Pengwei Huo

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.

Switched recognition and release ability of temperature responsive molecularly imprinted polymers based on magnetic halloysite nanotubes

CoFe2O4/halloysite nanotube magnetic composites (MHNTs) were firstly achieved via a wet impregnation technique, and then a thermal polymerization under (NH4)2S2O8 chain initiation in water was employed to obtain methacrylic acid-functionalized MHNTs (MAA-MHNTs). By decorating the MAA-MHNTs with the temperature responsive monomer N-isopropylacrylamide (NIPAM), a novel temperature responsive molecularly imprinted material based on the obtained NIPAM-MHNTs (TMMIPs) was synthesized by a surface imprinting technique. The results of characterization indicated that the TMMIPs exhibited magnetic sensitivity (Ms = 1.758 emu g−1), magnetic stability (in the pH range of 2.0–8.0), thermal stability (especially below 200 °C) and contained a temperature responsive imprinted layer (the lower critical solution temperature was 33.96 °C). Then the TMMIPs were applied to switched recognition and release of 2,4,5-trichlorophenol molecules (5-TCP) by changing the medium temperature. TMMIPs showed outstanding recognition ability towards the imprinted species under high temperature conditions (such as 60 °C), due to the loss of hydration and a collapsed state of inter-poly(N-isopropylacrylamide), which resulted in the formation of a specific structure between 5-TCP and the polymer network. In contrast, at relatively low temperatures (such as 20 °C), the captured 5-TCP was released from the swelled TMMIPs, which resulted from increasing the distance between 5-TCP and the polymer network. The selective analysis demonstrated the high affinity and selectivity of TMMIPs towards 5-TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional groups of the template molecules.

Transfer Charge and Energy of Ag@CdSe QDs-rGO Core–Shell Plasmonic Photocatalyst for Enhanced Visible Light Photocatalytic Activity

Plasmonic heteronanostructures in semiconductor type display extraordinary photocatalytic efficiency induced by the plasmonic energy that operates in the Ag@CdSe-rGO hybrid ternary composites. The obtained plasmonic photocatalysts in nanoscale were fabricated by using a one-step hydrothermal method, during which the in situ nucleation of Ag@CdSe core-shell nanoparticles and the reduction of GO to rGO occurred simultaneously. Three different roles of Ag core and the junction of synergistic properties arising from the introduced rGO jointly enhanced the optical properties of CdSe. Localized plasmon resonance (LPR) effects of plasmonic Ag contribute to the separation of photogenerated e(-)/h(+) pairs via the electrons and resonant energy transfer. Electrochemical investigations have further confirmed the enhanced separation of the photogenerated e(-)/h(+) pairs. From comparative photocatalytic experiments of Ag@CdSe-rGO and Ag/CdSe-rGO, the plasmonic effect of the Ag core in the Ag@CdSe-rGO nanostructure serves to prolong the charge separation under visible light beyond common attached trimers.

Molecularly imprinted polymer surfaces as solid‐phase extraction sorbents for the extraction of 2‐nitrophenol and isomers from environmental water

The novel surface molecularly imprinted polymer (MIP) with 2-nitrophenol (2-NP) as the template has been prepared and used as the adsorbent for the solid-phase extraction (SPE). The selectivity of the polymer was checked toward several selected nitrophenols (NPs) such as 2-NP, 3-nitrophenol (3-NP), 4-nitrophenol (4-NP) and 2,4,6-trichlorophenol (2,4,6-TCP). Under the optimized conditions, high sensitivity (detection limits: 0.07-0.12 ng/mL) and good reproducibility of analytes (2.3-4.8% for four cycles) were achieved. Then, the method was applied for the analysis of selected phenols in spiked tap, lake and river water samples. High recoveries (>83.3%) for nitrophenols (NPs) were obtained, but lower recoveries (<63.4%) were achieved for 2,4,6-TCP. The method was found to be linear in the range of 1-300 ng/mL with correlation coefficients (R(2) ) greater than 0.99 and repeatability relative standard deviation (RSD) below 7.2% in all cases. For analysis of 120 mL water samples, the method detection limits (LODs) ranged from 0.10 to 0.22 ng/mL and the limit of quantification (LOQs) from 0.33 to 0.72 ng/mL. These results showed the suitability of the MIP-SPE method for the selective extraction of a group of structurally related isomeric compounds.

