Selective vanadium activation and competitive sodium distribution during low-sodium Na2CO3 roasting of vanadium-titanium magnetite concentrate

Low-sodium Na 2 CO 3 roasting can reduce reagent consumption in vanadium extraction from vanadium-titanium magnetite, but Na distribution between V activation and gangue reactions remains unclear. Roasting and water leaching experiments were combined with thermodynamic calculations, XRD, XPS, SEM-EDS, and EPMA/WDS to examine V activation and Na retention. At 4 wt% Na 2 CO 3 , 900 °C, and 60 min, V leaching efficiency reached 76.8%, with 0.58 wt% Na 2 O in the washed residue. Of the added Na, 69.4% was recovered in the combined filtrate and washings, 23.2% remained in the residue, and 3.2% was recovered from boat and furnace-tube deposits, giving a Na balance closure of 95.7%. Total dissolved Na was distinguished from the stoichiometric Na requirement for vanadate formation and was not treated as a direct measure of effective Na utilization. Increasing Na 2 CO 3 dosage to 10 wt% raised V leaching efficiency to 81.2% but increased residual Na 2 O to 1.74 wt%. At 1050 °C, V leaching efficiency decreased to 68.5%, although the V 5+ fraction remained high. This decline was interpreted as a combined effect of Na redistribution and reduced leaching accessibility during over-roasting. Alkaline controls also indicated that Si and Al dissolution reflected both roasting-induced changes and solution alkalinity. Compared with the 10 wt% benchmark, the 4 wt% condition reduced reagent consumption by 60.0%, with little change in measured gross furnace electricity use. These results support balancing V recovery against reagent consumption, impurity dissolution, and residual Na burden.