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    Cationic microgels embedding metal nanoparticles in the reduction of dyes and nitro-phenols
    (Elsevier Science Sa, 2015) Rehman, Saif Ur; Siddiq, Mohammed; Al-Lohedan, Hamad; Şahiner, Nurettin
    Cationic microgels of p(3-Acrylamidopropy1)-trimethylammonium chloride (p(APTMACI)) were synthesized using the inverse suspension polymerization technique, and the obtained microgels were used as microreactor for in situ synthesis of Co, Ni, and Cu nanoparticles. The p(APTMAC1) microgels were loaded with Co,.Ni, and Cu after contact with chloride salts of the metals, CoCl2, NiCl2, and CuCl2, in ethanol and reduced to their respective metal nanoparticles by treating them with sodium borohydride (NaBH4) as reducing agent. The metal nanoparticle content of p(APTMAC1) microparticles were quantified for each composites by atomic absorption spectroscopy (AAS) after dissolution of the metal nanoparticles within microgel composites by concentrated hydrochloric acid (HCI). Dynamic light scattering (DIS) was used to monitor zeta potential of the microgel composites. Thermal properties of both cationic p(APTMAC1) microgel and its composites were investigated with a thermal gravimetric analyzer (TGA). It was also found that the p(APTMAC1) composites performed as excellent catalyst systems in the reduction of different aromatic pollutants like 2-nitrophenol, 4-nitrophenol and fluorescent dyes like eosin Y(EY), and methyl orange (MO). Various parameters such as metal types, and their respective amount, and temperature were investigated to determine the catalytic performances of the microgel-metal nanoparticle composites. (C) 2014 Elsevier B.V. All rights reserved.
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    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; Aktaş, Nahit; Şahiner, Mehtap; Demirci, Şahin; Şahiner, 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.
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    Removal of arsenate and dichromate ions from different aqueous media by amine based p(TAEA-co-GDE) microgels
    (Academic Press Ltd- Elsevier Science Ltd, 2017) Rehman, Saif Ur; Khan, Abdur Rahman; Şahiner, Mehtap; Bütün Şengel, Sultan; Aktaş, Nahit; Siddiq, Muhammad; Şahiner, Nurettin
    In this work, microgels based on tris(2-aminoethyl) amine (TAEA) and glycerol diglycidyl ether (GDE) via simple microemulsion polymerization was prepared as p(TAEA-co-GDE) microgels were used as adsorbent for removal of dichromate (Cr (VI)) and arsenate (As (V)) ions from different aqueous environments. The p(TAEA-co-GDE) microgels were demonstrated very efficient adsorption capacity for Cr (VI), and As (V) that are 164.98 mg/g, and 123.64 mg/g from distilled (DI) water, respectively. The effect of the medium pH on the adsorption capacity of p(TAEA-co-GDE) microgels for Cr (VI) and As (V) ions were investigated. The maximum adsorption capacity was obtained at pH 4.0 for both ions with maximum adsorbed amounts of 160.62, and 98.72 mg/g, respectively. In addition, the microgels were also shown moderate adsorption capacity for Cr (VI) and As (V) from other water sources; tap water with 115.18 mg/g and 82.86 mg/g, sea water with 64.24 mg/g and 46.88 mg/g and creek water with 73.52 mg/g and 59.33 mg/g, respectively. Moreover, the increase in adsorbent dose from 0.025 to 0.125 g enhanced % adsorption of Cr (VI) from 54.13 to 98.03, and As (V) from % 26.72-98.70, respectively. For the adsorption process Langmuir and Freundlich adsorption isotherms were applied and found that Langmuir adsorption isotherm with R-2 value of 0.99 for both the metal ions are suitable. Moreover, the experimental adsorption capacities of Cr (VI) and As (V) were found very close to the theoretical values calculated from Langmuir adsorption isotherm. More importantly, the microgels were made magnetic responsive to recover them easily from adsorption medium for reuse studies by applying external magnetic field with little decrease in adsorption capacity. Additionally, reusability of p(TAEA-co-GDE) microgels was also evaluated for adsorption of Cr (VI) and As (V) from DI water. (C) 2017 Elsevier Ltd. All rights reserved.
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    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, Nahit
    Herein, 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.