The efficiency of open lime-zeolite channel system in treatment of Acid Mine Drainage (AMD) released from Sungun copper nine

چکیده مقاله

Sungun copper mine is located inside Arasbaran forest protected area of Iran and AMD drained from tailing dump of the mine is a big challenge between the mine authorities and the residents, NGOs and Iranian Environmental Protection Organization. As the first AMD treatment system in Iran, a passive open lime-zeolite channel was implemented in Sungun mine and the effeciency was evaluated. Increasing of pH cannot decrease the concentration of heavy metal down to permissible level and need to be combined with another mechanism to increase the effeciency.  A system with combination of zeolite and lime would be an effective treatment method for Cu removal of AMD. The zeolite omits Cu from aqueous phase by means of adsorption (2.86 mg/g based on Langmuir isotherm model) whereas increasing of pH with limestone is recognized as effective mechanism for precipitation of Cu from AMD. However, based on experimental data and site specifications, zeolite- limestone open channel stablished at site to use two mechanisms of buffering and adsorption for treatment of AMD. Combining open zeolite channel with routine open lime channel (OLC) increased the effeciency of AMD treatment system. A few months after opening of AMD treatment system of Sungun copper mine, remediation effeciency of the system was evaluated using two rounds of sampling and comparing with the pre-treatment sampling results. The results showed that Cu concentration has been decreased from about 45 mg/L down to less than 4 mg/L implying a decrease of more than 91% percent in Cu concentration by lime part of the system. The second sampling which was done after complete installation of the system showed a complete restoration of the AMD related to the copper with decrease of concentration down to detection limit of the instrument (0.03 mg/L). The system also decreased Al concentration 69%, Fe concentration 55% and Zn below detection limit. Furthermore, the treatment system has increased pH value to neutral condition which has the main rule in immobilization of the metals.