Fractionation of rare earth elements and yttrium in aqueous media: the role of organotrophic bacteria

Abstract

The paper presents the experimental results of the rare earth elements and yttrium (REY) biosorption in the natural surface waters and groundwater in the presence of living and inactivated organotrophic bacteria (Curtobacterium sp., Ralstonia sp., Pseudomonas sp., Bacillus sp., Brevibacterium sp., Microbacterium sp.,) under different environmental pH conditions. We find that the biosorption process is mainly regulated by two factors: the aqueous solution’s pH and the bacteria strains concertation. The water acidity significantly effects on the bacteria sorption capacity for all studied strains. We discover a decrease in REY sorption with an increase in pH due to lower absorption of REY on the cell walls of bacteria. The process of REY biosorption proceeds more intensively by living bacteria than in the presence of inactivated microorganisms. We observe that at neutral pH values all studied bacterial strains sorb light REY (lanthanum, praseodymium, neodymium), in more acidic solutions (pH 2) the heavy ones (lutetium, europium). The REY sorption decreased with an increase in the living and inactivated bacterial concentration.