The efficient adsorption removal of Cr(vi) by using Fe<inf>3</inf>O<inf>4</inf>nanoparticles hybridized with carbonaceous materials

• Key Words:Chromium compounds;Adsorption - Adsorption isotherms - Carbonaceous adsorbents - Desorption - Dyes - Effluents - Graphene - Heavy metals - Iron oxides - Magnetite - Nanocomposites - Nanoparticles - Scanning electron microscopy - Sewage - Solutions - Synthesis (chemical) - X ray diffraction;Adsorption capacities - Adsorption performance - Adsorption-desorption process - Carbonaceous materials - Instantaneous adsorption - Intra-particle diffusion - Langmuir isotherm models - Pseudo second order kinetics
• Abstract:Fe<inf>3</inf>O<inf>4</inf>nanoparticles hybridized with carbonaceous materials, such as pinecone and graphene, were successfully synthesized by a facile hydrothermal method, which could be applied for Cr(vi) removal in aqueous solution. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N<inf>2</inf>adsorption-desorption isotherms. Due to the combination of pinecone and graphene, both the surface properties and morphologies of Fe<inf>3</inf>O<inf>4</inf>were modified. Fe<inf>3</inf>O<inf>4</inf>spherical particles were distributed and firmly anchored on the loose surface of pinecone or wrinkled graphene layers. The specific surface area increased from 23.85 to 27.86 and 121.17 m²g^-1for Fe<inf>3</inf>O<inf>4</inf>/P and Fe<inf>3</inf>O<inf>4</inf>/G, respectively. It enhanced the adsorption capacity for Cr(vi) of Fe<inf>3</inf>O<inf>4</inf>/P (62.5 mg g^-1) and Fe<inf>3</inf>O<inf>4</inf>/G (78.5 mg g^-1). Study of the kinetics and isotherms showed that the pseudo-second-order kinetic and Langmuir isotherm models fitted the adsorption data well. There were three steps in the adsorption process, namely an instantaneous adsorption step, intraparticle diffusion and a final equilibrium stage. The reaction rate decreased along with temperature increasing, which indicated that Cr(vi) adsorption was an exothermic process. The E<inf>a</inf>values were 34.39, 25.77 and 34.92 kJ mol^-1for Fe<inf>3</inf>O<inf>4</inf>, Fe<inf>3</inf>O<inf>4</inf>/P and Fe<inf>3</inf>O<inf>4</inf>/G, respectively, which illustrated that the adsorption of Cr(vi) onto the surface of the nanocomposites was a physical process. In no more than 5 h, about 92.6% and 94% Cr(vi) were desorbed from the surface of Fe<inf>3</inf>O<inf>4</inf>/P and Fe<inf>3</inf>O<inf>4</inf>/G, respectively, which indicated that the adsorption-desorption process for Cr(vi) was reversible. The results demonstrated that Fe<inf>3</inf>O<inf>4</inf>/P and Fe<inf>3</inf>O<inf>4</inf>/G exhibited excellent adsorption performance in the removal of Cr(vi). It was proved that carbonaceous materials, such as pinecone or graphene, could enhance the adsorption performance of Fe<inf>3</inf>O<inf>4</inf>, and could be used as adsorbents to remove heavy metals in industrial effluents.<br/> &copy; The Royal Society of Chemistry 2015.
• Volume:5
• Issue:74
• Translation or Not:no