Melike Fırlak

Removal of Lead and Cadmium Ions from Aqueous Solutions Using Sulphur and Oxygen Donor Ligand Bearing Hydrogels

A new thiourea and urea functional monomers were synthesized. A series of hydrogels were prepared by photopolymerization. The hydrogels were used for the removal of Pb(II) and Cd(II) ions from aqueous solutions. The influence of the uptake conditions such as the pH, the time, and the initial feed concentration on the metal ion binding capacity of hydrogel was tested. The selectivity of the hydrogels towards the different metal ions was also tested. The adsorption isotherm models were applied. The limits of detection and quantification were calculated. The usability of the hydrogels for preconcentration studies were also investigated.

Evaluation of different wastewater treatment techniques in three WWTPs in Istanbul for the removal of selected EDCs in liquid phase

Endocrine-disrupting compounds (EDCs) are exogenous substances that cause adverse health effects in an intact organism, or its progeny, subsequent to the changes in endocrine function. Recent studies have shown that wastewater treatment plant effluents play an important role in the release of EDCs into aquatic environments. Therefore, in this study, influent and effluent samples from three different wastewater treatment plants (WWTPs) in Istanbul were analysed for the presence of the principal EDCs. These chemicals include steroids and synthetic organic chemicals. Thus, the occurrence and fate of EDCs of great health concern were monitored at three WWTPs in Istanbul. Furthermore, these WWTPs are employing different treatment processes. Therefore, the EDC removal performances of different treatment regimes were also evaluated. Phytosterol was the most abundant EDC in the influent samples. Second group of compounds at high influent levels were alkyl phenols. Pesticide levels of all three WWTP influent samples were low. Pasakoy Advanced WWTP is more effective at eliminating EDCs. Kadikoy Primary WWTP exhibits the lowest EDC elimination efficiencies. To the best of our knowledge, this work comprises the first detailed report on the occurrence and behaviour of both natural and synthetic EDCs in WWTPs of Istanbul and Turkey. The steroid estrogen levels of this study are higher than the previously documented values, except the levels given for Gaobeidian WWTP in Beijing, China. This is attributed to higher population densities of Beijing and Istanbul and as well as to lower individual water consumption rates in the two cities.

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.

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.

Removal of Ag(I) from Aqueous Solutions by Thiol-ene-Based Hydrogel and Its Application to Radiographic Films

The thiol-ene-based P(Penta3MP4/PEGDA/AAc) hydrogels were prepared by UV curing technique, then characterized and used as adsorbents for the investigation of the effect of process parameters such as pH of solution, contact time, and initial concentration of solution, on the removal of Ag(I) from aqueous solution. The results indicate that the adsorption of Ag(I) ions from aqueous solutions is strongly dependent on pH under experimental conditions. Both Langmuir and Freundlich isotherm models were applied to experimental data, and the results show that the adsorption process is well fitted to the Langmuir isotherm model. Selectivity, reusability, and applicability of hydrogels to radiographic film waste were investigated.

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.