Browsing by Author "Demirci, Sahin"

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0d, 1d, 2d, and 3d Soft and Hard Templates for Catalysis
(Elsevier Science Bv, 2017) Butun, Sultan; Demirci, Sahin; Yasar, Alper O.; Sagbas, Selin; Aktas, Nahit; Sahiner, Nurettin
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, Sahin; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin
Monodispersed 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.
Betaine Microgel Preparation From 2-(methacryloyloxy) Ethyl] Dimethyl (3-Sulfopropyl) Ammonium Hydroxide and Its Use as a Catalyst System
(Elsevier, 2015) Ajmal, Muhammad; Demirci, Sahin; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin
We 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.
Catalytic Performance of Boron-Containing Magnetic Metal Nanoparticles in Methylene Blue Degradation Reaction and Mixture With Other Pollutants
(Elsevier, 2021) Meydan, Engin; Demirci, Sahin; Aktas, Nahit; Sahiner, Nurettin; Ozturk, Omer Faruk
The catalytic effects of metal nanoparticles (MNPs) synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsion system by using M(II) salts (M = Fe, Co, Ni) and NaBH4 reducing agent on methylene blue (MB) degradation reaction were investigated. It was determined that Co-MNPs gave the best catalytic activity among them. Influence of the reaction parameters e.g., reaction time, temperature, the size of catalyst and the MNP types on the catalytic performance were studied. It was found that 37 +/- 6 nm Co-MNPs revealed the best catalytic activity in all studies. The best activation parameters were calculated as 13.6 +/- 1.1 kJ mol(-1) and Delta H = 10.7 +/- 1.0 kJ mol(-1) and Delta S = -87.9 +/- 5.4 J mol(-1) K-1. The activity % of Co-MNPs was calculated as 85.4 after 30 days on the shelf life study. The reusability studies were carried out and the activity of Co-MNPs at the 5th reuse was calculated as 70 +/- 5%. Finally, the catalytic activity of Co-MNPs was investigated inside equal volumes of single and multiple solution mixtures containing MB, 4-Nitrophenol (4-NP) and Eosin Y (EY). In the examinations, it was observed that the nanocatalyst was effective as a reducing agent in all equal amount solutions (MB/4-NP, MB/EY, 4-NP/EY, and MB/4-NP/EY). And also, TOF (mole of MB/4-NP/EY) (mol catalyst.min)(-1) values of catalytic activities were also calculated.
Dichromate and Arsenate Anion Removal by Pei Microgel, Cryogel, and Bulkgel
(Elsevier Sci Ltd, 2021) Kubilay, Senol; Demirci, Sahin; Can, Mehmet; Aktas, Nahit; Sahiner, Nurettin
Among the various metal ions, chromate (Cr(VI)) and arsenate (As(V)) are the two most hazardous toxic ion species and are found in nature in the form of dichromate and arsenate anions. In this investigation, polyethyleneimine (PEI)-based hydrogels were prepared with microgel, cryogel, and bulkgel morphologies employing glycerol diglycidyl ether as a crosslinker. The prepared PEI-based hydrogels were used to remove dichromate and arsenate anions from aqueous media. PEI microgel, cryogel, and bulkgels weighing 50 mg of each adsorbed 84.7 +/- 0.8, 76.5 +/- 5.2, and 108.9 +/- 2.4 mg.g(-1) of dichromate anions and 15.9 +/- 0.7, 45.4 +/- 1.9, and 79.2 +/- 11.6 mg.g(-1) of arsenate anions in 30, 120, and 240 min, respectively. The dichromate and arsenate anions adsorption of PEI-based hydrogels were found to fit to the pseudo-second-order kinetic, and nonlinear Langmuir isotherm models, respectively with higher R-2 values. The highest distribution coefficient (K-d) value of PEI-based hydrogels for dichromate adsorption was obtained on the cryogel forms of PEI as 1.89 +/- 0.05. Likewise, the highest K-d value for the arsenate adsorption was calculated on PEI-based bulkgels as 0.46 +/- 0.01. The thermodynamic parameters of PEI based hydrogels in the adsorption of dichromate and arsenate anions e.g., Delta G (all negative (except for the arsenate adsorption by PEI microgels), and Delta H that is around 2-10 kJ.mol(-1), and Delta S what is around 0.01-0.02 kJ.mol(-1). K-1 were calculated. The reusability studies showed that PEI-based hydrogels can be used for at least 5 consecutive adsorption-desorption cycles with almost 70 % anion removal efficiency after the fifth cycle.
