An energy-efficient process of leaching vanadium from roasted tablet of ammonium sulfate, vanadium slag and silica

Abstract

The conventionally industrial method of recovering vanadium (V) from converter vanadium slag (V-slag) is sodium or calcification roasting process, which consumes high energy and emits quantities of environmental pollutants. We report an alternative process for the extraction of V from V-slag via ammonium sulfate ((NH4)2SO4) roasting. A possible mechanism of the thermal decomposition of V-slag and (NH4)2SO4 was identified in a range of 200 ℃ to 500 ℃. The phase transformation process of decomposing V-slag by (NH4)2SO4 indicated that sulfate salt containing V appeared at 350 ℃. The effect of roasting time and temperature and the amount of ammonia salt on V-slag decomposition was discussed. Furthermore, a tablet consisting of (NH4)2SO4, V-slag and silica (SiO2) was prepared to reduce the amount of ammonium sulfate added and avoid the formation of reaction products that would stick to the reactor. Characterization results indicated that the patterns of (NH4)2SO4, iron-vanadium oxide and ulvite disappeared at 390 ℃, SiO2 did not participate in the roasting process, and roasting products were attached to the surface of SiO2. Nearly 93% of V could be extracted from the (NH4)2SO4-V-slag-SiO2 tablet with a 2:1:2 mass ratio. Compared with conventionally industrial V-extraction method, (NH4)2SO4 roasting process could lower roasting temperature by 460 ℃, avoid marginal production of titania and treatment of water and gas emissions, and achieve energy-efficient production of V.