Halil Şahan

A graphene/Co3O4 nanocomposite as a new adsorbent for solid phase extraction of Pb(II), Cu(II) and Fe(III) ions in various samples

A graphene-based cobalt nanocomposite (G/Co3O4) was synthesized and used for the first time as an effective adsorbent for the preconcentration of the Pb(II), Cu(II) and Fe(III) ions in environmental water and food samples prior to flame atomic absorption detection. The properties of the graphene, Co3O4 and G/Co3O4 nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis. The experimental parameters affecting the solid phase extraction efficiency for analyte ions including sample pH, adsorption and elution contact time, volume and concentration of eluting reagent, sample volume and interfering ions were examined. The adsorption capacity of the G/Co3O4 composite was found to be 58, 77 and 78 mg g−1 for Pb(II), Cu(II) and Fe(III), respectively. The quantitative elution of the adsorbed metal ions was carried out by 2 mL of 2 mol L−1 HNO3. The preconcentration factor of the method was 175. The limit of detection was found to be ≤0.81 μg L−1. The accuracy of the method was studied by analyzing certified reference material (RM 8704 Buffalo River Sediment, SRM 1568a Rice Flour and SPS-WW1 Batch 111-Wastewater) and spiked real samples. The method was applied for the separation and preconcentration of trace metal ions in tap water, wastewater, dam water, well water, kiwi and wheat samples.

A Novel Method to Improve the Electrochemical Performance of LiMn2O4 Cathode Active Material by CaCO3 Surface Coating

Spinel LiMn2O4 was synthesized by glycine-nitrate method and coated with CaCO3 in order to enhance the electrochemical performance at room temperature (25°C) and 55°C. The uncoated and CaCO3-coated LiMn2O4 materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. XRD and SEM results indicated that CaCO3 particles encapsulated the surface of the LiMn2O4 without causing any structural change. The charge-discharge tests showed that the specific discharge capacity fade of pristine electrode at 25 and 55°C were 25.5% and 52%, respectively. However, surface modified cathode shows 7.4% and 29.5% loss compared to initial specific discharge capacity at 70th cycle for 25 and 55°C, respectively. The improvement of electrochemical performance is attributed to suppression of Mn2+ dissolution into electrolyte via CaCO3 layer.

Nano sponge Mn2O3 as a new adsorbent for the preconcentration of Pd(II) and Rh(III) ions in sea water, wastewater, rock, street sediment and catalytic converter samples prior to FAAS determinations

In this study, a nano sponge Mn2O3 adsorbent was synthesized and was used for the first time. Various parameters affecting the recovery values of Pd(II) and Rh(III) were examined. The tolerance limits (≥ 90 %) for both Pd(II) and Rh(III) ions were found to be 75,000 mg L(-1) Na(I), 75,000 mg L(-1) K(I), 50,000 mg L(-1) Mg(II) and 50,000 mg L(-1) Ca(II). A 30s contact time was enough for both adsorption and elution. A preconcentration factor of 100 was obtained by using 100mg of the nano sponge Mn2O3. The reusability of the adsorbent was 120 times. Adsorption capacities for Pd(II) and Rh(III) were found to be 42 and 6.2 mg g(-1), respectively. The detection limits were 1.0 µg L(-1) for Pd(II) and 0.37 µg L(-1) for Rh(III) and the relative standard deviations (RSD, %) were found to be ≤ 2.5%. The method was validated by analyzing the standard reference material, SRM 2556 (Used Auto Catalyst Pellets) and spiked real samples. The optimized method was applied for the preconcentration of Pd(II) and Rh(III) ions in water (sea water and wastewater), rock, street sediment and catalytic converter samples.

Nanosized spongelike Mn3O4 as an adsorbent for preconcentration by vortex assisted solid phase extraction of copper and lead in various food and herb samples

In this paper, a nanosized spongelike Mn3O4 was synthesized and used for the first time as an effective adsorbent for vortex-assisted separation and preconcentration of lead and copper from various food samples. Copper and lead were determined by flame atomic absorption spectrometry. The characterization of the nanosized spongelike Mn3O4 was performed by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, Brunauer, Emmett and Teller surface area and zeta potential measurement. The contact times for both adsorption and elution were only 3min. Under the optimized conditions, detection limits for copper and lead were found to be 2.6μgL(-1) and 3.0μgL(-1), respectively. The relative standard deviations were found to be ⩽3.2%. The accuracy of the method was confirmed by analyzing the standard reference materials (BCR-482 Licken and SRM 1573a Tomato Leaves) and spiked real food and herb samples.

