Recovery of cobalt and molybdenum from consumed catalyst using hydrochloric acid

Cobalt and molybdenum are valuable metals whose presence in nature is very limited. The consumed catalyst, which is abundantly available in the petroleum refinery industry, is a potential source of those metals. A hydrometallurgical process using acid as a leaching agent is usually used to extract and separate the metals more effectively. This method is considered capable of yielding recovery of a higher percentage of metal. In this study, hydrochloric acid solutions at various concentrations of 1.0, 1.5 and 2 M were used. The consumed catalyst was obtained from Pertamina Refinery Unit IV, Cilacap, Indonesia. Leaching experiment was carried out for 300 minutes and sampling was undertaken at 1, 3, 5, 15, 30, 90 and 300 minutes. The particle size and agitation speed were fixed at 200 mesh and 400 rpm. Samples of consumed catalyst were analyzed using EDXRF before the leaching process. Samples of solution were analyzed using ICP-EOS. Experimental results have shown that the recovery of cobalt and molybdenum increases with the increase of either concentration of hydrochloric acid or temperature. The highest recoveries in cobalt and molybdenum were 34.66% and 5.03%, respectively, obtained at a concentration of hydrochloric acid of 2 M and temperature 60°C.