Environmental Application of Pei Based Hydrogels in Different Morphology and Sizes: Bulk, Microgel, and Cryogel
(Amer Chemical Soc, 2015) Sahiner, Nurettin; Demirci, Sahin; Sahiner, Mehtap; Al-Lohedan, Hamad; Aktas, Nahit
Fast Removal of High Quantities of Toxic Arsenate Via Cationic P(Aptmacl) Microgels
(Academic Press Ltd- Elsevier Science Ltd, 2016) Rehman, Saif Ur; Siddiq, Mohammed; Al-Lohedan, Hamad; Aktas, Nahit; Sahiner, Mehtap; Demirci, Sahin; Sahiner, Nurettin
Hydrogels are resourceful materials and can be prepared in different morphology, size, surface charge and porosity adopting different polymerization techniques and reaction conditions. The cationic poly(3-acrylamidopropyl)trimethylammonium chloride (p(APTMACl)) microgels were synthesized by photo-initiated inverse suspension polymerization technique. These microgels were utilized as absorbents for the removal of toxic arsenate (As) from different aqueous environments. The experimental parameters affecting absorption efficiency were investigated, and it was demonstrated that these types of microgels are highly efficient in removing arsenate anions from different aqueous environments compared to the previously reported bulk hydrogel, and cryogel of the same material. A removal efficiency of approximately 97.25% was obtained by immersing 0.5 g microgel in 250 ppm 100 mL solution of arsenate anions for 60 min. Both Langmuir and Freundlich adsorption isotherms were applied to adsorption of arsenate anions by p(APTMACl) microgels, and the Langmuir isotherm was a better representation of the adsorption of arsenate with a high value of R-2 (0.9982). Furthermore, mag-p(APTMACl) microgels were synthesized for the adsorption of arsenate anions to provide easy removal of the microgel composite by using an externally applied magnetic field. Furthermore, re-usability of the p(APTMACl) microgels was also investigated for the adsorption of arsenate anions. CD 2015 Elsevier Ltd. All rights reserved.
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, Sahin; Uzun, Yusuf; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin
In 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.
Monodisperse Polymeric Ionic Liquid Microgels by Post Modifications and Their Versatile Biomedical Applications
(Amer Chemical Soc, 2015) Sahiner, Nurettin; Yasar, Alper; Yildiz, Sema; Demirci, Sahin; Aktas, Nahit
Nh3 Gas Sensing Applications of Metal Organic Frameworks
(Elsevier, 2015) Sel, Kivanc; Demirci, Sahin; Ozturk, Omer Faruk; Aktas, Nahit; Sahiner, Nurettin
Various MOFs as TMA-M derived from Ba(II), Cd(II), Pb(II), and Zn(II) as metal ions (M) and trimesic acid (TMA, benzene-1,3,5-tricarboxylic acid) as organic linker were prepared for the determination of their susceptibility against ammonia (NH3). FT-IR spectroscopy, thermogravimetric analysis, SEM images, BET surface area and porosity measurements were done. Furthermore, the room temperature conductivity of the synthesized TMA-M MOFs were investigated against room temperature NH3 vapor. The room temperature conductivities were determined 8.3E10(-11), 7.6E10(-11) and 1.7E10(-10) S cm(-1) for TMA-Zn, TMA-Cd and TMA-Pb, respectively. Among the TMA-M MOFs, it was observed that TMA-Zn MOF showed relatively higher response to NH3 vapor, where it's conductivity was increased about 50 times in comparison to the conductivity measurement of TMA-Zn MOF in the absence of NH3. Furthermore, a more detailed conductivity analysis of this response was investigated for TMA-Zn MOF as a function of various NH3 exposure times at room temperature. (C) 2015 Elsevier B.V. All rights reserved.
Ph-Responsive Amphoteric P (aptmacl-Co Hydrogel as Effective Multiple Dye Sponge Network From Aqueous Media
(Frontiers Media Sa, 2022) Demirci, Sahin; Ari, Betul; Aktas, Nahit; Sahiner, Nurettin
Here, the cationic poly (3-acrylamidepropyl trimethyl ammonium chloride) [p (APTMACl)], anionic poly (2-acrylamido-2methylpropane sulfonic acid) [p (AMPS)], and amphoteric poly (APTMACl-co-AMPS) hydrogels were prepared via free-radical polymerization techniques as pH-sensitive hydrogels. The prepared systems were used in methylene blue (MB), and Eosin Y (EY) removal from aqueous media. HCl-treated p (APTMACl-co-AMPS) hydrogels prepared in 1:3 mol ratio adsorbed higher amount of MB and EY from their corresponding 50 ml 50 ppm aqueous solutions that are 47.5 +/- 0.9, and 10.7 +/- 0.1 mg/g, respectively. Also, the adsorbed amount of MB and EY by HCl-treated p (APTMACl-co-AMPS) hydrogels decreased with the increase in the medium pH from 3.0 to 9.0. It was also observed that HCl-treated p (APTMACl-co-AMPS)-3 hydrogels removed 39.2 +/- 0.2, and 28.1 +/- 1.0 mg/g MB and EY dyes simultaneously from their corresponding 50 ml 50 ppm aqueous mixture solutions. MB and EY adsorption by HCl-treated p (APTMACl-co-AMPS)-3 hydrogels were found to abide by pseudo-first-order adsorption kinetics. Moreover, MB adsorption by HCl-treated p (APTMACl-co-AMPS) hydrogels were found to fit with Freundlich, EY adsorption fit with Langmuir isotherms. The distribution coefficient values of HCl-treated p (APTMACl-co-AMPS) hydrogels were calculated as 3.7 +/- 0.1 and 1.3 +/- 0.1 for MB and EY, respectively. The calculated selectivity coefficient value showed that HCl-treated p (APTMACl-co-AMPS) hydrogels are at least 3-fold higher selective to MB than EY.
