Removal of Heavy Metal Ions from One- and Two-Component Solutions via Adsorption on N-Doped Activated Carbon

This paper deals with the adsorption of heavy metal ions (Cu2+ and Zn2+) on the carbonaceous materials obtained by chemical activation and ammoxidation of Polish brown coal. The effects of phase contact time, initial metal ion concentration, solution pH, and temperature, as well as the presence of competitive ions in solution, on the adsorption capacity of activated carbons were examined. It has been shown that the sample modified by introduction of nitrogen functional groups into carbon structure exhibits a greater ability to uptake heavy metals than unmodified activated carbon. It has also been found that the adsorption capacity increases with the increasing initial concentration of the solution and the phase contact time. The maximum adsorption was found at pH = 8.0 for Cu(II) and pH = 6.0 for Zn(II). For all samples, better fit to the experimental data was obtained with a Langmuir isotherm than a Freundlich one. A better fit of the kinetic data was achieved using the pseudo-second order model.

Automated summary

This study found that activated carbons modified with nitrogen functional groups exhibit a higher capacity for heavy metal ion adsorption, with adsorption increasing with solution concentration and contact time. The optimal pH for adsorption was determined to be 8.0 for Cu(II) and 6.0 for Zn(II), with Langmuir isotherm providing a better fit to the experimental data than the Freundlich isotherm. The kinetic data was better described by the pseudo-second order model.