Adsorption of Ammonium Ions onto ACTF-Coated Silica Nanoparticles in Comparison with Reduced Graphene Oxide and Studying Its Equilibrium, Kinetics and Thermodynamics

摘要

The graphene materials are important for potential environmental applications due to their distinct adsorption characters. The considerable aggregation that may occur in graphene nanosheets decreases their powerful adsorption capacity and diminishes their practical applications. Toovercome this surface problem, graphene coated with some materials like silica nanoparticles ([email?protected]2) is employed. The ammonium ions adsorption onto graphene oxide- and amorphous carbon thin film ACTF-coated ([email?protected]2) materials was investigated using batch experimentstechnique. The results indicate obtained of ammonium adsorption onto hydrophilic graphene oxide displayed the lowest adsorption capacity. Meanwhile ammonium adsorption onto the reduced graphene oxide is considerably increased due to the availability of hydrophobic π-conjugated carbonatoms as active sites. The found high adsorption of ammonium onto reduced graphene oxide than on graphene oxide nano-sheets may be attributed to the greater numbers of defect sites in the first form. The microscopic morphology of ACTF is loosed when wrapped around the surface of silica particles.Consequently the porous and the hydrophilic surface of the silica particles become hydrophobic. It acquires an additional π-electron-conjugated structure, resulting in the highest affinity. The ammonium removal efficiency of the prepared [email?protected]2 and [email?protected]2nanocomposites increases with increasing initial ammonium concentration and with the loading amounts of the prepared nanocomposites. The adsorption isotherm results indicated that the Freundlich model provided the best fit for the equilibrium data with respect to [email?protected]2 and theLangmuir model provided the best fit for [email?protected]2. The adsorption process was found to be endothermic, as confirmed by the negative sign of the enthalpy (ΔHo).