Passive Remediation of Acid Mine Drainage Using Ball-Milling Modified Indonesian Natural Bentonite: Laboratory Batch and Column Sorption of Manganese

Manganese (Mn) is an essential element for human body. However, elevated concentration of manganese causes severe problem and disease. Acid mine drainage (AMD), wastewater generated due to open-pit mining, commonly contains Mn with exceeded concentration. This study is to investigate the improvement of ball-milling modified Indonesian natural bentonite (INB) for manganese (Mn) removal from AMD and to increase the pH through batch and column sorption test as a passive treatment system approach. The batch sorption test result showed the maximum Mn adsorbed (Qm) on INB from the Langmuir model increased from 4.69 to 17.12 mg/g after milling. The column sorption test result also showed the amount of Mn adsorbed on INB until breakthrough time (qu) and until saturation time (q) increased after milling. The qu increased from 1.27 to 10.06 mg/g, and the q increased from 4.55 to 12.91 mg/g. The mass transfer zone (MTZ) became significantly shorter after milling from 0.22 to 0.07 cm. The Thomas model exhibited the equilibrium uptake of Mn (q0) increased after milling from 3.91 to 13.72 mg/g. In equilibrium condition, both unmilled and milled INB showed the pH increased from ≈3 to 8.