Polyethyleneimine Based Ionic Liquid Colloids
(Amer Chemical Soc, 2014) Sahiner, Nurettin; Demirci, Sahin; Aktas, Nahit
Removal of As(V), Cr(Iii) and Cr(Vi) From Aqueous Environments by Poly(acrylonitril-Co Ammonium Chloride)-Based Hydrogels
(Academic Press Ltd- Elsevier Science Ltd, 2015) Dudu, Tuba Ersen; Sahiner, Mehtap; Alpaslan, Duygu; Demirci, Sahin; Aktas, Nahit
Cationic poly(Acrylonitril-co-Acrylamidopropyl-trimethyl Ammonium Chloride) (p(AN-co-APTMACl)) hydrogels in bulk were synthesized by using acrylonitrile (AN) and 3-acrylamidopropyl-trimethyl ammonium chloride (APTMACl) as monomers. The prepared hydrogels were exposed to amidoximation reaction to replace hydrophobic nitrile groups with hydrophilic amidoxime groups that have metal ion binding ability. Those replacements were increased the hydrogels absorption capacity for As(V) and Cr(VI). Langmuir and Freundlich isotherms equations were utilized to obtain the best-fitted isotherm model for the absorption of the ions at different metal ion concentrations. The absorption data of As(V) ion were fitted well to Freundlich isotherm while those of Cr(VI) and Cr(III) ions were fitted well to Langmuir isotherm. The maximum absorption of poly(3-acrylamidopropyl-trimethyl ammonium chloride (p(APTMACl)) and amid-p(AN-co-APTMACl) macro gels were 22.39 mg and 21.83 mg for As(V), and 30.65 mg and 18.16 mg for Cr(VI) ion per unit gram dried gel, respectively. Kinetically, the absorption behaviors of Cr(III) and Cr(VI) ions were fitted well to a pseudo 2nd-order kinetic model and those of As(V) ions were fitted well to a pseudo 1st order kinetic model. (C) 2015 Published by Elsevier Ltd.
Simultaneous Catalytic Degradation/Reduction of Multiple Organic Compounds by Modifiable P(Methacrylic Acid-Co (M: Cu, Co) Microgel Catalyst Composites
(Royal Soc Chemistry, 2016) Ajmal, Muhammad; Demirci, Sahin; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin
We 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.
Superporous Cryogel/Conductive Composite Systems for Potential Sensor Applications
(Springer, 2017) Sahiner, Nurettin; Demirci, Sahin; Aktas, Nahit
In situ synthesis of conductive polymers, poly(Aniline) (p(An)), poly(Pyrrole) (p(Py)), and poly(Thiophene) (p(Th)) within network of superporous cryogels with tunable functionalities as neutral poly(acrylamide) (p(AAm), anionic poly(acrylic acid) (p(AAc)), and cationic poly(4-vinylpyridine) (p(4-VP)) were carried out via oxidation polymerization technique. The highest conductivity values were measured for p(AAm)/p(An) semi-IPN cryogel with 1.4 x 10(-2) S. cm(-1) and for p(AAc)/p(Py) cryogel with 3.2 x 10(-4) S. cm(-1). In addition, to increase the amounts of conductive polymers within cryogel networks, reloading/ polymerization cycle was carried out thrice, and found that there is no significant increase in the amounts of conductive polymers and the measured conductivity values. The prepared p(AAm), p(AAc), and p(4-VP) cryogels and their corresponding p(An), p(Py), and p(Th) composites were tested potential sensor materials against HCl and NH3 vapor. The changes on conductivities for bare p(4-VP) cryogel were observed as 70 and 52-fold increase uponHCl and NH3 gas treatment, respectively. The p(4-VP)/p(An) p(An) composites showed 7-fold conductivity decrease upon the treatments of HCl and NH3 vapors. The p(AAm)/p(Py) composite responded 2-fold increase upon HCl vapor exposure and 50-fold decrease upon NH3 vapor exposure. Furthermore, p(AAm)/p(Th) cryogel composite responded 7-fold decrease and 300-fold increase in their conductivities upon HCl and NH3 vapor exposure, respectively.