Copper adsorption on arsenopyrite minerals has been investigated. The effect of solution pH, Cu(II) concentration, oxygen, and oxidation on Cu(II) adsorption were examined. The results indicate that activation of arsenopyrite by Cu(II) in acidic media proceeds according to an ion exchange mechanism. Quantities describing the adsorption processes and reaction time are related either parabolically or logarithmically, depending on the initial copper (II) concentration and solution pH. Oxygen inhibits the adsorption of Cu(II) on arsenopyrite in acidic media, but copper initially adsorbed on an arsenopyrite surface does not undergo desorption upon prolonged oxidation. Increasing the solution pH can reduce the effect of oxygen on copper adsorption. The principles underlying the processes are discussed.