Wanzhen Xu

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.

Preparation of molecularly imprinted polymer by surface imprinting technique and its performance for adsorption of dibenzothiophene.

The novel surface imprinted polymer composites (MIP/K(2)Ti(4)O(9)) were prepared using dibenzothiophene (DBT) as the template, 4-vinylpyridine as the functional monomer and potassium tetratitanate whisker (K(2)Ti(4)O(9)) as the carrier. The synthetic product was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Parameters influencing DBT adsorption such as contact time, temperature and DBT initial concentration were investigated. The adsorption kinetics were evaluated with the pseudo-first-order and pseudo-second-order models, and the adsorption isotherms were fitted by Langmuir and Freundlich models. Selectivity experiments showed that MIP/K(2)Ti(4)O(9) exhibited excellent recognition capacity and binding affinity to DBT compared with the comparative substrates. MIP/K(2)Ti(4)O(9) could also be easily regenerated and reused ten times with only about 20% loss of adsorption capacity.

Rational design and preparation of magnetic imprinted polymers for removal of indole by molecular simulation and improved atom transfer radical polymerization

Novel magnetic imprinted polymers are designed by molecular simulation from a comprehensive perspective and prepared rationally by combining the modified surface imprinting technique with the improved atom transfer radical polymerization. The simulation results show that interaction intensity between indole and monomers are simultaneously affected by complex conformation, charge transfer and binding energy. The optimal monomer for the removal of indole is AM and the best ratio is 1 : 4 in the studied three monomers. To verify the reliability and accuracy of the simulation results, three kinds of novel magnetic imprinted polymers are prepared with different monomers. The experimental results show that molecular simulation is reliable in processing the pre-assembled complexes of molecularly imprinted polymers (MIPs). The MIPs using AM as monomer display the highest selectivity (2.561) and bonding percentage (31.062%). Structural superiority of the optimal adsorbent is reflected by using several characterization methods. A series of static adsorption tests such as kinetic, isotherm and selectivity are used to analyse the adsorption performance. The test results show that the novel adsorbents conform to the Elovich kinetic equation and follow the Langmuir isotherm model. Meanwhile, they display higher selectivity towards indole than towards other analogues. The novel adsorbents have potential application value in the denitrogenation field.

Selective Adsorption of Dibenzothiophene using Magnetic Molecularly Imprinted Polymers

In this study, a novel and quick method for selective adsorption of dibenzothiophene (DBT) from gasoline using magnetic molecularly imprinted polymers (MMIPs) as the adsorbent has been employed. The MMIPs were prepared by a surface molecular imprinting technique, using Fe3O4 magnetite nanoparticles as a magnetically susceptible component, DBT as template molecule, 4-vinylpyridine (4-VP) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The synthetic MMIPs were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The adsorption performances of MMIPs were investigated by batch adsorption experiments in terms of adsorption kinetics, isotherms and selective recognition. The results of the study indicated that MMIPs were able to adsorb DBT well, the adsorption equilibrium time was about 5 h and the equilibrium adsorption amount was 22.23 mg/g at 318 K. In the corresponding selectivity test, MMIPs exhibited a greater adsorption capacity towards DBT than the other three analogues.

Computer-aided design and synthesis of magnetic molecularly imprinted polymers with high selectivity for the removal of phenol from water.

A molecular simulation method was introduced to compute the phenol-monomer pre-assembled system of a molecularly imprinted polymer. The interaction type and intensity between phenol and monomer were evaluated by combining binding energy and charge transfer with complex conformation. The simulation results indicate that interaction energies are simultaneously affected by the type of monomer and the ratio between phenol and monomers. At the same time, we considered that by increasing the amount of functional monomer is not always better for preparing molecularly imprinter polymers. In this study, three kinds of novel magnetic phenol-imprinted polymers with favorable specific adsorption effects were prepared by the surface imprinting technique combined with atom transfer radical polymerization. Various measures were selected to characterize the structure and morphology to obtain the optimal polymer. The characterization results show that the optimal polymer has suitable features for further adsorption process. A series of static adsorption experiments were conducted to analyze its adsorption performance, which follows the Elovich model from the kinetic analysis and the Sips equation from the isothermal analysis. To further verify the reliability and accuracy of the simulation results, the effects of different monomers on the adsorption selectivity were also determined. They display higher selectivity towards phenol than 4-nitrophenol.The results from the simulation of the pre-assembled complexes are in reasonable agreement with those from the experiment.

Thermosensitive molecularly imprinted polymers based on magnetic nanoparticles for the recognition of sulfamethazine

In this study, a thermosensitive molecularly imprinted polymer (TMIP) was successfully synthesized for the selective recognition of sulfamethazine (SMZ) on the surface of magnetic nanoparticles. N-Isopropylacrylamide (NIPAM) as the thermosensitive monomer, methacrylic acid (MAA) as the functional monomer, ethyleneglycol dimethacrylate (EGDMA) as the cross-linking agent and azodiisobutyronitrile (AIBN) as the initiator were selected to prepare the TMIPs. The thermosensitive magnetic molecularly imprinted polymers were sensitive to the temperature and the adsorption/desorption process could be controlled by changing the temperature because the thermoresponsive monomer NIPAM can undergo a reversible volume transition between the swollen and collapsed phases. Moreover, the resultant TMIPs showed high adsorption capacity and specific affinity towards SMZ. The adsorption capacity of TMIPs reached the maximum when the adsorption temperature was around the LCST of NIPAM. The magnetic property of TMIPs provided fast separation while the thermoresponsive property offered simple elution for templates. Finally, the imprinted polymers were used for the enrichment of SMZ from real water with recoveries ranging from 83.2% to 96.8% determined by high performance liquid chromatography. The results indicated that the TMIPs were efficient for thermally modulated capture and release of the template, which enable its application for trace sulfamethazine in complicated samples.

