Acid mine drainages at Mamut Copper Mine, Ranau, Sabah

• Main Author: Ho, Stella Yen Ling
• Format: Thesis
• Language: English; English
• Published: 2008
• Subjects: TD896-899 Industrial and factory wastes
• Online Access: https://eprints.ums.edu.my/id/eprint/10138/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/10138/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/10138/

Acid mine drainage (AMD) is an environmental problem of serious concern in most mining areas, particularly those with abandoned or closed mines. The existence of a closed mine in Sabah, namely Mamut Copper Mine (MCM), thereby indicates the potential occurrence of local AMD pollution. 5cientific information on the AMD at the mine area is crucial towards understanding the impacts as well as the development of appropriate treatment measures. AMD discharge points at the mine (MCM) area were identified and samples (S1 to S12) were taken periodically from up to 12 sites and analyzed for selected parameters namely pH, Ec, TDS, total acidity/alkalinity, sulfate and dissolved metals (Fe, AI, Mn, Cu, Zn, Cd and Cr) according to 5tandard Method. Water samples from selected river in the vicinity of the mine were also collected and analyzed for similar water quality parameters. The buffering characteristics of the AMD samples were also evaluated by potentiometric titration with NaOH solution. Additionally, the effect of neutralization on dissolved metal (Fe, AI, Mn, Cu and Zn) concentration of the AMD was investigated. The results showed that the AMDs at MCM have varying characteristics, with low pH(2.90-3.75), high total aCidity(176-1697 mg CaCO3/L), high TDS(302-2673 mg/L), high Ec(606-5370 µS/cm), sulfate(292 2808 mg/L) and elevated concentrations of dissolved Fe(0.12-7.13 mg/L), AI(12.24-192.14 mg/L), Mn(2.75-79.87 mg/L), Cu(2.02-47.03 mg/L), Zn(0.35-25.42 mg/L) and relatively low concentration of Cd(0.001-0.127 mg/L) and Cr(0.007-0.045 mg/L). The values of the selected parameters showed variation according to AMD sample and to some extent, sampling time. Amongst the various parameters, high correlations exist between total acidity and dissolved AI, TDS (or Ec and sulfate, AI and Zn, AI and Cu, and Zn and Cu. The total acidity is dominated (67-93%) by mineral acidity while the rest is attributed to free acidity. Based on its total acidity, the AMDs comprised of high strength, medium strength and low strength AMD. Comparatively, the characteristics of river water samples are as follows: pH(4.57-8.12), alkalinity(1.0-58.0 mg CaCO₅/L), Ee(63.8-652.0µS/cm), TD5(31.7-324.5 mg/L), dissolved sulfate(0.21-337.95 mg/L), dissolved metals Fe«0.02 mg/L), AI(<0.1- 3.43 mg/L), Mn( <0.01-4.07 mg/L), Cu( <0.1-1.11 mg/L), Zn( <0.1-0.6 mg/L), Cd(<0.01 mg/L) and Cr( <0.01 mg/L). Only one river, namely Mamut River, (R5) showed strong evidences of AMD pollution as shown by its acidic pH, low alkalinity, and relatively high T05, Ec, sulfate, Mn, AI, Cu and Zn. The titration data clearly showed that the amount of base required to increase the pH of the AMD up to pH~7.0 is strongly dependent (R²=0.9996) on the total acidity (or the strength) of the sample: S8>S7>S5>S4>S11>S6>S1~S2~S3>S10>S12>S9. The higher is the total acidity, the greater is the amount of base required for neutralization. The increase in pH during neutralization resulted in the decrease of dissolved Fe, AI, Mn, Cu and Zn concentrations. This trend was dependent on the type of metal but independent on the type of AMD. Fe was effectively removed from solution at Ph~4.0 while AI at Ph~5.0. By contrast, Cu, Zn and Mn were effectively removed at pH~7.0, pH~8.0 and Ph~10.0, respectively. The removal of the metals is attributed to precipitation reaction and the amount of precipitate formed increases with increase in pH, and total acidity of the AMD. Overall, the physicochemical characteristics of AMDs at MCM are generally similar to AMDs elsewhere. Nevertheless, due to its strong ability to buffer pH and greater preCipitate production, the high strength AMDs from two sites (S8 and S7) can potentially pose more severe impacts to the receiving surface water while its treatment can be more complicated compared to other AMDs in the area.