Functional Study of Metal Complex Formation with Sulfosalicylic Acid on Targeted Extraction of Vanadium

To address the low selectivity of vanadium extraction from shale-hosted vanadium leaching solution using D2EHPA solvent extraction caused by coexisting impurities, this study proposes an organic coordination regulation strategy. Sulfosalicylic acid (SSA) was selected as the optimal coordination agent. Under the optimal extraction conditions, the single-stage extraction efficiency of vanadium reached 89.2%, which is 11.5% higher than that of the conventional D2EHPA system. After stripping with H₂SO₄, the vanadium concentration in the vanadium-rich solution reached 32.67 g/L, while the Fe²⁺ concentration was only 0.61 g/L. Mechanism studies indicate that vanadium mainly exists in the form of VO-[C₇H₄O₆S] complex. The V-O coordination bond in VO-[C₇H₄O₆S] is relatively long and its binding energy is low, making it easy to dissociate and release VO²⁺. In contrast, Fe-[C₇H₄O₆S] formed between Fe²⁺ and SSA has the shortest coordination bond and the highest binding energy, allowing it to be stably fixed in the aqueous phase, thereby effectively reducing the interference of iron ions in the extraction process. At the extraction interface, VO-[C₇H₄O₆S] acts as a carrier to transport VO²⁺ while capturing H⁺ released by D2EHPA, thus promoting the forward extraction reaction. In summary, the SSA-D2EHPA system achieves efficient vanadium extraction through a "selective coordination-interface dissociation" mechanism.