Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Shahwan, TalalWoS Q: search.filters.wosQuartile.Q1

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Now showing 1 - 10 of 26
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Speciation of Inorganic and Organometallic Arsenic in Various Matrices With a Novel Spme Fiber Functionalized With Iron Nanoparticles Prior To Lc-Icp Determination
    (Elsevier, 2025) Boyaci, Ezel; Cagir, Ali; Shahwan, Talal; Eroglu, Ahmet E.
    A novel SPME-LC-ICP-MS methodology is described for the simultaneous microextraction/speciation/determination of the metabolically critical inorganic and organoarsenic species, namely, As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) in natural waters such as drinking and geothermal waters, and biological fluids such as urine. The novelty of the study stems also from the use of home-made SPME fibers for the extraction process, and from the proposed methodology needing no derivatization step. SPME fibers were prepared with in-tube capillary template approach through the immobilization of iron nanoparticles into agarose matrix. The fibers demonstrated reproducible extraction (<10 % RSD), good mechanical strength and good solvent resistivity. The separation of the analytes was realized by HPLC with a strong anion exchange column via gradient elution using different concentrations of (NH4)(2)CO3 (pH 8.50), and the on-line detection of eluted analytes was achieved by ICP-MS. The validity of the proposed methodology was verified via the analysis of certified reference materials (SRM 1643e, Natural Water-Trace Elements, and SRM 2669, Arsenic Species in Frozen Human Urine) and through spike recovery tests. The values of percentage recovery for SRM 2669 were 90.7 % for As(III), 99.8 % for As(V), 93.6 % for DMA, and 85.9 % for MMA. A good correlation was also found between the certified (60.45 mu gL(-1)) and determined (59.00 mu gL(-1)) values for SRM 1643e. Moreover, the speciation capability of the method was demonstrated on various natural waters and biological fluids.
  • Article
    Citation - WoS: 41
    Citation - Scopus: 40
    Biosorption of Cu(ii) and Pb(ii) Ions From Aqueous Solution by Natural Spider Silk
    (Elsevier Ltd., 2011) Pelit, Levent; Ertaş, Fatma Nil; Eroğlu, Ahmet Emin; Shahwan, Talal; Tural, H.
    Aside from its excellent mechanical properties, spider silk (SS) would offer an active surface for heavy metal interaction due to its rich protein structure. The present study describes the potential use of natural (SS) as a sorbent of heavy metals from aqueous solutions. Single and multi-species biosorption experiments of heavy metals by natural SS were conducted using batch and column experiments. The biosorption kinetics, in general, was found to follow the second-order rate expression, and the experimental equilibrium biosorption data fitted reasonably well to Freundlich isotherm. From the Freundlich isotherm, the biosorption capacities of Cu(II) and Pb(II) ions onto SS were found as 0.20 and 0.007mmolg -1, respectively. The results showed a decrease in the extent of metal ion uptake with lowering the pH.
  • Article
    Citation - WoS: 45
    Citation - Scopus: 55
    Incorporation of Iron Nanoparticles Into Clinoptilolite and Its Application for the Removal of Cationic and Anionic Dyes
    (Korean Society of Industrial Engineering Chemistry, 2015) Nairat, Muath; Shahwan, Talal; Eroğlu, Ahmet Emin; Fuchs, Harald
    This study reports the preparation of composite sorbents of iron nanoparticles (nZVI) and clinoptilolite at various iron/clinoptilolite ratios. The composites were characterized using various characterization techniques. The material was used for the removal of methylene blue (MB) and methyl orange (MO) as model cationic and anionic dyes. The experiments investigated the effects of time, loading, initial pH, reusability, and temperature on the removal process. According to the results, Cl-nZVI showed fast and quantitative removal over a wide range of concentrations. The removal process was endothermic in nature, and the composite demonstrated reusability for several trials.
  • Other
    Corrigendum To “modification of a Montmorillonite–illite Clay Using Alkaline Hydrothermal Treatment and Its Application for the Removal of Aqueous Cs+ Ions” [j. Colloid Interface Sci. 295 (2006) 303–309]
    (Elsevier Ltd., 2006) Öztop, Bahar; Shahwan, Talal
    Unfortunately, we noticed that Ref. [8], which was cited three times in our article, was mistakenly not cited also in the experimental part as the reference on which we based our hydrothermal treatment process. In light of this, the first paragraph of the experimental section (pages 303 and 304) should read...
  • Article
    Citation - WoS: 33
    Citation - Scopus: 33
    Modification of a Montmorillonite-Illite Clay Using Alkaline Hydrothermal Treatment and Its Application for the Removal of Aqueous Cs+ Ions
    (Elsevier Ltd., 2006) Öztop, Bahar; Shahwan, Talal
    A montmorillonite-illite clay was modified using alkaline hydrothermal treatment (reflux method) and applied to the removal of aqueous Cs+ ions. The alkaline solutions were prepared by dissolving NaOH in seawater and in distilled water, and the effect of the two alkaline media on the sorption capacities of the modified clay was discussed. The modified materials were characterized using XRD, SEM/EDS, and FTIR. As a result of the modification, the original mineral was partially transformed into a zeolitic material with spherical morphology. The results showed that the modification improved the Cs+ uptake capacity of the starting clay, with the clay modified in distilled water medium demonstrating higher sorption capacity. The sorption data were adequately described using the Freundlich and Dubinin-Radushkevich isotherm models.