Ultralayered Co3O4 as a new adsorbent for preconcentration of Pb(II) from water, food, sediment and tobacco samples

In this study, ultralayered Co3O4 adsorbent was synthesized and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface area of the solid material was found to be 75.5m(2)g(-1) by BET method. The ultralayered Co3O4 was used for the first time as an effective adsorbent for the preconcentration of the Pb(II) ions in various samples prior to flame atomic absorption detection. Analytical parameters affecting the solid phase extraction of Pb(II) such as pH, adsorption and elution contact time, eluent volume and concentration, sample volume and common matrix ions were investigated. The recovery values for Pb(II) were found to be ≥ 92% even in the presence of 75,000 mg L(-1) Na(I), 75,000 mg L(-1) K(I), and 75,000 mg L(-1) Ca(II) ions. 10s vortexing time was enough for both adsorption and elution contact times. The elution was easily made with 2 mL of 2.0 mol L(-1) HNO3. The reusability (170 cycles) and adsorption capacity (35.5 mg g(-1)) of ultralayered Co3O4 were excellent. The preconcentration factor of the method and detection limit were found to be 175 and 0.72 µg L(-1), respectively. The described method was validated with certified reference material (RM 8704 Buffalo River Sediment, BCR-482 Licken and SPS-WW1 Batch 111-Wastewater) and spiked real samples. It was also applied for the preconcentration of Pb(II) ions in various water (well water, mineral water, waste water and sea water), food (cauliflower and barley), street sediment and tobacco samples.

Synthesis and cycling performance of double metal doped LiMn2O4 cathode materials for rechargeable lithium ion batteries

In order to improve the cycling performance of LiMn2O4, the spinel phases LiCo0.15Mn1.85O4 and LiCo0.05M0.1Mn1.85O4 (M = Ni, Zn, Cu) were prepared by the sol-gel method. Their structures have been investigated by x-ray diffraction. Electrochemical studies were carried out using the Li | LixMn2O4 (x = 1.05, 1.1), LiCo0.15Mn1.85O4, and LiCo0.05M0.1Mn1.85O4 (M = Ni, Zn, Cu) cells. The capacity loss of Li | LixMn2O4 (x = 1.05, 1.1) cells is about 21.7 and 6.4% after 30 cycles, whereas that for Co, Co-Ni, Co-Zn, and Co-Cu doped spinel materials is about 4.0, 2.0, 1.0, and 1.9%, respectively. The good capacity retention of LiCo0.05M0.1Mn1.85O4 (M = Ni, Zn, Cu) electrodes is attributed to stabilization of spinel structure by double metal doping for Mn ion sites. Double substituted spinels display better performance in terms of cycle-life compared with LiMn2O4.

Ionic liquid coated carbon nanospheres as a new adsorbent for fast solid phase extraction of trace copper and lead from sea water, wastewater, street dust and spice samples.

In this study a new adsorbent, ionic liquid (1,8-naphthalene monoimide bearing imidazolium salt) coated carbon nanospheres, was synthesized for the first time and it was used for the solid phase extraction of copper and lead from various samples prior to determination by flame atomic absorption spectrometry. The ionic liquid, carbon nanospheres and ionic liquid coated carbon nanospheres were characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, (1)H NMR and (13)C NMR, Brunauer, Emmett and Teller surface area and zeta potential measurements. Various parameters for method optimization such as pH, adsorption and elution contact times, eluent volume, type and concentration, centrifuge time, sample volume, adsorption capacity and possible interfering ion effects were tested. The optimum pH was 6. The preconcentration factor, detection limits, adsorption capacity and precision (as RSD%) of the method were found to be 300-fold, 0.30µgL(-1), 60mgg(-1) and 1.1% for copper and 300-fold, 1.76µgL(-1); 50.3mgg(-1) and 2.2%, for lead, respectively. The effect of contact time results showed that copper and lead were adsorbed and desorbed from the adsorbent without vortexing. The equilibrium between analyte and adsorbent is reached very quickly. The method was rather selective for matrix ions in high concentrations. The accuracy of the developed method was confirmed by analyzing certified reference materials (LGC6016 Estuarine Water, Reference Material 8704 Buffalo River Sediment, and BCR-482 Lichen) and by spiking sea water, wastewater, street dust and spice samples.

