STRATEGIES FOR SEPARATING METALS FROM ACID-MINE WATERS

Strategies for the precipitation and separation of the primary metal i ons, Fe(II), Cu(II), Zn(rn, Mn(II), and Cd(II) in acid waste waters su ch as those in tributaries of the upper Sacramento River in northern C alifornia, are discussed. The strategies exploit the: (1) differential oxygen and hydrogen peroxide oxidation and precipitation properties o f the metal ions as a function of pH, (2) the addition of ions, such a s Mg2+ and Cl-, to reduce unfavorable coprecipitation, and (3) the fac ilitation of oxidation-reduction reactions between metal ions and the stabilization of particular oxidation states. This may be accomplished with specific complexing agents such as thiocyanate, SCN-, and thiour ea (TU), S = C(NH2)(2) in order to separate copper at low pH as Cu(I) using Fe(II) as a reducing agent.