Enhanced iron oxidation to improve AMD treatment

Abstract

Fe(II) and acidity are the most commonly encountered contaminants in acid mine drainage (AMD). Passive treatment for AMD involves addition of alkalinity, aerobic processes that result in oxidation of Fe(II) to Fe(III) oxides, and anoxic treatments in which sulfate is reduced to sulfide with consequent precipitation of Fe(II) sulfides. Alkalinity is usually provided by dissolution of limestone in passive treatments or by addition of lime or caustic in active systems. This paper focuses on the chemistry of AMD treatment, the mechanisms and the rates of oxidation of Fe(II) to produce Fe(III) oxides and strategies that can be used to manipulate the treatment chemistry in order to control the rate of oxidation and the quality of the residual Fe(III) oxides.