Application of geopolymers for treatment of water contaminated with organic and inorganic pollutants: State-of-the-art review

Abstract

This study aims to provide a state-of-the-art review on application of geopolymer (inorganic polymer) materials for treatment of waters and wastewaters contaminated with organic pollutants (such as dyes), and inorganic pollutants (such as heavy metals). Geopolymer materials possess good surface and interface properties for immobilization, encapsulation, and adsorption of pollutants from waters and wastewaters. Special focus is given to available studies conducted over the last ten years (2010–2020) to draw an in-depth knowledge on the formulation and characterization of geopolymers as efficient, environmentally-friendly low-cost adsorbents for elimination, decontamination, and purification of inorganic and organic hazardous pollutants from aqueous environments. The ability of geopolymer materials to remove hazardous compounds from aqueous mediums and wastewaters was assessed to be comparable to that of other composites. The nature, mechanism of adsorption, and interaction between adsorbents (geopolymers) and adsorbates (dyes and heavy metals) are investigated by the isotherm and kinetic models, respectively. The thermodynamic study between geopolymers and pollutants was also evaluated to assess the feasibility and favorability of the adsorption process. Most kinetic and isothermal studies showed that the adsorption of heavy metal ions and dyes (cationic and anionic) on geopolymers synthesized by different aluminosilicate sources are described by pseudo-second-order and Langmuir models, respectively. Future studies could target the improvement of geopolymers capabilities, to be applied to other pollutants, such as herbicides and pesticides, as well as monitoring their efficiency in remediation processes, such as photo-degradation, encapsulation, and immobilization.