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    Biochar-Embedded Soft Hydrogel and Their Use in Ag Nanoparticle Preparation and Reduction of 4-Nitro Phenol
    (Taylor & Francis As, 2013) Şahiner, Nurettin; Karakoyun, Necdet; Alpaslan, Duygu; Aktaş, Nahit
    The authors report the synthesis of a composite hydrogel based on acrylamide-chicken biochar(AAm)-CBand its use as a template in the preparation of silver metal nanoparticles. Moreover, we demonstrate the efficient utilization of p(AAm)-CB composite hydrogel as a reactor vessel in the reduction of an organic contaminant 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Experimental parameters affecting 4-NP reduction rate were investigated. The kinetics of the reduction reaction under different reaction conditions were also evaluated to determine the activation parameters. Activation energy for the reduction of 4-NP was 15.25kJmol1 and p(AAm)-CB-Ag composites possessed 99.45% activity after five repetitive uses.
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    Hydrogel-Biochar composites for effective organic contaminant removal from aqueous media
    (Elsevier, 2011) Karakoyun, Necdet; Kubilay, Şenol; Aktaş, Nahit; Turhan, Ömer; Kasımoğlu, Murat; Yılmaz, Selahattin; Şahiner, Nurettin
    In this study, p(acrylamide)-chicken biochar (p(AAm)-CB), p(acrylamide)-wood biochar (p(AAm)-WB), and p(acrylamide)-tire biochar (p(AAm)-TB) hydrogel composites were prepared using acrylamide (AAm) as monomer with the corresponding biochars, with N,N'-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. P(AAm)-CB, p(AAm)-WB, and p(AAm)-TB were used as adsorbents to remove phenol from aqueous environments. The synthesized p(AAm)-CB, p(AAm)-WB, p(AAm)-TB and p(AAm) hydrogel composites had swelling values of 1112, 1045, 847, and 623%, respectively in distilled water. The prepared hydrogel biochar material compositions were examined using an elemental analyzer. Absorption of phenol into p(AAm)-WB was studied at different pHs to determine the optimum pH for maximum removal of phenol. The ionic strength of the medium was varied between 0.01 and 1 mol L-1 to determine the effect of salt (NaCl) on the absorption characteristics and it was found that the absorption of phenol increased with a decrease in the amount of salt. Langmuir and Freundlich isotherms were applied to describe the absorption characteristics and the Langmuir isotherm describes the absorption phenomena in this study much better than the Freundlich isotherm. Pseudo-first-order and pseudo-second-order kinetic studies were also applied to determine absorption characteristic. (C) 2011 Elsevier B.V. All rights reserved.
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    Reusable Soft Hydrogels for Gold Recovery from Acidic Environments
    (Taylor & Francis Inc, 2013) Şahiner, Nurettin; Karakoyun, Necdet; Şahan, Tekin; Bütün, Sultan; Aktaş, Nahit
    In this study, poly((N-(hydroxymethyl) acrylamide) co-1-allyl-2-thiourea) hydrogels were synthesized by free radical crosslinking copolymerization of N-(hydroxymethyl) acrylamide monomer with the addition of a co-monomer 1-allyl-2-thiourea, and N, N'-methylenebisacrylamide as the crosslinker. The copolymer, poly((N-(hydroxymethyl) acrylamide) co-1-allyl-2-thiourea), was used as a specific sorbent for the recovery of gold. The characteristics of the hydrogels were examined by elemental analyzer and swelling experiments. The effect of pH on the absorption of gold, and the separation and recovery of gold ions from ore samples were investigated. Measurement of absorbed gold was determined by using F-AAS and GF-AAS.