Experimental Study On Recovery Of Valuable Metals From Spent SCR Catalyst

Spent SCR catalyst contains V, W, Ti and many other valuable metals. Direct discard will not only cause environmental pollution, but also be a waste of natural resources, so the recovery of valuable metals from spent catalyst have great significance. In this paper, by hydrometallurgical methods, we use NaOH solution to leach V and W from spent catalyst. The solid remaining undissolved in the main component is titanium dioxide, thereby separating the Ti. Then precipitated leaching liquid with calcium and use formic acid selective leaching V from calcium formate. Impurity and added with Ammonia, Vanadium will precipitate in the form of ammonium metavanadate. After acid leaching, tungsten in the precipitate is added with Hydrochloric acid, and converted to tungstate. Burning generating tungsten trioxide. The optimum conditions determined by NaOH alkaline leaching experiments are: for vanadium, NaOH concentration is 20%, solid-liquid ratio is 1:7, the catalyst particle size is about 125~180μm, temperature around 50℃, extraction time about 60 min, in this condition the efficiency of leaching of vanadium is more than 93%; for tungsten, NaOH concentration is 30%, solid-liquid ratio is 1:7, the catalyst particle size is about 125~180μm, temperature around 60℃, extraction time about 60 min, in this condition the efficiency of leaching of tungsten is over 87%. For selectivity formic acid leaching process, the optimal reaction conditions are: temperature about30 ℃, pH = 5, the solid-liquid ratio is 1:5, reaction time about 40 min, in this condition about 94.88% vanadium was extracted, while the tungsten leaching rate(loss rate) is only 3.99%. From raw materials to the final product,the recovery of vanadium and tungsten were: 82.25% and 78.48%, titanium(containing impurities) recovery is over 99%.