Magnetic Graphene Nanoplatelet Composites toward Arsenic Removal

Abstract

Magnetic graphene nanoplatelet composites (MGNCs) decorated with core-shell Fe-Fe 2 O 3 nanoparticles (NPs) have been synthesized using a facile one-pot thermal decomposition method. The graphene nanoplatelets (GNPs) decorated with uniformly dispersed NPs are observed to exhibit a strong magnetization and can be magnetically separated from the liquid mixture by a permanent magnet. These MGNCs demonstrate an effective and efficient adsorption of arsenic(III) in the polluted water due to the increased adsorption sites in the presence of magnetic NPs. The adsorption behavior is well fitted with both Langmuir and Freundlich models, which show a significantly higher adsorption capacity (11.34 mg/g) than the other adsorption values reported on the conventional iron oxide based adsorbents (∼1 mg/g). The results show a nearly complete As(III) removal within 1 ppb. © 2012 The Electrochemical Society. [DOI: 10.1149/2.010201jss] All rights reserved.Manuscript received March 8, 2012. Published July 17, 2012 Arsenic is known for its toxicity and carcinogenicity to human beings, 1-3 the contaminated water with arsenic is becoming a significantly increasing issue in drinking water throughout the world. Longterm exposure to arsenic can cause cancers of the bladder, lungs, skin, kidney, liver and prostate. 4 Arsenic contaminates include both natural and anthropogenic sources. Anthropogenic arsenic pollutants originate from mining and smelting of non-ferrous metals, burning of fossil fuels, usage of arsenic-containing pesticides in the agriculture 5 and arsenic-containing chemicals in the preservation of timber.6 Arsenic can exit in both inorganic and organic forms. In general, inorganic arsenic compounds are more toxic than organic arsenic compounds, and arsenite [As(III)] is considerably more mobile and toxic than arsenate [As(V)].7 Arsenate (i.e., HAsO 4 2− ) is the primary anion in the aerobic surface water and arsenite (i.e., H 3 AsO 3 or H 2 AsO 3 − ) is the primary species in the ground water. The actual valence states and chemical form, however, depend on the redox environments in the water systems including pH, oxidation-reduction potential, and the presence of complexing ions. There are several requirements that need to be met for arsenic removal such as safe and easy operation, high efficiency and low cost.7 Compared to the conventional water treatment techniques including oxidation/precipitation, 21 membrane/reverse osmosis, coagulation/coprecipitation, 22 and ion exchange, 7 adsorption has the following advantages. For example, it does not need a large volume or additional chemicals for treatment and it is easier to be deployed * Electrochemical Society Active Member.z E-mail: suying.wei@lamar.edu; zhanhu.guo@lamar.edu as a Point of Entry/Point of Use (POE/POU) arsenic removal process. Moreover, adsorption processes produce no sludge as met in the coagulation approach 7 and it does not need a strict control of pH values as met in the oxidation process.23 Adsorption can be dealt with low cost medium, low-tech operatio...

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