Phosphate Carbonated Wastes Used as Drains for Acidic Mine Drainage Passive Treatment

This study focused on the removal of heavy metals from a synthetic acid mine water by using continuous column experiments and Phosphate carbonated Wastes as alkaline drains. The passive treatment system targeted aims in neutralizing the acid mine drainage (AMD) containing high concentrations of dissolved iron and other metals. In Morocco, the phosphate mine industry produces huge quantities of overburden waste rocks (named herein PLW) which contain significant quantities of carbonates (calcite (46 wt %) and dolomite (16 wt %). The column experiments were set-up in laboratory and the testing were run under anoxic and oxic conditions by using a hydraulic retention time was 15 hours. The inflow to the treatment system ranged 5.5 mL/min, with acidic pHs of around 3, concentrations of dissolved Fe, Mn, Al, Ca, Zn and Cu were 600, 20,166, 350, 15 and 23 mg/L respectively, containing also some traces of Co, Cr and Ni. The test results showed that pH became neutral and a significant decrease in terms of metal concentrations; in particular for Fe (600 to 120 mg/L), Al (160 to 1.7 mg/L) and Cu (23 to 0.002 mg/L)