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    Adsorption of Malachite Green from Aqueous Solution Using Hydroxyethyl Starch Hydrogel Improved by Graphene Oxide
    (Springer, 2022) Onder, Alper; Kivanc, Mehmet Riza; Durmus, Secil; Ilgin, Pinar; Ozay, Hava; Özay, Özgür
    This study is the first report of the preparation of hydroxyethyl starch (HES) hydrogels rapidly crosslinked with divinyl sulfone in a single step and single pot. To develop the physical and chemical features of hydrogels, Graphene oxide (GO) nanoparticles were combined with the crosslinked HES. In addition to swelling studies, structural characterization of the samples was conducted with a scanning electron microscope (SEM) and transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). For the removal of malachite green model dye by GO-HES, the effects of GO content, solution concentration, temperature, contact duration, dosage and pH on varying adsorption features were researched. Additionally, adsorption isotherms, kinetic and thermodynamic systematics were analyzed. The maximum adsorption capacity of GO-HES composite hydrogel was found to be 89.3 mg/g for Langmuir isotherm. The possible adsorption mechanism of the composite hydrogels for malachite green dye involved electrostatic, hydrogen bonding, and pi-pi interactions. In addition to reasonable cost and simple synthesis method, the prepared composite materials have potential use in wastewater treatment as adsorbents for the removal of dye from aqueous solutions due to efficient adsorption capacity.
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    An innovative approach to use zeolite as crosslinker for synthesis of p(HEMA-co-NIPAM) hydrogel
    (Springer Wien, 2022) Durmus, Secil; Yilmaz, Betul; Onder, Alper; Ilgin, Pinar; Ozay, Hava; Özay, Özgür
    This study introduced a modified method to synthesize organic-inorganic hybrid crosslinker based on zeolite. First, zeolite nanoparticles were modified with 3-(aminopropyl)trimethoxysilane. Then, the amine-functionalized zeolite has been reacted with the glycidyl methacrylate via an epoxide ring-opening mechanism. The vinyl-functionalized zeolite was applied as a crosslinking agent to form hydrogel network. A novel temperature-sensitive nanocomposite hydrogel was prepared by crosslinking N-isopropylacrylamide as a comonomer and 2-hydroxyethyl methacrylate as a monomer with free-radical polymerization. Results showed that p(2-hydroxyethyl methacrylate-co-N-isopropylacrylamide)/vinyl-functionalized zeolite nanocomposite hydrogel has a chemically crosslinked and porous network structure. The content of crosslinker and monomers had obvious effects on the swelling ratio of the nanocomposite hydrogel. The temperature and salt-sensitive behavior of the hydrogels are also discussed. We offer a multifunctional crosslinker for preparing sensitive materials that can serve biomedical or environmental applications.
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    Fly ash as catalyst support material in the hydrolysis of ethylenediamine bisborane for hydrogen production: The use of coal-fired power plant waste
    (Pergamon-Elsevier Science Ltd, 2020) Onder, Alper; Özay, Özgür
    Efficient, low-cost and safe new systems are still needed for the storage and usage of hydrogen energy, which is considered the most important energy source of the future. For this reason, the aim of this study was to prepare Co-0, Ni-0, and Cu-0 composite catalysts with fly ash (FA) formed by combustion of coal in thermal power plants to be used for the dehydrogenation of ethylenediamine bisborane (EDAB) as a hydrogen source. In the hydrolysis reactions of EDAB, parameters such as metal type, catalyst concentration, temperature, and EDAB concentration were investigated. The FA-Cu-0 composite catalyst was determined to be an effective catalyst system for hydrogen production by hydrolysis of EDAB from among the FA-M-0 composite catalysts. Besides, FA can be used as an effective support material in order to prevent agglomeration of metal particles. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Graphene nanoplate incorporated Gelatin/poly(2-(Acryloyloxy)ethyl trimethylammonium chloride) composites hydrogel for highly effective removal of Alizarin Red S from aqueous solution
    (Springer, 2022) Ozsoy, Fatma; Ozdilek, Batuhan; Onder, Alper; Ilgin, Pinar; Ozay, Hava; Özay, Özgür
    The increasing water pollution day by day has increased the importance of developing new adsorbent materials. In this study, composite hydrogel containing gelatin, [2-(Acryloyloxy)ethyl] trimethylammonium chloride (AETAC) and Graphene Nanoplate (GNPt) was developed as an adsorbent for the removal of dyes from wastewater. Fourier Transform Infrared Spectrophotometer, Scanning Electron Microscope, X-Ray Diffractometer results confirmed the crosslinked polymer structure of Gelatin/p(AETAC)/GNPt composite hydrogel (Gel 5). In addition, equilibrium swelling ratio, which is a parameter affecting the adsorption behavior, was 48.22 g(water) /g(gel). The adsorption behavior of Alizarin Red S anionic dyestuff on composite hydrogel from aqueous solutions was investigated under various experimental conditions such as initial dye concentration of solution, amount of adsorbent, contact time, pH of solution, temperature of solution. ARS dye adsorption on composite hydrogel is consistent with Pseudo-Second-Order kinetic model and Langmuir isotherm with max adsorption capacity of 649.35 mg/g. The composite hydrogel with high mechanical strength has high dye removal ability in the ranging pH from 4 to 8. Therefore, it can be said that Gelatin/p(AETAC)/GNPt composite hydrogel has a substantial potential for the removal of anionic dyes from wastewater in a wide pH range.
