Reclamation of tungsten from spent HDS catalyst: a detailed study

The awareness of the depletion of high grade ore is of paramount importance now-a-days for all the metallurgical industries and researchers. For the conservation of resources, processing of low and lean grade ores is very much essential. Moreover, the recycling and reuse of the secondaries must be the core strength in that context. The spent catalyst obtained from a petroleum refinery was having 20.33% WO3 and 49.14% Al2O3 as major part of the matrix. The spent catalyst was devolatilized at 650°C to remove the oils, organics and other volatile matter. The devolatilized spent catalyst was processed treated with 8% NaOH at 90°C for 3 h to dissolve tungsten as sodium tungstate. The W bearing liquor was treated with H2SO4 to precipitate tungstic acid at pH 1.0. and subsequent production of tungsten trioxide by roasting at 700°C and tungsten metal with 99.91% purity by reduction roasting by H2 gas has also been reported. The alkali leached residue was leached with 10% sulphuric acid at 80°C for 2 h so as to extract nickel and later on precipitated as nickel hydroxide.