Alkali-activated mechanochemical decontamination of spent SCR catalysts: phase reconstruction for selective arsenic removal and vanadium recovery

Spent SCR catalysts contain toxic arsenic (As), valuable vanadium (V) and tungsten (W), posing dual hazards and resource challenges. Conventional recycling methods struggle with the selective removal of arsenic without compromising the carrier or fully recovering valuable metals. Here, an alkali-activated mechanochemical process that overcomes these limitations, achieving >99% As removal and 97% V recovery, while retaining approximately 23.4% of W in the TiO 2 carrier, allowing for direct catalyst regeneration. Mechanistic analyses confirm NaOH-triggered surface TiO 2 dissolution causes pore collapse, liberating encapsulated As/V species for reconstruction into soluble NaAsO 2 /NaVO 3 . XRD/EPR/XPS characterization verifies Na 2 WO 4 formation through W-O bond restructuring. DFT calculations link reduced interatomic distances (below 2 Å) during ball milling to enhanced electron transfer, driving phase transformations. This work provides a sustainable and economically favorable strategy for hazardous waste valorization, highlighting a closed-loop recycling pathway with clear environmental benefits and industrial potential for spent catalyst management.