Spectrophotometric determination of basic fuchsin from various water samples after vortex assisted solid phase extraction using reduced graphene oxide as an adsorbent.

In this study, a fast and simple vortex assisted solid phase extraction method was developed for the separation/preconcentration of basic fuchsin in various water samples. The determination of basic fuchsin was carried out at a wavelength of 554 nm by spectrophotometry. Reduced graphene oxide which was used as a solid phase extractor was synthesized and characterized by X-ray diffraction, scanning electron microscopy and the Brunauer, Emmett and Teller. The optimum conditions are as follows: pH 2, contact times for adsorption and elution of 30 s and 90 s, respectively, 10 mg adsorbent, and eluent (ethanol) volume of 1 mL. The effects of some interfering ions and dyes were investigated. The method was linear in the concentration range of 50-250 μg L(-1). The adsorption capacity was 34.1 mg g(-1). The preconcentration factor, limit of detection and precision (RSD, %) of the method were found to be 400, 0.07 μg L(-1) and 1.2%, respectively. The described method was validated by analyzing basic fuchsin spiked certified reference material (SPS-WW1 Batch 114-Wastewater) and spiked real water samples.

Preconcentration of Ag and Pd ions using graphite oxide and 2,6-diaminopyridyne from water, anode slime and catalytic converter samples

In this work, graphite oxide was used for the first time as an effective adsorbent for the separation/preconcentration of Ag and Pd ions in various samples prior to flame atomic absorption detection. 2,6-diaminopyridyne was used as a chelating reagent. Analytical parameters affecting the solid phase extraction of Ag and Pd such as pH, adsorption and elution contact time, centrifugation time, reagent amount, eluent concentration and volume, sample volume and matrix ions were investigated. The recovery values for Ag and Pd were found to be ≥ 95%. The adsorption and elution contact times were 60 s. The preconcentration factor of the method was 120 for a 600 mL sample using 100 mg of the graphite oxide. The elution was easily performed using 5 mL of 2.0 mol L−1 HCl. The graphite oxide was reusable for 150 cycles. The detection limits of Ag and Pd were 0.39 μg L−1 and 0.94 μg L−1, respectively. The relative standard deviations (RSD, %) were ≤2.5%. The proposed method was validated by analysing the certified reference materials SRM 2556 (used auto catalyst pellets) and TMDA-70 lake water, and spiked real samples. The optimized method was applied for the preconcentration of Ag and Pd ions in various water (tap water, mineral water and wastewater), anode slime and catalytic converter samples.

Dispersive Solid-Phase Extraction of Rhodium from Water, Street Dust, and Catalytic Converters Using a Cellulose–Graphite Oxide Composite

ABSTRACT A cellulose–graphite oxide composite was synthesized and characterized as an adsorbent for dispersive solid-phase extraction of rhodium from various samples before atomic absorption detection. The pH, adsorbent volume, centrifugation time and rate, eluent concentration, volume and type, adsorption and elution contact time, sample volume, and matrix interferences were optimized. The developed method is simple, rapid, and inexpensive. The tolerance limits for rhodium were 10,000 mg L−1 sodium, 25,000 mg L−1 potassium, 10,000 mg L−1 magnesium, and 20,000 mg L−1 calcium. The recovery for rhodium exceeded 95%. Elution was performed with 10 mL of 2.5 mol L−1 H2SO4. The adsorption and elution contact times were 30 and 60 s, respectively. The detection limit of the method for rhodium was 5.4 µg L−1 and the precision as the relative standard deviation was 1.6%. A certified reference material 2556 (used auto catalyst pellets) and fortified samples were analyzed to evaluate the accuracy of the method. The optimized method was used for the preconcentration of rhodium from tap water, well water, wastewater, seawater, catalytic converters, and street dust.