Xubiao Luo

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.

Facile One-Step Synthesis of Inorganic-Framework Molecularly Imprinted TiO2/WO3 Nanocomposite and Its Molecular Recognitive Photocatalytic Degradation of Target Contaminant

Inorganic-framework molecularly imprinted TiO2/WO3 nanocomposites with molecular recognitive photocatalytic activity were first prepared successfully by a facile one-step sol-gel method using 2-nitrophenol and 4-nitrophenol as template molecules, and tetrabutyl orthotitanate as titanium source as well as the precursor of functional monomer which could complex with template molecules. The template molecules could be completely removed by means of high-temperature calcination, avoiding the traditional extraction procedures that are time- as well as solvent-consuming. Compared to nonimprinted TiO2/WO3, the molecularly imprinted TiO2/WO3 shows a much higher adsorption capacity and selectivity toward the template molecules. The enhancement in terms of adsorption capacity and selectivity can be attributed to the chemical interaction between target molecules and imprinted cavities, as well as size matching between imprinted cavities and target molecules. The photocatalytic activity of molecularly imprinted TiO2/WO3 toward the target molecules is more than two times that of non-imprinted TiO2/WO3, a result of selective adsorption of target molecules on molecularly imprinted TiO2/WO3. The formation pathway of intermediate products in 2-nitrophenol and 4-nitrophenol degradation process was provided. Moreover, molecularly imprinted TiO2/WO3 exhibits high stability. The results indicate that inorganic-framework molecularly imprinted TiO2/WO3 nanocomposites have a promising prospect in the treatment of wastewater for irrigation.

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 ion-imprinted polymer using crown ether as a functional monomer for selective removal of Pb(II) ions in real environmental water samples

A novel Pb(II) ion-imprinted crown ether (Pb(II)-IIP) was prepared by inverse emulsion polymerization using 4-vinylbenzo-18-crown-6 as a functional monomer. Pb(II)-IIP showed higher capacity and selectivity than the non-imprinted crown ether (NIP). The monolayer adsorption capacities of Pb(II)-IIP and NIP for Pb(II) ions were 27.95 and 13.54 mg g−1, respectively. The relative selectivity coefficients of Pb(II)-IIP for Pb(II)/Zn(II), Pb(II)/Co(II), Pb(II)/Ni(II) and Pb(II)/Cd(II) were 617.79, 500.56, 52.28 and 201.15, respectively. Kinetics studies showed that the adsorption process closely agreed with a pseudo-second-order model. Pb(II)-IIP exhibited good regeneration, and the adsorption capacity of Pb(II)-IIP was stable within the first three cycles without obvious decrease. Moreover, Pb(II)-IIP showed almost 100% removal efficiency for Pb(II) ions in real environmental water samples, indicating that Pb(II)-IIP could have wide application prospects in Pb(II) removal.

A copper-catalyzed bioleaching process for enhancement of cobalt dissolution from spent lithium-ion batteries.

A copper-catalyzed bioleaching process was developed to recycle cobalt from spent lithium-ion batteries (mainly LiCoO(2)) in this paper. The influence of copper ions on bioleaching of LiCoO(2) by Acidithiobacillus ferrooxidans (A.f) was investigated. It was shown that almost all cobalt (99.9%) went into solution after being bioleached for 6 days in the presence of 0.75 g/L copper ions, while only 43.1% of cobalt dissolution was obtained after 10 days without copper ions. EDX, XRD and SEM analyses additionally confirmed that the cobalt dissolution from spent lithium-ion batteries could be improved in the presence of copper ions. The catalytic mechanism was investigated to explain the enhancement of cobalt dissolution by copper ions, in which LiCoO(2) underwent a cationic interchange reaction with copper ions to form CuCo(2)O(4) on the surface of the sample, which could be easily dissolved by Fe(3+).

Visible-light photocatalytic degradation performances and thermal stability due to the synergetic effect of TiO2 with conductive copolymers of polyaniline and polypyrrole

Conductive polypyrrole-polyaniline/TiO2 nanocomposites (PPy-PANI/TiO2) were prepared by in situ oxidative copolymerization of pyrrole and aniline monomers in the presence of TiO2. For comparison studies, polypyrrole/TiO2 (PPy/TiO2) and polyaniline/TiO2 (PANI/TiO2) were also prepared. The samples were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, zeta potential analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and photocurrent tests. In contrast to PPy/TiO2 and PANI/TiO2, PPy-PANI/TiO2 exhibits obvious absorption in the visible-light range, and is much superior to PPy/TiO2 and PANI/TiO2 in thermal stability. It is found that PPy-PANI/TiO2 performs well in the visible-light photocatalytic degradation of 4-nitrophenol. The optimized pyrrole : aniline : TiO2 molar ratio for best performance is 0.75 : 0.25 : 100. The efficacy of PPy-PANI/TiO2 is attributed to its conductivity, conjugated structure, as well as to the synergy amidst polypyrrole, polyaniline and TiO2.

Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity.

Sol-hydrothermal synthesis of inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite and its preferential photocatalytic degradation towards target contaminant.

Inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite (MIP-TiO2/SiO2) was successfully prepared by sol-hydrothermal method using 4-nitrophenol as template. The morphology, structure, optical property, zeta-potential and photocurrent of MIP-TiO2/SiO2 were characterized. The adsorption performance and photocatalytic selectivity were also studied. MIP-TiO2/SiO2 shows higher adsorption capacity and selectivity than the non-imprinted TiO2/SiO2 (NIP-TiO2/SiO2). Kinetics results show that the adsorption equilibrium of 4-nitrophenol on MIP-TiO2/SiO2 is established within 20 min, and the adsorption process obeys the pseudo-second-order model. Moreover, MIP-TiO2/SiO2 can completely degrade 4-nitrophenol within 30 min, while NIP-TiO2/SiO2 takes 110 min. It was found that the MIP-TiO2/SiO2 photocatalyst shows molecular recognition ability, leading to selective adsorption and molecular recognitive photocatalytic degradation of 4-nitrophenol. Furthermore, because of its inorganic framework, MIP-TiO2/SiO2 shows excellent reusability.

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.