Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg 2+ removal
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NANO EXPRESS
Open Access
Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg2+ removal Jian Bao1*, You Fu2 and Zhihao Bao2*
Abstract A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction. It exhibited a higher adsorption capacity compared to the bare graphene oxide and MGO due to the combined adsorption of thiol groups and magnetite nanocrystals. Its capacity reached 289.9 mg g−1 in a solution with an initial Hg2+ concentration of 100 mg l−1. After being exchanged with H+, the adsorbent could be reused. The adsorption of Hg2+ by the thiol-functionalized MGO fits well with the Freundlich isotherm model and followed pseudo-second-order kinetics. Keywords: Mercury ion; Magnetite; Adsorption capacity; Graphene oxide; Hybrid
Background Due to the development and expansion of industry, pollution of heavy metals in water supplies increases in the recent years. The pollution is seriously threatening the ecological systems as well as human health. Among them, mercury is one of the most hazardous elements due to its toxicological and biogeochemical behavior [1,2]. A lot of adsorbents have been employed to extract Hg2+ from the industrial wastewaters. For example, thiol-functionalized adsorbents exhibited a specific binding capability toward highly toxic heavy metal ions including Hg2+ due to the existence of the thiol groups [3-6]. While for iron oxides, their adsorption mechanism was attributed to the complexation of Hg2+ and surface hydroxyl group at the iron oxide/water interface [7-9]. Iron oxide nanocrystals can further enhance the adsorption capacities because of their high specific surface area [6,10]. Another advantage of using iron oxide-based adsorbents is that they can be easily extracted from wastewater by applying an external magnetic force. However, few research works have reported on adsorbents with both adsorption effects. The emergence of graphene oxide makes such combination possible due to its abundant functional moieties (hydroxyl and carboxyl groups)
[11,12], which enable possible metal oxide deposition and functional organic group grafting on its surface [13-15]. In this work, we deposited Fe3O4 nanoparticles on graphene oxide and then grafted thiol groups on the Fe3O4/graphene oxide (MGO). The thiol-functionalized MGO exhibited relatively high Hg2+ adsorption capacity. The adsorbent could be separated from the water solutions easily and reused after it was exchanged with H+.
Methods Chemicals and materials
Natural graphite (500 mesh), 98 wt.% H2SO4, 5 wt.% HCl aqueous solution, 30 wt.% H2O2 aqueous solution, acetone, and Na2CO3 were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). 1-Methyl-2-pyrrolidone (NMP), ferric acetylacetonate (Fe(acac)3), potassium permanganate (KMnO4), NaHCO3, 1-ethy-3-(3-dimethyllaminopropyl) carvodiimide hydrochloride (EDC), and 2mercaptoethylamine (MEA) were purchased from Aladdin Reagent Company (Shanghai, China). Other reagents use
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