Synthesis of novel zeolites produced from fly ash by hydrothermal treatment in alkaline solution and its evaluation as an adsorbent for heavy metal removal

[Display omitted] •FA24 has a zeolite P structure and highly specific surface area.•Adsorption of Hg2+ and Pb2+ were related to ion exchange with Na+ in FA24.•New Pb (4f) peaks at 136.6 and 141.5 eV were detected after adsorption. In this study, zeolites (FA6, FA12, and FA24) were prepared from JIS Type-II fly ash (FA) by alkaline hydrothermal treatment, and their physicochemical characteristics were investigated. In addition, their adsorption capability for heavy metals ions (Hg2+ and Pb2+) was evaluated. Zeolites have Hydrosodalite and/or Zeolite P structure, and the specific surface area of FA24 was greater than that of FA6 and FA12. A higher amount of heavy metals ions was adsorbed by FA24 than by FA6 and fA12. After adsorption using FA24, the binding energy of Pb2+ was detected, on the other hand, the binding energy of Hg2+ was not detected under our experimental conditions. These results suggest that FA24 surface properties shows a low adsorption capability of Hg2+. In addition, ion exchange with sodium ions in the adsorbent was also related to the adsorption capability of heavy metals ions (correlation coefficient: 0.965–0.973). A pH of approximately 5 was found to be optimal for the adsorption of heavy metals ions under our experimental conditions.