Laser synthesis of magnetite-partially reduced graphene oxide nanocomposites for arsenate removal from water

Herein, we report the development of a facile process for the synthesis of magnetite-partially reduced graphene oxide (Mag-PRGO) without the use of chemical reducing agents or solvents for the efficient removal of arsenate As(V) ions from contaminated water. The Mag-PRGO is synthesized using the laser vaporization-controlled condensation method where a compressed target consisting of metallic iron (Fe) powder and solid graphene oxide (GO) is laser vaporized in an O 2 –He atmosphere resulting in the simultaneous oxidation of the Fe nanoparticles and the partial reduction of the GO to form the Mag-PRGO nanocomposite where the magnetic Fe 3 O 4 nanoparticles are anchored to the surface of the PRGO nanosheets. FTIR, Raman, XPS, XRD, TEM, and SEM confirm the successful attachment of the magnetic Fe 3 O 4 nanoparticles to the PRGO nanosheets. The Mag-PRGO (50 wt% Fe) adsorbent shows exceptional selectivity for the extraction of As(V) ions with a capacity of 132 mg/g with no leaching of Fe ions into the solution, placing it among the best carbon-based materials for the efficient removal of As(V) from aqueous solutions. The Mag-PRGO displays a 100% removal of As(V) at concentrations up to 100 ppm with 98% and 100% removal within 15 min and 30 min, respectively, at 50 ppm concentration. The excellent agreement of the experimental sorption isotherms with the Langmuir model suggests a monolayer adsorption behavior. The mechanism of As(V) removal is based on surface complexation between the protonated hydroxyl groups on the surface of Mag-PRGO and the monobasic and dibasic arsenate anions forming (Fe–O–As) bonds as confirmed by FTIR and XPS. The Mag-PRGO is easily regenerated with the desorption of the As(V) ions reaching 99% from their maximum sorption capacities using NaOH. The efficient magnetic separation and high chemical stability of Mag-PRGO are demonstrated over six adsorption–desorption cycles of As(V). The Mag-PRGO is proposed as an excellent remediation adsorbent for the extraction of As(V) from contaminated water.