Xinman Tu

Removal of water-soluble acid dyes from water environment using a novel magnetic molecularly imprinted polymer

Novel magnetic and hydrophilic molecularly imprinted polymers (mag-MIPs) were prepared by an inverse emulsion-suspension polymerization to remove water-soluble acid dyes from contaminated water with 1-(α-methyl acrylate)-3-methylimidazolium bromide (1-MA-3MI-Br) being utilized as a new functional monomer. The thermal stability, chemical structure and magnetic property of the 1-MA-3MI-Br-mag-MIPs were characterized by the thermal-gravimetric analyzer (TGA), Fourier transform infrared spectrometer (FT-IR) and vibrating sample magnetometer (VSM), respectively. Moreover, effect of concentration and pH value of water-soluble acid dye solutions was optimized. Compared with the methyl acrylic acid and 4-vinylpyridine modified mag-MIPs, the 1-MA-3MI-Br-mag-MIPs showed enhanced removal efficiency. Kinetic studies depicted that the adsorption process on 1-MA-3MI-Br-mag-MIPs followed pseudo-second-order rate mechanism. Investigation results of 5 times removal-regeneration cycles by employing the 1-MA-3MI-Br-mag-MIPs showed that the resulting material was with high stability.

Novel Cu (II) magnetic ion imprinted materials prepared by surface imprinted technique combined with a sol–gel process

A novel Cu (II) magnetic ion-imprinted polymer (MIIP) was synthesized by surface imprinting technique combined with a sol-gel process. The adsorbent of Cu (II)-MIIP shows higher capacity and selectivity than that of magnetic non-imprinted polymers (MNIP). Adsorption capacities of Cu (II)-MIIP and MNIP are 24.2 and 5.2mg/g for Cu (II) ions, respectively. The selectivity coefficients of the Cu (II)-MIIP for Cu (II)/Zn (II) and Cu (II)/Ni (II) are 91.84 and 133.92, respectively. Kinetics studies show that the adsorption process obeys pseudo-second-order rate mechanism with an initial adsorption rate of 132.48 for Cu (II)-MIIP and 2.41mgg(-1)min(-1) for MNIP. In addition, no obvious decrease was observed after up to five adsorption cycles, indicating that the Cu (II)-MIIP is of high stability.

Novel molecularly imprinted polymer using 1-(α-methyl acrylate)-3-methylimidazolium bromide as functional monomer for simultaneous extraction and determination of water-soluble acid dyes in wastewater and soft drink by solid phase extraction and high performance liquid chromatography

Novel water-compatible molecularly imprinted polymers were synthesized in methanol-water systems with Tratarzine as template and 1-(α-methyl acrylate)-3-methylimidazolium bromide (1-MA-3MI-Br) as functional monomer, which has π-π hydrophobic, hydrogen-bonding and electrostatic interactions with template molecule. 1-MA-3MI-Br molecularly imprinted polymers (1-MA-3MI-Br-MIPs) were used as selective sorbents for the solid-phase extraction (SPE) of water-soluble acid dyes from wastewater and soft drink. The good linearity of the method was obtained in a range of 5.0-2000 μg/L with the correlation coefficient of > 0.999. The detection limits were in a range of 0.13-0.51 μg/L for the water-soluble acid dyes in wastewater and 0.095-0.84 μg/L for those in soft drink. The mean recoveries for the acid dyes are from 89.1% to 101.0% in spiked wastewater and 91.0-101.3% in spiked soft drink. Compared with strongly anion exchange solid phase extraction (SAX-SPE), mixture anion exchange solid phase extraction (MAX-SPE), and 1-MA-3MI-Br non-imprinted solid phase extraction (1-MA-3MI-Br-NISPE), almost all of the matrix interferences were removed by 1-MA-3MI-Br-MISPE, exhibiting higher selectivity, recovery and enrichment ability for the acid dyes and better baselines in the results of HPLC analysis.

