The Experts below are selected from a list of 4923 Experts worldwide ranked by ideXlab platform

Yuqi Feng - One of the best experts on this subject based on the ideXlab platform.

  • combining poly methacrylic acid co Ethylene Glycol Dimethacrylate monolith microextraction and octadecyl phosphonic acid modified zirconia coated cec with field enhanced sample injection for analysis of antidepressants in human plasma and urine
    Electrophoresis, 2010
    Co-Authors: Jin Fan, Fang Wei, Mingming Zheng, Yuqi Feng
    Abstract:

    A method based on poly (methacrylic acid-co-Ethylene Glycol Dimethacrylate) monolith microextraction and octadecylphosphonic acid-modified zirconia-coated CEC followed by field-enhanced sample injection preconcentration technique was proposed for sensitive CE-UV analysis of six antidepressants (doxepin, clozapine, imipramine, paroxetine, fluoxetine and chlorimipramine) in human plasma and urine. A poly(methacrylic acid-co-Ethylene Glycol Dimethacrylate) monolithic capillary column was introduced for the extraction of antidepressants from urine and plasma samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the desorption solvent, which normally provided an excellent medium to ensure direct compatibility for field-enhanced sample injection in CE, was analyzed by CE directly. By the use of alkylphosphonate-modified zirconia-coated CEC for separation of the basic compounds of antidepressants, high separation efficiency and resolution were achieved because that both hydrophobic interaction between analytes and alkylphosphonate-modified zirconia coat and electrophoretic effect work on the separation of antidepressants. The best separation was achieved using a buffer composed of 0.3 M ammonium acetate (adjusted to pH 4.5 with 1 M acetic acid) and 35% ACN v/v, with a temperature and voltage of 20 degrees C and 20 kV, respectively. By applying both preconcentration procedures, LODs of 11.4-51.5 and 3.7-17.0 microg/L were achieved for the six antidepressants in human plasma and urine, respectively. Excellent method of reproducibility was found over a linear range of 50-5000 microg/L in plasma and urine sample.

  • application of poly methacrylic acid Ethylene Glycol Dimethacrylate monolith microextraction coupled with capillary zone electrophoresis to the determination of opiates in human urine
    Electrophoresis, 2006
    Co-Authors: Min Zhang, Yuqi Feng
    Abstract:

    : A novel poly(methacrylic acid-Ethylene Glycol Dimethacrylate) (MAA-EGDMA) monolith microextraction method coupled with CZE was proposed for rapidly determining a mixture of opiates comprising heroin, 6-monoacetylmorphine, morphine, codeine, papaverine, and narcotine in human urine. The extraction device contained a regular plastic syringe, the poly(MAA-EGDMA) monolithic capillary tube (530 microm id x 3 cm) and a plastic pinhead, which connected the monolithic capillary tube and the syringe without leakage. In the polymer monolith microextraction, the sample solution was ejected via the monolithic capillary tube by a programmable syringe pump, followed by desorption with an aliquot of appropriate solution, which was collected into a vial for the subsequent analysis by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v with temperature and voltage of 25 degrees C and 25 kV, respectively. By applying electrokinetic injection with field-enhanced sample stacking, detection limits of 6.6-19.5 ng/mL were achieved. Excellent method of reproducibility was found over a linear range of 80-2000 ng/mL.

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolith in tube solid phase microextraction coupled to high performance liquid chromatography and analysis of amphetamines in urine samples
    Journal of Chromatography A, 2005
    Co-Authors: Yuqi Feng, Shilu Da, Jiantao Zhang, Min Zhang
    Abstract:

    Abstract In-tube solid-phase microextraction (SPME) based on a poly(methacrylic acid-Ethylene Glycol Dimethacrylate) monolithic capillary column was investigated for the extraction of amphetamine, methamphetamine and their mEthylenedioxy derivatives. The monolithic capillary column showed high extraction efficiency towards target analytes, which could be attributed to its larger loading amount of extraction phase than conventional open-tubular extraction capillaries and the convective mass transfer procedure provided by its monolithic structure. The extraction mechanism was studied, and the results indicated that the extraction process of the target analytes was involved with hydrophobic interaction and ion-exchange interaction. The polymer monolith in-tube SPME-HPLC system with UV detection was successfully applied to the determination of amphetamine, methamphetamine and their mEthylenedioxy derivatives in urine samples, yielding the detection limits of 1.4–4.0 ng/mL. Excellent method reproducibility (RSD

