Comparative study of long-term laboratory and field kinetic test for potential acid forming (PAF) materials

Abstract

Acid Mine Drainage (AMD) comes from open pit and underground mining activities, characterized by high level of acidity and high metal solubility. AMD is formed from sulfide minerals that are exposed from mining activities, undergo oxidation by oxygen and contact with rainwater. AMD formation reaction rate must be studied to prevent AMD from being released to the environment. Reaction rate of acid formation can be determined by kinetic test. This study used the Free Draining Column Leach (FDCL) test method for the kinetic test, performed in laboratory scale and field scale. Laboratory scale experiment was done in a cylinder reactor, with 15 cm diameter and 35 cm height. Meanwhile the field scale was carried out in greater amount of rock material and reactor volume. The test was carried out in a weekly cycle for a total of 83 weeks. This study states that field scale experiments tend to produce higher concentrations of ORP, conductivity, sulfate, iron (Fe) and manganese (Mn) rather than the laboratory scale. The pH parameter on field scale experiment is around 1.91 to 3.18, meanwhile on the laboratory scale experiment is around 2.18 to 3.47. It can be interpreted that the field scale experiment tends to produce more acidic pH compared to the laboratory scale experiment. This research is expected to find the differences between laboratory scale and field scale experiments in long-term kinetic tests.