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4-vinylpyridine and 2-hydroxyethylmethacrylate monomer mixture graft copolymerization onto poly(ethylene terephthalate) fibers using benzoyl peroxide
(Springer, 2007) Yigitoglu, Mustafa; Arslan, Metin
Poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) and 2-hydroxyethylmethacrylate (HEMA) using benzoyl peroxide (Bz(2)O(2)) as initiator in aqueous media. PET fibers were swelled in dichloroethane (DCE) for 2 h at 90 degrees C to promote the incorporation and the subsequent polymerization of 4-VP/HEMA onto PET fibers. Variations of graft yield with time, temperature, initiator concentration and monomer mixture ratio were investigated. The optimum initiator concentration was found to be 8x10(-3) mol/L. The maximum graft yield was obtained 280%. The optimum temperature and polymerization time was found to be 85 degrees C and 100 min. respectively. The rate of grafting was found to be proportional of the 1.5 and 0.3 powers of 4-VP/HEMA and Bz(2)O(2) concentrations, respectively. The grafted PET fibers were characterized by thermo gravimetric analysis and scanning electron microscopy (SEM). Further changes in properties of grafted PET fibers such as water absorption capacity, intrinsic viscosity and diameter were determined. The dye ability of the PET fibers increased with an increase in grafting with diazo and basic dyes.
Adsorption behavior of congo red from an aqueous solution on 4-vinyl pyridine grafted poly(ethylene terephthalate) fibers
(John Wiley & Sons Inc, 2008) Arslan, Metin; Yigitoglu, Mustafa
In this study, a reactive fibrous adsorbent was prepared through the grafting of 4-vinyl pyridine monomer onto poly(ethylene terephthalate) (PET) fibers for the removal of Congo red (CR) dye from an aqueous solution with the batch adsorption method. Effects of various parameters such as the grafting yield, pH, treatment time, and initial dye concentration on the amount of adsorption of the dye onto the reactive fibers were investigated. The effective pH was 4.0 for adsorption on grafted PET fibers. The sufficient time to attain equilibrium was 150 min. The maximum adsorption capacity of the reactive fibers for CR was 17.3 mg/g of fiber. The rates of adsorption conformed to pseudo-second-order kinetics with good correlation. The adsorption isotherm of CR fit a Langmuir-type isotherm. The reactive fibers were stable and regenerable by acid and base without loss of activity. (c) 2007 Wiley Periodicals, Inc.
Biodegradation of 2,4,6-Trinitrotoluene (TNT) with Bacteria Isolated from TNT-polluted Waste Pink Water
(Budapest Univ Technology Economics, 2019) Gok, Zehra Gun; Inal, Murat; Yigitoglu, Mustafa
In this study, bacterial strains that can use TNT as a nitrogen source isolated from TNT contaminated pink water. We isolated 5 bacterial strains and the isolated bacteria were cultured in medium containing TNT and TNT degradation capacities of isolates were determined by spectrophotometric analysis. According to the results of the analysis that have done, 3 bacterial isolates that have high TNT degradation capacity were selected and the isolates were identified with firstly Gram-staining then with 16S rRNA sequence analysis method. According to the sequence of 16S rRNA, water isolates were identified as Stenotrophomonas maltophilia (SU K2), Klebsiella pneumoniae (SU K3), Raoultella planticola (SU K4). During the TNT degradation studies, at the end of 24 h incubation time, in the medium containing 100 mg/L TNT, TNT degradation rate for SU K2, SU K3 and SU K4 were determined 70 %, 96 % and 93 % respectively. 4-aminodinitrotoluene and 2-aminodinitrotoluene accumulations were detected in the culture medium of all isolates as intermediate products formed during the degradation of TNT by HPLC analysis. Additionally, nitrite accumulation was detected in the culture medium of all isolates and the influence of temperature and pH on the degradation of TNT was also investigated. It was determined that SU K2 isolates have the highest TNT degradation capacity at 35 degrees C, the others have at 30 degrees C and all isolates degraded TNT fastest at pH 7. The results of the study show that the new isolates can be useful for the removal of TNT in a wastewater treatment system.
