Hongxiang Ou

Synthesis of chitosan/γ-Fe2O3/fly-ash-cenospheres composites for the fast removal of bisphenol A and 2,4,6-trichlorophenol from aqueous solutions.

The chitosan/fly-ash-cenospheres/γ-Fe(2)O(3) (CTS/γ-Fe(2)O(3)/FACs) magnetic composites were prepared by microemulsion process. The resulting composites were characterized by XRD, FT-IR, SEM, TGA, DTG and VSM, and the results indicated that CTS/γ-Fe(2)O(3)/FACs exhibited magnetic property (M(s)=6.553 emu g(-1)) and thermal stability, and composed of chitosan wrapping magnetic γ-Fe(2)O(3) and fly-ash-cenospheres (thickness of the cross-linked chitosan was about 5.2 μm). Then the CTS/γ-Fe(2)O(3)/FACs were employed as adsorbents for the fast removal of bisphenol A (BPA) and 2,4,6-trichlorophenol (TCP) from aqueous solutions. The adsorption performances of CTS/γ-Fe(2)O(3)/FACs were investigated by batch mode experiments with respect to pH, temperature, initial concentration, contact time and binary solution system. The Langmuir isotherm model was fitted to the equilibrium data better than the Freundlich model, and the kinetic properties were well described by the pseudo-second-order equation. The effects of binary solution systems also demonstrated that BPA adsorption onto CTS/γ-Fe(2)O(3)/FACs was more affected by the simultaneous presence of competitive phenolic compound than that of TCP. In addition, the resulting composite reusability without obviously deterioration in performance was demonstrated by at least three repeated cycles.

Selective recognition of 2,4,5-trichlorophenol by temperature responsive and magnetic molecularly imprinted polymers based on halloysite nanotubes

Fe3O4/Halloysite nanotube magnetic composites (MHNTs) were firstly prepared via an effective polyol-medium solvothermal method, and then the surface of the MHNTs was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). Based on the MHNTs-MPS, temperature responsive and magnetic molecularly imprinted polymers (t-MMIPs) were further synthesized by adopting methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) as the functional monomer and temperature responsive monomer, respectively. The as-prepared t-MMIPs were characterized by FT-IR, TEM, TGA and VSM, which indicated that the t-MMIPs exhibit magnetic sensitivity (Ms = 2.026 emu g−1), magnetic stability (especially in the pH range of 4.0–8.0) and thermal stability and are composed of an imprinted layer. The molecular interaction between 2,4,5-trichlorophenol (TCP) and MAA was investigated by 1H-NMR spectroscopy and ultraviolet absorption spectroscopy, which suggest that hydrogen bonding may be largely responsible for the recognition mechanism. The t-MMIPs were then applied to selectively recognise and release TCP molecules at 60 °C and 20 °C, respectively. The maximum amount of binding at 60 °C was 197.8 mg g−1 and 122.6 mg g−1 for t-MMIPs and temperature responsive and magnetic non-imprinted polymers (t-MNIPs), respectively. At 20 °C, about 32.3%–42.7% of TCP adsorbed by t-MMIPs was released, whereas 25.3%–39.9% of TCP was released by t-MNIPs. The selective recognition experiments demonstrated the high affinity and selectivity of t-MMIPs towards TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

Acid–chromic chloride functionalized natural clay-particles for enhanced conversion of one-pot cellulose to 5-hydroxymethylfurfural in ionic liquids

By grafting –SO3H and Cr(III) onto the surface of treated attapulgite (ATP) and halloysite nanotubes (HNTs), two acid–chromic chloride bi-functionalized catalysts i.e. ATP–SO3H–Cr(III) and HNTs–SO3H–Cr(III) were successfully synthesized. Then the as-prepared catalysts were characterized by SEM, TEM, EDS, XPS, BET, NH3–TPD, nitrogen adsorption–desorption and TG analysis. The catalytic activities of the synthesized ATP–SO3H–Cr(III) and HNTs–SO3H–Cr(III) were evaluated for the conversion of one-pot cellulose to 5-hydroxymethylfurfural (HMF) in an ionic liquid ([EMIM]-Cl) system. The amount of catalyst, reaction time and reaction temperature were optimized for cellulosic conversion over the two catalysts, resulting in a maximum yield of 31.20% for ATP–SO3H–Cr(III) and 41.22% for HNTs–SO3H–Cr(III) under the optimized conditions. The clay supported catalysts developed in this work showed greatly improved performances in cellulose-to-HMF conversion over other solid catalysts. In addition, the prepared catalysts could be very easily recycled, at least three times for ATP–SO3H–Cr(III) and twice for HNTs–SO3H–Cr(III) without significant loss of activity.

Selective removal of erythromycin by magnetic imprinted polymers synthesized from chitosan-stabilized Pickering emulsion.

Magnetic imprinted polymers (MIPs) were synthesized by Pickering emulsion polymerization and used to adsorb erythromycin (ERY) from aqueous solution. The oil-in-water Pickering emulsion was stabilized by chitosan nanoparticles with hydrophobic Fe3O4 nanoparticles as magnetic carrier. The imprinting system was fabricated by radical polymerization with functional and crosslinked monomer in the oil phase. Batches of static and dynamic adsorption experiments were conducted to analyze the adsorption performance on ERY. Isotherm data of MIPs well fitted the Freundlich model (from 15 °C to 35 °C), which indicated heterogeneous adsorption for ERY. The ERY adsorption capacity of MIPs was about 52.32 μmol/g at 15 °C. The adsorption kinetics was well described by the pseudo-first-order model, which suggested that physical interactions were primarily responsible for ERY adsorption. The Thomas model used in the fixed-bed adsorption design provided a better fit to the experimental data. Meanwhile, ERY exhibited higher affinity during adsorption on the MIPs compared with the adsorption capacity of azithromycin and chloramphenicol. The MIPs also exhibited excellent regeneration capacity with only about 5.04% adsorption efficiency loss in at least three repeated adsorption-desorption cycles.

Removal of cefalexin using yeast surface-imprinted polymer prepared by atom transfer radical polymerization.

The first use of yeast as a support in the molecular imprinting field combined with atom transfer radical polymerization was described. Then, the as-prepared molecularly imprinted polymers were characterized by Fourier transmission infrared spectrometry, scanning electron microscope, thermogravimetric analysis, and elemental analysis. The obtained imprinted polymers demonstrated elliptical-shaped particles with the thickness of imprinting layer of 0.63 μm. The batch mode experiments were adopted to investigate the adsorption equilibrium, kinetics, and selectivity. The kinetic properties of imprinted polymers were well described by the pseudo-second-order kinetic equation, indicating the chemical process was the rate-limiting step for the adsorption of cefalexin (CFX). The equilibrium data were well fitted by the Freundlich isotherm, and the multimolecular layers adsorption capacity of imprinted polymers was 34.07 mg g(-1) at 298 K. The selectivity analysis suggested that the imprinted polymers exhibited excellent selective recognition for CFX in the presence of other compounds with related structure. Finally, the analytical method based on the imprinted polymers extraction coupled with high-performance liquid chromatograph was successfully used for CFX analysis in spiked pork and water samples.