Preparation of alkali-activated fly ash-based geopolymer and their application in the adsorption of copper (II) and zinc (II) ions

Alkali activation of fly ash can a promising alternative of the system to improve adsorption capability of fly ash. In finding the best chemical composition of the activator solution, geopolymer has been synthesized using molar ratios of Na2O/SiO2 0.16, 0.3, and 0.5 (Gr1, Gr3, Gr5). The results indicated that the geopolymer synthesized with a ratio molar of Na2O/SiO2 0.3 (Gr3) improved the adsorption properties of fly ash substantially. Gr3 was characterized by BET, XRD, and FTIR. The batch experiment was conducted at the different duration and initial concentrations. The equilibrium sorption data were fitted for the Langmuir and Freundlich equations. The maximum sorption capacities calculated from Langmuir isotherm was 54 mg g -1 and 47 mg g -1 for Cu (II) and Zn (II) respectively. The kinetic data reveal that the pseudo-second order model was appropriate for a description of the kinetic performance.