Determination of malachite green in fish water samples by cloud‐point extraction coupled to cation‐selective exhaustive injection and sweeping‐MEKC

We have employed a high‐sensitivity off‐line coupled with on‐line preconcentration method, cloud‐point extraction (CPE)/cation‐selective exhaustive injection (CSEI) and sweeping‐MEKC, for the analysis of malachite green. The variables that affect CPE were investigated. The optimal conditions were 250 g/L of Triton X‐100, 10% of Na2SO4 (w/v), heat‐assisted at 60°C for 20 min. We monitored the effects of several of the CSEI‐sweeping‐MEKC parameters – including the type of BGE, the concentrations of SDS, the injection length of the high‐conductivity buffer, and the injection time of the sample – to optimize the separation process. The optimal BGE was 50 mM citric acid (pH 2.2) containing 100 mM SDS. In addition, electrokinetic injection of the sample at 15 kV for 800 s provided both high separation efficiency and enhanced sweeping sensitivity. The sensitivity enhancement for malachite green was 1.9×104 relative to CZE; the coefficients of determination exceeded 0.9928. The LOD, based on an S/N of 3:1, of CSEI‐sweeping‐MEKC was 0.87 ng/mL; in contrast, when using off‐line CPE/CSEI‐sweeping‐MEKC the sensitivity increased to 69.6 pg/mL. This proposed method was successfully applied to determine trace amounts of malachite green in fish water samples.

Square wave anodic stripping voltammetric determination of Cd2+ and Pb2+ at bismuth-film electrode modified with electroreduced graphene oxide-supported thiolated thionine

Graphene oxide (GO)-thionine (TH) nanocomposite was prepared by π-π stacking. The nanocomposite was cast-coated on a glassy carbon electrode (GCE) to prepare an electroreduced GO (ERGO)-TH/GCE, then 2-mercaptoethanesulfonate (MES) was covalently tethered to ERGO-TH by potentiostatic anodization to form an ERGO-TH-MES/GCE. The thiolation reaction was monitored by electrochemical quartz crystal microbalance (EQCM). Square wave anodic stripping voltammetry (SWASV) was used to determine Cd(2+) and Pb(2+) at the ERGO-TH-MES/GCE further modified with Nafion and Bi. Under the optimal conditions, the linear calibration curves for Cd(2+) and Pb(2+) are from 1 to 40 μg L(-1), with limits of detection (S/N=3) of 0.1 μg L(-1) for Cd(2+) and 0.05 μg L(-1) for Pb(2+), respectively. The electrode was used for the simultaneous analysis of Cd(2+) and Pb(2+) in water samples with satisfactory recovery.

Synthesis of hierarchical flower-like Bi2MoO6 microspheres as efficient photocatalyst for photoreduction of CO2 into solar fuels under visible light

Hierarchical flower-like Bi2MoO6 microspheres were successfully synthesized via a facile hydrothermal approach, employing PVP as the crystal growth modifier. The building units of the hierarchical flower-like Bi2MoO6 were constructed by two-dimensional thin flakes, which intercrossed with each other and aggregated together to form the three-dimensional flower-like structure. The PVP amount and hydrothermal duration played crucial roles in the formation of the Bi2MoO6 architectures with evolving morphologies. The Bi2MoO6 samples were first evaluated for the photocatalytic reduction of CO2 into methanol and ethanol as solar fuels under visible-light irradiation. It has been found that the hierarchical flower-like Bi2MoO6 exhibits highly efficient photocatalytic activity. After 4 hours of irradiation, the yields of methanol and ethanol were 24.8 and 18.8 μmol gcat−1 respectively, higher than those obtained over previously-reported Bi2WO6 hollow microspheres. This demonstrates that the hierarchical flower-like Bi2MoO6 is a simple, efficient and promising visible-light-driven photocatalyst for the photoreduction of CO2 into solar fuels.

Synthesis of Novel Biocompatible Composite Fe3O4/ZrO2/Chitosan and Its Application for Dye Removal

A novel biocompatible composite Fe3O4/ZrO2/chitosan was synthesized in a simple way and its capacity of dye removal was investigated in this study. The morphology of the material was examined by SEM and TEM and found to be nanosized and spheroidal. Equilibrium adsorption isotherms and dynamic behaviors of the adsorption process were investigated in detail. The material saturated with dye could be regenerated by treatment with strong alkali solution. The composite has high adsorption capacity towards acidic dyes represented by amaranth and tartrazine, and remains intact under conditions that are strongly acidic or alkali. The material has high potential to be applied for the removal of acidic dyes in industrial wastewater in large scale.

