Ümit H. Kaynar

An efficient removal of RB5 from aqueous solution by adsorption onto nano-ZnO/Chitosan composite beads

In this study, the removal of Reactive Black 5 (RB-5) by nano-ZnO/Chitosan composite beads (nano-ZnO/CT-CB) from aqueous solution was investigated. ZnO nanoparticles were prepared by the via the microwave-assisted combustion technique. And then nano-ZnO/Chitosan composite beads were prepared by polymerization in the presence of nano-ZnO and chitosan. Characterization of composite beads were conducted using SEM, TEM, FTIR, TGA and XRD. Several important parameters influencing the removal of RB 5 such as contact time, pH and temperature were investigated systematically by batch experiments. At optimum conditions of pH 4 and adsorbent concentration of 0.2g, dye removal efficiency was found 76%. Langmuir, Freundlich and Temkin adsorption models were used to describe adsorption isotherms and constants. The maximum adsorption capacity (qm) by Langmuir isotherm has been found to be 189.44mg/g. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (32.7kJ/mol) indicated that the adsorption is an endothermic process. The obtained results showed that the tested adsorbents are efficient and alternate low-cost adsorbent for removal of dyes from aqueous media.

Modeling of thorium (IV) ions adsorption onto a novel adsorbent material silicon dioxide nano-balls using response surface methodology

The silicon dioxide nano-balls (nano-SiO2) were prepared for the adsorption of thorium (IV) ions from aqueous solution. The synthesized silicon dioxide nano-balls were characterized by Scanning Electron Microscopy/Energy Dispersive X-ray, X-ray Diffraction, Fourier Transform Infrared and BET surface area measurement spectroscopy. The effects of pH, concentration, temperature and the solid-liquid ratio on the adsorption of thorium by nano-balls were optimized using central composite design of response surface methodology. The interaction between four variables was studied and modelled. Furthermore, the statistical analysis of the results was done. Analysis of variance revealed that all of the single effects found statistically significant on the sorption of Th(IV). Probability F-values (F=4.64-14) and correlation coefficients (R(2)=0.99 for Th(IV)) indicate that model fit the experimental data well. The ability of this material to remove Th(IV) from aqueous solution was characterized by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption capacity of thorium (IV) achieved 188.2mgg(-1). Thermodynamic parameters were determined and discussed. The batch adsorption condition with respect to interfering ions was tested. The results indicated that silicon dioxide nano-balls were suitable as sorbent material for adsorption and recovery of Th(IV) ions from aqueous solutions.

Preparation and cathodoluminescence characteristics of rare earth activated BaAl 2 O 4 phosphors

Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF♯17-306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln=Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition 4G5/2 → 6H7/2 located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule ΔJ = ± 1. For the Tb3+ doped samples, they exhibit D45 green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.

A modeling and optimization study by response surface methodology (RSM) on UO22+ ions adsorption using nano-MgO particles prepared with combustion synthesis

Abstract Nano-MgO particles were made for the adsorption of UO22+ from aqueous solutions. The obtained MgO nanoparticles were characterized by FTIR, XRD and SEM. The adsorption of UO22+ by particle was optimized with RSM. Coefficients of correlation (R2 = 0.99) and probability F-values (F = 3.1  10−10) reveal that the model is very good for the experimental data. Under optimum conditions, the adsorption capacity of nano-MgO particles was found to be 128.4 mg g−1. The results showed that nano-MgO particles were suitable for the sorption of UO22+ ions from aqueous solutions. In addition, the adsorption isotherms and the thermodynamic parameters were examined.

DEEA-Volkanit Üzerine Toryum(IV) Adsorpsiyonunun Yanıt Yüzey Metodu (YYM) ile Optimizasyonu

Bu calismada, Th(IV) adsorpsiyonu icin ekonomik ve bol miktarda bulunan alkali bazaltik yapidaki Kula volkanitinin DEEA organik katyonu ile modifiye edilip adsorpsiyon kapasitesinin artirilarak kullanilmasi amaclanmistir. Oncelikle hazirlanan DEEA-volkanitin XRF, FT-IR, SEM ve BET yuzey alani gibi yapisal karakteristik ozellikleri incelendi, daha sonra sulu cozeltilerden Th(IV) adsorpsiyonu endustriyel arastirmalarda genis bir kullanima sahip yanit yuzey metodu (YYM) ile optimize edildi. Adsorpsiyon verimi uzerine etkin deneysel kosullar: pH (3-8), Th(IV) konsantrasyonu (20-100 mg/L), sicaklik (20-60 °C) ve sure (15-120 dakika) olarak secildi. Bu parametrelerin en iyi muhtemel kombinasyonlari Yanit Yuzey Metodu (YYM) ile elde edildi. Deneysel kosullarin tasarimi icin merkezi kompozit dizayn (CCD) secildi. RSM verilerine gore, tasarimin ikinci dereceden (kuadratik) modele uydugu ve model uyumunu gosteren parametrelerden R 2 ve R 2 Ayarli degerlerinin sirasiyla 0,99 ve 0,99 oldugu gorulmustur. Optimum kosullarinda DEEA-Volkanit icin adsorpsiyon kapasitesi 38,94 mg/g elde edilmistir. Ayrica, calismada Th (IV) adsorpsiyonunun izotermlere uygunlugu arastirilmis ve termodinamik parametreler hesaplanmistir.