abstract
Low recycling rates of rare earth elements (REEs) are a consequence of inefficient, expensive and/or contaminating methods currently available for their extraction from solid wastes or from liquid wastes such as acid mine drainage or industrial wastewaters. The search for sustainable recovery alternatives was the motivation for this study. For the first time, the capabilities of 6 living macroalgae (Ulva lactuca, Ulva intestinalis, Fucus spiralis, Fucus vesiculosus, Osmundea pinnatifida and Gracilaria sp.) to remove REEs (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy) from laboratory-prepared seawater spiked with REE solutions were evaluated. The assays lasted 72 h with REEs concentrations ranging from 10 to 500 mu g L-1. The link between REEs uptake and algal metabolism, surface morphology and chemistry were addressed. Kinetics varied among the species, although most of the removal occurred in the first 24 h, with no equilibrium being reached. Lack of mortality reveal that the algae maintained their metabolism in the presence of the REEs. Green alga U. lactuca stood out as the only capable of efficiently removing at least 60% of all elements, reaching removals up to 90% in some cases. The high bioconcentration factors, derived from mass balance analysis (c.a. 2500) support that the REEs enriched algal biomass (up to 1295 mu g g(-1)) may constitute an effective and environmentally friendly alternative source of REEs to conventional extraction from ores.
keywords
BROWN MARINE ALGA; SOLVENT-EXTRACTION; FUCUS-VESICULOSUS; ULVA-LACTUCA; RECOVERY; BIOSORPTION; APATITE; BIOACCUMULATION; RESOURCES; SCENARIOS
subject category
Environmental Sciences & Ecology
authors
Pinto, J; Henriques, B; Soares, J; Costa, M; Dias, M; Fabre, E; Lopes, CB; Vale, C; Pinheiro-Torres, J; Pereira, E
our authors
Elaine Fabre
PhD Studentacknowledgements
Bruno Henriques benefited from a Research position funded by national funds (OE), through FCT -Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. Thanks are also due to the financial support to REQUIMTE, CESAM and CIIMAR (UIDB/50006/2020, UID/AMB/50017 and UID/Multi/04423/2019, respectively), to FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020, and to N9VE -Nature, Ocean and Value, Lda, for their cooperation in this work.