Study on Leaching of Molybdenum from a Spent HDS Catalyst

The aim of this study is to investigate the extraction of molybdenum from the spent HDS catalyst. The experiment was performed by using the pyro-hydrometallurgical process; calcination and leaching. The spent catalyst was calcined at different temperatures in order to investigate the effect of calcination temperature on the recovery of molybdenum in the subsequent process. Leaching of the calcined samples was subsequently performed by using the different concentrations of leaching reagent. The leaching was conducted by varying the concentration of NaCO3 of 20 g/L, 30 g/L and 40 g/L with a fixed leaching temperature of 90°C, a S/L ratio (weight of calcined sample/volume of leaching reagent) of 100 g/L and leaching time of 1 hrs. under the stirring condition at a speed of 250 rpm. It was found that carbon and sulfur contained in the spent HDS catalyst could be reduced by the calcination process and resulting in enhanced extraction efficiency of molybdenum. The extraction efficiency of molybdenum increased with increasing concentration of leaching reagent. At a certain concentration of leaching reagent, the extraction efficiency of the sample calcined at lower temperatures was higher than the sample which was subjected to calcination at a higher temperature.