Improvement in Metal Dissolution from Spent Catalyst by Adapted Acidithiobacillus ferrooxidans

Abstract

The improvement in the leaching rate of Ni, V, Mo, and Al present in a spent catalyst sample was evaluated by the bacterial adaptation technique. For this purpose, leaching of the metals from the spent catalyst sample was conducted using both adapted and unadapted bacteria cultures. The evaluation was done on the basis of the variation of different leaching parameters such as pH, temperature, particle size, pulp density, and initial Fe(II) concentration. The adaptation technique was found to be fruitful as the leaching equilibrium reduced from 240 to 40hr. Further, the leaching rate of Ni and V was improved by 10%(w/w) due to bacterial adaptation. The leaching rate of Mo was lower due to combining the action of different factors like the presence of impervious elemental sulfur, refractory nature, and low solubility. The lower leaching rate of Al observed due to the refractoriness of the alumina matrix present in the spent catalyst sample. The pseudo rate order with respect to all leaching parameters was determined and found to be significant for the adaptation process.