Leaching of impurities for the up-gradation of molybdenum oxide and cementation of copper by scrap iron

Molybdenum is widely used for the production of ferro-molybdenum, which is required for the manufacturing of alloyed steel. The use of molybdenum oxide containing copper for steel making has deleterious effects on the mechanical properties of produced alloyed steel. Therefore, a process has been proposed for simultaneous up-gradation of molybdenum oxide and recovery of copper using controlled sulphuric acid leaching and cementation by scrap iron. The molybdenum oxide containing 70.00% MoO3, 2.49% Cu2O, 1.97% Fe2O3 and 11.22% SiO2 obtained after roasting of molybdenite concentrate was used for the experimental purpose. Major impurities such as copper and iron were leached out from molybdenum oxide using 1.5% H2SO4 while maintaining a solid to liquid (S/L) ratio of 1 with a mixing time of 10 min at room temperature (22 °C). Partially leached molybdenum was precipitated by holding it for 30 min at pH 1.78. Subsequently, copper present in the leach liquor was recovered as metallic copper by a cementation process using scrap iron splinter and addition of 7% (v/v) concentrated sulphuric acid into the leach liquor. By the proposed leaching and cementation process, the molybdenum oxide could be upgraded to 80% (recovery 99.50%) and copper could be recovered as metal powder. The 0.5 to 1% loss of molybdenum could also be reclaimed by the treatment of generated waste liquid using solvent extraction or ion-exchange processes.