Review on the effect collision between hazardous metal ions and geopolymer as adsorbents or in situ stabilization/solidification

An imbalance between available resource reserves generated by human activities and disposal measures causes a series of harmful problems related to water, soil and human health, such as those from hazardous metal ions (HMs) and their carrier materials (LMs). As excellent intermediates with adjustable spatial structures and many active sites, geopolymers can be directly used as adsorbents to remove HMs from wastewater or produced by LMs via in situ stabilization/solidification methods. This paper first reviews the common methods used to optimize the pore structures of geopolymers and then reports the common methods for optimizing LM-based geopolymers. For geopolymers-based adsorbents, the pore structure is vital in the adsorption of the target ions, and the application of functional auxiliary materials among adsorbents has been summarized. The feasibility of using geopolymers for in situ stabilization/solidification of HMs is highlighted, but instability and low mechanical strength remain significant factors hindering their development. Finally, the mechanism for bonding between HMs and geopolymers is summarized, and future developments, challenges, and possible solutions are briefly described.