Hazardous waste to materials : Recovery of molybdenum and vanadium from acidic leach liquor of spent hydroprocessing catalyst using alamine 308

Abstract

Recovery of valuable materials/metals from waste goes hand in hand with environmental protection. This paper deals with the development of a process for the recovery of metals such as Mo, V, Ni, Al from spent hydroprocessing catalyst which may otherwise cause a nuisance if dumped untreated. A detailed study on the separation of molyb-denum and vanadium from the leach solution of spent hydro-processing catalyst of composition: 27.15% MoO3, 1.7% V2O5, 3.75% NiO, 54.3% Al2O3, 2.3% SiO2 and 10.4% LOI is reported in this paper. The catalyst was subjected to roasting under oxidizing atmosphere at a temperature of about 550°C and leaching in dilute sulphuric acid to diss-olve molybdenum, vanadium, nickel and part of aluminium. Metals from the leach solution were separated by solvent extraction. Both molybdenum and vanadium were selectively extracted with a suitable organic solvent leaving nickel and dissolved aluminium in the raffinate. Various para-meters such as initial pH of the aqueous feed, organic to aqueous ratio (O:A), solvent concentration etc. were opti-mized for the complete extraction and recovery of Mo and V. Molybdenum and vanadium from the loaded organic were stripped by ammonia solution. They were recovered as their corresponding ammonium salt by selective precipitation, and were further calcined to get the corresponding oxides in pure form.