Rare earths elements cycling in reclaimed ion-adsorption mine tailings

Noemie Janot (1, 2) , Hermine Huot (3) , Sophie Leguédois (2) , Geoffroy Séré (2) , Ye-Tao Tang (3) , Jean-Louis Morel (2) , Rong-Liang Qiu (3) , Jan E. Groenenberg (1, 4)

1 LIEC - Laboratoire Interdisciplinaire des Environnements Continentaux
2 LSE - Laboratoire Sols et Environnement
3 SYSU - Sun Yat-sen University [Guangzhou]
4 WUR - Wageningen University and Research [Wageningen]

Rare Earth Elements (REEs) have become essential components of many high-tech products. Among the various known REEs deposits, the ion-adsorption ones, only found in Southern China, represented around 30% of the worldwide production in 2017. Reclamation of the resulting mine tailings is limited by theirpoor physical conditions, their low organic matter and nutrient levels as well as their relatively high residual REEs content.Reclamation practicesof such sites caninclude natural attenuationor phytoremediation, usingsoil amendment or construction, and planting of tolerant speciesor economic crops. These practices induce drastic changes in the biogeochemical conditions of the soils and thus potentially modify REEs and nutrients availability, impacting the sustainability of the reclamation.To gain understanding on the impactof reclamation practiceson REEs dynamics, we studya minetailing in Ganzhou city, Jiangxi province, that has been abandoned for 10y. Phytoremediation techniques are currently tested on the tailings material in experimental plots (2x2m) in which plants and soil development are monitored over time. More specifically, the techniques includephytostabilization using perennial grasses or fiber plants, and phytoextraction using REEs hyperaccumulators. Anobjective of thisstudy is to develop a geochemical model to be able to evaluate the various practices. A process-based multi-surface model has been parameterized for REEs in soils and sedimentsin the platform ORCHESTRA.Based on measured contents of REEs, clays and Al/Fe-(hydr)oxides and solution pH and DOC concentration, we predicted dissolved REEs concentrations in pore water and CaCl2-extract. The model is evaluated by comparing modelled vs.measured REEs solid:solution partitioning. Once validated, such a model could be used to gain more detailed insights on the impact of organic exudate or amendment rates on reclamation sustainability.

Domaines: Géochimie; Minéralogie

Noemie Janot, Hermine Huot, Sophie Leguédois, Geoffroy Séré, Ye-Tao Tang, et al.. Rare earths elements cycling in reclaimed ion-adsorption mine tailings. Goldschmidt, Geochemical Society, Aug 2018, Boston, United States. ⟨hal-02473680⟩