Bihter Zeytuncu

Platinum uptake from chloride solutions using biosorbents

Present work investigates platinum uptake from synthetically prepared, dilute platinum-bearing solutions using biomass residues, i.e. pistachio nut shell and rice husk, which are abundant in Turkey, and provides a comparison between these two biosorbents. Effects of the different uptake parameters, sorbent dosage, contact time, temperature and pH of solution on platinum uptake (%) were studied in detail on a batch sorption. Before the pistachio nut shell was activated, platinum uptake (%) was poor compared to the rice husk. However, after the pistachio nut shell was activated at 1000 °C under an argon atmosphere, the platinum uptake (%) increased two-fold. The pistachio nut shell (original and activated) and rice husk were shown to be better than commercially available activated carbon in terms of adsorption capacity. These two sorbents have also been characterized by FTIR and SEM. Adsorption equilibrium data best complied with the Langmuir isotherm model. Maximum adsorption capacities, Qmax, at 25 °C were found to be 38.31 and 42.02 mg.g - 1for the activated pistachio nut shell and rice husk, respectively. Thermodynamic calculations using the measured ∆H°, ∆S° and ∆G° values indicate that the uptake process was spontaneous and endothermic. The experimental data were shown to be fit the pseudo-second-order kinetic model.

Preparation and Characterization of UV-Cured Hybrid Polyvinyl Alcohol Nanofiber Membranes by Electrospinning

/N=N nanofiber membranes were synthesized. These membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller analysis. According to results, fine polymeric nanofibers were obtained in the size range of 100-200 nm for pure PVA nanofibers and 150-250 nm for PVA/SiO

Adsorption of Ag (I) Ions from Aqueous Solutions Using Photocured Thiol-Ene Hydrogel

In this present work, we reported the adsorption and recovery studies of a P(Penta3MP4/PEG-DA/HEMA) thiol-ene based hydrogel. Real-time infrared spectroscopy technique was used to identify the photopolymerization kinetics of thiol-ene based formulations. The chemical composition and surface morphology of hydrogels were also characterized. The influence of the adsorption conditions such as pH, hydrogel formulations, contact time, initial metal ion concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, were tested. Both the Langmuir and Freundlich isotherm models were applied to the method. The reusability of the hydrogels and the usability of the hydrogels for preconcentration studies were also investigated. The analytical parameters of the method were calculated and the recovery of silver ions from waste radiographic films was also applied to the hydrogels.

Studies of Gold Adsorption from Chloride Media

In this paper, adsorption of gold from chloride media using commercial sorbent (Lewatit TP 214 (L-214)) and biomass residue (rice hull (RH)) were investigated. The different adsorption parameters, sorbent dosage, contact time, temperature and pH of solution on adsorption (%) were studied in detail on a batch sorption. Before the RH was activated, adsorption (%) was poor compared with L-214. However, after the RH was activated at 1000 °C under an argon atmosphere, the gold adsorption (%) increased four-fold. X-ray fluorescence (XRF) was used to explore the feasibility this material as an adsorbent for the removal of gold from aqueous solutions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Qmax, at 25 °C were found to be 93.46 and 108.70 mg/g for the activated rice hull (ARH) and L-214, respectively. Thermodynamic calculations using ΔH°, ΔS°, ΔG° and Ea values indicate that the adsorption process was spontaneous and endothermic.

SORPTION OF GOLD FROM ELECTRONIC WASTE SOLUTIONS BY A COMMERCIAL SORBENT

In this work, sorption of gold from electronic waste solutions using a commercial sorbent, Lewatit TP 214, was investigated. The effects of the different parameters on gold sorption (%) were studied in detail. Sorbent dosage, contact time, temperature, and solution pH were selected as sorption parameters. Additionally, the gold sorption by Lewatit TP 214 is a diffusion-controlled process with activation energies of 12.28 kJ/mol. The thermodynamic values such as ΔG°, ΔH°, and ΔS° were calculated by experimentally obtained results. The reaction was spontaneous and endothermic. The gold sorption capacity for the sorbent was 100.1 mg gold per gram. XRD patterns revealed that the gold was in its metallic form. The results indicated that Lewatit TP 214 can be effectively used for the sorption of gold from waste solution.

