STUDIES ON THE SOLVENT EXTRACTION OF RARE EARTH METALS FROM FLUORESCENT LAMP WASTE USING CYANEX 923

The growing need for materials such as rare earth metals (REMs) has focused attention towards their recovery from various end-of-life products. Fluorescent lamps are considered a viable target, and can be a source of up to six REMs: lanthanum, cerium, europium, gadolinium, terbium, and yttrium. In this study a commercial mix of trialkylphosphine oxides (Cyanex 923) was investigated for the extraction of REMs from fluorescent lamp waste leachates. The kinetics of the extraction is addressed, together with the co-extraction of undesired elements (iron and mercury), the influence of temperature, nitric acid concentration in the aqueous phase and ligand concentration in the organic phase. The extraction of REMs was found to be enthalpically driven, with good separation factors between the light and heavier elements. Selective stripping of REMs was possible in a single step using 4 M hydrochloric acid solution. Further recovery of iron and mercury was carried out using nitric and oxalic acid solutions.