Geopolymerization enhanced hydrothermal synthesis of analcime from steel slag and CFBC fly ash and heavy metal adsorption on analcime

This work is focused on crystal phase transition of solid wastes and functional application of crystal analcime in waste water purification, which provide a new environment-friendly route. In this paper, analcime was synthesized from steel slag and Circulating fluidized bed combustion (CFBC) fly ash (CFA) by hydrothermal method enhanced via geopolymerization (non-crystallized process). Then the analcimes were used for the removal of heavy metal ions (Pb2+, Cu2+) in aqueous solutions. Both the raw materials and products were characterized by XRF, XRD, FT-IR, SEM-EDS, and TEM. The results showed that non-crystallized process reduced the time of hydrothermal reaction and promoted the purity of analcime. The adsorption kinetics of analcime were all well fitted the pseudo-second-order model, and adsorption isotherms were well described by the Langmuir model. The maximum adsorption capacity of analcime for Pb2+ and Cu2+ were around 75.76, and 21.83 mg/g, respectively. The preference order observed for adsorption is Pb2+ > Cu2+.