Preparation and performance of a novel magnetic conductive imprinted photocatalyst for selective photodegradation of antibiotic solution

In order to achieve the treatment of antibiotic pollutants by solid waste, and for the purpose of improving the selectivity while enhancing the photocatalytic efficiency, this work used fly-ash cenospheres (FC) (obtained from coal fly ash, a typical solid waste) as the carrier, o-phenylenediamine (OPD) as the imprinted functional monomer, a conductive polymerizable monomer, enrofloxacin hydrochloride (EH) as the molecular template and TiO2@magnetic floating fly-ash cenospheres (TMFFC) as the matrix material. A magnetic conductive imprinted photocatalyst (MCIP) was synthesized via surface imprinting technology and a one-pot photo-induced method. The as-prepared MCIP was extensively characterized by SEM, N2 adsorption–desorption analysis with the Brunauer–Emmett–Teller (BET) method, FT-IR, elemental analysis, TGA, UV-vis and vibrating sample magnetometry (VSM). The results showed that the MCIP possessed a hollow spherical structure, floating and magnetic separation properties (Ms = 9.16 emu g−1), the conductive polymer (POPD) was successfully introduced into the surface-imprinted layer, and the electrical conductivity of MCIP was 0.359 us cm−1. The photodegradation rate, pseudo-first-order constant and coefficient of selection were calculated in detail, and all these data indicated that the MCIP not only had higher photocatalytic efficiency for the degradation of EH compared with other photocatalysts (such as the traditional surface-imprinted photocatalysts and TMFFC), but also possessed better selection for adsorption and photodegradation of EH in single/binary antibiotic solution. The mechanism of selective photodegradation of EH was also investigated.

Molecularly imprinted polymers based on magnetic fly-ash-cenosphere composites for bisphenol A recognition

Magnetic composites (MCs) were achieved via coating a chitosan layer containing γ-Fe2O3 nanoparticles onto the surface of aldehyde-functionalized fly-ash-cenospheres. Based on these MCs, the magnetic molecularly imprinted polymers (MMIPs) were further synthesized and characterized, and used to selectively recognise bisphenol A (BPA) molecules. Owing to the intrinsic advantages of cross-linked chitosan, magnetic γ-Fe2O3 nanoparticles and spherical FACs, the results demonstrated that these spherical shaped MMIPs particles had magnetic sensitivity (Ms = 2.221 emu g−1) and magnetic stability (especially over the pH range of 6.0–12). Batch mode adsorption studies were carried out to investigate the specific adsorption equilibrium, kinetics and selective recognition. The Langmuir isotherm model was fitted well to the equilibrium data of the MMIPs, and the monolayer adsorption capacity of the MMIPs was 135.1 mg g−1 at 298 K. The kinetic properties of the MMIPs were well described by the pseudo-second-order equation, indicating the chemical process could be the rate-limiting step in the adsorption process for BPA. Selective recognition experiments demonstrated the high affinity and selectivity of MMIPs towards BPA over competitive phenolic compounds. The molecular interaction between BPA and methacrylic acid (MAA) was investigated by the 1H-NMR spectrum. Hydrogen bonding was proved to be mainly responsible for the recognition mechanism, and the specific recognition effect may be based on the distinct size, structure and functional group of the template molecules.

