Selective separation of yttrium and europium using Cyanex 572 for applications in fluorescent lamp waste processing

摘要

The quest for a circular economy has directed attention towards processing of end-of-life products and industrial streams to recover the valuable fractions these contain. Fluorescent lamp waste is acknowledged to be an important source of yttrium and europium, two of the rare earth elements presently regarded as having critical supply risk. In this study, a commercial extractant for solvent extraction separations of REEs, Cyanex 572, was successfully applied to separate yttrium and europium from solutions obtained during processing of fluorescent lamp waste streams. Yttrium was selectively separated from europium at pH(eq) = 0, followed by further recovery of europium at pH(eq) = 1. Better extraction efficiencies of REEs were achieved using aliphatic diluents e.g. kerosene in comparison to aromatic diluents or long chain alcohols. Increases in temperature in the range 25-65 degrees C led to decreases in the separation factors between yttrium and europium. Stripping with hydrochloric acid solutions at concentrations higher than 3 M led to complete recovery of extracted yttrium and europium. Precipitation of these elements from their respective stripping products with oxalic acid, followed by calcination of the precipitate, led to yttrium and europium oxides of 99.82% and 91.60% purity, respectively. A flowsheet that encompass the main steps for fluorescent lamp waste processing is also presented. (C) 2016 Elsevier B.V. All rights reserved.