Incorporation of activated carbon into red mud/fly ash-containing 3D-printed alkali-activated materials for enhanced acid mine drainage remediation

• Advanced use of 3D-printed activated carbon AAMs in acid mine drainage remediation. • Inks containing varying amounts of activated carbon were successfully 3D- printed. • Higher specific surface area for lattices containing 30 wt% of activated carbon. • Best-reported metals extraction performance from acid mine drainage by AAMs. Alkali-activated materials have emerged as highly effective sorbents for metal removal, due to their zeolitic-like structure, intrinsic porosity and ion exchange properties. Combined with the sorbent benchmark activated carbon, these capabilities can be further enhanced. In this study, activated carbon was integrated for the first time into 3D-printed waste-based alkali-activated materials (incorporating biomass fly ash and red mud), and investigated their potential for treating real acid mine drainage waters. Activated carbon loadings of 10, 20, and 30 wt% were incorporated into a fly ash, red mud and metakaolin composition with a weight ratio of 30:40:30. The ink formulations were optimised by fine-tuning the liquid-to-solid ratio to ensure printability. As activated carbon content increased, the specific surface area of the materials improved significantly, from 40 to 95 m 2 /g. Incorporating 30 wt% of activated carbon notably enhanced the removal efficiency of target cations in a fixed-bed continuous flow process. After 8 h of contact time, the removal rates for Fe, Cu, Zn, Mn, Ni, and Pb increased from 99 %, 55 %, 27 %, 38 %, 13 %, and 95 % (structure without activated carbon) to 99 %, 90 %, 82 %, 80 %, 69 %, and 96 % (structure with 30 wt% of activated carbon), respectively. This approach demonstrates the potential of combining a well-established sorbent, such as activated carbon, with waste-derived alkali-activated materials to significantly enhance the remediation of acid mine drainage, a critical global source of environmental pollution.