Selective Chemical Etching of Vanadium Slag Enables Highly Efficient and Clean Extraction of Vanadium

Vanadium slag with high calcium and phosphorus contents (HCPVS) is considered an inadequate raw material for vanadium extraction. Existing vanadium extraction techniques are incapable of efficiently extracting vanadium from HCPVS due to the severe interference of phosphorus and silicon impurities. This study proposed selective chemical etching to remove phosphorus and silicon prior to vanadium extraction under mild conditions. Results showed that the (Mn,Fe)V₂O₄ spinels in HCPVS were enveloped by a silicate matrix comprising Ca₂SiO₄–Ca₃(PO₄)₂ and CaFeSiO₄. Chemical etching with 1.5 mol/L hydrochloric acid for 30 min effectively removed the silicate matrix, yielding the etched slag for further processing. The etched slag underwent magnesiation roasting at a Mg/V molar ratio of 1.0 for 60 min at 1173 K. Subsequent leaching with sulfuric acid at pH 3.5 and 313 K for 10 min yielded a vanadium extraction efficiency of 93.2%. V₂O₅ with a purity of 98.6% was obtained after ammonium precipitation and calcination. The resulting leaching residue and wastewater are recyclable, demonstrating the proposed vanadium extraction process as environmentally friendly and sustainable. This study sheds light on a novel way for sustainable resource extraction from low-grade ores.