Study on the metakaolin-based geopolymer pervious concrete (MKGPC) and its removal capability of heavy metal ions

A metakaolin-based geopolymer pervious concrete (MKGPC) was developed to reduce the pollution of groundwater. In addition to the compressive strength, void ratio and permeability, the capacity of MKGPC on the removal of heavy metal ions in solution was focused. Its mechanisms were revealed from two aspects: the characteristics of binder and the volume structure of pervious concrete. The results showed that MKGPC has an excellent removal capacity of the heavy metal ions. In addition, we found that a low SiO2/Al2O3ratio at 2.0 could significantly improve the MKGPC's capability of removing heavy metal ions in solution, due to the formation of Natrolite. We also found that the decreases in the open void ratio and the permeability of MKGPC extend the contact time between the solution containing heavy metal ions and the MKG binder, thus improving the capacity of removing heavy metal ions in solution. Finally, the result indicated that pores of smaller size facilitate the adsorption of the heavy metal ions on MKGPC. To manufacture MKGPC which can purify water effectively, it is necessary to improve the adsorption ability of MKG binder and keep the balance between the open void, the permeability and the pore structure of MKGPC.