Impact of fertilization strategies on Phytolacca americana phytoextraction of rare earth elements from modified bauxite residue
Résumé
Rare earth elements (REEs) are critical materials facing supply challenges, making their recovery from secondary sources increasingly important. With increasing interest in developing eco-friendly technologies for metal extraction, this study investigated the potential of Phytolacca americana-a known REE hyperaccumulator plant-for REE extraction from bauxite residue (BR), a by-product of alumina extraction. Indeed, BR contains promising concentrations of REEs but presents severe constraints for plants growth due to its high pH, salinity and nutrient deficiency. Due to its unsuitability for supporting plant growth, BR of different origins (i.e. lateritic or karstic bauxite ore) requires modification through gypsum input to obtain modified bauxite residue (MBR) with lower salinity and alkalinity. Here we applied several MBR fertilization treatments involving organic (i.e. sewage sludge or compost) or mineral (mineral nutrient solutions with/without P) amendments to assess their effects on P. americana growth and REE phytoextraction. The results revealed efficient P. americana growth in MBR following organic amendment, while the physicochemical characteristics of these amendments significantly modulated the REE extraction yield. Notably, phosphorus availability emerged as a key determinant with a major impact on the REE phytoextraction efficiency from MBR. The use of amendments containing P reduced the REE phytoextraction efficiency up to 94%, while the absence of P in the amendment appeared to enhance REE uptake up to 16-fold. This suggests that P availability modulated REE phytoextraction from MBR, likely through P-induced acquisition mechanisms. Managing the growth substrate nutritional status is thus essential to enhance the efficiency of REE phytoextraction from BR