Porous geopolymer with controllable interconnected pores-a viable permeable reactive barrier filler for lead pollutant removal.

Most of the commonly used traditional permeable reactive barrier (PRB) fillers have many drawbacks, such as poor retention of hydraulic conductivity, high cost, and a complex preparation process. Porous geopolymers (PGPs) with controllable pore structures could circumvent these drawbacks owing to their high adsorption capacity, cost-effective synthesis, and good chemical stability. In this study, based on our previous research, the "foaming-liquid film" balance control method was proposed and used to fabricate three PGPs with gradient pore connectivity. The influence of pore structure on the Pb removal performance and migration mechanism were investigated by conducting both batch and column experiments. Closed, dead-end, capillary, and interconnected pores exist in the PGPs, and results indicated that interconnected pores effectively promote the migration of solute in the main flow channels to the deeper matrix, thereby enhancing the long-term dynamic removal efficiency. At breakthrough, the Pb uptake of PGP-3 reached 146 mg g. Further, the proposed "foaming-liquid film" balance control method is effective to prepare PGPs with controllable connectivity, and the PGP-PRBs with a high proportion of interconnected pores exhibit excellent performance for the removal of heavy metals, which is advantageous for their future applications in groundwater decontamination.