb-type automobile catalytic converter contains appreciable amount of PGMs. These valuable substances, which are embedded in the catalyst layer and covered on the surface of the supporting matrix, were selectively recovered by attrition scrubbing. The attrition scrubbing was effective for the selective recovery of catalyst layer. The process was convinced as the comminution and separation process by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles by attrition scrubbing. The recovery of Al(2)O(3) and total PGMs in the fraction less than 300 μm increased with the residence time whereas their contents in the recovered materials slightly decreased. The interparticle scrubbing became favorable when the initial input size increased. However, the solid/liquid ratio in the mixing vessel was slightly affected by the low density of converter particles.

Recovery of LaPO4:Ce,Tb from waste phosphors using high-gradient magnetic separation

LaPO4:Ce,Tb (LAP) containing high terbium concentration was successfully recovered from waste phosphor from end-of-life fluorescent lamps by high-gradient magnetic separation (HGMS). In addition to HGMS, some contaminants in the waste phosphor, e.g., iron oxide and glass powder, were also removed by sieving and sedimentation. Repeating the magnetic separation procedure three times yielded LAP with a purity of 87%. Luminescence spectra intensities of recovered LAP were as high as 95% compared with virgin LAP. This recovery method will be useful during rare-earth crises.