In-situ chromium and vanadium recovery of landfilled ferrochromium and stainless steel slags

•NaOCl assisted alkaline heap leaching of Cr and V from slags was investigated.•The matrix material of stainless steel slag and ferrochromium slag remains intact.•11–19% Cr and 7.0–7.5% V were leached selectively after 64 days.•A model shows that Cr will leach for 4–5 years at chosen heap leaching conditions.•Cr and V extraction potentially improves the slags’ environmental quality.

A novel heap leaching method was investigated for selective removal of chromium (Cr) and vanadium (V) from ferrochromium (FeCr) and stainless steel (SS) slags. In particular, alkaline oxidative heap leaching was simulated on lab-scale by batch and column leaching tests. The results show a selective leaching of Cr (11–19%) and V (7.0–7.5%) after 64 days of column leaching, with a very low dissolution (<2.2% (FeCr slag) and <0.15% (SS slag)) of matrix elements (e.g. Al, Fe, Si, Mg, Ca), when NaOCl is applied as oxidation agent and NaOH as alkaline agent. Furthermore, the used leaching liquor is reactive for a longer period of time, indicating that circulation of leaching liquor could be possible. Finally, the experimental results were fed into a first-order model which predicts that Cr will continue to leach from the tested slags for 4–5 years at a chosen infiltration rate of 73,000 l/(y m2).