Erdal Uğuzdoğan

The use of polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-co-VI) microspheres for the removal of nickel(II) and chromium(VI) ions

The polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-VI) copolymers, that can be used in heavy metal removal applications, were synthesized and characterized; and their use as sorbents in heavy metal removal was investigated. It was determined that the ligand vinylimidazole was successfully inserted into the polymer structure. Then, chromium (Cr(VI)) and nickel (Ni(II)) ions were used as model species to investigate the usability of the obtained microspheres in heavy metal removal. The effects of pH of the adsorption medium, initial concentration of the metal ions and VI content of PEGMA-VI microspheres were investigated as the effective parameters on the adsorption capacities of the microspheres. The adsorption rate of the microspheres was also investigated for determination of the optimum adsorption time which is the required time for maximum adsorption capacity. The adsorption capacities under optimum conditions were also determined. The order of adsorption affinities of PEGMA-VI microspheres with respect to the used metals was determined by competitive adsorption studies. According to the obtained results, the highest adsorption affinity of the PEGMA-VI microspheres was towards Cr(VI) ions, the adsorption affinity was less for Ni(II) and the least affinity was towards Cu(II) ions. The adsorption-desorption studies showed that the microspheres were reusable without a significant decrease in the ion adsorption capacities.

Preparation and characterization of polyethyleneglycolmethacrylate (PEGMA)-co-vinylimidazole (VI) microspheres to use in heavy metal removal.

Polyethyleneglycolmethacrylate (PEGMA) and vinylimidazole (VI) were used in order to obtain microspheres of PEGMA-VI copolymers that can be used in heavy metal removal applications. The obtained copolymers were characterized and their use as sorbents in heavy metal removal was investigated. In the first part of the study, PEGMA-VI microspheres were prepared by suspension polymerization method. The obtained swellable microspheres with 10-50 microm average diameter did not have permanent porosity according to the morphological and physicochemical determinations. The sizes of microspheres became smaller with increasing VI and cross-linker ethyleneglycoldimethacrylate (EGDMA) contents and increasing agitation rate. The VI content, EGDMA ratio, pH and ionic strength were determined as the effective parameters on the swelling behavior of PEGMA-VI microspheres. In the second part of the study, Cu(II) ions were used as a model species in order to investigate the usability of the obtained PEGMA-VI microspheres in heavy metal removal. Adsorption capacities under optimum conditions were determined. The Cu(II) ion adsorption capacity increased by increasing the initial Cu(II) ion concentration, and it reached the maximum value (i.e., 30 mg Cu(II)/g PEGMA-VI microspheres) at 400 mg Cu(II)/L initial Cu(II) ion concentration under the determined optimum conditions. Microspheres were found to be reusable after desorption for several times.

Aqueous size exclusion chromatography in semimicro and micro-columns by newly synthesized monodisperse macroporous hydrophilic beads as a stationary phase

A new class of monodisperse macroporous beads in the hydrophilic form were synthesized by seeded microsuspension copolymerization of two acrylic crosslinking agents, glycerol dimethacrylate (GDMA) and glycerol-1,3-diglycerolate diacrylate (GDGDA). The monodisperse porous poly(glycerol dimethacrylate-co-glycerol-1,3-diglycerolate diacrylate), poly(GDMA-co-GDGDA) beads were highly hydrophilic in nature due to hydroxyl functionality resulting from both crosslinking agents. The beads with different particle sizes between 4.5 and 6.7 μm and with different porous properties were obtained by changing the seed latex to monomer ratio. The bead size decreased, the average pore size increased and the specific surface area decreased with increasing seed latex to monomer ratio. Poly(GDMA-co-GDGDA) beads were slurry packed in microbore and semimicro-HPLC columns and successfully used as a stationary phase in aqueous size exclusion chromatography (SEC) mode in a micro-liquid chromatography system. The aqueous SEC runs were performed by using dextran standards in the molecular weight range of 1000-670,000 Da. SEC calibration curves exhibiting linearity in a wider range of molecular weight were obtained with the semi-micro and micro-HPLC columns packed with the poly(GDMA-co-GDGDA) beads synthesized with the seed latex to monomer ratios of 0.038 and 0.058 g/mL. The dextran standards could be eluted in an analysis time shorter than 2 min using micro or semi-micro columns packed with poly(GDMA-co-GDGDA) beads as stationary medium. These packings are suitable for molecular weight determination between 5×10(3) and 5×10(5) Da in the aqueous medium by using mobile phase flow rates in the range of 25-250 μL/min. The average molecular weight determinations of different water soluble polymers, an ionic polymer, poly(2-dimethylaminoethyl methacrylate), a zwitterionic polymer, poly([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide), and a non-ionic polymer, poly(vinyl alcohol) were performed on a semimicro-column packed with the poly(GDMA-co-GDGDA) beads. Satisfactory results were obtained in the molecular weight determination of hydrophilic polymers by aqueous SEC.

Synthesis and characterization of hydrophilic and spherical poly(glycerol dimethacrylate-co-glycerol-1,3-diglycerolate diacrylate) microbeads

A new class of spherical and swellable microbeads was obtained by a newly proposed suspension polymerization protocol. Hydrophilic monomers in the form of crosslinking agent, glycerol dimethacrylate (GDMA), and glycerol 1,3-diglycerolate diacrylate (GDGDA) were copolymerized in an aqueous suspension medium. Poly(GDMA-co-GDGDA) microbeads were highly hydrophilic due to hydroxyl functionality from both crosslinking agents. In the proposed method, the organic phase including monomers and diluent (i.e. cyclohexanol) was dispersed in an aqueous medium by using poly(vinyl alcohol) as the stabilizer. Poly(GDMA-co-GDGDA) microbeads were obtained by changing GDMA/GDGDA ratio, monomer/diluent ratio, and stirring rate. The average size and size distribution properties, microbead yields, and the equilibrium swelling behavior of the gel beads were presented. Spherical and swellable bifunctional microbeads carrying hydroxyl–carboxyl or hydroxyl–amine groups were also obtained by including amine and carboxyl carrying functional monomers, 2-(dimethylamino)ethyl methacrylate, and methacrylic acid, respectively, in the suspension copolymerization proposed.