Xiaojiao Wang

Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment

Magnetic chitosan and graphene oxide-ionic liquid (MCGO-IL) composites as biodegradable biosorbents were synthesized by impregnating MCGO with ionic liquid. The characteristic results of FTIR, SEM, and XRD showed that MCGO-IL were successfully prepared with large surface area and good magnetic responsiveness. They were used for the removal of Cr(VI) from simulated wastewater with a fast solid-liquid separation in the presence of external magnetic field. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, contact time, and initial ion concentration were studied in detail. The adsorption followed a pseudo-second-order kinetics. The equilibrium adsorption was well-described by the Langmuir isotherm mode and the maximum adsorption capacity was 145.35 mg/g. The stronger intermolecular hydrogen bond between MCGO-IL and Cr(VI) and the hydroxyl and amine groups were believed to be the metal ion binding sites. Moreover, the MCGO-IL could be repeatedly used by simple treatment without obvious structure and performance degradation. The obtained results indicated that the impregnation of the room temperature IL significantly enhances the removal efficiency of Cr(VI). The MCGO-IL may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.

Electrochemical sensor based on magnetic graphene oxide@gold nanoparticles-molecular imprinted polymers for determination of dibutyl phthalate

A novel composite of magnetic graphene oxide @ gold nanoparticles-molecular imprinted polymers (MGO@AuNPs-MIPs) was synthesized and applied as a molecular recognition element to construct dibutyl phthalate (DBP) electrochemical sensor. The composite of MGO@AuNPs was first synthesized using coprecipitation and self-assembly technique. Then the template molecules (DBP) were absorbed at the MGO@AuNPs surface due to their excellent affinity, and subsequently, selective copolymerization of methacrylic acid and ethylene glycol dimethacrylate was further achieved at the MGO@AuNPs surface. Potential scanning was presented to extract DBP molecules from the imprinted polymers film rapidly and completely. As a consequence, an electrochemical sensor for highly sensitive and selective detection of DBP was successfully constructed as demonstration based on the synthesized MGO@AuNPs-MIPs composite. Under optimal experimental conditions, selective detection of DBP in a linear concentration range of 2.5 × 10(-9)-5.0 × 10(-6)mol/L was obtained. The new DBP electrochemical sensor also exhibited excellent repeatability, which expressed as relative standard deviation (RSD) was about 2.50% for 30 repeated analyses of 2.0 × 10(-6)mol/L DBP.

Removal of Pb(2+) from water environment using a novel magnetic chitosan/graphene oxide imprinted Pb(2+).

A novel, magnetic chitosan coating on the surface of graphene oxide was (Pb-MCGO) successfully synthesized using Pb(2+) as imprinted ions for adsorption and removal of Pb(2+) from aqueous solutions. The magnetic composite bioadsorbent was characterized by SEM, FTIR and XRD measurements. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity and reusability. The results showed that the maximum adsorption capacity was 79 mg/g, observed at pH 5 and 303K. Equilibrium adsorption was achieved within 40 min. The kinetic data could be fitted with a pseudo-second order equation. Adsorption process could be well described by Langmuir adsorption isotherms. The selectivity coefficient of Pb(2+) and other metal cations onto Pb-MCGO indicated an overall preference for Pb(2+), which was much higher than non-imprinted MCGO beads. Moreover, the sorbent was stable and easily recovered, the adsorption capacity was about 90% of the initial saturation adsorption capacity after being used five times.

Adsorption property of Cr(VI) on magnetic mesoporous titanium dioxide–graphene oxide core–shell microspheres

Novel Fe3O4@mTiO2@GO microspheres for the fast removal of Cr(VI) were synthesized by immobilizing a mesoporous TiO2 shell on the surface of magnetic Fe3O4 nanoparticles prior to binding with GO. The characterization results from FTIR, SEM, VSM and XRD showed that Fe3O4@mTiO2@GO was successfully prepared with a large surface area and good magnetic responsiveness. It was shown that the sorption of the microspheres for Cr(VI) was strongly dependent on pH value and contact time. As Cr-removal adsorbents, the maximum Cr-removal capability of microspheres was 117.94 mg g−1. The equilibrium adsorptions were well-described by the Freundlich isotherm mode and its kinetics followed pseudo-second-order rate equation. Moreover, the Fe3O4@mTiO2@GO microspheres could be regenerated and used repeatedly by simple treatment without obvious structure and performance degradation. These results demonstrated the potential applications of Fe3O4@mTiO2@GO microspheres in the efficient Cr-removal from wastewater and purification of polluted water.

Based on magnetic graphene oxide highly sensitive and selective imprinted sensor for determination of sunset yellow

A new imprinted material based on β-cyclodextrin/ionic liquid/gold nanoparticles functionalized magnetic graphene oxide has been successfully synthesized and modified to the glassy carbon electrode surface to constructed imprinted electrochemical sensor to detect sunset yellow. The sensitivity and electrochemical response of the electrode can be improved by nanomaterials. The surface morphology and crystal structure of the hybrid nanomaterial has been characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy. The electrochemical behaviors of the hybrid nanomaterials based sensor were evaluated through cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized conditions, the proposed electrochemical sensor showed a fast rebinding dynamics, which was successfully applied to sunset yellow detection with a wide linear range from 5.0×10(-9) to 2.0×10(-6)mol L(-1) and a detection limit of 2.0×10(-9)mol L(-1). The electrochemical sensor has been successfully applied in the determination of SY in spiked water samples, mirinda drink and minute maid, and the recoveries for the standards added are 97-105%.

