Synthesis, Characterization, and Application of Geopolymer/TiO2 Nanoparticles Composite for Efficient Removal of Cu(II) and Cd(II) Ions from Aqueous Media

The use of fly ash wastes as inexpensive sorbents, mostly for heavy metal cations, is one method of recycling the millions of tons of fly ash waste produced each year. In this paper, a fly ash-based geopolymer was used as an adsorbent for Cu2+ and Cd2+ from an aqueous solution. To improve geopolymer sorption efficiency, fly ash was modified by incorporating titanium oxide (TiO2) nanoparticles that were synthesized hydrothermally and annealed at a temperature of 500 °C. The adsorbents were characterized before and after adsorption by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM-EDX). Regarding the developed materials, Cu2+ and Cd2+ adsorption equilibria (Langmuir model and Freundlich model) and kinetics (pseudo-first-order and pseudo-second-order model) were investigated. The results show that geopolymer-NanoTiO2 adsorbs heavy metal cations better, which is superior to geopolymer. The maximum experimental adsorption capacity of geopolymer-NanoTiO2 composite for Cu2+ and Cd2+ was 1708.2 mg/g and 706.9 mg/g, respectively. Therefore, geopolymer-NanoTiO2 composite has shown great application prospects in the prevention and control of heavy metal pollution.