Thermal power plants ash as sorbent for the removal of Cu(II) and Zn(II) ions from wastewaters

This study concerns the sorption of copper(II) and zinc(II) ions on an energy pit coal fly ash, a massive by-product of a thermal power station in Iaşi, Romania. In order to establish the optimum conditions of Cu(II) and Zn(II) sorption on the fly ash, the influence of experimental conditions (solution pH, adsorbent dose and metal ion concentration, temperature and contact time) was studied. The equilibrium data at three different temperatures were processed using the Langmuir isotherm model. The monolayer sorption capacities of energy pit coal fly ash are 4.71 mg/g and 5.75 mg/g for copper and zinc ions, respectively, at 18 °C. The thermodynamic parameters of Cu(II) and Zn(II) sorption process on the fly ash were also evaluated based on the Langmuir constant. Finally, the kinetic description of Cu(II) and Zn(II) sorption was performed by using the Lagergren pseudo-first-order equation. The results of this study suggest that fly ash may be a promising sorbent provided for environmental technologies in the future.