PIT WALL LEACHING TEST AND PREDICTION WATER QUALITY OF PIT LAKE IN MINE CLOSURE IN COAL MINE

• Main Author: Zanno, Mochammad
• Format: Theses
• Language: Indonesia
• Subjects: Pertambangan dan operasi berkaitan
• Online Access: https://digilib.itb.ac.id/gdl/view/51581
• Institution: Institut Teknologi Bandung

The main activity of coal mining with an open pit system is extracting coal from the overburden. Overburden can contain sulfide minerals so that when exposed to air and water it will produce acid mine drainage. The biggest impact due to coal mining activities with an open pit system is the formation of a pit lake. The quantity and quality of pit lakes can be predicted and known so that prevention or control can be made. Geochemical characterization of rocks is an initial step in understanding the process of forming acid mine drainage which consists of static test and can be validated by kinetic tests. The kinetics testing method used is pit wall leaching. The results of the static test sample PRI-01 were categorized as NAF, samples PRI- 02 and PRI-03 were categorized as PAF. The results of the pit wall leaching test, the pH value of the PRI-01 sample was 7.59, the pH value of the PRI-02 sample was 2.15, and the pH value of the PRI-03 sample was 3.51. The pyrite oxidation rate based on moles of iron is much smaller than the pyrite oxidation rate based on moles of sulfate and the geochemical modeling of PHREEQC. The PRI-01 samples had iron species Fe(OH)3 which tended to settle in the leach water, while the PRI- 02 and PRI-03 samples had iron Fe2+ species which tended to be dissolved in the leach water. The results of the pit lake prediction scheme, the former coal mining pit will be fully filled with water in year 5.5 with a total water volume of 45,238,444 m3 at an elevation of 14 masl and in the first year the water quality of the pit lake has a pH value of 2.81 which is not much different from the pH value of the sump of 2.86 and in the final year of filling the pit lake or in the year 5.5 the water quality of the pit lake has a pH value of 4.6.