Effects of metal extraction liquors from electric vehicle batt 2022 Minerals

This study reports the effects of metal extraction liquors that are used for production of electric vehicle batteries on biological iron and sulfur oxidation. These liquors include ammonium sulfate and organic solvent constituents, and thus are potentially stimulatory or inhibitory for heap bioleaching microorganisms. The effects of the liquors and their constituents were studied in batch bioassays at pH 2 and 27 ± 2 °C. Both metal extraction liquors had a negative effect on biological iron oxidation at > 2% (v/v), whereas biological sulfur oxidation was enhanced with ≤ 8% (v/v) metal extraction liquor 1. Biological iron oxidation was negatively affected by ammonium sulfate at above 20 g/L. From the studied low-solubility organic solvents (neodecanoic acid, Nessol D100, Cyanex 272, and Baysolvex D2EHPA), neodecanoic acid was the only one negatively affecting biological iron oxidation, and this effect occurred at ≥ 6.3 mg/L (2.5% of its aqueous solubility). Since these extraction liquors and some of their potential constituents inhibited biological iron oxidation, they may also inhibit heap bioleaching and have adverse impacts in recipient waters, if released to the environment. With ammonium limited culture, iron oxidation was stimulated with ≤ 1% (v/v) of metal extraction liquor 1 and 2, and therefore, would also likely enhance heap bioleaching.