Recovery of carbon and molybdenum from spent Co–Mo catalyst

Abstract

This study aims to separate fractions, enriched with carbon and a metal such as molybdenum or cobalt, from spent molybdenum catalyst prior to chemical extraction. The experimental programme involved grinding, sieving, and conditioning the ground products in a high-speed blinder in the presence of a mixture of kerosene and water. The parameters studied were grinding time, particle size, kerosene to water ratio and pulp density. A preliminary leaching test was carried out using sulphuric acid. Results showed that at a particle size less than 45 μm, a water-to-kerosene ratio of 50% and solid-to-liquid ratio of 5%, the separation of carbon and molybdenum was more efficient. The carbon percentage in the float fraction increased from 17% to 34% with a recovery of 71%; in the sink fraction, the molybdenum percentage increased from 17% to 24% with a recovery of about 91%. The results of leaching showed that, at 10% sulphuric acid, the extraction percentage of molybdenum was 97%, 89% and 73% by weight for the sink, the original and the float fractions, respectively. The results are discussed according to a model based on the assumption that, during conditioning at high speed in the presence of kerosene and water, an emulsion with fine particles distributed throughout is generated. On separation columns, organic and inorganic layers were formed. The carbon tends to distribute to the organic layer while molybdenum tends to locate in the inorganic layer.