Coating of modified poly(ethylene terephthalate) fibers with sericin-capped silver nanoparticles for antimicrobial application
(Springer, 2020) Gok, Zehra Gun; Gunay, Kubra; Arslan, Metin; Yigitoglu, Mustafa; Vargel, Ibrahim
In this work, a kind of amine-type PET fibers was synthesized by reacting hexamethylenediamine (HMDA) with methacrylic acid-g-poly(ethylene terephthalate) (PET-g-MAA) fibers for the adsorption of silk sericin-capped silver nanoparticles (S-AgNPs) to produce antimicrobial fibers. Firstly, PET fibers were grafted MAA by using free radical polymerization technique and HMDA was covalently connected to the grafted PET fibers. Then, for S-AgNPs synthesis, 10 mL of AgNO3 solution (1 mM, 5 mM and 10 mM) was mixed with 10 mL of 1% sericin solution at pH 11. The obtained solution was stirred at room temperature for 24 h. The color change from transparent to yellow-brown indicated the formation of S-AgNPs. AgNPs formation was also determined by measuring the absorbance spectra of S-AgNPs between 300 and 600 nm using UV-Vis spectrophotometer. To determine the antimicrobial properties of S-AgNPs, agar-well diffusion tests were performed. 5 mM and 10 mM S-AgNPs groups showed antimicrobial activity on Escherichia coli and Staphylococcus aureus. After characterization of the synthesized S-AgNPs with UV-Vis spectrophotometer, Zetasizer, FTIR and TEM, the modified PET fibers were coated with S-AgNPs (5 mM and 10 mM). The S-AgNPs coated PET fibers were characterized by FTIR, SEM and X-ray fluorescence spectroscopy. The antimicrobial activities of the obtained PET fibers were investigated on S. aureus and E. coli bacteria by using disk diffusion test. It was found that the S-AgNPs coated modified PET fibers exhibited antimicrobial activities toward both gram-positive and gram-negative bacteria. The resulting polymeric PET fibers containing nano-silver can be used as an antimicrobial surface for many applications such as wound dressing.
Controlled release of indomethacin from crosslinked alginate beads
(Walter De Gruyter Gmbh, 2008) Inal, Murat; Yigitoglu, Mustafa; Isiklan, Nuran
Beads of the sodium alginate ( NaAlg) were prepared by dropping aqueous sodium alginate ( NaAlg) into glutaraldehyde ( GA) as a crosslinker and HCl as a catalyst mixture solution. Beads prepared were used to deliver a model non-steroid, anti-inflammatory drug, indomethacin ( IM). The beads were characterized with Fourier transform infrared spectroscopy ( FTIR), differential scanning calorimetry ( DSC) and scanning electron microscopy ( SEM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. SEM photograph indicated that alginate bead has spherical shape and rough surface. Preparation conditions of the beads were optimized by considering the percentage of entrapment efficiency, swelling capacity of the beads, particle size and their release data. In vitro release studies were performed in simulated gastric fluid ( pH 1.2) for the initial 2 h, followed by simulated intestinal fluid ( pH 7.4) for 4 h. Effects of variables such as, GA concentration, exposure time to GA, drug/ polymer ( d/ p) ratio and percentage of HCl on the release of the IM were investigated. It was observed that, IM release from the beads decreased with increasing GA concentration, exposure time to GA, d/ p ratio and percentage of HCl. The highest cumulative IM release obtained at the end of 6 h was 68% for alginate beads which were prepared with 0.5% HCl. On the other hand the least cumulative IM release obtained was to be 20 % for alginate beads which were prepared with 30 min exposure time to GA. In order to understand the crosslinking of the polymeric matrix, the molar mass between crosslinks were calculated using the swelling parameters. It was also found from the swelling experiments that swelling degree of the beads increases with increase in the temperature. The release data have been fitted to an empirical equation to estimate the kinetic parameters. The diffusion coefficient was also calculated for the transport of the drug through the polymeric beads. Values of these parameters were found to be consistent with the release data.
