Recovery of vanadium from hydrodesulfurization waste catalyst using calix[4]resorcinarenes

Hydrodesulfurization (HDS) waste catalyst is regulated as a hazardous waste because of its substantial metal content. HDS contains (wt.%) 33.4% Al, 6.8% Mo, 3.6% V, 1.5% Co and 0.7% Ni. Therefore, it must be treated for detoxification or for the recovery of these metals as secondary resources. In this work, recovery of metal ions using calix[4]resorcinarenes hydroxamic acid was investigated. The factors affecting the extraction method such as aqueous phase acidity, type of organic solvent, shaking time, the capacity of calix[4]resorcinarenes to extract vanadium, and the selectivity of V over the other metal ions were studied. The optimal conditions of extraction were found to be as follows: aqueous acidity of 6 M, ethyl acetate as the solvent, and shaking times of 15 min; the extraction of vanadium is effective with most of the vanadium selectively extracted with calix[4]resorcinarenes, whereas all other metal ions remain in the aqueous phase