Removal of Metal(Loids) from Acid Mine Drainage Using Manganese Oxide Wastes from a Mining-Metallurgical Process

Abstract This study focused on treating acid mine drainage (AMD) from a Zn-sulfide mine with a composition that includes Al = 445 mg/L, Fe = 263 mg/L, Mn = 364 mg/L, Cd = 2.8 mg/L, and Zn = 4,830 mg/L. After treatment with regional alkaline minerals, the pH increased from 3.0 to 6.3 and metal concentrations decreased mainly by precipitation, falling below Mexico’s permissible limits (MPL) for river discharges, except for Cd 2+ and Zn 2+ , which exceeded their MPLs with concentrations of 0.4 and 1,110 mg/L, respectively. We tested the use of waste materials from a Mn mine containing Mn carbonates (R3) and Mn oxides (R6) for removal of these contaminants. Several Mn oxides have been reported as promising adsorbents and indeed the R6 waste was more efficient than the R3. At a ratio of 0.75 g/L of R6, with 30 h of contact or a ratio of 0.2 with 60 h of contact, Cd 2+ and Zn 2+ concentrations were decreased to below their MPLs. The evaluation of removal mechanisms was hindered by the complexity of the waste’s composition. However, contact with the AMD increased the zeta potential from negative to positive values, indicating a cation sorption process. Mn wastes can be used without prior alkaline mineral treatment, but their technical and economic viability is less. The results suggest that this process is suitable for treating AMD at abandoned mines sites. Additionally, the Mn wastes can potentially be sold as a sorbent material for other processes, offering a recycling option.