Removal of Cr(III) and Cu(II) from aqueous solution by fulvic acid functionalized magnetite nanoparticles

Novel Fe3O4 nanoparticles coated with fulvic acid (FA-Fe3O4) were developed to remove selected metals (Cr3+ and Cu2+) from water. Taking advantage of the chelation between the functional groups of FA and iron, FA-Fe3O4 nanoparticles were synthesized via the chemical coprecipitation method. The multiple characterizations indicated that FA was successfully bonded onto Fe3O4 through carboxyl and carbonyl, with a stable performance. It was demonstrated that nanoscale material with an average size of 15 nm and a specific surface area of 55.16 m(2)/g was obtained through scanning electron microscopy and Brunauer-Emmett-Teller characterization. The adsorption experiments indicated that the adsorption capability for Cr3+ and Cu2+ were 11.59 and 3.44 mg/g and the removal of metals were enhanced with increasing pH. The Freundlich model was adopted to depict the isotherms. The kinetic constants with pseudo-second-order model were 0.056 and 0.232 g/(mg.min), respectively, obtained from adsorption of Cr3+ and Cu2+. The thermodynamic analysis results demonstrated that the adsorption mechanism for Cr3+ and Cu2+ using FA-Fe3O4 was endothermic and spontaneous. Based on the excellent reusability of FA-Fe3O4, this study demonstrates a novel method for environmentally friendly removal of aquatic metals, with easier separation.