Combination of chemical and biological-chemical methods for elimination of metals from acid mine drainage

Each acid mine drainage has a specific composition, but always contains sulphuric acid, dissolved heavy metals, sulphates, iron pre- cipitates and their pH can be very low. The elimination of metals form the acid mine drainage is a severe environmental problem and has been a long-standing major concern to scientists, engineers, industry and governments. Various methods are used for the metals removal from waters, but any of them have been applied under commercial-scale conditions. Mostly studied are chemical and biolog - ical-chemical methods. Main aim of the paper was to interpret the combination of chemical and biological-chemical methods for the heavy metals elimination from the synthetic solution of acid mine drainage, coming from the zinc mine located in Tùnel Kingsmill outlet of the Rio Yaulì (district of Yauli - Perù). The metals selective precipitation as hydroxides (chemical method) and sulphides (biological-chemical method) at the various values of pH acid mine drainage is the fundamental of the examined process. For the hydrogen sulphide production the sulphate-reducing bacteria of genus Desulfovibrio was used. The selective sequential precipitation process reaches the selective precipitation of chosen metals with 97-99% efficiency - Fe, As, Al and Mn in the form of metal hydroxides, Cu and Zn as metal sulphides.