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Selective separation of molybdenum(Mo) and vanadium(V) from hazardous secondary resources containing Mo and V has become a technical bottleneck of its resource utilization. In this work, the selective separation of Mo and efficient recovery of V from simulated leaching solutions of spent hydrodesulfurization (HDS) catalysts were investigated via solvent extraction and chemical precipitation. The result indicates that the D 2 EHPA(P204) exhibits higher selectivity for Mo in strongly acidic conditions. Under optimum experimental conditions of hydrochloric acid of 1 mol/L, extractant concentration of 20 % (v/v), O/A ratio of 1:3 and contact time of 50 min, the single-stage extraction ratio of Mo reached 98.63 %, meanwhile, the co-extraction ratio of vanadium was less than 5 %. Additionally, over 97 % of Mo could be stripped from loaded organic phase at O/A ratio of 1 with 50 g/L NH 4 HCO 3. The mechanism analysis revealed that selective extraction of Mo was mainly through the cation exchange mechanism. Moreover, the enthalpy changes in the molybdenum extraction were 44.1 kJ mol−1, which demonstrated that was an endothermic reaction. Furthermore, the Fe(III) was adopted to fabricate FeVO 4 by precipitating vanadium from raffinate, and the precipitation efficiency of vanadium reached 97.71 % at a Fe/V molar ratio of 5/2, meanwhile, the precipitation product was further confirmed by XRD, XPS and SEM-EDS. Ultimately, a conceptual flowsheet for recovering completely Mo and V from simulated leaching solutions of spent HDS catalysts was proposed, which provides theoretical guidance for the resource utilization of containing molybdenum and vanadium secondary resources. [Display omitted] • Selective extraction of Mo from leaching solutions containing Mo and V was realized. • The V was precipitated to fabricate FeVO 4 by adding Fe(III) in the raffinate. • Ion exchange mechanism of extraction process were further confirmed. • A flowsheet for the resource utilization of spent HDS catalysts was proposed. [ABSTRACT FROM AUTHOR]

Polymetallic vanadium titano-magnetite (VTM) is recognized as one of the most refractory mineral resources because of its multiple-element composite symbiosis feature. Conventional carbothermic reduction and smelting separation treatment are characterized by high energy consumption and large greenhouse gas emissions. Considering the material attribute, an alternative and clean utilization of refractory VTM via the pyrometallurgically oriented phase transformation in air atmosphere to prepare the composite electromagnetic wave absorbing material was proposed for the first time in this work. The theoretical foundation of the oriented composite material design, phase transformation, microstructure and interfacial element migration, magnetism, electromagnetic properties, and wave absorbing properties were investigated via thermodynamic calculations, XRD, XPS, optical microscope, SEM‒EDS, VSM, and VNA analyses. Theoretical calculations indicated that the formation of composite ferrites was thermodynamically feasible over 1085 °C. In the oriented phase reconstruction, the symbiotic structure of the VTM was reconstructed via MnO 2 addition at 1150 °C, and almost all the Fe, Mn, Ti, and V were concentrated in the composite ferrites, in which the Ti and V were doped in the octahedral structure (B site) of spinel-type crystalline structure. The as-purified composite ferrite material from the VTM+80%MnO 2 mixture roasted at 1150 °C for 2 h showed good electromagnetism performance. A minimum RL peak of −50 dB was obtained at a veneer thickness of 11 mm, and the RL value less than −20 dB had a big frequency bandwidth of 9 GHz (frequency range of 8 GHz–17 GHz). It's inferred that this low-cost and abundant composite ferrite material can be economically applied in the construction industry. This work provided a clean and higher-value application of abundant refractory polymetallic VTM resources. [ABSTRACT FROM AUTHOR]