Speciation and solubility relationships of Al, Cu and Fe in solutions associated with sulfuric acid leached mine waste rock

Solutions from oxidized waste rock originating from an acid-leached waste d ump were studied. The dissolution data suggest that after the majority of t he soluble solid phases are removed, remaining solid phases continued to bu ffer the solutions in the acidic pH range. Incorporating the solution data into MINTEQA2 identified controls on the solubility of Al, Cu and Fe at pH values from about 2.5 to slightly over 5. Sulfate appears to play a signifi cant role in the formation of solubility controlling solid phases for Al an d Cu. This is not the case for Fe, and is suggested that Fe and Cu solubili ty may be controlled by cupric ferrite at low pH values.