Abstract
Abstract
Shungite-bearing rocks from the Zazhoginsky deposit in Karelia, Russia, are Maksovite-type metamorphic formations containing 30–45 % carbonaceous matter and trace amounts of rare earth elements (REEs, totalling ∼50 ppm), primarily light REEs (La, Ce and Nd), which are associated with phosphate minerals. This study evaluated the efficiency of mild water-based extraction methods for leaching and retaining REEs during concentration, using natural spring water and deionised controls at a rock loading of 200 g/L. The experiments (
n
= 3) included passive infusion (static or stirred), boiling for 5–30 min, and concentration via boiling evaporation or vacuum rotary evaporation. The REEs were quantified by ICP-MS. Passive infusion yielded total REEs of 118 ± 12 μg/L (approximately 7 % extraction efficiency), with no diffusion limitation (
p
= 0.139). Boiling increased the release of REEs in a time-dependent manner, reaching 195 ± 21 μg/L after 30 min (
p
p
< 0.01). The extracts were free of toxic metals exceeding WHO limits. These low-impact methods provide reproducible REE leaching from low-grade, carbon-rich rocks. Vacuum concentration enables stable preparations for potential environmental or analytical applications.