Thesis Archive
Synthetic Acid Mine Drainage Treatment Using Serpentinite from Nickel Laterite Ore Mines
Fabella, Divina Joyce, A.
Sadol, Kim Ahmed, N
Abstract:
Passive abiotic treatment of acid mine drainage (AMD) is conventionally done by limestone beds/drains. However, recent studies have pointed to serpentinite, which is reportedly in abundance in silicate ores from nickel laterite mines, as an effective alternative material to limestone. In this paper, mined, but unused low-grade nickel ore from a mining site in Mindanao, Philippines were characterized, and its capabilities to neutralize AMD, remove dissolved metals and sulfates from AMD were investigated. Upon characterization using XRD and XRF, the low-grade ore was found to be mainly goethite, and almost without any trace of serpentinite. To test its treatment capabilities, jar test was done on the mixture of AMD and the low-grade ore with the ratio being varied and compared against the standard treatment material, limestone. A ratio of 0.5 mL AMD/g low-grade showed the greatest AMD pH elevation from 2.21 to 5.36 after two hours of rapid mixing (180 RPM) followed by six hours of settling. The greatest change in ORP, conductivity and TDS, and removal of sulfates (92.89%), Fe (>99%), Al (>99%) and Ni (93.66%) were also observed at this ratio. Batch tests were then done on a layered low-grade nickel ore and limestone and put under anoxic and oxic conditions. The retention time was varied from 1 to 60 minutes but had barely any effect on the results. The pH under oxic conditions reached up to 6.09 at 10 minutes while pH under anoxic conditions only peaked at 5.91 at the 60th minute. Within the hour, the pH only fluctuated with small differences below their peak. The other parameters TDS, ORP and conductivity all dropped immediately from the 1st minute and fluctuated around it to a small degree. The DO parameter showed no trend and finished the hour still very close to the initial measurement. Removal of Al and Fe were almost complete even at the first minute, while Ni and sulfates showed greatest reduction at that time, too.
Adviser:
Orbecido, Aileen, H