Potential of the macroalga Ulva sp. for the recovery of yttrium obtained from fluorescent lamp waste

Secondary sourcing of Rare-Earth elements (REEs) from electronic waste can compensate for supply bottlenecks as well as environmental and health issues associated with ore mining. In this study, recovery of yttrium (Y) from real fluorescent lamp waste (FLW) through biosorption onto the macroalga Ulva sp. is proposed. The initial waste was composed mainly of yttrium oxides (49%) and calcium hydroxides/phosphates (23%). Response surfaces revealed that lower salinity (10) and higher sorbent mass (9 g L-1) improved sorption efficiency (maximum removal of 52% and 32% for initial concentrations of 20 and 120 mg L-1, respectively). Higher concentrations of Y accelerated the sorption kinetics, achieving equilibrium after 3 h. The amount of Y accumulated on the algal tissue (maximum of 22 mg g(-1)) was not affected by algae dosage. Results show that algal-based sorbents are efficient when applied to real wastes under optimal conditions. While leachate purity still requires optimization, fast kinetics and high concentrations in the biomass indicate that Ulva sp. may constitute a viable material for the biosorption of Y obtained from FLW. Incorporating Ulva sp. biosorption into an Y recovery process will thus contribute to a green and circular economy, compensating the negative effects associated with primary ore mining.