As coal combustion in thermal power plants generates huge amounts of waste such as bottom ash and
fly ash, there is a need to find new applications for these materials. One of the ways of its reuse is
chemical or thermal modification of the ash in order to obtain new materials, which can be further
used as adsorbents of various pollutants from water. The subject of this research was the alkali
modification and alkali activation of fly ash in purpose to increase the adsorption capacity towards
heavy metal ions. The success of modification process and characterization of the obtained materials
was monitored by Fourier transform infrared spectroscopy, X-ray fluorescence spectroscopy and
scanning electron microscopy. The concentration of zinc and cadmium ions after adsorption was
determinated by atomic absorption spectroscopy. The kinetics of the adsorption process on the most
efficient adsorbent were examined and the experimental data were compared with pseudo-first and
pseudo-second order models. The achieved results show a positive effect of alkaline modification of
fly ash on adsorption efficiency of both metals, while alkaline activation gives an exceptionally
effective adsorbent in the case of zinc.
