Rare earths stick to rare cyanobacteria: Future potential for bioremediation and recovery of rare earth elements

Abstract

Biosorption of metal ions by phototrophic microorganisms is regarded as a sustainable and alternative method for bioremediation and metal recovery. In this study, 12 cyanobacterial strains, including 7 terrestrial and 5 aquatic cyanobacteria, covering a broad phylogenetic diversity were investigated for their potential application in the enrichment of rare earth elements through biosorption. A screening for the maximum adsorption capacity of cerium, neodymium, terbium, and lanthanum was conducted in which Nostoc sp. 20.02 showed the highest adsorption capacity with 84.2–91.5 mg g-1. Additionally, Synechococcus elongatus UTEX 2973, Calothrix brevissima SAG 34.79, Desmonostoc muscorum 90.03, and Komarekiella sp. 89.12 were promising candidate strains, with maximum adsorption capacities of 69.5–83.4 mg g-1, 68.6–83.5 mg g-1, 44.7–70.6 mg g-1, and 47.2–67.1 mg g-1 respectively. Experiments with cerium on adsorption properties of the five highest metal adsorbing strains displayed fast adsorption kinetics and a strong influence of the pH value on metal uptake, with an optimum at pH 5 to 6. Studies on binding specificity with mixed-metal solutions strongly indicated an ion-exchange mechanism in which Na+, K+, Mg2+, and Ca2+ ions are replaced by other metal cations during the biosorption process. Depending on the cyanobacterial strain, FT-IR analysis indicated the involvement different functional groups like hydroxyl and carboxyl groups during the adsorption process. Overall, the application of cyanobacteria as biosorbent in bioremediation and recovery of rare earth elements is a promising method for the development of an industrial process and has to be further optimized and adjusted regarding metal-containing wastewater and adsorption efficiency by cyanobacterial biomass.

Rare earth element stripping from kaolin sands via mild acid treatment

“…Recently, this process was reported showing the efficiency of REE recovery. 21 Here, the influence of the concentration of REEs, the acidity of the solvent, and the type of REEs on the adsorption capacity of different cyanobacteria was evaluated. Five cyanobacteria (Nostoc sp.…”

“…One example of REE recycling of dissolved REE ions in aqueous solution was recently reported, and the potential of cyanobacteria for the adsorption and enrichment of REEs was tested 21 . REEs were coordinated effectively to functional groups at the surface of these cyanobacteria at pH values between 5 and 6.…”

“…One example of REE recycling of dissolved REE ions in aqueous solution was recently reported, and the potential of cyanobacteria for the adsorption and enrichment of REEs was tested. 21 REEs were coordinated effectively to functional groups at the surface of these cyanobacteria at pH values between 5 and 6. With this study, we intend to illustrate an effective way to access REEs from mineral residues capable to be utilized in modern REE recycling processes.…”

Learning from nature: recovery of rare earth elements by the extremophilic bacterium Methylacidiphilum fumariolicum

“…10,23,24 High adsorption capacities of REE were lately discovered for 12 cyanobacterial strains. 25 The Ln-utilizing bacterium strain AM1 was genetically modified for a selective uptake of heavier Ln, such as Gd. 26 For our studies, we used the native Ln-dependent strain SolV 11 to accumulate and enrich certain Ln from a variety of natural and artificial REE sources.…”

“…10,23,24 High adsorption capacities of REE were lately discovered for 12 cyanobacterial strains. 25 The Ln-utilizing bacterium strain AM1 was genetically modified for a selective uptake of heavier Ln, such as Gd. 26…”