Integrated phytomining red mud: Scandium uptake by Dracaena fragrans with amendment of acid mine drainage and indigenous bacterial

Scandium (Sc) is a rare earth element with high economic value, detected in red mud at concentrations ranging from 0.004-0.01% of total metals, which is considered relatively high. Phytomining offers an environmentally friendly alternative for Sc extraction from red mud. This study aims to evaluate the effect of acid mine drainage (AMD) and bioaugmentation on Sc uptake by the test plant Dracaena fragrans. The growth medium consisted of 90% red mud and 10% manure, with the addition of AMD at a 7.5% dose and bioaugmentation using indigenous bacteria (Staphylococcus warneri and Chromobacterium piscinae). Harvesting was carried out on days 0, 14, and 28, while physico-chemical parameters such as pH and electrical conductivity (EC) were measured every two days. Results showed a reduction of pH from 9.4 to 7 and an EC increase of approximately 50% over the 28-day phytomining experiment. The highest scandium uptake was observed on day 28, with 1.95 mg/kg for Staphylococcus warneri and 5.15 mg/kg for Chromobacterium piscinae. Meanwhile, the combination of S. warneri with AMD resulted in 3.35 mg/kg, and C. piscinae with AMD reached 5.8 mg/kg. In conclusion, AMD and bioaugmentation significantly enhanced Sc uptake in Dracaena fragrans.