Competition among rare earth elements on sorption onto six seaweeds

Abstract

Sorption has been proposed as a promising approach towards a sustainable water decontamination and recently to the recycling of rare earth elements (REE). Although living seaweed have been shown to be capable of removing REE from contaminated solutions, no studies have yet compared the effects of REE competition on sorption onto different groups of seaweed. These effects were analysed in the present study by exposing six living seaweeds (Ulva lactuca, Ulva intestinalis, Fucus spiralis, Fucus vesiculosus, Gracilaria sp. and Osmundea pinnatifida) (3 g/L, fresh weight) to mono-element and multi-element solutions of Y, La, Ce, Pr, Nd, Eu, Gd, Tb and Dy (1 μmol/L). Results show a preference towards light REE in mono-element solutions, which is reduced when in competition with other REE. The competitive effect is less pronounced in heavy REE indicating that these are still able to bind to the macroalgae despite the presence of competing ions. Contrary to water content (%), seaweed specific surface area (cm2/g) shows to be an important factor in the sorption of REE, since larger surface area is associated with higher removal and larger competitive effect.