Rhodium cementation from spent plating solution using Taguchi’s method

Abstract The Taguchi method was used as the experimental design to determine the optimum conditions of cementation behaviour of the spent rhodium sulphate plating solution. Cementation was carried out using metallic zinc powder. The experimental conditions were studied in the range of 25–45°C for reaction temperature (A), 0·5–1·5 for pH of solution (B), 30–50 mg for zinc powder (C) and 30–60 min for reaction time (D). Experimental parameters and their levels were determined in the light of preliminary tests. An orthogonal array (OA) L934 consisting of four parameters each with three levels, was chosen. The optimal conditions found for cementation of rhodium, such as: reaction temperature, pH of the solution, mass of zinc and reaction time are respectively: 45°C, 1·5, 50 mg and 60 min. A verification experiment was conducted under optimum conditions and it was found that theoretically calculated and experimentally obtained results were in good agreement at 99·98 and 99·95% respectively. On a utilisé la méthode de Taguchi comme plan expérimental dans la détermination des conditions optimales du comportement de cémentation de la solution usée de sulfate de rhodium pour galvanoplastie. On a effectué la cémentation en utilisant de la poudre métallique de zinc. On a étudié les conditions expérimentales dans la gamme de 25 à 45°C pour la température de la réaction (A), 0·5 à 1·5 pour le pH de la solution (B), 30 à 50 mg pour la poudre de zinc (C) et 30 à 60 min pour la durée de réaction (D). On a déterminé les paramètres expérimentaux et leurs niveaux au moyen d’essais préliminaires. On a choisi un arrangement orthogonal (OA) L9(34) comprenant quatre paramètres, chacun à trois niveaux. Les conditions optimales de la cémentation du rhodium, incluant la température de réaction, le pH de la solution, la masse du zinc et la durée de réaction étaient respectivement de 45°C, 1·5, 50 mg et 60 min. On a effectué une expérience de vérification sous les conditions optimales et l’on a trouvé que les résultats calculés théoriquement et les résultats obtenus expérimentalement étaient en bon accord, avec 99·98 et 99·95% respectivement

Fabrication and Characterization of Antibacterial Polyurethane Acrylate-based Materials

In this paper, the fabrication of the photocured materials which contained silver nanoparticles (Ag-NPs) was studied on the properties of materials such as physical, mechanical and thermal properties, especially antibacterial activity. Therefore, silver nanoparticles were prepared and added into the polyurethane based matrix. Chemical and morphological structures of the photocured materials were characterized by FTIR and SEM analysis. SEM images proved the size of the silver nanoparticles and their dispersion into polymer matrix. Thermal, mechanical and optical properties of photocured materials results showed that the prepared polymer compositions containing Ag-NPs exhibited high modulus and better thermal property. Moreover, the antibacterial properties of the polyurethane based materials and polymer material containing AgNPs were determined and these AgNPs containing photocured materials pointed out good antibacterial activity against Escherichia coli and Staphylococcus aureus.

Synthesis of Nanofiber Membrane by Electrospinning Technique

Novel imidazole functionalized mesoporous poly (vinyl alcohol) (PVA)/SiO2, PVA/SiO2 organic-inorganic hybrid nanofiber membranes and pure PVA nanofiber membranes were synthesized by electrospinning combined with UV-curable system. PVA and Geniosil XL 33 (as a SiO2 source) were mixed with N-Vinyl Imidazole (NVI) to prepare the nanofiber polymer solution. To obtain nanofiber membrane, a strong electrostatic force by a high static voltage was applied to the polymer solution by exposuring to UV radiation at the same time. The experimental parameters such as voltage, flow rate, distance from syringe-tip to the collector were optimized. The synthesized membranes were characterized by Fourier-transform infrared spectroscopy (FTIR). Nanofiber diameter and surface area were measured by scanning electron microscopy (SEM) and Brunauer-Emmert-Teller (BET) analysis, respectively. Thermal property of membranes was examined by Thermogravimetric-Differential Thermal Analysis (TG-DTA).

Recovery of Platinum from Dilute Chloride Media Using Biosorbents

Pistachio nut shells and Rice husk, a biomass residue, were investigated as adsorbents for the platinum uptake from synthetically prepared dilute chloroplatinic acid solutions. The effects of the different uptake parameters on platinum uptake (%) were studied in detail on a batch sorption. Before the pistachio nut shell material was activated, platinum uptake (%) was poor compared with rice husk. However, after the pistachio nut shell material was activated at 1000°C under an argon atmosphere, the platinum uptake (%) increased two-fold. The pistachio nut shell (inactivated and activated) and rice husk were characterized by Attenuated Total Reflection-Fourier transform infrared spectroscopy (ATR-FTIR).