Experimental Study on Direct Leaching of Black Shale- hosted Vanadium-bearing Clay Mineral Concentrates by H₂SO₄

Vanadium-bearing clay mineral is one of typical vanadium resources which are difficult to utilize.The feasibility of direct leaching of black shale-hosted vanadium-bearing clay mineral concentrates by H₂SO₄-CaF₂-NaClO₃ system was studied.Furthermore,the influencing factors of leaching were investigated.The results show that H-SO₄-F acid solution system with high concentration can effectively destroy the mineral structures of mica,clay minerals and limonite.Vanadium leaching rate reaches 90.0% or above with 85% of concentrates' sizes smaller than -74 μm,reaction temperature at 80℃,liquid to solid ratio(volume/mass,mL/g) of 2.5 to 4.0:1、H₂SO₄ (98%) addition amount higher than 54%, stirring speed of 400 r/min,NaClO₃ addition amount of 1.25%,CaF₂ addition amount of 12%,and leaching time of 11 h.under the conditions,vanadium leaching rate is higher than that of the traditional roasting method.sulfuric acid and fluoride ions can be effectively recovered by diffusion dialyzer.