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Öğe Amidoximated poly(acrylonitrile) particles for environmental applications: Removal of heavy metal ions, dyes, and herbicides from water with different sources(Wiley, 2016) Ajmal, Muhammad; Demirci, Şahin; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, NurettinMonodispersed poly(acrylonitrile) [p(AN)] particles were prepared by surfactant free emulsion polymerization and the hydrophobic nitrite groups were converted to hydrophilic amidoxime groups by treatment with hydroxylamine hydrochloride (NH2OH center dot HCl) in water. The p(AN) and amidoximated p(AN) [amid-p(AN)] particles were characterized by Fourier transformation infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The prepared particles were used as adsorbents in the removal from aqueous media of three different types of pollutants; organic dyes methylene blue (MB), and rhodamine 6 G (R6G), a heavy metal ion Cd (II), and a herbicide paraquat (PQ). The effects of various parameters such as amidoximation, pH of solution, amount of particles, and the initial concentration of solution were investigated. Upon amidoximation, a great increase in the adsorption capacity of the prepared particles was observed as the adsorbed amounts were increased to 87, 91, 74, and 91 mg/g from 5, 1.54, 1.06, and 1.22 mg/g for Cd (II), MB, R6G, and PQ, respectively. The amid-p(AN) particles were also able to remove considerable amounts of these pollutants from tap, river, and sea water. Langmuir, Freundlich, and Temkin adsorption isotherms were applied and it was found that the adsorption of Cd (II) and PQ followed the Langmuir adsorption model, whereas the adsorption of MB was found to obey the Freundlich adsorption isotherm. Pseudo first-order and pseudo second-order kinetics were also applied and the results showed that the adsorption processes of Cd (II), PQ, MB, and R6G follow pseudo second-order kinetics. (C) 2015 Wiley Periodicals, Inc.Öğe Betaine microgel preparation from 2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide and its use as a catalyst system(Elsevier, 2015) Ajmal, Muhammad; Demirci, Şahin; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, NurettinWe demonstrate the synthesis of poly(sulfobetain methacrylate) (p(SBMA)) hydrogels of micro dimensions by inverse suspension polymerization of a zwitterionic monomer 2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide (SBMA). The prepared microgels were used as microreactors for the synthesis of nickel (Ni) nanoparticles by in situ reduction of Ni (II) loaded into microgels from an aqueous medium. The prepared microgels and microgel metal nanoparticle composites were characterized by Fourier Transformation Infrared (FT-IR) Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Thermal properties of the microgels were studied by thermal gravimetric analysis (TGA). The amount of Ni nanoparticles generated within the microgels was determined by Atomic Absorption Spectroscopy (AAS) after dissolving the Ni nanoparticles to form Ni (II) ions by treating with concentrated hydrochloric acid (5 M HCl). The prepared composites were used as catalysts for the reduction of nitro aromatic compounds such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP) and 4-nitroaniline (4-NA) and excellent catalytic performances were observed. The effects of temperature and amount of catalyst were also evaluated. A mild activation energy in comparison to the literature was calculated as 35.64 kJ/mol, and very high k p value of 0.42 min(-1) as a function of temperature was estimated for the reduction of 4-NP catalyzed by p(SBMA)-Ni composite catalyst system. (C) 2015 Elsevier B.V. All rights reserved.Öğe Gum Arabic Microgels As Template for In Situ Metal-Sulfide Based Quantum Dots Preparation and Their Thermal, Spectroscopic, Optical, and Magnetic Characterization(Springer, 2017) Farooq, Muhammad; Sağbaş, Selin; Yıldız, Mustafa; Meral, Kadem; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, NurettinHere, gum arabic (GA) microgel in 5-50 mu m size range was used as a template for in situ quantum dot (QD) preparation. The in situ synthesis of metal sulfide quantum dots (QDs) such as CdS, PbS, CuS, ZnS, CoS, and MnS was accomplished by the absorption of the corresponding metal ions from aqueous solutions and then in situ precipitation with S2- treatments within GA microgels. Transmission electron microscopy (TEM) confirmed the existence of the evenly distributed QDs within GA microgel matrices for each of the prepared QDs. All the fabricated GA-QD composites have shown excellent semiconducting behaviors with relatively larger band gap values of 4.87 eV, 4.60 eV, 6.71 eV, 4.81 eV, 3.68 eV, 5.2 eV, and 4.0 eV for CdS, PbS, ZnS, CuS, CoS, MoS, and MnS, respectively. The results revealed that CdS and ZnS are found to be the most efficient florescence materials amongst the all QDs with 630 and 70 cd/cm(2) fluorescence intensities, respectively. Moreover, the magnetic susceptibility study suggests that Mn(IV), Co(III), and Mo(IV), have mononuclear octahedral geometries whereas Zn(II), Cd(II), and Pb(II) show binuclear geometries.