Direct removal of aqueous As(III) and As(V) by amorphous titanium dioxide nanotube arrays

Amorphous titanium dioxide nanotube arrays (TiO2 NTs) were prepared by a simple anodization process without subsequent calcination at high temperature, and the effectiveness of amorphous TiO2 NTs as adsorbents in removing arsenite (As(III)) and arsenate (As(V)) was investigated. The TiO2 NTs were not only effective for arsenic removal without a pre-oxidation of As(III) to As(V) and/or adjusting the pH value of water before the adsorption process, but also can be separated and recovered easily from the solution. The adsorption kinetics and adsorption capacity of the amorphous TiO2 NTs for As(III) and As(V) were studied separately by batch experiments. The apparent values for Langmuir monolayer sorption capacities were 28.9 mg/g for As(III) and 24.7 mg/g for As(V) at pH 7. Kinetics studies indicated that the adsorption process on TiO2 NTs followed a pseudo-second-order kinetics model. Arsenic adsorption of TiO2 NTs remains stable over a broad pH range. Moreover, the TiO2 NTs have excellent stability and regeneration, and they can be used repeatedly at least five times.

Ultrasonic-assisted facile synthesis of plasmonic Ag@AgCl cuboids with high visible light photocatalytic performance for Rhodamine B degradation

Using amino acids as shape-directing and reducing agents, a plasmonic photocatalyst of Ag@AgCl cuboids is rapidly prepared through a one-step ultrasonic-assisted approach. By controlling the species of amino acid, the Ag0 content on the AgCl surface and surface plasmon resonance (SPR) adsorption of Ag@AgCl can be rationally tailored simultaneously, which are responsible for the excellent photocatalytic activity of Ag@AgCl photocatalysts. Among the as-synthesized Ag@AgCl samples, the Ag@AgCl-Lys synthesized by using L-lysine had the highest Ag0 content and showed the best photocatalytic activity for the degradation of Rhodamine B (RhB) and formic acid (FA) under visible light irradiation. In addition, the Ag@AgCl photocatalyst exhibited good stability and recyclability. After 5 runs, Ag@AgCl-Lys did not have any significant loss of activity. Moreover, the photocatalytic mechanism was investigated by active species-trapping experiments, which shows that the ·O2− is the main reactive species for the degradation of RhB. This study may provide a novel strategy for design and preparation of advanced visible light sensitized photocatalysts.

Application of 1-Alkyl-3-methylimidazolium-Based Ionic Liquids as Background Electrolytes in Nonaqueous Capillary Electrophoresis for the Analysis of Coptidis Alkaloids

Interest in ionic liquids (ILs) for their potential in analytical chemistry is increasing because they are environmentally benign and are good separation solvents. The aim of the presented investigation was to verify whether ILs would be a suitable background electrolyte (BGE) in nonaqueous capillary electrophoresis (NACE) for organic cations analysis of the closely related analogues. In this study, a novel and very simple NACE method has been established for analyzing seven quaternary alkaloids in Coptis rhizome using 1-alkyl-3-methylimidazolium tetrafluoroborate-based ionic liquid as BGE. The effects of the alkyl group, imidazolium counterion (anionic part), along with the concentration of IL, are investigated and discussed. Baseline separation, high efficiencies, and symmetrical peaks of the seven alkaloids were obtained. The separation mechanism could be hydrophobic and hydrogen-bonding interactions between the alkaloids and the imidazolium cations. The optimum conditions were 70 mM 1-decyl-3-methylimidazolium tetrafluoroborate (1D-3MI-TFB) methanol solution (apparent pH 2.66) and 30 kV applied voltage. The detection was performed at 254 nm. Seven quaternary alkaloids in Coptis rhizome were separated within 14 min. The proposed NACE separation procedure is highly reproducible and can be applied in the qualitative and quantitative analysis of Coptidis alkaloids.