Cengiz Kavaklı

Adsorption of heavy metal ions onto dithizone-anchored poly (EGDMA-HEMA) microbeads

The dithizone-anchored poly (EGDMA-HEMA) microbeads were prepared for the removal of heavy metal ions (i.e. cadmium, mercury, chromium and lead) from aqueous media containing different amounts of these ions (25-500 ppm) and at different pH values (2.0-8.0). The maximum adsorptions of heavy metal ions onto the dithizone-anchored microbeads from their solutions was 18.3, Cd(II); 43.1, Hg(II); 62.2, Cr(III) and 155.2 mg g(-1) for Pb(II). Competition between heavy metal ions (in the case of adsorption from mixture) yielded adsorption capacities of 9.7, Cd(II); 28.7, Hg(II); 17.6, Cr(III) and 38.3 mg g(-1) for Pb(II). The same affinity order was observed under non-competitive and competitive adsorption, i.e. Cr(III)>Pb(II)>Hg(II)>Cd(II). The adsorption of heavy metal ions increased with increasing pH and reached a plateaue value at around pH 5.0. Heavy metal ion adsorption from artificial wastewater was also studied. The adsorption capacities are 4.3, Cd(II); 13.2, Hg(II); 7.2, Cr(III) and 16.4 mg g(-1) for Pb(II). Desorption of heavy metal ions was achieved using 0.1 M HNO(3). The dithizone-anchored microbeads are suitable for repeated use (for more than five cycles) without noticeable loss of capacity.

Dye-incorporated poly(EGDMA-HEMA) microspheres as specific sorbents for aluminum removal.

Aluminum [Al(III)] adsorption onto dye-incorporated poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) [poly(EGDMA-HEMA)] microspheres was investigated. Poly(EGDMA-HEMA) microspheres, in the size range of 150-200 microm, were produced by a modified suspension polymerization of EGDMA and HEMA. The reactive dyes (i.e., Congo Red, Cibacron Blue F3GA and Alkali Blue 6B) were covalently incorporated to the microspheres. The maximum dye load was 14.5 micromol Congo Red/g, 16.5 micromol Cibacron Blue F3GA/g and 23.7 micromol Alkali Blue 6B/g polymer. The maximum Al(III) adsorption on the dye microspheres from aqueous solutions containing different amounts of Al(III) ions were 27.9 mg/g, 17.3 mg/g and 12.2 mg/g polymer for the Congo Red, Cibacron Blue F3GA and Alkali Blue 6B, respectively. The maximum Al(III) adsorption was observed at pH 7.0 in all cases. Non-specific Al(III) adsorption was about 0.84 mg/g polymer under the same conditions. High desorption ratios (95%) were achieved in all cases by using 0.1 M HNO3. It was possible to reuse these dye-incorporated poly(EGDMA-HEMA) microspheres without significant losses in the Al(III) adsorption capacities.

Synthesis and characterization of 1,4,8,11-tetraazacyclotetradecane carrying poly(p-chloromethyl styrene-ethylene glycol dimethacrylate) microbeads and its metal ion-chelated forms

Poly(p-chloromethyl styrene-ethylene glycol dimethacrylate) polymeric microbeads, poly(p-CMS-EGDMA), with an average size of 186 μm were synthesized by the suspension polymerization of p-CMS conducted in an aqueous medium. To increase the rigidity of the polymeric microbeads, EGDMA monomer was added to polymerization medium in the 25% for the cross-linking. 1,4,8,11-Tetraazacyclotetradecane ligand was reacted with polymer active groups that was p-CMS under a nitrogen atmosphere for 18 h at 65 °C. The maximum cyclam attachment was found 2.24 mmol/g polymer using an elemental analyser. Fourier transform infrared (FT-IR) spectrophotometer, thermogravimetric analyser (TGA) and differential scanning calorimeter (DSC) were used to characterize the plain, ligand modified microbeads and metal ion-chelated microbeads. TGA and DSC characterization of modified microbeads showed that stability of cyclam was increased attaching onto the polymer and metal ion-chelated form of the cyclam-modified polymer were more stable at high temperature for different applications.

Preparation and characterization of ethylenediamine modified glycidyl methacrylate-grafted nonwoven cotton fabric adsorbent

Abstract In this study, plasma-initiated graft polymerization of glycidyl methacrylate (GMA) onto nonwoven cotton fabric (NCF) and its modification with ethylenediamine (EDA) was performed. To determine the optimum conditions for plasma treatment, a comprehensive analysis of different parameters such as plasma power, applied pressure, applied plasma gas, and exposure time were conducted using both air- and Ar-plasma. The concentration of radicals generated on the NCF surface after plasma treatment was examined using ESR spectroscopy. The effects of plasma pretreatment conditions, namely GMA concentration, grafting temperature, and grafting time were investigated. Plasma treated NCF has been grafted with GMA (GMA-g-NCF) was functionalized with ethylenediamine (EDA-GMA-g-NCF) to develop an efficient arsenic adsorbent. NCF, GMA-g-NCF and EDA-GMA-g-NCF samples were characterized by using FTIR, SEM, EDX, XPS, elemental analysis, TGA, and contact angle.

Scanning tunnelling microscopy for characterization of metathesis catalysts based on photogenerated W(CO)6/CCl4

Abstract We attempted to form a W(CO) 6 /CCl 4 catalyst from the gas phase reaction of W(CO) 6 and CCl 4 by UV-irradiation and used this catalyst in a model metathesis reaction of 1-heptene. We analyzed both the intermediate volatile compounds using an on-line mass spectrometer and the structure of the solid polymer by FIMS and DSC. Scanning tunnelling microscopy (STM) was used in order to study the structures of W(CO) 6 and photogenerated W(CO) 6 /CCl 4 catalyst on HOPG. Color changes observed during UV-irradiation were considered to be an indication of the formation of the W(CO) 6 /CCl 4 catalyst. The volatile compounds identified by mass spectrometry supported the formation of the catalyst. The mass spectra obtained with the field ionization mass spectrometer revealed that the catalyst may be in an oligomeric form with [(CO) 4 WC 2 Cl 2 ] + repeating units. Thermal transitions observed in the DSC thermograms indicated the existence of oligomeric chains. STM images clearly showed the structure of the W(CO) 6 molecules with some atomic level displacements. The STM images of the catalyst verified that the W(CO) 6 /CCl 4 based metathesis catalyst is composed of oligomeric chains with four tungsten atoms.