Preparation of a fly ash-based porous geopolymer material for copper ion removal

The pursuit of novel and efficient adsorbents is vital in potentially toxic elements wastewater treatment. A block-like geopolymer, utilizing 92 wt.% of fly ash, was synthesized to serve as a cost-effective adsorbent for Cu(II). Fly ash-based porous geopolymer (FAPGM) with 80.11% of porosity, 38.080 m² g⁻¹ of specific surface area and 0.886 MPa of compression strength was obtained through process parameters optimization. FAPGM exhibited excellent adsorption performance, with a maximum capacity of 62.70 mg g⁻¹ for Cu(II). The adsorption process can be described by Langmuir and quasi-second-order kinetic models. The mechanism of Cu(II) adsorption onto FAPGM involves chemisorption, electrostatic interactions, ion exchange chemical precipitation, spontaneous and endothermic. The research indicates blocky porous geopolymer can serve as a promising candidate material for treating copper-containing wastewater.