||I. Combined Tween 20-stabilized Gold Nanoparticles and Reduced Graphite Oxide-Fe3O4 |
Nanoparticle Composites for Rapid and Efficient Removal of Mercury Species in
This study describes a simple method for removing mercuric ions (Hg2+) from a high-salt matrix based on the use of Tween-20-stabilized gold nanoparticles (Tween 20-Au NPs) as Hg2+ adsorbents and composites of reduced graphite oxide and Fe3O4 NPs as NP collectors. Citrate ions adsorbed on the surface of the Tween 20-Au NPs reduced Hg2+ to Hg0, resulting in the deposition of Hg0 on the surface of the NPs and the formation of an Au–Hg amalgam. To circumvent time-consuming centrifugation and transfer steps, the Hg0-containing gold NPs were collected using reduced graphite oxide-Fe3O4 NP composites. Compared with the reported NP-based methods for removing Hg2+, Tween 20-Au NPs offered the rapid (within 30 min), efficient (> 99% elimination efficiency), durable (> 10 cycles), and selective removal of Hg2+, CH3Hg+, and C2H5Hg+ in a high-salt matrix, without the interference of other metal ions. This was attributed to the fact that the Tween 20-Au NPs were dispersed in a high-salt matrix, providing them with large surface to volume ratio to interact with Hg2+. The formation of graphite oxide sheets and reduced graphite oxide-Fe3O4 NP composites was demonstrated using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectrometry, and/or transmission electron microscopy. The mechanism of interaction between Tween 20-Au NPs and Hg2+ was studied using visible spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy.
II. Synthesis of Ruduced Graphite Oxide-Fe3O4 Nanoparticle Composites for Rapid
Removal of Environmental Contaminants:(1)Methylene blue; (2)Bisphenol A; (3)Oil;
Developing of a rapid, simple, efficient method for removing methylene blue, bisphenol A, oil and arsenic ion from aqueous media using reduced graphite oxide-Fe3O4 nanoparticle composites. The nanocomposites with both magnetic and good adsorption capacity have been one-pot synthesized via PDDA-modified and coprecipitation process. Here we demonstrated the potential environmental engineering application of this nanocomposite by taking organic dye and emerging contaminants, methylene blue and bisphenol A, as our model system. Methylene blue and bisphenol A are heterocyclic aromatic chemical compound, and adsorb on the surface of ruduced Graphite Oxide-Fe3O4 nanoparticle composites through strongly π-π interaction between aromatic ring structure and sp2 orbital. Reduced graphite oxide-Fe3O4 nanoparticle composites with hydrophobic but oleophilic coating, such as reduced graphite oxide, a selectivity oil-adsorbing material capable of floating on sea water is achieved. Because of the low density and the ability to absorb nonpolar liquids and oils, the nanomaterials allow to collect organic contaminants from the water surface. The hybrids show a high binding capacity for As(III) and As(V), whose presence in the drinking water in wide areas of South Asia has been a huge problem. The formation of As-Fe complex lead to a deposition of arsenic ion on the surface of nanocomposites. Their high binding capacity is due to the increased adsorption sites in the RGO-Fe3O4 NPs composites which occur by reducing the aggregation of bare magnetite. Since the composites show near complete (over 98.0%) arsenic removal within 10 μM, they are practically usable for arsenic separation from environmental water.