Heteropolyacid–chitosan/TiO2 composites for the degradation of tetracycline hydrochloride solution

Heteropolyacid–chitosan/TiO2 composites were modified by the conducting polymers and synthesized via a solvothermal method. The conducting polymers were prepared via the synthesis of heteropolyacids (H3PMo12O40, H3PW12O40, H4SiW12O40) and chitosan. It was found that the conducting polymers (heteropolyacids–chitosan) could improve the photocatalytic activity of TiO2 a lot, and the H3PMo12O40–chitosan/TiO2 sample possessed the highest photocatalytic activity among the composite samples. The compound photocatalysts were characterized by X-ray diffraction, UV–Vis diffuse reflectance spectra, Fourier transform infrared spectroscopy and scanning electron microscopy.

Enhanced photocatalytic degradation of tetracycline antibiotics by reduced graphene oxide–CdS/ZnS heterostructure photocatalysts

In this work, reduced graphene oxide (RGO)–CdS/ZnS heterostructure composites have been successfully synthesized by a hydrothermal method by assembling the CdS/ZnS heterostructure nanoparticles on RGO sheets and the reduction of GO occurs simultaneously. The as-prepared RGO–CdS/ZnS composites with the content of 15% RGO exhibit highly active photodegradation of TC. A possible mechanism for the enhanced photocatalytic activity has been discussed. The CdS/ZnS heterostructure facilitates the transformation of electrons, which is excited by light irradiation in the conduction band of CdS. RGO is supposed to be an electron transfer channel, which is used to reduce the recombination of electron–hole pairs, thus enhancing the photo-conversion efficiency. By profiting from the synergy of RGO and CdS/ZnS heterostructure, the photocatalysts not only show a better photocatalytic activity in tetracycline antibiotics but also prevent pure CdS or ZnS from photocorrosion. At last, RGO–CdS/ZnS shows remarkable stability and cyclic performances.

Preparation and photodegradation properties of transition metal ion–poly-o-phenylenediamine/TiO2/fly-ash cenospheres by ion imprinting technology

Transition metal ions have been immobilized on TiO2/fly-ash cenospheres (TiO2/FACs) with poly-o-phenylenediamine (OPD). The as-prepared ion imprinting photocatalyst (M-POPD/TiO2/FACs) has been characterized by SEM, XRD, FT-IR, UV-vis DRS and ICP-AES. The results demonstrated that the polymer and mental ions existed in the M-POPD/TiO2/FACs. The photocatalytic activity of M-POPD/TiO2/FACs was studied by the degradation of tetracycline, oxytetracycline, ciprofloxacin, tetracycline hydrochloride and chloromycetin in simulated wastewater under visible light irradiation. The results showed that the M-POPD/TiO2/FACs could effectively increase the separation rate of photoelectrons and holes in the cycling system and improve the photocatalytic activity for the degradation of antibiotics in solution. Experimental data showed that the as-prepared M-POPD/TiO2/FACs were more suitable for degradation of tetracycline (5 mg L−1), and the photodegradation rate could reach 71.7%. In addition, possible formation and photocatalytic mechanisms were proposed.

Fabrication and evaluation of artemisinin-imprinted composite membranes by developing a surface functional monomer-directing prepolymerization system.

Inspired by a surface functional monomer-directing prepolymerization system, a straightforward and effective synthesis method was first developed to prepare highly regenerate and perm-selective molecularly imprinted composite membranes of artemisinin (Ars) molecules. Attributing to the formation of the prepolymerization system, Ars molecules are attracted and bound to the membrane surface, hence promoting the growth of homogeneous and high-density molecular recognition sites on the surface of membrane materials. Afterward, a two-step-temperature imprinting procedure was carried out to prepare the novel surface functional monomer capping molecularly imprinted membranes (FMIMs). The as-prepared FMIMs not only exhibited highly adsorption capacity (11.91 mg g(-1)) but also showed an outstanding specific selectivity (imprinting factor α is 4.50) and excellent perm-selectivity ability (separation factor β is 10.60) toward Ars molecules, which is promising for Ars separation and purification.