Open AccessRECOVERY OF METALS FROM ELECTROACTIVE COMPONENTS OF SPENT Ni-MH BATTERIES AFTER LEACHING WITH FORMIC ACID
Author(s) -
Pedro Rosário Gismonti,
Jéssica Frontino Paulino,
Júlio Carlos Afonso
Publication year - 2021
Publication title -
detritus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.279
H-Index - 7
eISSN - 2611-4135
pISSN - 2611-4127
DOI - 10.31025/2611-4135/2021.14063
Subject(s) - chemistry , formic acid , inorganic chemistry , aqueous solution , oxalate , nickel , raffinate , nuclear chemistry , leaching (pedology) , formate , sodium formate , cobalt , extraction (chemistry) , chromatography , organic chemistry , environmental science , soil science , soil water , catalysis
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 for 1-4 h. Under the best conditions leaching yields surpassed 99 wt.%, except for iron. The insoluble matter contains almost solely iron as iron(III) basic formate. The leachate went through six separation procedures, combining solvent extraction with D2EHPA as extractant, and precipitation reactions. Fe2+ and Zn2+ were extracted together (> 99 wt.%) from the original leachate (pH ~1.5). Yttrium and lanthanides were precipitated as oxalates directly from the raffinate (> 99.9 wt.%) upon addition of sodium oxalate. In the next steps, Mn2+ and Co2+ were extracted with D2EHPA at buffered pH (3 and ~4.8, respectively), after adding NaOHaq. About 10 wt.% of leached Ni2+ was coextracted with Co2+. The remaining Ni2+ was precipitated from the raffinate after addition of aqueous sodium oxalate at pH 6. After precipitation of Al3+ upon addition of NaOHaq. until pH ~8, sodium formate was recovered after slow evaporation of the final aqueous solution at 60oC. It contains ~90 wt.% of the formate present in the leachant.