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    Removal of dye from aqueous medium with pH-sensitive poly [(2-(acryloyloxy)ethyl]trimethylammonium chloride-co-1-vinyl-2-pyrrolidone] cationic hydrogel
    (Elsevier Sci Ltd, 2020) Onder, Alper; Ilgin, Pinar; Ozay, Hava; Özay, Özgür
    In this study, p([2-(acryloyloxy)ethyl]trimethylammonium chloride-co-1-vinyl-2-pyrrolidinone) (p(AETAC-co-NVP) hydrogels containing positive charge in the structure were synthesized for the removal of anionic dyes from the aqueous media. The swelling behaviors affecting the adsorption properties of hydrogels structurally characterized by FTIR, SEM and EDX/mapping analysis were investigated. The effects of pH, dye concentration, adsorbent amount, dissolved anions and temperature on the adsorption of methyl orange (MO) and alizarin red S(AR) from aqueous media using p(AETAC-co-NVP) hydrogels were investigated. Using data obtained in adsorption studies, the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms and pseudo-first order (PFO), pseudo-second order (PSO), intra-particular diffusion, and Elovich kinetic model analyses were performed. The results showed that the p(AETAC-co-NVP) hydrogel was a good adsorbent for MO and AR anionic dyes and the adsorption process for both dyes complied with the Freundlich isotherm and PSO kinetic model. This situation indicates that the dominant mechanism for the adsorption of MO and AR dyes by the p(AETAC-co-NVP) hydrogel is strong electrostatic interactions and occurs as multilayered adsorption, not only on a planar region. Additionally, to the maximum adsorption values using p(AETAC-co-NVP) hydrogel for MO and AR dyes were reached at pH values of 7.0 and 5.0, respectively. According to all these findings, it can be said that the p (AETAC-co-NVP) hydrogel containing positivelly charged groups is a super adsorbent for adsorption of anionic dyes.
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    Synthesis, spectroscopic, and thermal properties of some azomethine complexes of Cu(II), Ni(II), and Pt(II)
    (Springer, 2012) Turkyilmaz, Murat; Onder, Alper; Baran, Yakup
    Four polydentate azomehines and their mono- and binuclear Pt(II), Cu(II), and Ni(II) complexes were synthesized and characterized. The resulting complexes were characterized by FTIR, magnetic measurements, elemental analysis, conductivity measurements, and thermal analysis. Electronic spectra and magnetic susceptibility measurements sustain the proposed distorted square-planar structures for the copper complexes. The electronic spectra display the characteristic pattern of square-planar stereochemistry for the other complexes. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Azomethine complexes have a similar thermal behavior for the selected metal ions. The decomposition processes as water elimination, chloride anion removal as well as degradation of the organic ligands were observed.
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    Synthesis, spectroscopic, magnetic and thermal properties of copper(II), nickel(II) and iron(II) complexes with some tetradentate ligands: Solvatochromism of iron(II)-L2
    (Elsevier Science Sa, 2012) Onder, Alper; Turkyilmaz, Murat; Baran, Yakup
    The tetradentate azomethines were prepared by condensation of 2-piperazin-1-ylethanamine, (3-morpholin-4-ylpropyl)amine with 3-methylthophene-2-carbaldehyde, salicylaldehyde and 1H-imidazole-5-carbaldehyde. The ligands were characterized based on mass, H-1 and C-13 NMR, FTIR, and elemental analyses. New complexes of ligands with copper(II), iron(II) and nickel(II) were synthesized. Metal complexes are reported and characterized by magnetic, conductivity measurements, FTIR, elemental and thermal analyses (TG-DTA). Spectral analyses show that all the ligands behave as neutral tetradentate ligands and bind to the metal via azomethine N, piperazine N, salicylaldehyde O, morpholine O, imidazole N and thiophene S. Results of magnetic measurements and thermal studies show that the geometrical structures of the nickel(II) complexes are square planar while copper(II) and iron(II) are octahedral. The thermal behaviors of these complexes show that the hydrated complexes lose the hydration water molecule in the first step, followed immediately by decomposition of the anion and ligand molecules in subsequent steps. The solvatochromic behavior of the iron(II)-(L)2 complex was investigated using the electronic spectra of 1 x 10 (3) M in four different solvents. The solvatochromism was explained in terms of MLCT transition and solvent characteristics such as polarity, nature and acceptor-donor properties. (C) 2012 Elsevier B.V. All rights reserved.