Öğe Introduction of double amidoxime group by double post surface modification on poly(vinylbenzyl chloride) beads for higher amounts of organic dyes, As (V) and Cr (VI) removal(Academic Press Inc Elsevier Science, 2016) Ajmal, Muhammad; Demirci, Şahin; Uzun, Yusuf; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, NurettinIn this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subsequent conversion of the reactive chloromethyl groups to double amidoxime group containing moieties by post modification is reported. The prepared beads were characterized by SEM and FT-IR spectroscopy. The amidoximated p(VBC) beads were used as adsorbent for the removal of organic dyes, such as eosin y (EY) and methyl orange (MO), and heavy metals containing complex ions such as dichromate (Cr2O72- and arsenate (HAsO42-) from aqueous media. The effect of the adsorbent dose on the percent removal, the effect of initial concentration of adsorbates on the adsorption rate and their amounts were also investigated. The Langmuir, Freundlich and Temkin adsorption isotherms were applied to the adsorption processes. The results indicated that the adsorption of both dichromate and arsenate ions obeyed the Langmuir adsorption model. Interestingly, it was found that the prepared beads were capable of removing significant amounts of arsenate and dichromate ions from tap and river (Sancay, Canakkale-Turkey) water. (C) 2016 Elsevier Inc. All rights reserved.Öğe Simultaneous catalytic degradation/reduction of multiple organic compounds by modifiable p(methacrylic acid-co-acrylonitrile)-M (M: Cu, Co) microgel catalyst composites(Royal Soc Chemistry, 2016) Ajmal, Muhammad; Demirci, Şahin; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, NurettinWe prepared poly(methacrylic acid-co-acrylonitrile) (p(MAc-co-AN)) microgels by inverse suspension polymerization, and converted the nitrite groups into amidoxime groups to obtain more hydrophilic amidoximated poly(methacrylic acid-co-acrylonitrile) (amid-p(MAc-co-AN)) microgels. Amid-microgels were used as microreactors for in situ synthesis of copper and cobalt nanoparticles by loading Cu(II) and Co(II) ions into microgels from their aqueous metal salt solutions and then converted to their corresponding metal nanoparticles (MNPs) by treating the loaded metal ions with sodium borohydride (NaBH4). The characterization of the prepared microgels and microgel metal nanoparticle composites was carried out by SEM, TEM and TG analysis. The amounts of metal nanoparticles within microgels were estimated by MS measurements by dissolving the MNP entrapped within microgels by concentrated HCl acid treatment. Catalytic performances of the prepared amid-p(MAc-co-AN)-M (M: Cu, Co) microgel composites were investigated by using them as catalysts for the degradation of cationic and anionic organic dyes such as eosin Y (EY), methylene blue (MB) and methyl orange (MO), and for the reduction of nitro aromatic pollutants like 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) to their corresponding amino phenols. Here, we also report for the first time, the simultaneous degradation/reduction of MB, EY and 4-NP by amid-p(MAc-co-AN)-Cu microgel composites. Different parameters affecting the reduction rates such as metal types, the amount of catalysts, temperature and the amount of reducing agent were investigated.Öğe Synthesis, characterization and modification of Gum Arabic microgels for hemocompatibility and antimicrobial studies(Elsevier Sci Ltd, 2017) Farooq, Muhammad; Sağbaş, Selin; Şahiner, Mehtap; Siddiq, Mohammad; Türk, Mustafa; Aktaş, Nahit; Şahiner, NurettinGum Arabic (GA) microgels were successfully prepared via reverse micellization method with high yield (78.5 +/- 5.0%) in 5-100 mu m size range using divinyl sulfone (DVS) as a crosslinker. The GA microgels were degraded hydrolytically 22.8 +/- 3.5% at pH 1 in 20 days, whereas no degradation was observed at pH 7.4 and pH 9 at 37 degrees C. By using diethylenetriamine (DETA), and taurine (TA) as chemical modifying agents, GA microgels were chemically modified as GA-DETA and GA-TA, and the zeta potential values of 5.2 +/- 4.1 and -24.8 +/- 1.3 mV were measured, respectively in comparison to -27.3 +/- 4.2 mV for GA. Moreover, blood compatibility of GA, GA-TA, and GA-DETA microgels was tested via in vitro protein adsorption, % hemolysis ratio, and blood clotting index. All the microgels were hemocompatible with% hemolysis ratio between 0.23 to 2.05, and the GA microgels were found to be highly compatible with a blood clotting index of 81 +/- 40. The biocompatibility of GA, GA-DETA and GA-Taurine microgels against L929 fibroblast cells also revealed 84.4, 89.1, and 67.0% cell viability, respectively, at 25.0 mu g/mL concentration, suggesting great potential in vivo biomedical applications up to this concentration. In addition, 5 and 10 mgImL minimum inhibition concentrations of protonated GA-DETA microgels (GA-DETA-HCl) were determined against E. coli and S. aureus, respectively. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Synthesis, Characterization, and Use of Carbon Microspheres for Removal of Different Dyes from Aqueous Environments(Springer, 2017) Şahiner, Nurettin; Farooq, Muhammad; Rehman, Saif Ur; Sağbaş, Selin; Şahiner, Mehtap; Siddiq, Mohammad; Aktaş, NahitHerein, we report the synthesis of carbon spheres (CS) using a relatively low-temperature hydrothermal technique using lactose as precursor pre-treated with HCl. The successful synthesis, spherical morphology, porous morphology, and monodispersed nature of CS were confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Isoelectric point (IEP) was determined as 3.8, and at neutral conditions the prepared carbon particles are negatively charged at - 43 +/- 2.50 mV. Owing to their spherical morphology, almost uniform distribution and negatively charged surface at neutral conditions, the prepared CS were used as adsorbent for the removal of methylene blue (MB) and Geimsa stain (GS) from aqueous environments at pH 7. It was shown that CS has 97% adsorption capability for GS, whereas for methylene MB, the maximum adsorption capacity was 67% for 0.1-g CS from 50-ppm dye solutions in DI water. The adsorption studies revealed that the Langmuir and modified Fruendlich (MFE) adsorption models resulted in considerably high linear correlation coefficient (r(2)) values and the efficient adsorption of positively charged species on CS can be represented better with the MFE model.
