Home – Home – Jornals – Chemistry for Sustainable Development 2006 number 4

Natural experiment with underground draining of high-sulphide waste products from Karabash Copper-Smelting Combine (Chelyabinsk Region) by natural neutral water has been performed. An oxyntic potential and a quantity of Cu, Zn, and Fe that passed into solution has been determined; a change in fractional distribution of chemical forms of these elements in the solution and in saturation indexes of mineral phases with an increase in the water/rock ratio (W/R) during the course of the experiment has been calculated. It has been demonstrated that interaction of natural neutral water with the material of waste products yields acids and results in that more than 50 % Cu and Zn, and about 30 % Fe passes into solution to yield the ratio W/R = 400 : 1. It has been observed that at low W/R ratios in acidic medium, copper and zinc exist in the form of sulphate neutral complexes and activated ions, and zinc additionally forms an anionic sulphate complex. As washing of acid proceeds, the fraction of sulphate complexes decreases; the metals remain preferentially in the form of aqua ions. Iron that exists in the solution predominantly in a sulphate complex during the beginning of the experiment then changes to a hydroxide form. Processes of dissolution and deposition of mineral phases actively proceed during the experiment. Ferrihydrite Fe(OH)3 and goethite FeOOH that are produced by the end of the experiment facilitate sorption and coprecipitation of copper and zinc. Formation of a secondary sulphate, jarosite KFe3(SO4)2(OH)6, during the experiment is confirmed by data of X-ray crystal analysis.