Preparation And Extraction Performance Of Graphene Composite Materials

Graphene(G) possesses extraordinary properties, including, ultrahigh specific area, hydrophobicity, stability physical and chemical properties and large delocalized π-electron system, which makes it promises to be a good adsorbent material in separation and analysis field. However, G sheets tend to form irreversible agglomerates through van der Waals and π-π interactions, which make it difficult to disperse in water or organic solvents. G can possess other new properties and will have wide application through functionalization. In this article, G functional composites were systhesized and theirs extraction performance for organic pollutants in the environment sample were also described.1-vinyl-3-hexylimidazolium bromide ionic liquid was attached onto graphene oxide sheets through the electrostatic interaction between ionic liquid and graphene oxide. After polymerization and reduction, a poly(ionic liquid)-stabilized G composite material(Poly(VHIm+Br-)-G) was obtained and was characterized by fourier transform infrared spectroscopy, scanning electron microscope and ultraviolet-visible spectroscopy. Poly(VHIm+Br-)-G was firstly used as solid-phase extraction(SPE) adsorbent for extraction and determination of organophosphorus pesticides(OPPs) in environmental water. The factors that effected the extraction efficiency of analytes, including adsorbent amount, sample volume, sample flow rate, eluent solvent and its volume, addition of NaCl were optimized. Combined with HPLC method, good linearity for OPPs was obtained in a range of 5-200 μg L-1 with correlation coefficients(r2) of 0.9908-0.9995. The recoveries of OPPs at three spiked levels ranged from 80.0% to 110.0% with RSD less than 4.5%. In comparison with G, Poly(VHIm+Br-)-G materials as SPE adsorbent could enhance the dispersion of G and exhibited higher extraction efficiency for OPPs. Poly(VHIm+Br-)-G-SPE-HPLC-UV was suitable for the determination of OPPs in environmental water samples.A three-dimensional graphene-based magnetic composite(3D-G-Fe3O4) was synthesized through the synergistic effects of the self-assembly of graphene oxide sheets and in situ simultaneous deposition of Fe3O4 particles on G sheets induced by ferrous ions as a reducing agent to reduce the graphene oxide sheets under alkaline condition. 3D-G-Fe3O4 was characterized by fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis and the analysis of nitrogen adsorption-desorption and pore size. 3D-G-Fe3O4 was usd as magnetic solid-phase extraction(MSPE) adsorbent for extraction and determination of naphthalene, biphenyl, phenanthrene and anthracene in environmental water. The factors that effected the extraction efficiency of analytes, including adsorbent amount, sample volume, adsorbent time, desorption solvent and its volume, addition of NaCl were optimized. Combined with HPLC method, good linearity for naphthalene, biphenyl, phenanthrene and anthracene was obtained in a range of 0.1-40 μg L-1, 0.05-20 μg L-1, 0.6-100 μg L-1 and 0.2-40 μg L-1, respectively, with correlation coefficients(r2) of 0.9994-0.9997. The recoveries of PAHs at different spiked levels ranged from 84.2% to 107.0% with RSD less than 5.8%. Compared with some other reported methods for the determination of PAHs, the proposed method demonstrated good repeatability and wide linear range, less adsorption amount and quick. It turned out that 3D-G-Fe3O4-MSPE-HPLC-UV was suitable for the determination of PAHs in environmental water samples.In order to further explore the 3D-G-Fe3O4 adsorption efficiency and the adsorption mechanism for different types of analytes, it was used as MSPE adsorbent for adsorption and determination of polycydic aromatic hydrocarbon(naphthalene, phenanthrene, fluoranthene), carbamate pesticide(1-naphthalenyl, fenobucarb, isoprocarb) and phenols(p-Nitrophenol, α-Naphthol, bisphenol A) in aqueous solution, meanwhile, the isotherms and kinetics parameters of the adsorbents were evaluated. Research showed that the distinct interactions of different analytes with the active sites result in different adsorption behaviors. 1-naphthalenyl, p-nitrophenol, α-naphthol and bisphenol A were fitted to Langmuir isotherm model, while fenobucarb, isoprocarb, naphthalene, phenanthrene and fluoranthene were fitted to Freundlich isotherm model. The adsorption processes of all analytes were followed pseudo-second order kinetics model.