Soner Çubuk

Uptake of Pb2+ Using N-Vinyl Imidazole Based Uniform Porous Hydrogels

The uniform porous and continuous phase lead (II) adsorbent hydrogel, was prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AAc), and N,N′-methylenebisacrylamide (MBAAm), with n-vinyl imidazole (VIM). A series of hydrogels, including different ratios of VIM, were prepared by photopolymerization and characterized. The influence of the uptake conditions such as pH, functional monomer percent, contact time, initial feed concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, were also tested. The selective chelation of heavy metal ions from synthetic wastewater was also studied. The affinity order on molar basis was observed as follows: Pb (II) > Zn (II) > Cd (II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms and it was seen that the Langmuir isotherm model was the best fit for the adsorption of Pb (II) ions in P(VIM/AAc/HEMA) hydrogel. Moreover, the limits of detection and the quantification values were determined. Regeneration of the hydrogels was easily performed with 1 M HCl and the same hydrogel can be reused five times almost without any loss of adsorption capacity. All these features make P(VIM/AAc/HEMA) hydrogels potential candidate adsorbent for heavy metal removal.

Nutrient dynamics and eutrophication in the Sea of Marmara: Data from recent oceanographic research

This work was implemented to study the physicochemical and biological characteristics of the Sea of Marmara and the Turkish straits (TSS: Bosporus and Dardanelles straits) for the period 2010-2013 and to calculate winter and summer fluxes of nutrients (nitrates, phosphates) between the Aegean and Black Seas through the TSS. The brackish Black Sea waters reach the Dardanelles Strait with modified biochemical properties. The salinity and phosphates of the surface waters increased westwards. Biologically labile nutrients of Black Sea origin are utilized through biological processes in the Marmara Sea. On the other hand, increase of nutrients due to land based sources has led to eutrophication problems in the area. The sub surface water layer of Mediterranean origin is oxygen depleted (saturation<30%) and rich in nutrients. Higher oxygen values indicated water mixing of the Sea of Marmara during winter 2012. Ammonium was the predominant form of inorganic nitrogen. The study area has been classified from Moderate to Bad trophic status. İzmit Bay also faced serious eutrophication problems together with hypoxic conditions below the halocline. Nutrient fluxes through the TSS showed temporal variation in the upper and lower layers related to changes in both nutrient concentrations and the water mass volume fluxes. Surface nitrates and phosphates outflux from the Sea of Marmara to the Aegean Sea was higher than the influx from the Black Sea through Bosporus strait, indicating high enrichment of nutrients in the Sea of Marmara from anthropogenic sources.

Recovery of Au(III) ions by Au(III)-imprinted hydrogel

A new Au(III)-imprinted hydrogel (Au(III)-Imp) was prepared by the photopolymerisation of 4-acryloylmorpholine (AcM), 2-hydroxyethyl acrylate (HEA), and poly(ethylene glycol) diacrylate (cross-linking monomer, PEG-DA) in the presence of gold ions. In addition, non-imprinted hydrogel (N-Imp) was similarly prepared without Au(III) ions The Au(III)-Imp hydrogel was characterised by several techniques. To achieve the optimal conditions, effect of pH, time, and initial metal ion concentrations were investigated using a batch system. The pre-concentration factor for Au(III) ions was found to be at least 100. The analytical parameters of the method were determined and the method was also successfully applied to computer circuit board scrap samples. The reusability of the Au(III)-Imp hydrogel was also determined.

Photocured thiol-ene based optical fluorescence sensor for determination of gold(III).

This study describes the preparation and the characterization of a new thiol-ene based polymeric fluorescence sensor by photo initiated polymerization of trimethylolpropane tris(3-mercaptopropionate), 2-hydroxyethylacrylate, and 2,4,6-triallyloxy-1,3,5-triazine which are used as monomers and also a photo initiator (2,2-dimethoxy-2-phenylacetophenone) for its usage as optical sensor for gold ions. The thiol-ene based polymeric membrane sensor was characterized by using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). The response characteristics of the sensors including dynamic range, pH effect, response time, and the effect of foreign ions were investigated. Fluorescence spectra showed that the excitation/emission maxima of the membrane were at 379/425 nm, respectively.

Reusable fluorescent photocrosslinked polymeric sensor for determining lead ions in aqueous media.

In this study, 1-vinylimidazole units bearing photocured films were prepared as fluorescent sensors towards Pb(2+) in aqueous solutions. The influence of experimental parameters such as pH, time and foreign ion concentrations were investigated. Sensor response was linear over a concentration range of 4.83×10(-8) to 4.83×10(-7) mol L(-1). The sensor was highly sensitive with a detection limit as low as 1.87×10(-8)molL(-1), and having a selectivity of over four thousand fold. The response time of the sensor was found to be 5 min. When stored in a desiccator at room temperature the sensor showed good stability after a 5 month period. The fluorescence sensors were successful in the determination of Pb(2+) in water samples as well as in the determination of the quantitative amount of lead and the results were satisfying. Compared with previously reported literature, the prepared new sensor is highly sensitive and selective.