Selective leaching of vanadium and silver from silver-associated vanadium shale by stepwise leaching

Silver-associated vanadium shale is a large vanadium-silver composite deposit with great development potential discovered in recent years. Recovering this type of resource comprehensively is challenging due to its complexity, difficulty in selection, and high carbonate content. In this study, the effective recovery of V and Ag can be achieved by adopting a stepwise leaching process. Initially, V is leached from the raw ore using the system of H2SO4-CaF2, followed by the leaching of Ag from the resulting leaching residue through the system of H2SO4NaClO3-NaCl. Under the optimal vanadium leaching conditions, the leaching efficiency of V and Ag reached 82.25 % and 0.81 % respectively, achieving the separation of V and Ag at the source. The leaching efficiency of Ag was 92.09 % under the optimum silver leaching conditions. V2O5 products with a purity of 98.31 % has been successfully prepared. The vanadium leaching process has a pre-destructive effect on the silver-bearing minerals and reduces the amount of Cl-containing reagents compared with direct silver leaching. The vanadium-bearing muscovite was structurally disrupted by H2SO4 and CaF2 to achieve vanadium release. Ag+ was ultimately present in solution as AgClx(x- 1)-(x = 2,3,4) through coordination regulation. The vanadium-silver stepwise leaching process and leaching mechanism are proposed to provide technical support for the comprehensive recycling of vanadium and silver resources.