Effective adsorption of bovine serum albumin by polyethylene terephthalate (PET) fibers modified with glycidyl methacrylate grafting, hexamethylenediamine attachment and Cu2+ adsorption
(Springer, 2023) Tastan, Samet; Gunay, Kubra; Arslan, Metin; Yigitoglu, Mustafa; Gok, Zehra Gun
In this work, the glycidyl methacrylate-grafted (GMA) PET fibers were modified with hexamethylenediamine (HMDA) attachment and Cu2+ adsorption to synthesize an effective adsorbent for removal of bovine serum albumin (BSA) from the aqueous environment. The original PET fibers were grafted with GMA monomers (PET-g-GMA) at 30%, 50%, 100%, 150% and 200% grafting yields, and HMDA was covalently connected to the fibers through to the epoxy groups. The obtained fibers were characterized with the scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy (C-13-NMR) techniques. Afterward, Cu2+ ions were adsorbed to graft copolymers modified with HMDA and it was observed that the protein adsorption ability of Cu2+ ions containing fibers increased. In the adsorption study performed with PET-g-GMA and PET-g-GMA fibers modified with HMDA, the highest Q value was found to be 1.7 and 1.98, respectively, while this value was found to be 16.4 for HMDA-modified PET fibers containing Cu2+ ions. In the adsorption experiments, it was observed that the fibers with the highest BSA adsorption capacity were those modified (with HMDA and Cu2+) PET-g-GMA fibers that have 200% grafting yield. The effects of various parameters on BSA adsorption with the fibers with the highest adsorption capacity were investigated. In the experiment carried out with the selected fibers, pH optimization was made in the range of pH 3-9 and the optimum pH value was found to be pH 5. The Q value of the fiber at this pH was found to be 24.85 mg/g. During the adsorption process carried out at pH 5, it was found that the amount of adsorbed BSA reached equilibrium after the 9 h. Temperature optimization was carried out between 25 and 55 & DEG;C at optimum pH and incubation time. Q values were found as 24.8 mg/g at 25 & DEG;C, 44 mg/g at 35 & DEG;C, 47 mg/g at 45 & DEG;C and 22 mg/g at 55 & DEG;C. According to these results, the temperature at which the maximum adsorption took place was determined as 45 & DEG;C. In the next step where the initial protein concentration upon adsorption was investigated, it was concluded that the fibers reached saturation after an initial concentration of 200 ppm BSA concentration. As a result of the desorption study carried out for 2 h in acetate buffer containing 1 M NaCl at 25 & DEG;C, it was observed that approximately 85% of the loaded protein desorbed from the fibers after 75 min. It has been seen that the modified PET-g-GMA fibers used as adsorbent in this study can be used in separation and purification processes of BSA by adsorption process, due to its advantages such as high production, low cost, high processability, and easy modification.
Immobilization of Saccharomyces cerevisiae on to modified carboxymethylcellulose for production of ethanol
(Springer, 2011) Gokgoz, Murat; Yigitoglu, Mustafa
In this work, modified carboxymethylcellulose (CMC) was used as a new support material for production of ethanol. Crosslinked graft copolymers of CMC with N-vinyl-2-pyrrolidone (N-VP) were prepared in different grafting yields. The beads material was characterized by means of fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and swelling experiment. Saccharomyces cerevisiae was immobilized using entrapment method in the graft copolymers of carboxymethylcellulose-g-poly(N-vinyl-2-pyrrolidone) (CMC-g-PVP) for ethanol fermentation. The effects of grafting yield, initial glucose concentration and crosslinker concentration on the yield of ethanol process were investigated. Reusability of the immobilized yeasts was investigated and found that the materials can be used four times without losing their activity. Ethanol production increased to 59.3 g/L from 46.4 g/L when percentage of N-VP in the graft copolymer was increased. The highest ethanol productivity was found to be 1.75-2.25 g/L h. Fermentation time decreased with the decreasing of crosslinker concentration. The results suggest that the proposed method for immobilization of Saccharomyces cerevisiae has potential in industrial applications for ethanol process.
Improvement of Bioethanol Productivity of Immobilized Saccharomyces Bayanus with Using Sodium Alginate-Graft-Poly(N-Vinyl-2-Pyrrolidone) Matrix
(Springer, 2012) Inal, Murat; Yigitoglu, Mustafa
In this study, immobilization conditions and bioethanol production characteristics of immobilized Saccharomyces bayanus were investigated into sodium alginate-graft-poly(N-vinyl-2-pyrrolidone; NaAlg-g-PVP) matrix. The matrix that crosslinked with calcium clorid was used for immobilization of S. bayanus. Bioethanol productivity of the NaAlg-g-PVP matrix was found to increase from 4.21 to 4.84 gL(-1) h(-1) when compared with the convential sodium alginate matrix. The production of bioethanol was affected by initial glucose concentration and percentage of immobilized cell beads in fermentation medium. Bioethanol productivity was increased from 3.62 to 4.84 gL(-1) h(-1) while the glucose concentration increasing from 50 to 100 gL(-1). Due to the increase in percentage from 10 to 20 % of immobilized cell beads in the fermentation medium, bioethanol productivity was increased from 4.84 to 8.68 gL(-1) h(-1). The cell immobilized NaAlg-g-PVP beads were protected 92 % of initial activity after six repeated fermentation.
