RECOVERY OF METALS FROM ELECTROACTIVE COMPONENTS OF SPENT Ni-MH BATTERIES AFTER LEACHING WITH FORMIC ACID

this work describes a route for recovering nickel, cobalt, iron, zinc and lanthanides from spent nickel-metal hydride batteries. Formic acid was used as leachant. Experiments were run at 25-50°C 1-4 h. Under the best conditions leaching yields surpassed 99 wt.%, except iron. The insoluble matter contains almost solely iron iron(III) basic formate. leachate went through six separation procedures, combining solvent extraction with D2EHPA extractant, precipitation reactions. Fe2+ Zn2+ extracted together (> wt.%) original (pH ~1.5). Yttrium precipitated oxalates directly raffinate 99.9 upon addition of sodium oxalate. In next steps, Mn2+ Co2+ buffered pH (3 ~4.8, respectively), after adding NaOHaq. About 10 wt.% leached Ni2+ coextracted Co2+. remaining aqueous oxalate 6. After Al3+ until ~8, formate recovered slow evaporation final solution 60oC. It ~90 present in