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolithic capillary for in tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum
    Analytica Chimica Acta, 2004
    Co-Authors: Yuqi Feng, Shilu Da
    Abstract:

    Abstract A poly (methacrylic acid–Ethylene Glycol Dimethacrylate) monolithic capillary column was prepared for in-tube solid-phase microextraction. Comparing with the commonly used open tubular extraction capillary, which cannot provide sufficient extraction efficiency since the ratio of its coating volume to that of the capillary void volume is relatively small, the monolithic column with greater phase ratio combined with convective mass transfer provides the possibility to improve the extraction efficiency with shorter capillary. As to poly (methacrylic acid–Ethylene Glycol Dimethacrylate), its hydrophobic main chains and acidic pendant groups make it a superior material for extraction of basic analytes from aqueous matrix. An on-line monolithic capillary column solid phase microextraction (SPME) method was developed for determination of theobromine, theophylline and caffeine in serum samples. The high extraction efficiency was obtained for all the three analytes, yielding the detection limits of 12, 8 and 6.5 ng/mL by UV detection, respectively. Excellent method reproducibility (R.S.D.

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolithic capillary for in tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum
    Analytica Chimica Acta, 2004
    Co-Authors: Yuqi Feng, Shilu Da
    Abstract:

    A poly (methacrylic acid–Ethylene Glycol Dimethacrylate) monolithic capillary column was prepared for in-tube solid-phase microextraction. Comparing with the commonly used open tubular extraction capillary, which cannot provide sufficient extraction efficiency since the ratio of its coating volume to that of the capillary void volume is relatively small, the monolithic column with greater phase ratio combined with convective mass transfer provides the possibility to improve the extraction efficiency with shorter capillary. As to poly (methacrylic acid–Ethylene Glycol Dimethacrylate), its hydrophobic main chains and acidic pendant groups make it a superior material for extraction of basic analytes from aqueous matrix. An on-line monolithic capillary column solid phase microextraction (SPME) method was developed for determination of theobromine, theophylline and caffeine in serum samples. The high extraction efficiency was obtained for all the three analytes, yielding the detection limits of 12, 8 and 6.5 ng/mL by UV detection, respectively. Excellent method reproducibility (R.S.D. < 2.9%) was found over a linear dynamic range of 0.05–2 μg/mL in serum sample. The monolithic capillary column was proved to be reusable in coping with serum samples, which would facilitate practical determination of basic drugs.

Shilu Da - One of the best experts on this subject based on the ideXlab platform.

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolith in tube solid phase microextraction coupled to high performance liquid chromatography and analysis of amphetamines in urine samples
    Journal of Chromatography A, 2005
    Co-Authors: Yuqi Feng, Shilu Da, Jiantao Zhang, Min Zhang
    Abstract:

    Abstract In-tube solid-phase microextraction (SPME) based on a poly(methacrylic acid-Ethylene Glycol Dimethacrylate) monolithic capillary column was investigated for the extraction of amphetamine, methamphetamine and their mEthylenedioxy derivatives. The monolithic capillary column showed high extraction efficiency towards target analytes, which could be attributed to its larger loading amount of extraction phase than conventional open-tubular extraction capillaries and the convective mass transfer procedure provided by its monolithic structure. The extraction mechanism was studied, and the results indicated that the extraction process of the target analytes was involved with hydrophobic interaction and ion-exchange interaction. The polymer monolith in-tube SPME-HPLC system with UV detection was successfully applied to the determination of amphetamine, methamphetamine and their mEthylenedioxy derivatives in urine samples, yielding the detection limits of 1.4–4.0 ng/mL. Excellent method reproducibility (RSD

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolithic capillary for in tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum
    Analytica Chimica Acta, 2004
    Co-Authors: Yuqi Feng, Shilu Da
    Abstract:

    Abstract A poly (methacrylic acid–Ethylene Glycol Dimethacrylate) monolithic capillary column was prepared for in-tube solid-phase microextraction. Comparing with the commonly used open tubular extraction capillary, which cannot provide sufficient extraction efficiency since the ratio of its coating volume to that of the capillary void volume is relatively small, the monolithic column with greater phase ratio combined with convective mass transfer provides the possibility to improve the extraction efficiency with shorter capillary. As to poly (methacrylic acid–Ethylene Glycol Dimethacrylate), its hydrophobic main chains and acidic pendant groups make it a superior material for extraction of basic analytes from aqueous matrix. An on-line monolithic capillary column solid phase microextraction (SPME) method was developed for determination of theobromine, theophylline and caffeine in serum samples. The high extraction efficiency was obtained for all the three analytes, yielding the detection limits of 12, 8 and 6.5 ng/mL by UV detection, respectively. Excellent method reproducibility (R.S.D.

