Successive alkali diffusion ceramic reactor: Long-term removal of acidity and heavy metals in acid mine drainage

A novel alkali diffusion reactor using ceramic porous media (ceram-ADR) was newly developed for long-term treatment of acidity and heavy metals in acid mine drainage (AMD) without external energy. The batch and column tests were performed to investigate the neutralization capabilities of six alkaline chemicals (i.e., MgO, CaCO3, CaO, SiO2, Na2CO3, and NaHCO3) and the effects on pore size and hydraulic retention time (HRT) of ceram-ADRs. Among these six alkaline chemicals, the ceram-ADR containing NaHCO3 yielded a suitable pH range for water quality guideline (pH values from 5.0 to 9.5) for an HRT of 1-2 days as well as had the best efficiency in terms of consistent alkaline diffusion and long-term heavy metal removal (>99 %). The precipitation process was found to be a major mechanism in the removal of heavy metals. Based on the continuous column tests, it was evaluated that the ceram-ADR successfully treated three consecutive runs with approximately 340 bed volumes of AMD for neutralization and heavy metal removal, indicating that the ceram-ADR can be maintained for over three years without a lapse in performance. Capsule abstract: An alkali diffusion reactor based on porous ceramic media is developed for the long-term remediation of acidity and heavy metals in AMD.