Geopolymers are extremely versatile materials synthetized through eco-sustainable processes. Modifying the initial composition and applying different production processes it is possible to obtain geopolymers, which differ in regards structure, porosity and final properties. They are easily shaped (monoliths, beads, granules) and reproducible on large scale and their porosity can be tailored from the micro to the macro scale employing several techniques. Furthermore, geopolymers have ionic exchange and electrostatic interaction properties, in analogy with zeolites, deriving from their 3-dimensional structure. To broaden the spectrum of applications, geopolymer matrices can be functionalized with fillers in order to create more performing composite materials. For these reasons, different geopolymers and composites have been recently produced as adsorbents and characterized with functional test to assess the removal of pollutants from gaseous or liquid systems.
Regarding the use of geopolymers as adsorbents in liquid phase, geopolymers granules have been employed for the recovery of ammonium using real municipal and saline wastewater treated in a continuous flow pilot plant.  Geopolymer resulted to be a cost-effective adsorbent for wastewater treatment capable to adsorb cations by ion exchange, allowing a fractionated desorption procedure to recover ammonium in a product potentially usable as fertilizer.
Regarding the removal of pollutants from gaseous flow, geopolymer-zeolite composites were employed to selectively remove CO₂ at low temperature. In this case, geopolymer matrices were prepared, varying the molar ratio Si:Al and the type of cation (sodium or potassium). Since the presence of NaA crystalline phase is desirable, due to its adsorbing capacity towards CO₂, starting from the geopolymer matrices, the composites were prepared adding synthetic zeolite Na4A. The sodium-based geopolymer zeolite composite was the best performing in term of CO₂ adsorption capacity, nearly equivalent to synthetic zeolite Na4A and zeolite Na13X, the current benchmark material for carbon capture application.