Pilot-scale field study for vanadium removal from mining-influenced waters using an iron-based sorbent

Highlights: • Pilot-scale experiments effectively removed vanadium from mining streams. • Neither of the pilot filter systems were fully exhausted with vanadium. • No new phases were formed during the pilot study. • Leaching of non-toxic impurities was observed at an early stage. • Iron coagulant was also able to remove vanadium for the mining stream efficiently. This study investigated the removal of vanadium from mining waters at a closed mine site (Mustavaara, Finland) using granular ferric oxyhydroxide (CFH-12) on pilot scale. Two filter systems, pilot A and pilot B, were placed in different streams, where the influent in pilot A contained a higher and very variable vanadium concentration (6.46–99.1 mg/L), while the pilot B treated influent had lower vanadium concentrations (0.443–2.33 mg/L). The operation periods were 51 days for pilot A and 127 days for pilot B. Water quality analyses revealed that vanadium was efficiently captured in the filter system in both pilots. X-ray fluorescence analysis revealed that the filter beds were not fully saturated with vanadium. X-ray photoelectron spectroscopy confirmed that oxidised vanadium (5⁺) existed in the used CFH-12 and the carbon content in the used material had increased due to the adsorbed organic compounds. For comparison, lab-scale coagulation experiments were conducted using ferric sulphate for the influent of pilot A (the sampled batch contained 15.9 mg/L V). The optimum coagulant dosage was 350 mg/L (> 93% vanadium removal) at the original pH (7.8–7.9) of the influent, whereas the required coagulant amount decreased when the influent pH was adjusted to 4.6–4.8.