Physical-chemical and biological-chemical methods for treatment of acid mine drainage

The main goal of the article was to demonstrate the technical feasibility of the heavy metals removal from the acid mine drainage coming from a lead and zinc mine located in Tùnel Kingsmill outlet of the Rio Yaulì (district of Yauli - Perù) using physical-chemical and biological-chemical methods. The base of the physical-chemical method was the electrowinning. The principle of the biological-chemical method was the selective sequential precipitation of metals with the application of H2S produced by the sulfate-reducing bacteria and NaOH solution. The experimental tests were conducted by the synthetic solutions of the acid mine drainage. Electrowinning tests were carried out after the chemical ironaluminum precipitation that permitted a complete Fe-Al removal. By electrochemical experiments, high metals removal were achieved: in particular, by Zn and Mn electrodeposition, it was possible to achieve about 95 - 97% Zn and Mn removal (as MnO2), with a relatively low energetic consumption. The results of the selective sequential precipitation documented that the pre-treatment of the synthetic solution by the H2O2 addition improved the selectivity of the process, except Fe and As. 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 sulfides.