Solvent extraction of molybdenum (VI) from spent hydroprocessing catalyst

Abstract

This article investigated extraction process of molybdenum (VI) from acid leaching solution to explore the basic data for the recovery of Mo resources from spent hydroprocessing catalyst. The extractant 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (P507) was adopted as the extractant, and the effects of specific operating parameters on Mo extraction and stripping were systematically investigated. The Mo extraction was greater than 99.5%, and the co‐extraction of Al and Co were less than 0.2% under optimal conditions. The corresponding stripping processes were also performed focusing on reducing phase‐separation time and preventing third‐phase generation. Almost 100% (>99%) Mo was easily stripped using 0.9 mol/L NH3·H2O with the addition of NH4NO3 ranging from 0.3 to 1.2 mol/L. Saturation extraction capacity method was applied to explore extraction mechanism. Results indicated that the molar ratio of Mo to P507 in the saturated organic phase was approximately 1:1, so the extraction reaction can be expressed as follows: 2H3MoO4++trueH2A2¯→2trueH3MoO4normalA¯+2H+ H6Mo2O82++trueH2A2¯→trueH6Mo2O8A2¯+2H+ © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019