Targeting fluorescent lamp waste for the recovery of cerium, lanthanum, europium, gadolinium, terbium and yttrium

Abstract

Owing to the ever-growing demand and supply problems, rare earth elements (REEs) are now considered to be some of the most critical elements. This has focused attention towards their recovery from end-of-life products and industrial waste streams. A hydrometallurgical approach was carried out to assess the recycling potential of REEs from fluorescent lamp waste. In comparison to other efforts in this field, these investigations were carried out using real waste samples originating from a discarded lamp processing facility. Leaching of metals from the waste was studied using nitric, hydrochloric, sulphuric and methane sulphonic acid solutions. Separation of REEs from nitric acid media was investigated using solvent extraction. Batch extraction experiments were carried out using Cyanex 923, a commercial mix of trialkylphosphine oxides. Separation of heavier REEs (terbium, europium and gadolinium) and yttrium from lighter REEs (cerium and lanthanum) is possible due to larger separation factors. Selective stripping of REEs from the co-extractable species (iron and mercury ions) was easily achieved using 4 M hydrochloric acid. Further recovery of the extracted iron and mercury, with either oxalic acid or nitric acid solutions, allows for the subsequent re-use of the organic phase in the process.