Abstract
Encapsulation is a typical method used to prevent potential acid mine drainage (AMD) in overburden piles. In this method, Potentially Acid-Forming (PAF) material is covered with either Non-Acid-Forming (NAF) material or alkaline material to minimize water infiltration and/or oxygen diffusion through rock pores. The physical and chemical characteristics and thickness of the NAF material layer are critical factors affecting the successful prevention of AMD. Therefore, this study evaluated the method of NAF material layering using laboratory-scale column leaching tests. NAF layers with a ratio of 25 and 50% were used to cover PAF material containing pyrite and jarosite sourced from the Sangatta and Bengalon mining areas, East Kalimantan. The physical and chemical characteristics of leachate collected from samples watered on a weekly wet-dry cycle were analyzed by kinetic tests over a period of 23 weeks. The results showed a trend of increasing pH values and decreasing sulfate and metal concentrations in the leachate. This study shows that NAF layering is an effective method to prevent or minimize the generation of AMD.
Highlights
In 2016, Indonesia had considerable coal resources of 127 billion tons and coal reserves of 32.3 billion tons (Outlook Energy Indonesia, 2016)
Static tests were performed to determine the capacity for acid mine drainage (AMD) generation; these included the paste pH, Total Sulfur, Acid-Base Account (ABA), and Net Acid Generation (NAG) tests
The analysis was conducted by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), and Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) in accordance with standard procedures
Summary
In 2016, Indonesia had considerable coal resources of 127 billion tons and coal reserves of 32.3 billion tons (Outlook Energy Indonesia, 2016). In 2018, Indonesia produced approximately 528 million tons of coal (Ministry of Energy and Mineral Resources, 2019). In open-pit mines, AMD forms by the release of sulfide minerals contained in the overburden or waste rock produced during excavation and backfilling activities. The sulfide minerals react with oxygen in the air and with rainwater flowing on the ground surface or infiltrated into rocks with acid-forming potential. These reactions produce ferrous Fe, sulfate, and acidity (Singer and Stumm, 1970) as follows: Reaction 2
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