Slurry catalyst and slurry flakes valorization

A method for recycling molybdenum, vanadium and nickel contained in a spent catalyst and/or a metal containing hydrocarbon feedstock, wherein said spent catalyst and/or metal containing hydrocarbon feedstock successively undergoes (i) calcination performed so as to collect carbon monoxide and hydrogen and to remove carbon containing material, (ii) washing with water, (iii) acidification with sulfuric acid to obtain an acidic water and a first precipitate which is separated, (iv) alkalinization of said acidic water with sodium hydroxide to obtain an alkaline water and a second precipitate which is separated, wherein said spent catalyst and/or metal containing hydrocarbon feedstock is obtained by the treatment of a metal containing hydrocarbon feedstock issued from an industrial unit using a metal containing catalyst, and wherein before step (i) said spent catalyst and/or metal containing hydrocarbon feedstock are collected and treated to produce carbon monoxide, hydrogen and a metal containing residue, said metal containing residue being processed by steps (i) to (iv).