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolithic capillary for in tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum
    Analytica Chimica Acta, 2004
    Co-Authors: Yuqi Feng, Shilu Da
    Abstract:

    A poly (methacrylic acid–Ethylene Glycol Dimethacrylate) monolithic capillary column was prepared for in-tube solid-phase microextraction. Comparing with the commonly used open tubular extraction capillary, which cannot provide sufficient extraction efficiency since the ratio of its coating volume to that of the capillary void volume is relatively small, the monolithic column with greater phase ratio combined with convective mass transfer provides the possibility to improve the extraction efficiency with shorter capillary. As to poly (methacrylic acid–Ethylene Glycol Dimethacrylate), its hydrophobic main chains and acidic pendant groups make it a superior material for extraction of basic analytes from aqueous matrix. An on-line monolithic capillary column solid phase microextraction (SPME) method was developed for determination of theobromine, theophylline and caffeine in serum samples. The high extraction efficiency was obtained for all the three analytes, yielding the detection limits of 12, 8 and 6.5 ng/mL by UV detection, respectively. Excellent method reproducibility (R.S.D. < 2.9%) was found over a linear dynamic range of 0.05–2 μg/mL in serum sample. The monolithic capillary column was proved to be reusable in coping with serum samples, which would facilitate practical determination of basic drugs.

Adil Denizli - One of the best experts on this subject based on the ideXlab platform.

  • concanavalin a immobilized poly Ethylene Glycol Dimethacrylate based affinity cryogel matrix and usability of invertase immobilization
    Journal of Chromatography B, 2012
    Co-Authors: Murat Uygun, Deniz Aktas Uygun, Emir Ozcaliskan, Sinan Akgöl, Adil Denizli
    Abstract:

    Abstract Concanavalin A (Con A) immobilized supermacroporous poly(Ethylene Glycol Dimethacrylate) [poly(EGDMA)] monolithic cryogel column was prepared by radical cryocopolymerization of EGDMA as a monomer and N , N ′-mEthylene-bisacrylamide as a crosslinker. Bioligand Con A was then immobilized by covalent binding onto poly(EGDMA) cryogel via glutaraldehyde activation [Con A–poly(EGDMA)]. Con A–poly(EGDMA) cryogel was characterized by swelling studies and scanning electron microscopy. The monolithic cryogel contained a continuous polymeric matrix having interconnected pores of 10–50 μm size. The equilibrium swelling degree of the cryogel was 15.01 g H 2 O/g dry cryogel. Con A–poly(EGDMA) cryogel was used in the adsorption/desorption of invertase from aqueous solutions. The maximum amount of invertase adsorption from aqueous solution in acetate buffer was 55.45 mg/g polymer at pH 5.0. Con A–poly(EGDMA) cryogels were used for repetitive adsorption/desorption of invertase without noticeable loss in invertase adsorption capacity after 10 cycles.

  • synthesis and characterization of poly Ethylene Glycol Dimethacrylate 1 vinyl 1 2 4 triazole copolymer beads for heavy metal removal
    Journal of Applied Polymer Science, 2006
    Co-Authors: Lokman Uzun, Ali Kara, Necati Besirli, Nalan Tuzmen, Abdulkerim Karabakan, Adil Denizli
    Abstract:

    We prepared poly(Ethylene Glycol Dimethacrylate–1-vinyl-1,2,4-triazole) [poly(EGDMA–VTAZ)] beads (average diameter = 150–200 μm) by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with 1-vinyl-1,2,4-triazole (VTAZ). The copolymer composition was characterized by elemental analysis and found to contain five EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads had a specific surface area of 65.8 m2/g. Poly(EGDMA–VTAZ) beads were characterized by Fourier transform infrared spectroscopy, elemental analysis, surface area measurements, swelling studies, and scanning electron microscopy. Poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used for the heavy-metal removal studies. The adsorption capacities of the beads for Cd(II), Hg(II), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(EGDMA–VTAZ) beads were 85.7 mg/g (0.76 mmol/g) for Cd(II), 134.9 mg/g (0.65 mmol/g) for Pb(II), and 186.5 mg/g (0.93 mmol/g) for Hg(II). The affinity order toward triazole groups on a molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). pH significantly affected the adsorption capacity of the VTAZ-incorporated beads. The equilibrium data were well fitted to the Redlich–Peterson isotherm. Consideration of the kinetic data suggested that chemisorption processes could have been the rate-limiting step in the adsorption process. Regeneration of the chelating-beads was easily performed with 0.1M HNO3. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4276–4283, 2006

