A significant decrease in pyrite dissolution rate can be achieved by subjecting it to a humic acids treatment. In this study, the following two sources of pyrite were used: (i) an acid refuse (coal slurry) sample, and (ii) a coal pyrite sample. In addition to pyrite dissolution rate measurements, column studies also were carried out. The leachate iron, sulfur, chromium, vanadium and cadmium metal contents were determined. Pyrite passivation was also studied using some model compounds of humic acids. The data obtained suggest that catechol and 4-aminophenol addition to pyrite can result in a significant suppression of pyrite dissolution under nitrogen and air atmospheres whereas oxalic acid addition enhances pyrite dissolution. In a related research work, it is shown that lignin addition also results in a decrease in pyrite dissolution rate.