Study On The Leaching Behavior Of Vanadium And Chromium From Vanadium-Chromium Slag

Vanadium and chromium were important strategic resources.Because of their excellent physical and chemical properties,they played an important role in the field of steel,aerospace,military,chemical and battery industries.In the process of leaching vanadium and chromium,there were many problems,such as high roasting temperature,high energy consumptions,and heavy pollutions,so it was necessary for us to further improve and optimize the smelting method of extracting vanadium and chromium.In this paper,the vanadium-chromium slag in a steel plant in Sichuan as the research object,we studied the leaching behavior of vanadium and chromium in the direct acid leaching process,and researched the method of partial oxidizing calcification roasting-acid oxidation leaching to extract vanadium which was different from the traditional way of roasting-leaching.Moreover,the influence of partial oxidizing calcification roasting in the efficiency of vanadium and chromium and the leaching process were also discussed.The conclusions were as follows:(1)Leaching vanadium and chromium of hydrometallurgical leaching process from vanadium-chromium slag.Adding manganese dioxide(MnO2)and sodium dodecyl sulfate(SDS)in the experiment to enhance the leaching process,the results showed that SDS could change the surface chemical properties of water slurry,and increase the surface wettability of slag to enhance the reaction between slag and sulfuric acid.MnO2 could oxidize the low valence vanadium and chromium to get high leaching efficiency of vanadium and chromium.Under the synergistic action of MnO2 and SDS,the leaching efficiency of vanadium and chromium were 68.93 % and 30.74 %,respectively.The percentage points were 33.46 and 20.02 higher than the leaching efficiency attained under the same conditions without adding MnO2 and SDS.(2)Leaching vanadium and chromium from vanadium-chromium slag intensified with partial oxidizing calcification roasting.Vanadium and chromium were existed in form of vanadium-iron spinel,chromium-iron spinel,silicate phase and oxide phases in vanadium-chromium slag,which were difficult to leach out through direct sulfuric acid leaching.The experiment was carried out by calcification roasting method.The results showed that the process of partial oxidizing calcification roasting could destroy the spinel phase and silicate phase of vanadium-chromium slag in order to change the form and the valence composition of vanadium and chromium in vanadium-chromium slag.After roasting process,the valence state ratios of V(III),V(IV)and V(V)were from 39.27 %,18.44 % and 42.29 % to 9.55 %,34.12 % and 56.33 %;the valence state ratios of Cr(III)and Cr(VI)were from 82.84 % and 17.16 % to 80.32 % and 19.68 %.(3)Acid leaching process of vanadium and chromium from partial oxidizing calcification roasting clinker.The acid leaching process was strengthened by the introduction of manganese dioxide(MnO2)and sodium dodecyl sulfate(SDS)in roasting clinker.The results showed that SDS could change the chemical properties of the solution,and MnO2 might oxidize the low valence vanadium to achieve the intention of extracting vanadium selectively.Under the synergistic effect of MnO2 and SDS,the leaching efficiency of vanadium was up to 93.87 %,the leaching efficiency of chromium was only 13.86 %.