A sensitive and selective chemiluminescence sensor for the determination of dopamine based on silanized magnetic graphene oxide-molecularly imprinted polymer.

Based on silanized magnetic graphene oxide-molecularly imprinted polymer (Si-MG-MIP), a sensitive and selective chemiluminescence sensor for dopamine measurement was developed. Si-MG-MIP, in which silanes was introduced to improve the mass transfer, graphene oxide was employed to improve absorption capacity, Fe3O4 nanoparticles were applied for separation easily and molecularly imprinted polymer was used to improve selectivity, demonstrated the advantages of the sensor. All the composites were confirmed by SEM, TEM, XRD and FTIR. Under the optimal conditions of chemiluminescence, dopamine could be assayed in the range of 8.0-200.0 ng/mL with a correlation coefficient of linear regression of 0.9970. The detection limit was 1.5 ng/mL (3δ) and the precision for 11 replicate detections of 80.0 ng/mL dopamine was 3.4% (RSD). When the sensor was applied in determining dopamine in actual samples, recovery ranged from 94% to 110%, which revealed that the results were satisfactory.

Multiwalled carbon nanotubes-doped polymeric ionic liquids coating for multiple headspace solid-phase microextraction

Multiple headspace solid-phase microextraction (SPME) has proved high efficiency in analysis of volatile compounds in complex samples. Fibers used in multiple headspace SPME must provide a logarithm relationship between peak areas and extraction times. The aim of this work was to investigate the potential of a carbon nanotube doped-polymeric ionic liquid (PILs) fiber for multiple headspace SPME of 2-naphthol in fruit samples, using gas chromatography (GC) for analysis. Based on theory of multiple headspace SPME, β parameters of fruit and aqueous samples were obtained and used for quantitation. The interference effects of sample matrix on proposed multiple headspace SPME method were investigated and compared with that of headspace SPME by determination of significant differences (P) of peak areas. It showed high independence from matrix effects. The proposed multiple headspace SPME-GC method also exhibited high repeatability (relative standard deviation of 2.56%) and recoveries (81.9-110%) for the analysis of real samples.

Graphene coating bonded onto stainless steel wire as a solid-phase microextraction fiber.

A graphene coating bonded onto stainless steel wire was fabricated and investigated as a solid-phase microextraction fiber. The coating was characterized by scanning electron microscopy and energy-dispersive X-ray spectrometer. The coating with rough and crinkled structure was about 1 μm. These characteristics were helpful for promoting extraction. Using five n-alkanes (n-undecane, n-dodecane, n-tridecane, n-tetradecane and n-hexadecane) as analytes, the fiber was evaluated in direct-immersion mode by coupling with gas chromatography (GC). Through optimizing extraction and desorption conditions, a sensitive SPME-GC analytical method was established. SPME-GC method provided wide linearity range (0.2-150 μg L(-1)) and low limits of determination (0.05-0.5 μg L(-1)). It was applied to analyze rain water and a soil sample, and analytes were quantified in the range of 0.85-1.96 μg L(-1) and 0.09-3.34 μg g(-1), respectively. The recoveries of samples spiked at 10 μg L(-1) were in the range of 90.1-120% and 80.6-94.2%, respectively. The fiber also exhibited high thermal and chemical stability, due to the covalent bonds between graphene coating and wire, and the natural resistance of graphene for thermal, acid and basic conditions.

Dicationic imidazolium ionic liquid modified silica as a novel reversed‐phase/anion‐exchange mixed‐mode stationary phase for high‐performance liquid chromatography

A dicationic imidazolium ionic liquid modified silica stationary phase was prepared and evaluated by reversed-phase/anion-exchange mixed-mode chromatography. Model compounds (polycyclic aromatic hydrocarbons and anilines) were separated well on the column by reversed-phase chromatography; inorganic anions (bromate, bromide, nitrate, iodide, and thiocyanate), and organic anions (p-aminobenzoic acid, p-anilinesulfonic acid, sodium benzoate, pathalic acid, and salicylic acid) were also separated individually by anion-exchange chromatography. Based on the multiple sites of the stationary phase, the column could separate 14 solutes containing the above series of analytes in one run. The dicationic imidazolium ionic liquid modified silica can interact with hydrophobic analytes by the hydrophobic C6 chain; it can enhance selectivity to aromatic compounds by imidazolium groups; and it also provided anion-exchange and electrostatic interactions with ionic solutes. Compared with a monocationic ionic liquid functionalized stationary phase, the new stationary phase represented enhanced selectivity owing to more interaction sites.

The preparation of novel adsorbent materials with efficient adsorption performance for both chromium and methylene blue

The hydroxy-functionalized ionic liquids (ILs) modified with magnetic chitosan/grapheneoxide (MG-ILs-OH) were synthesized. The surface morphology of MG-ILs-OH was characterized by transmission electron microscopy, X-ray diffraction, thermo gravimetric analysis and Fourier transform infrared spectroscopy techniques. It was found that the adsorption kinetics is well fitted by a pseudo-second-order model and the adsorption isotherms agree well with the Langmuir model, and the MG-ILs-OH could be repeatedly used by simple treatment. The results showed that the addition of ILs-OH can largely increase the adsorption sites (hydroxy and amino groups) and adsorption properties. The MG-ILs-OH were used as adsorbent for the removal of methylene blue (MB) and Cr(VI) from simulated wastewater with a fast solid-liquid separation in the presence of external magnetic field. The maximum obtained adsorption capacities of MB and Cr(VI) were 243.31 and 107.99 mg/g, respectively. The application of MG-ILs-OH could effectively solve the problem that the adsorbent only adsorb similar adsorbate.