The utilization of geopolymer as a pH neutralizer of acid mine drainage

Geopolymer has been widely used in various fields. This paper reports the pH increase of acid mine drainage (AMD) by treatment with geopolymer materials. The test specimens were made from fly ash, sandstone, and crystalline limestone from waste mining materials in East Kalimantan. They were made by mixing 14 M NaOH solution, Na2SiO3, and waste mining materials. The crushed geopolymer with 80 mesh in particle size was applied for treating the acid solution. The increased pH of acid mine drainage solution may be mainly caused by combination of CaO and soluble Na2O content in the geopolymer materials. The formula codes V3 and V4 were found to be the more effective in treating the acidity, increasing up to 6.3 with geopolymer powder as much as 1.5 gram in 200 ml of acid mine drainage (AMD) solution. Meanwhile, the role of sandstone has an inverse effect on the resulting pH. This experiment can be of practical implication in either developing geopolymer products for AMD remediation in a passive way or recycling geopolymer residue for AMD treatment in an active method.