EVALUATION OF FLY ASH UTILIZATION IN BLENDING METHOD TO PREVENT ACID MINE DRAINAGE GENERATION

• Main Author: Handa Nuraga, Welly
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69378
• Institution: Institut Teknologi Bandung

Exposure and oxidation of sulfide minerals in oxic-aqueous condition can potentially produce Acid Mine Drainage (AMD). One of the methods used to prevent AMD formation is the dry cover method by placing non-acid forming (NAF) material to cover potentially acid forming (PAF) material. The availability of NAF material in mine sites is often limited. Thus, substitution of NAF material is needed. Therefore, further assesment to evaluate the substitution of NAF materials is urgently needed. One of substitution material of NAF is blending material consisting of PAF and fly ash. This research aims to evaluate the utilization of blending fly ash and PAF from various scenarios using free draining column leach tets (FDCLT) kinetic test in laboratory and field, as well as using field dumping model. Kinetic test are conducted using folows scenarios: Control column of PAF and fly ash, blending material of various fly ash ratios of 5%, 15%, and 25%. In the other hand, field dumping model, PAF material at the bottom of part with thicness of 30 cm; in the middle blending of fly ash and PAF with ratio of 1:2 with thicness of 90 cm and on the top 30cm of topsoil were placed respectively. Oxygen and moisture levels were placed in the middle of each layer in order to record physical properties of materials during the field dumping test. Physicochemical properties of leachates and geochemical reaction and equilibrium were analyted in order to explain the belending performance of method and scenarios. Based on XRD and XRF results, sulphide minerals in the form is pyritic (FeS2) was founded in PAF material in the oter hand fly ash containing alkaline materials such as Mg and Caoxide which plays important role in neutralizing AMD. The greater of fly ash addition ratio into the blending material, the higher alternatif relased in order to neutralize and prevent AMD formation. In the other hand, material size distribution and the homogenity of blending material would affect the produced leachates. In the field dumping model, blending material is more heterogenous of those material used in field and laboratory kinetic test due the differences in scale of material size distribution. The large size of PAF material is further breaking apart into smaller fragment which not to covered by fly ash. Newly formed surface of PAF fragment is generating more AMD as shown in more acidic leachates. This study shows that geochemically balances between PAF and fly ash material, is not only the main factor of AMD formation and blending performances but also the size distribution, physical and chemical characterization had an important role in preventing the formation of AMD.