Optimized two-step sulfuric acid leaching for sustainable recovery of valuable metals from hazardous sodium carbonate roasting–leaching residues of spent hydrodesulfurization catalysts

Optimized two-step sulfuric acid leaching converts hazardous Na 2 CO 3 roasting residues from spent HDS catalysts into valuable Mo, Co and Al, with acid recycling and selective oxidants enabling high recovery and sustainable waste valorization.