Process for recovering vanadium in the form of iron vanadate from a gasifier slag

A process for recovering vanadium in the form of iron vanadate from a gasifier slag, said process comprising the following steps:

• a) pulverizing gasifier slag to a particle size less than 100 μm to obtain pulverized slag;
• b) soaking said pulverized slag in water and alkali salt to obtain a slurry;
• c) roasting said slurry in the presence of air at a temperature in the range of 750° C. to 1100° C. to obtain roasted slag;
• d) leaching said roasted slag in water heated to a temperature below its boiling point to obtain a first biphasic mixture comprising a first solid phase and a first liquid phase;
• e) filtering said first biphasic mixture to obtain a first solid residue and a first solution comprising vanadium compounds;
• f) heating said first solution to a temperature in the range of 60° C. to 80° C. while adding therein, an iron salt in an amount in the range of 10 wt % to 60 wt % at a pH in the range of 4 to 10, to obtain a second biphasic mixture comprising a second solid phase and a second liquid phase;
• g) filtering said second biphasic mixture to obtain a second solid residue comprising iron vanadate and a second solution comprising said alkali salt;
• and
• h) drying said second solid residue at a temperature in the range of 300° C. to 500° C. to obtain iron vanadate.