Synthesis of Three-Dimensional Fe3O4/Graphene Aerogels for the Removal of Arsenic Ions from Water

Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 864864, 6 pages http://dx.doi.org/10.1155/2015/864864 Research Article Synthesis of Three-Dimensional Fe3O4/Graphene Aerogels for the Removal of Arsenic Ions from Water Yan Ye,1 Da Yin,2 Bin Wang,2 and Qingwen Zhang1 1 College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China Institute of Drilling Engineering, South West Petroleum University, Chengdu 610500, China 2 Correspondence should be addressed to Yan Ye; Received 7 April 2015; Revised 7 June 2015; Accepted 8 June 2015 Academic Editor: William W. Yu Copyright © 2015 Yan Ye et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We report the synthesis of three-dimensional Fe3 O4 /graphene aerogels (GAs) and their application for the removal of arsenic (As) ions from water. The morphology and properties of Fe3 O4 /GAs have been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum inference device. The 3D nanostructure shows that iron oxide nanoparticles are decorated on graphene with an interconnected network structure. It is found that Fe3 O4 /GAs own a capacity of As(V) ions adsorption up to 40.048 mg/g due to their remarkable 3D structure and existence of magnetic Fe3 O4 nanoparticles for separation. The adsorption isotherm matches well with the Langmuir model and kinetic analysis suggests that the adsorption process is pseudo-second-ordered. In addition to the excellent adsorption capability, Fe3 O4 /GAs can be easily and effectively separated from water, indicating potential applications in water treatment. 1. Introduction Arsenic’s history in science, medicine, and technology has been overshadowed by its notoriety as a poison in homicides. Arsenate and arsenite contaminants in groundwater threaten ecological balance and human health and result in several diseases such as skin or lung cancer [1]. What is worse, with the intensification of human activities, especially mining activities, combustion of fossil fuels has led to more arsenic species pollute groundwater [2]. Thus the remediation of arsenic pollution by way of adsorption has attracted worldwide attention [3–5]. Compared with other adsorbents, magnetic adsorbents such as Fe3 O4 exhibit unique advantages due to their quick and effective magnetic separation [6, 7]. However, the absorption capacity of most synthesized adsorbents and its efficient magnetic separation are difficult to balance as decreasing magnetic particles size enhances adsorption capacity which would undesirably decrease response to an external magnetic field [8, 9]. Graphene, a two-dimensional atomically thick carbon atom arranged in a honeycomb lattice, has attracted much attention for its potential applications in sensors, catalysis, energy-storage devices, and environmental fields because of its excellent electronic, mechanical, and other properties [10– 15]. Generally, graphite can be oxidized by strong oxidants and easily exfoliated to the formation of graphene oxide (GO) and reduced graphene oxide (RGO) by reductants. The chemical oxidation modification methods generate plenty of oxygen-containing functional groups in GO and RGO, which offer a potential way to produce large scale of graphenebased materials with a low cost [16]. The unique surface property enables GO as an ideal substrate to anchor inorganic nanoparticles (NPs) for many applications, such as lithium ion battery [17] and water purification [11]. GO is employed as a scaffold for modifying metal oxide nanoparticles to improve their adsorption performance for its lateral dimension up to micrometers and thickness under several nanometers [18–20]. Although GAs supported Fe3 O4 NPs (Fe3 O4 /GAs) have been employed for some applications, such as oxygen reduction reaction [21], there are limited reports on the fabrication of Fe3 O4 /GAs as absorbent for removing As ions from water up to now. In this study, 3D Fe3 O4 /GAs have been fabricated through hydrothermal method, which have macroporous framework of graphene sheets with uniform deposition of Fe3 O4 NPs. Three-dimensional (3D) graphene aerogels (GAs) 2 Journal of Nanomaterials 80 60 220 111 222 400 511 440 422 533 40 20 0 Magnetization (emu/g) Magnetization (emu/g) Intensity (a.u.) 311 −20 −40 −60 10 20 30 40 50 2𝜃 (deg) 60 70 80 (a) −80 −20 −10 20 10 0 −10 −20 −100 0 Magnetic field (kOe) 50 0 −50 Magnetic field (Oe) 10 100 20 (b) Figure 1: (a) XRD pattern of Fe3 O4 /GAs and (b) the magnetization hysteresis loops of Fe3 O4 /GAs. with interconnected mesoporous network, allowing access and diffusion of ions and molecules, seem to be a good candidate as support for iron oxide Fe3 O4 NPs. It was found that Fe3 O4 /GAs as self-supported structured adsorbent show excellent capability of removal of As(V) ions in water treatment. Additionally, our results have confirmed that Fe3 O4 /GAs can be easily removed from water by magnetic separation. 2. Experimental GO was synthesized using the modified Hummers method [22]. Briefly, 0.5 g of graphite powder and 3 g of potassium permanganate were placed in a 250 mL flask; 60 mL of concentrated sulfuric acid and 6.6 mL of concentrated nitric acid were slowly dropped into the flask under stirring for 12 h at 60∘ C. Then the mixture was diluted with 0.5 L of deions (DI) water, and excessive 15 mL of hydrogen peroxide (30 wt%) was dumped into the mixture to make bright yellow solution in an ice bath. After repeated centrifugation until neutral (pH = 7) with excessive deionized water (DI), graphite oxide was obtained. Exfoliation of graphite oxide to graphene oxide was achieved by ultrasonication. Then 150 mg of FeC2 O4 ⋅2H2 O was added to 35 mL of 2.0 mg⋅mL−1 GO suspension under magnetic stirring for 0.5 h. The stable suspension was sealed in a 50 mL telfon-lined autoclave and hydrothermally treated at 180∘ C for 12 h and subsequently freeze-dried for 12 h. Finally, after thermal treatment at 600∘ C for 5 h in Ar gas with 400 sccm, 3D Fe3 O4 /GAs were obtained. The structure and surface morphology of Fe3 O4 /GAs were investigated by X-ray diffraction (XRD), FEI Quanta 200F scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Tecnai G2 F20 transmission electron microscopy (TEM) equipped with selected area electron diffraction (SAED) patterns and scanning TEM (STEM). The adsorption capability of Fe3 O4 /GAs for As(V) ions from water was performed at room temperature. Firstly, individual stock solutions of 1000 mg⋅L−1 and 100 mg⋅L−1 As(V) ions were prepared by dissolving Na2 HAsO4 ⋅7H2 O in deionized water, respectively. Fe3 O4 /GAs equivalent to 2 mg of aerogels were added into 10 mL of As(V) co (...truncated)