ANALYSIS OF SEDIMENTATION AND PHYSIC-GEOCHEMICAL STABILITY OF FLY ASH FOR NEUTRALIZING ACID MINE DRAINAGE IN A PIT LAKE AT LABORATORY SCALE

• Main Author: Febriana, Dian
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85192
• Institution: Institut Teknologi Bandung

Mining activities often lead to form acid mine drainage (AMD). In open-pit mining, the excavated pits frequently create a lake (pit lake) with acidic water due to AMD forming. One of the in situ treatment methods for this issue is to spread an alkaline neutralizing material over the entire surface of the water. Fly ash (FA) is one of the neutralizing agents that can be used. Although FA is no longer classified as hazardous waste, it must be managed properly to avoid negative impacts. Given the number of open-pit mines in Indonesia and the extensive pit lakes formed postmining, the use of FA needs to be optimized. Therefore, this research was conducted on a laboratory scale to gain a more detailed understanding of this treatment mechanism. The sedimentation of FA in AMD was observed using acrylic tubes with a diameter of 11.2 cm and varying water volumes of 5, 10, and 15 liters. The tests maintained a consistent solid-to-water ratio of 1:5. FA was allowed to settle for 24 hours, after which grain size distribution, mineralogy, and elemental analysis, such as static tests, were conducted. The final FA characteristics experiment was compared to its initial properties. Post-neutralization water was tested using IC and ICP-MS, then analyzed using PHREEQC software. The test results showed an improvement in AMD quality. The post-neutralization pH levels were 6.24 in Tube 1, 6.81 in Tube 2, and 7.65 in Tube 3. The Fe and Al metals concentration decreased by nearly 100%, while Mn concentrations decreased between 19.88% and 40.06%. The improvement in AMD quality was directly proportional to the contact time between FA and AMD. Smaller FA particles have a larger surface area in contact with AMD and will settle in AMD for a longer time. This results in a more effective neutralization of AMD. At the end of the testing, stratification of the FA sediment was observed. The sediment sorting led to greater stability, reducing the likelihood of material dispersion.