煅烧-碱浸法从钒铬还原渣中分离回收钒铬

通过煅烧-碱浸法从钒铬还原渣中分离回收钒铬，考察了煅烧反应过程并探讨了煅烧-碱浸条件对浸出钒的影响。结果表明：煅烧过程中Cr（Ⅲ）和V（Ⅳ） 反应生成中间产物CrVO₄，随后CrVO₄分解为Cr₂O₃和V₂O₅；相同浓度条件下，在V₂O₅浸出效果方面NaOH要优于Na₂CO₃，提高浸出介质浓度和延长浸出时间有利于V₂O₅的浸出，而浸出温度对V₂O₅浸出无明显影响，钒铬还原渣在850℃煅烧1.5 h后经3 mol·L^-1 NaOH在90℃浸出1.5 h，滤渣中的Cr₂O₃质量分数高于96%，钒、铬的浸出率分别为87.3%和小于1%，另外，利用酸性铵盐法能够沉淀滤液中97%的钒。

Separation and recovery of chromium and vanadium from reduced vanadium-chromium precipitate by calcinations-alkaline leaching

Separation and recovery of chromium and vanadium from reduced vanadium-chromium precipitate were implemented by calcination followed by alkaline leaching. The reaction process during calcination and the factors, such as temperature, time and alkaline medium, affecting leaching vanadium were investigated. Cr(Ⅲ) and V(Ⅳ) could form CrVO₄, and then CrVO₄ was decomposed into Cr₂O₃ and V₂O₅ during calcinations. The appropriate conditions for calcination were temperature of 950℃ and time of 1.0—3.0 h. Under the same molarity conditions, NaOH was better than Na₂CO₃ for leaching V₂O₅. Increasing NaOH concentration and time was favorable for leaching of V₂O₅ while temperature had little effect on leaching of V₂O₅. When reduced vanadium-chromium precipitate was calcined for 1.5 h at 850℃ and was treated for 1.5 h using 3 mol·L^-1 NaOH, the content of Cr₂O₃ in the residue was more than 96%, and leaching rates of vanadium and chromium were 87.3% and less than 1%, respectively. Additionally, 97% of vanadium in the filtrate could be precipitated by acidic ammonium salt.