  • Letter
    Citation - WoS: 46
    Citation - Scopus: 53
    A Characterization Study of Some Aspects of the Adsorption of Aqueous Co2+ Ions on a Natural Bentonite Clay
    (Elsevier Ltd., 2006) Shahwan, Talal; Erten, Hasan N.; Ünügür, S.
    The natural bentonite used in this study contained montmorillonite in addition to low cristobalite. The uptake of aqueous Co2+ ions was investigated as a function of time, concentration, and temperature. In addition, the change in the interlayer space of montmorillonite was analyzed using XRPD, and the distribution of fixed Co2+ ions on the heterogeneous clay surface was recorded using EDS mapping. The sorbed amount of Co2+ appeared to closely follow Freundlich isotherm, with the sorption process showing apparent endothermic behavior. The relevance of the apparent Δ Ho values is briefly discussed. Analysis of the Co-sorbed bentonite samples using SEM/EDS showed that the montmorillonite fraction in the mineral was more effective in Co2+ fixation than the cristobalite fraction. XRPD analysis demonstrated that the interlayer space of montmorillonite was slightly modified at the end of sorption.
  • Article
    Citation - WoS: 109
    Citation - Scopus: 119
    Synthesis of Amidoximated Polyacrylonitrile Fibers and Its Application for Sorption of Aqueous Uranyl Ions Under Continuous Flow
    (Elsevier Ltd., 2012) Horzum Polat, Nesrin; Shahwan, Talal; Parlak, Onur; Demir, Mustafa Muammer
    This study reports a feasible method for the removal of radioactive U(VI) ions from aqueous systems via column sorption under continuous flow. Electrospun polyacrylonitrile (PAN) fibers were used as sorbent materials in a homemade minicolumn. The nitrile groups on the fibers' surface were modified to amidoxime groups using hydroxylamine hydrochloride. Surface modification was observed to enhance the sorption capacity of PAN fibers toward uranium ions by more than 4-fold by virtue of the chelating ability of the amidoxime groups. The experiments investigated the effect of pH, initial concentration, and repetitive loading on the sorption properties of amidoximated PAN fibers. Based on the overall results, the surface-modified fibers seem to be a suitable potential sorbent material for applications in environmental cleanup, particularly for nuclear plants.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 4
    Tof-Sims Depth Profiling Analysis of the Uptake of Ba2+ and Co2+ Ions by Natural Kaolinite Clay
    (Elsevier Ltd., 2004) Shahwan, Talal; Erten, Hasan N.; Black, Leon; Allen, Geoffrey Charles
    The sorption behavior of Ba2+ and Co2+ ions on a natural clay sample rich in kaolinite was studied using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Depth profiling at 10-Å steps was performed up to a 70-Å matrix depth of the clay prior to and following sorption. The results showed that Co2+ is sorbed in slightly larger quantities than Ba2+, with significant numbers of ions fixed on the outermost surface of the clay. Depletion of the ions K+, Mg 2+, and Ca2+ from the clay lattice was observed to accompany enrichment with Co2+ and Ba2+ ions. The data obtained using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) indicated insignificant structural and morphological changes in the lattice of the clay upon sorption of both Ba2+ and Co2+ ions. Analysis using energy dispersive X-ray spectroscopy (EDS) showed that the average atomic percentage (±S.D.) of Ba and Co on kaolinite surface were 0.49±0.11 and 0.61±0.19, respectively, indicating a limited uptake capacity of natural kaolinite for both ions.
  • Article
    Citation - WoS: 87
    Citation - Scopus: 108
    Synthesis and Characterization of Bentonite/Iron Nanoparticles and Their Application as Adsorbent of Cobalt Ions
    (Elsevier Ltd., 2010) Shahwan, Talal; Üzüm, Çağrı; Eroğlu, Ahmet Emin; Lieberwirth, Ingo
    This study reports the synthesis and characterization of iron nanoparticles in the presence of K10 bentonite. Introducing K10 during synthesis of iron nanoparticles resulted in a partial decrease in the aggregation of the nanoparticles. The dispersed nanoparticles showed a typical core–shell structure and were predominantly within the 10–60 nm size range. The composite adsorbent was tested for the removal of Co2+ ions in aqueous solution at various contact times, concentrations, pH, and repetitive loadings. The rate of adsorption was evaluated using first and second order rate equations. The adsorption was described by the Freundlich model. The adsorbent showed effective removal after re-use and the adsorption increased with increasing initial pH.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 17
    Separation of Trace Antimony and Arsenic Prior To Hydride Generation Atomic Absorption Spectrometric Determination
    (Elsevier Ltd., 2005) Ural, Müşerref Yersel; Erdem, Aslı; Eroğlu, Ahmet Emin; Shahwan, Talal
    A separation method utilizing a synthetic zeolite (mordenite) was developed in order to eliminate the gas phase interference of Sb(III) on As(III) during quartz furnace hydride generation atomic absorption spectrometric (HGAAS) determination. The efficiency of the proposed separation method in the reduction of suppression effects of transition metal ions on As(III) signal was also investigated. Among the volatile hydride-forming elements and their different oxidation states tested (Sb(III), Sb(V), Se(IV), Se(VI), Te(IV), and Te(VI)), only Sb(III) was found to have a signal depression effect even at low (μg l−1) concentrations under the experimental conditions employed. It has been shown that mordenite adsorbs Sb(III) quantitatively, even at a concentration of 1000 μg l−1, at pHs greater than two, and also, it reduces the initial concentrations of the transition metal ions to lower levels which can be tolerated in many studies. The adsorption of Sb(III) on mordenite follows the Freundlich isotherm and is endothermic in nature.