Functionalized MgO, CeO2 and ZnO nanoparticles with humic acid for the study of nitrate adsorption efficiency from water

In this study, the removal of nitrate using ZnO, MgO, and CeO2 nanoparticles (NPs) modified by humic acid from water was tested. Nanoparticles were modified by humic acid using the microwave-assisted technique and then modified ZnO (Zn-H), modified MgO (Mg-H), and modified CeO2 (Ce-H) were characterized through SEM, EDX, FTIR, and XRD analysis. Several important parameters influencing the removal of nitrate such as contact time, pH, adsorbent dosage and temperature were explored systematically by batch experiments. Isotherm studies were set up with the following optimum conditions: pH = 5, adsorbent concentration of 1 g L-1, 180 min and 25 degrees C. The results revealed that the adsorption were best fitted to pseudo-second order and simple Elovich kinetics models. Langmuir, Freundlich and linear adsorption models were fitted to describe adsorption isotherms and constants. The isotherm analysis indicated that the adsorption data can be represented by both Freundlich and linear isotherm models. The maximum adsorption capacity (q(m)) was obtained at 55.1, 74.2 and 75.8 mg g(-1) for Zn-H, Ce-H, and Mg-H, respectively. The thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were obtained. From the thermodynamic parameters, it is suggested that the adsorption of nitrate on modified NPs (MNPs) followed the exothermic and spontaneous processes. The obtained results showed that the MNPs were efficient adsorbents for removing nitrate from aqueous media.