  • immobilization of α amylase on cu2 chelated poly Ethylene Glycol Dimethacrylate n vinyl imidazole matrix via adsorption
    Reactive & Functional Polymers, 2005
    Co-Authors: Ali Kara, Bilgen Osman, Necati Besirli, Handan Yavuz, Adil Denizli
    Abstract:

    Abstract Poly(Ethylene Glycol Dimethacrylate- n -vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150–200 μm) was prepared by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with n -vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m 2 /g. Poly(EGDMA-VIM) beads were characterized by swelling studies and SEM. Cu 2+ ions were chelated on the poly(EGDMA-VIM) beads, then these beads were used in the adsorption of α-amylase from Aspergillus Oryzae in batch system. The maximum α-amylase adsorption capacity of the poly(EGDMA-VIM)–Cu 2+ beads was observed as 38.9 mg/g at pH 4.0. The K m values for immobilized α-amylase (poly(EGDMA-VIM)–Cu 2+ ) (22.5 mM) was higher than that of free enzyme (15.8 mM). Storage stability was found to increase with immobilization. It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity or enzyme activity.

  • poly Ethylene Glycol Dimethacrylate n vinyl imidazole beads for heavy metal removal
    Journal of Hazardous Materials, 2004
    Co-Authors: Ali Kara, Necati Besirli, Lokman Uzun, Adil Denizli
    Abstract:

    Abstract Poly(Ethylene Glycol Dimethacrylate- n -vinyl imidazole) [poly(EGDMA–VIM)] hydrogel (average diameter 150–200 μm) was prepared by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with n -vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA–VIM) beads had a specific surface area of 59.8 m 2 /g. Poly(EGDMA–VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA–VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10–750 mg/l) and at different pH values (3.0–7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA–VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II)>Cd(II)>Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO 3 . These features make poly(EGDMA–VIM) beads potential candidate adsorbent for heavy metal removal.

  • cibacron blue f3ga and zn ii containing poly Ethylene Glycol Dimethacrylate hydroxyethyl methacrylate microbeads for albumin adsorption
    Journal of Macromolecular Science Part A, 1997
    Co-Authors: Adil Denizli, Bekir Salih, Erhan Pişkin
    Abstract:

    Abstract Swellable poly (Ethylene Glycol Dimethacrylate-hydroxyethyl methacryate) [poly(EGDMA-HEMA] microbeads, in the size range of 150–200 μm, were produced by a modified suspension copolymerization of EGDMA and HEMA. Cibacron Blue F3GA was attached, then Zn(II) ions were incorporated within the microbeads by chelating with the Cibacron Blue F3GA molecules. The maximum amount of Cibacron Blue F3GA attachment was 16.5 μmol/g polymer. Different amounts of Zn(II) ions (0.4–32.4 mg/g polymer were incorporated on the microbeads by changing the initial concentration of Zn(II) ions and medium pH. Bovine serum albumin (BSA) adsorption onto unmodified, Cibacron Blue F3GA-attached and Cibacron Blue F3GA-Zn(II)-derivatized microbeads was investigated. The non-specific adsorption of BSA was very low (0.051 mg/g polymer). Cibacron Blue F3GA attachment significantly increased the BSA adsorption (60.5 mg/g polymer). The maximum BSA adsorption (122 mg/g polymer) was observed at pH 6.0 when Cibacron Blue F3GA-Zn(II)-der...

Min Zhang - One of the best experts on this subject based on the ideXlab platform.

