Application of Silicate-Based Coating on Pyrite and Arsenopyrite to Inhibit Acid Mine Drainage

The prevention of acid generation from sulfidic mine wastes is a problem that challenges the global scientific community for decades. A promising strategy is related to the formation of coating layer around sulfides for inhibiting surface oxidation. In the current research, the conditions favoring the formation of an efficient silicate-based coating around pyrite and arsenopyrite were studied, using batch tests. The coating solutions contained silicate-oxyanions, an oxidant (H₂O₂) and buffered at pH 6. The effect of Si concentration (0.1-50 mM), liquid/solid ratio (5-100 mL/g) and contact time (up to 24 h) was investigated. Pyrite tailings treated with a solution of 1 mM Si/0.1 M H₂O₂ at L/S:100 mL/g for 24 h resulted in the optimum formation of a coating, which reduced the amount of SO₄^-2-released by 72%, compared to the sample treated in the absence of Si. However, silicate treatment had a negative effect on arsenopyrite tailings inducing As mobilization.