Hydrometallurgical Treatment for Valuable Metals Recovery from Spent CoMo/Al₂O₃ Catalyst. 2. Oxidative Leaching of an Unroasted Catalyst Using H₂O₂

Abstract

This study deals with the feasibility of the oxidative leaching of molybdenum and cobalt sulphides contained in a spent hydrodesulphurisation catalyst using H2O2 in acidic medium. The study was first carried out with MoS2 in order to define the important parameters of the leaching procedure and then applied to an unroasted CoMo/Al2O3 spent catalyst containing 11 wt % of Mo and 2.7 wt % of Co. In both cases, a 23 factorial design was used. The results obtained with MoS2 highlighted the necessity to limit the increase in temperature of the medium to minimize the decomposition of H2O2 and the necessity to keep pH constant to avoid an important acidification of the medium which could cause dissolution of alumina matrix when leaching will be applied to spent catalysts. The oxidative leaching of the unroasted CoMo/Al2O3 spent catalyst was performed without previous grinding. In a single-step, at pH = 1.3 with a stoichiometric factor equal to 2.4, an L/S ratio equal to 7.5, and an H2O2 concentration of 3.75 mol·L−1, it was possible to recover molybdenum and cobalt simultaneously with leaching yields of 90% and 83%, respectively, without dissolving more than 8% Al. In these conditions, the maximal temperature recorded during the experiment was about 60 °C.

Spontaneous exfoliation and tailoring of MoS2in mixed solvents

“…25 Unfortunately, MoS 2 is unstable in the presence of oxidants; for example, hydrogen peroxide (H 2 O 2 ) is a leachant of molybdenite in hydrometallurgy, in which it is often used to extract the element molybdenum by oxidative dissolution. 26 This makes the reported exfoliation of MoS 2 be accomplished mostly through the intercalation of reductants such as alkaline metal compounds and hydrazine hydrate. 1,2,5,12,16,17 Here, we demonstrate an oxidant-prompted spontaneous exfoliation process of MoS 2 nanosheets, and we achieve size evolution from large sheets to small sheets to nanodots (Fig.…”

“…The dissolution of MoS 2 in H 2 O 2 is a spontaneous, selfaccelerated, exothermic process according to the reaction in eqn (1). 26 This reaction is highly dependent on the experimental…”

Molybdate Recovery by Adsorption onto Silica Matrix and Iron Oxide Based Composites

“…A possible way to recover molybdenum from spent HTC catalysts is by pyro metallurgical and hydro-metallurgical processes [ 7 , 8 , 12 , 13 , 14 , 15 ]. Such recovery processes start with thermal pre-treatment when sulphur and coke are removed, concomitant with the transformation of Mo, Ni, Co, and V in oxides.…”

Metal valorization from the waste produced in the manufacturing of Co/Mo catalysts: leaching and selective precipitation

“…The leaching of spent catalysts from oil industry, waste electric, WEEEs, landfill deposits has retained a great attention for the last decades and an abundant amount of literature is available in this field [6][7][8][9][10][11][12]. Many techniques have been proposed using acidic leaching [3,[13][14][15], alkaline leaching [16,17], chlorination process [18,19] or bioleaching [20] for metal transfer from the solid waste or low-grade ore to the aqueous phase.…”