  • application of poly methacrylic acid Ethylene Glycol Dimethacrylate monolith microextraction coupled with capillary zone electrophoresis to the determination of opiates in human urine
    Electrophoresis, 2006
    Co-Authors: Min Zhang, Yuqi Feng
    Abstract:

    : A novel poly(methacrylic acid-Ethylene Glycol Dimethacrylate) (MAA-EGDMA) monolith microextraction method coupled with CZE was proposed for rapidly determining a mixture of opiates comprising heroin, 6-monoacetylmorphine, morphine, codeine, papaverine, and narcotine in human urine. The extraction device contained a regular plastic syringe, the poly(MAA-EGDMA) monolithic capillary tube (530 microm id x 3 cm) and a plastic pinhead, which connected the monolithic capillary tube and the syringe without leakage. In the polymer monolith microextraction, the sample solution was ejected via the monolithic capillary tube by a programmable syringe pump, followed by desorption with an aliquot of appropriate solution, which was collected into a vial for the subsequent analysis by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v with temperature and voltage of 25 degrees C and 25 kV, respectively. By applying electrokinetic injection with field-enhanced sample stacking, detection limits of 6.6-19.5 ng/mL were achieved. Excellent method of reproducibility was found over a linear range of 80-2000 ng/mL.

  • poly methacrylic acid Ethylene Glycol Dimethacrylate monolith in tube solid phase microextraction coupled to high performance liquid chromatography and analysis of amphetamines in urine samples
    Journal of Chromatography A, 2005
    Co-Authors: Yuqi Feng, Shilu Da, Jiantao Zhang, Min Zhang
    Abstract:

    Abstract In-tube solid-phase microextraction (SPME) based on a poly(methacrylic acid-Ethylene Glycol Dimethacrylate) monolithic capillary column was investigated for the extraction of amphetamine, methamphetamine and their mEthylenedioxy derivatives. The monolithic capillary column showed high extraction efficiency towards target analytes, which could be attributed to its larger loading amount of extraction phase than conventional open-tubular extraction capillaries and the convective mass transfer procedure provided by its monolithic structure. The extraction mechanism was studied, and the results indicated that the extraction process of the target analytes was involved with hydrophobic interaction and ion-exchange interaction. The polymer monolith in-tube SPME-HPLC system with UV detection was successfully applied to the determination of amphetamine, methamphetamine and their mEthylenedioxy derivatives in urine samples, yielding the detection limits of 1.4–4.0 ng/mL. Excellent method reproducibility (RSD

Ali Kara - One of the best experts on this subject based on the ideXlab platform.

  • sulfonic acid functionalized poly Ethylene Glycol Dimethacrylate 1 vinyl 1 2 4 triazole as an efficient catalyst for the synthesis of methyl propionate
    Reactive & Functional Polymers, 2011
    Co-Authors: Beyhan Erdem, Ali Kara
    Abstract:

    Abstract Sulfonic acid functionalized poly (Ethylene Glycol Dimethacrylate-1-vinyl-1,2,4-triazole), poly (EGDMA–VTAZ–SO3H) (average diameter 1.0–1.5 mm), was found to be efficient solid acid catalyst for the esterification of methanol and propionic acid under heterogeneous reaction conditions. The pristine polymer, poly (EGDMA–VTAZ), was produced by suspension polymerization and then proton-conducting polymer was obtained by blending of poly (EGDMA–VTAZ) with different percentage of H2SO4 solutions. The protonation of aromatic heterocyclic rings was proved with Fourier-transform infrared spectroscopy (FT-IR). Thermo gravimetric (TG) analysis showed that the catalyst is thermally stable up to 573 K. The surface morphology of the catalyst was characterized by scanning electron microscopy (SEM). Poly (EGDMA–VTAZ–SO3H) beads can be regenerated and reused, so this provides a potential application. It has a rate constant which exceeds that of Amberlyst-15 by a factor of about four at 333 K. As for the reaction equilibrium constant (Ke), which is independent of temperature ranging from 318 to 343 K, was determined to be 3.16. The apparent activation energy was found to be 41.6 kJ mol−1 for poly (EGDMA–VTAZ–SO3H).