Rational design and preparation for novel denitrogenation adsorbents by computational simulation and improved atom transfer radical polymerization

Novel denitrogenation adsorbents with favourable specific adsorption effect were designed by computational simulation and prepared rationally by combining the modified surface imprinting technique with improved atom transfer radical polymerization. The simulated results show that interaction energies are simultaneously affected by both the type of monomer and the ratio between indole and monomers. Adding more monomers wrongly will affect the interaction energy between template and monomer. The structural properties of the adsorbents are discussed by using various characterization measures such as nitrogen sorption measurements, infrared spectrophotometry, scanning electron microscopy and thermogravimetric analysis. A series of static adsorption tests such as kinetic, isotherm, thermodynamic and selectivity were used to analyse the adsorption performance. The test results show that the novel adsorbents conformed to the Elovich kinetic equation and followed the Langmuir isothermal model. Meanwhile, they display higher selectivity towards indole than towards other analogues. The novel adsorbents have a potential application value in the denitrogenation field.

Synthesis of a Molecularly Imprinted Polymer on Silica-Gel Surfaces for the Selective Adsorption of Indole from Fuel Oil

We report a successful synthesis of a molecularly imprinted polymer (MIP) by surface imprinting technique. The polymer was then used for selective adsorption of indole from fuel oil. Nitrogen adsorption, Fourier transform-infrared spectrometry and scanning electron microscopy were used to characterize the morphology of indole–MIP. The study results show that indole–MIP has a large specific surface area and enhanced porosity. Static adsorption data indicate that the adsorption capacity of indole–MIP is 54.6639 mg g−1, with the adsorption equilibrium achieved in 40 minutes. The indole–MIP molecule has a high adsorption and elution rate due to the presence of hydrogen bond between the functional monomer (4-vinylpyridine) and the template molecule (indole). According to the results of thermodynamic analysis, the adsorption process is spontaneous. In addition, based on the results of kinetics and isotherm analysis, adsorption performances obey pseudo-second-order model and Langmuir equation. The selectivity of indole–MIP is favourable and can be reused even after 10 cycles.

Synthesis of Potassium Tetratitanate-Based Molecularly Imprinted Polymer for Selective Adsorption of Dibenzothiophene

A potassium tetratitanate–based molecularly imprinted polymer (MIP) was prepared by surface molecule–imprinting technique, which involves coating potassium tetratitanate whiskers with silica and modification with 3-methacryloxypropyltrimethoxysilane. The structural properties of the synthesized MIP were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption and scanning electron microscopy. Adsorption behaviour studies were conducted on the prepared MIP, the results of which showed that it has a porous and large surface area. In addition, the prepared MIP showed good adsorptive capacity and selectivity for dibenzothiophene; the adsorption equilibrium time was 180 minutes and the equilibrium adsorption capacity was 20.86 mg/g at 318 K. The adsorptive behaviour followed the Lagergren pseudo-second-order kinetic model and the Freundlich isotherm model. Thermodynamic parameters demonstrated that the adsorption process was spontaneous and endothermic. Thus, based on the study results it can be concluded that the synthesized adsorbent (i.e. MIP) has potential applications for deep desulphurization of gasoline.

Electrochemical sensor based on lead ion-imprinted polymer particles for ultra-trace determination of lead ions in different real samples

In this paper, a self-manufactured lead(II)-selective electrode, which was based on the use of lead(II) ion imprinted polymer particles (IIPs) to detect lead ions, was studied using differential pulse voltammetry. The synthesis and preparation of the IIPs was by precipitation polymerization with methacrylic acid (function monomer and lead-binding ligand), ethylene glycol dimethacrylate (the cross-linker) 2,2-azobisisobutyronitrile (the initiator) and lead ions (the template ion) in an acetonitrile solution. The IIPs were prepared to establish the electrochemical sensor by leaching out the lead(II) from the imprinted polymer particles, and a carbon paste electrode was modified with lead(II) IIPs. There is a distinct difference in the response between the electrodes modified with IIPs and the electrodes modified with NIPs, which included the open circuit sorption of Pb2+ on the electrode and its reduction to its metallic form. The influence factors on the response behavior of the electrodes were investigated and optimized. The results show the introduced sensor was linear from 1.0 × 10−9 to 7.5 × 10−7 mol L−1, and the limit of detection (LOD) was 1.3 × 10−11 mol L−1 (S/N = 3). Finally, the sensor was successfully applied to the trace determination of lead ions in various real samples.