Co-recovery of Mn and Fe from pyrolusite and copper slag with hydrometallurgy process: Kinetics and leaching mechanisms

With the shortage of high-quality raw materials and increasingly strict environmental regulations, the recovery of metals from copper slag and pyrolusite has become a research hotspot. A novel method for simultaneously extracting Mn and Fe from pyrolusite and copper slag has been proposed. Under the optimal conditions (Copper slag / Pyrolusite = 2, H 2 SO 4  = 2 M, liquid—solid ratio = 10, T = 90 ℃, holding time = 60 min), the leaching efficiencies of Mn and Fe can reach 98.28% and 99.04%, respectively. In addition, the treated residue containing 60.04 wt% SiO 2 can be used as a raw building material. Through chemical kinetics and mineralogical transformation analyses, Fe 2 SiO 4 in copper slag decomposes to release Fe 2+ , which can reduce and leach Mn from pyrolusite. The unreacted shrinkage nuclear reaction model under the control of the surface chemical reaction is the most suitable model to describe the process, and when the apparent activation energy is 35.50 kJ/mol, the apparent rate equation is: $$1-{\left(1-\times \right)}^{1/3}=979.65{\left[\mathrm{CS}/\mathrm{Pyrolusite}\right]}^{2.6072}{\left[{\mathrm{H}}_{4}{\mathrm{SO}}_{4}\right]}^{1.3143}{\left[\mathrm{L}/\mathrm{S}\right]}^{0.5649}e\mathrm{xp}\left(-35.50/\mathrm{RT}\right)$$ Graphical Abstract