  • adsorption of cr vi ions onto poly Ethylene Glycol Dimethacrylate 1 vinyl 1 2 4 triazole
    Journal of Applied Polymer Science, 2009
    Co-Authors: Ali Kara
    Abstract:

    Poly(Ethylene Glycol Dimethacrylate-1-vinyl-1,2,4-triazole) [poly(EGDMA-VTAZ)] beads (average diameter = 150–200 μm) were prepared by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with 1-vinyl-1,2,4-triazole (VTAZ). Poly(EGDMA-VTAZ) beads were characterized by swelling studies and scanning electron microscope (SEM). The adsorption of Cr(VI) from solutions was carried at different contact times, Cr(VI) concentrations, pH, and temperatures. High adsorption rates were achieved in about 240 min. The amount of Cr(VI) adsorbed increased with increasing concentration and decreasing pH and temperature. The intraparticle diffusion rate constants at various temperatures were calculated. Adsorption isotherms of Cr(VI) onto poly(EGDMA-VTAZ) have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The pseudo first-order kinetic model was used to describe the kinetic data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (RL) showed that the adsorption of metal ions onto poly(EGDMA-VTAZ) was favorable. It was seen that values of distribution coefficient (KD) decreasing with Cr(VI) concentration in solution at equilibrium (Ce) indicated that the occupation of activate surface sites of adsorbent increased with Cr(VI). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

  • synthesis and characterization of poly Ethylene Glycol Dimethacrylate 1 vinyl 1 2 4 triazole copolymer beads for heavy metal removal
    Journal of Applied Polymer Science, 2006
    Co-Authors: Lokman Uzun, Ali Kara, Necati Besirli, Nalan Tuzmen, Abdulkerim Karabakan, Adil Denizli
    Abstract:

    We prepared poly(Ethylene Glycol Dimethacrylate–1-vinyl-1,2,4-triazole) [poly(EGDMA–VTAZ)] beads (average diameter = 150–200 μm) by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with 1-vinyl-1,2,4-triazole (VTAZ). The copolymer composition was characterized by elemental analysis and found to contain five EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads had a specific surface area of 65.8 m2/g. Poly(EGDMA–VTAZ) beads were characterized by Fourier transform infrared spectroscopy, elemental analysis, surface area measurements, swelling studies, and scanning electron microscopy. Poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used for the heavy-metal removal studies. The adsorption capacities of the beads for Cd(II), Hg(II), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(EGDMA–VTAZ) beads were 85.7 mg/g (0.76 mmol/g) for Cd(II), 134.9 mg/g (0.65 mmol/g) for Pb(II), and 186.5 mg/g (0.93 mmol/g) for Hg(II). The affinity order toward triazole groups on a molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). pH significantly affected the adsorption capacity of the VTAZ-incorporated beads. The equilibrium data were well fitted to the Redlich–Peterson isotherm. Consideration of the kinetic data suggested that chemisorption processes could have been the rate-limiting step in the adsorption process. Regeneration of the chelating-beads was easily performed with 0.1M HNO3. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4276–4283, 2006

  • immobilization of α amylase on cu2 chelated poly Ethylene Glycol Dimethacrylate n vinyl imidazole matrix via adsorption
    Reactive & Functional Polymers, 2005
    Co-Authors: Ali Kara, Bilgen Osman, Necati Besirli, Handan Yavuz, Adil Denizli
    Abstract:

    Abstract Poly(Ethylene Glycol Dimethacrylate- n -vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150–200 μm) was prepared by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with n -vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m 2 /g. Poly(EGDMA-VIM) beads were characterized by swelling studies and SEM. Cu 2+ ions were chelated on the poly(EGDMA-VIM) beads, then these beads were used in the adsorption of α-amylase from Aspergillus Oryzae in batch system. The maximum α-amylase adsorption capacity of the poly(EGDMA-VIM)–Cu 2+ beads was observed as 38.9 mg/g at pH 4.0. The K m values for immobilized α-amylase (poly(EGDMA-VIM)–Cu 2+ ) (22.5 mM) was higher than that of free enzyme (15.8 mM). Storage stability was found to increase with immobilization. It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity or enzyme activity.

  • poly Ethylene Glycol Dimethacrylate n vinyl imidazole beads for heavy metal removal
    Journal of Hazardous Materials, 2004
    Co-Authors: Ali Kara, Necati Besirli, Lokman Uzun, Adil Denizli
    Abstract:

    Abstract Poly(Ethylene Glycol Dimethacrylate- n -vinyl imidazole) [poly(EGDMA–VIM)] hydrogel (average diameter 150–200 μm) was prepared by copolymerizing Ethylene Glycol Dimethacrylate (EGDMA) with n -vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA–VIM) beads had a specific surface area of 59.8 m 2 /g. Poly(EGDMA–VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA–VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10–750 mg/l) and at different pH values (3.0–7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA–VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II)>Cd(II)>Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO 3 . These features make poly(EGDMA–VIM) beads potential candidate adsorbent for heavy metal removal.