Removal of atrazine as an organic micro-pollutant from aqueous solutions: a comparative study

In the present study, different adsorbents were prepared: activated carbon (AC), MgO and ZnO nanoparticles, and the composite of AC/MgO/ZnO. The AC was prepared from oak charcoals, as low-cost and abundantly available materials in Iran, by chemical activation. MgO and ZnO nanoparticles were synthesized using a sol gel method. The adsorbents were characterized using Powder X-ray diffraction (XRD), Field Emission-Scanning Electron Microscope (FESEM), and Energy Dispersive X-ray Spectroscopy (EDS). Then, the adsorption behavior of the adsorbents was tested for the removal of atrazine (ATZ) herbicide as a model of organic micro-pollutant. The average crystallite size of MgO and ZnO nanoparticles was calculated from their XRD data using the Scherrer equation. The results showed that the MgO and ZnO nanoparticles had a size in nano scale, which was supported by FESEM images. The experimental data showed that the pH of solution had no considerable effect on the adsorption of ATZ herbicide. The experimental data obtained for the AC and AC/MgO/ZnO composite were fitted to nonlinear pseudo first-order, pseudo-second order, and general order kinetic models. The general order kinetic model provided the best fit to experimental data compared with the other models. The adsorption isotherm data of these two adsorbents at different temperatures fitted well to the Langmuir and Liu models, but followed the Liu isotherm model most precisely, based on the lowest SD value provided by this model. The results of this study indicate that the chemically prepared AC has excellent adsorptive capacity and can be used as an effective adsorbent for the removal of ATZ from aqueous solutions. However, MgO and ZnO nanoparticles exhibited low adsorptive capacity for ATZ and could not be suitable adsorbents for the removal of this pollutant. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.