Separation of molybdenum from spent HDS catalysts using emulsion liquid membrane system

Abstract

In this study, the selective extraction of molybdenum (Mo) from the spent hydrodesulfurization (HDS) catalysts using emulsion liquid membrane method was investigated. Cyanex 272 and ammonium fluoride (NH4F) had excellent efficiency in selective extraction of Mo from the spent catalysts as extractant and stripping agent, respectively. Other parameters including surfactant concentration, speed of agitation, contact time, treat ratio (external to emulsion phase volume ratio), and internal to membrane phase volume ratio were effective on the performance of the emulsion liquid membrane system. Besides, the stability of emulsion was determined by specifying the emulsion breakage and swelling at each stage. The optimal separation of Mo under operating conditions consists of 0.3 M Cyanex 272, 3 %wt. Span 80, 1 M ammonium fluoride, 25 min contact time with the agitation speed of 350 rpm, treat ratio of 2.5 and, internal to membrane phase volume ratio of one was obtained. Under these conditions, more than 75 % of the Mo was selectively transferred to the internal phase.