STUDY OF ACID MINE DRAINAGE FORMATION BY REVIEWING THE CHARACTERISTICS OF THE OXIDATION RATE OF SULFIDE MINERALS IN HIGH SULPHIDATION EPITHERMAL DEPOSITS

• Main Author: Prihartini, Rahayanti
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69551
• Institution: Institut Teknologi Bandung

Mining activities include stockpiling gold mine waste rock with a high sulphidation epithermal (HSE) deposit type, allowing the exposure of materials containing sulfides in contact with water and air so that it is possible to cause acid mine drainage (AMD). AMD is water with a low pH and a high level of complexity, so it can impact the ecosystem and affect water quality. The purpose of this study was to determine the formation of AMD by reviewing the rate of oxidation of sulfide minerals by calculating the total moles of iron and moles of sulfate and modeling using PHREEQC software on HSE deposits. The samples used in this study were six rock samples originating from HSE deposits based on geological domains representing completely oxidized (COX) levels and un-oxidized (UOX). Rock samples with this oxidation state were chosen to characterize the potential for forming AMD. Characterization was carried out using a mineralogical, static, and kinetic test. Based on the mineralogical test, the HSE deposit is dominated by sulfide minerals in the form of pyrite and iron oxides hematite, goethite, and jarosite. It produces a geochemical characterization classified as potential acid forming (PAF) based on static tests. Geochemical modeling using PHREEQC was carried out to simulate changes in pH and solute concentration produced during laboratory-scale kinetic tests using aqueous equilibrium and kinetic models. The resulting leachate water has an average pH range between 2.5 to 4.5, accompanied by an increased sulfate concentration, iron, aluminum, and other constituents. And on the quality of the leachate produced, there is a tendency to deposit jarosite, goethite, and gibbsite. The oxidation rate And the quality of leachate produced tends to deposit jarosite, goethite, and gibbsite. The oxidation rate obtained from the total moles of iron (3.10x10-18 – 9.09x10-09 mol/m2s), sulfate (6.59x10-10 – 2.84x10-08 mol/m2s), and pyrite oxidation rate based on the model (4.49x10-11 – 4.96x10-09 mol/m2s), rate of oxidation of AMD formation based on moles of sulfate is closer to the mole transfer value of pyrite from the PHREEQC modeling, this condition is caused by the Fe content in the leachate water that settles more than sulfate.