In situ synthesis of silver nanoparticles on modified poly(ethylene terephthalate) fibers by grafting for obtaining versatile antimicrobial materials
(SPRINGER, 2020) Gun Gok, Zehra; Demiral, Ayse; Bozkaya, Ogun; Yigitoglu, Mustafa
Because of having high mechanical properties and cheapness of PET textiles, functionalization of them for new properties is an active research area. In the present work, methacrylic acid (MAA)-grafted PET fibers (PET-g-MAA) were obtained by grafting of MAA monomers to PET surface for an antimicrobial material synthesis. The morphologies of the obtained graft copolymers were examined with a scanning electron microscopy (SEM), and the chemical modification after grafting was determined with Fourier-transform infrared spectroscopy (FTIR) analysis. Subsequently, silver ions were adsorbed onto the PET-g-MAA fibers surface and the adsorbed ions to the surface were reduced to silver nanoparticles (AgNPs) by UVC light. The morphology of fiber surfaces modified with MAA and coated with AgNPs was examined by SEM studies, and it was observed that AgNPs were disturbed along the fibers. The presence of silver on the surface was also confirmed by energy-dispersive X-ray spectroscopy (EDS) and energy dispersion X-ray fluorescence spectrometry (EDXRF). The crystalline structure of the original PET fiber, PET-g-MAA fiber and PET-g-MAA fiber modified with AgNPs was investigated by X-ray diffraction (XRD). The thermal properties of the obtained fibers were investigated by thermogravimetric analysis (TGA). The immobilization of AgNPs on the grafted fibers leads to a change on the patterns of TGA curves. The most significant change is the less weight reduction in the temperature range of 200-300 degrees C. Disk diffusion test was performed using Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25,922) bacteria in order to investigate the antibacterial ability of the obtained fibers, and it was found that the fibers coated with AgNPs had antibacterial effect on both bacterial species. The cytotoxicity of the groups with the best antibacterial properties was determined by MTT test, and the synthesized material did not have cytotoxic effects on L929 fibroblast cells. The material obtained has the potential to be used in antimicrobial applications.
Investigation of the in vitro antibacterial, cytotoxic and in vivo analgesic effects of silver nanoparticles coated with Centella asiatica plant extract
(Ankara Univ, 2023) Bozkaya, Ogun; Ekici, Husamettin; Gun Gok, Zehra; Arat, Esra; Ekici, Seda; Yigitoglu, Mustafa; Vargel, Ibrahim
In recent years, researchers have shown an increased interest in using medicinal plants for the synthesis of silver nanoparticles (AgNPs) having various therapeutic properties. Centella asiatica (CA), a medicinal plant, has been used to treat minor burn wounds, psoriasis, and hypertrophic wounds among many other pathological conditions. The current study aimed to synthesize CA coated AgNPs (CA-AgNPs) with appropriate biocompatibility and various therapeutic properties, including antimicrobial and analgesic activities. The synthesized CA-AgNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, zeta potential measurements, and fourier transform infrared (FT-IR) spectroscopy. The formation of spherical CA-AgNPs was confirmed by a single surface plasmon resonance (SPR) peak emerging at 420 nm wavelength by UV-Vis. The average hydrodynamic diameter and zeta potential of the particles were found to be 29.5 nm and -24.5 mV, respectively. The FT-IR analyses showed that the AgNPs were coated and stabilized by bioactive compounds from the CA extract. MTT cytotoxicity assay revealed that CA-AgNPs at <= 1 mM concentrations exhibited biocompatibility for L929 fibroblast cells. The antimicrobial activity of CA-AgNPs was confirmed by significant inhibition of Staphylococcus aureus and Escherichia coli. In addition, the analgesic effect of CA-AgNPs was investigated for the first time in the literature by tail-flick and hot plate methods, and statistically significant results were obtained for both methods. Taken together, these results suggest that CA-AgNPs can be used as an effective antibacterial and analgesic agent in a variety of biomedical applications, including coating wound dressings.
Investigation on selective adsorption of Hg(II) ions using 4-vinyl pyridine grafted poly(ethylene terephthalate) fiber
(Wiley, 2012) Bozkaya, Ogun; Yigitoglu, Mustafa; Arslan, Metin
In the work, poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) monomer using benzoyl peroxide (Bz(2)O(2)) as initiator in aqueous media. The removal of Hg(II) ions from aqueous solution by the reactive fiber was examined by batch equilibration technique. Effects of various parameters such as pH, graft yield, adsorption time, initial ion concentration, and adsorption temperature on the adsorption amount of metal ions onto reactive fibers were investigated. The optimum pH of Hg(II) was found 3. The maximum adsorption capacity was found as 137.18 mg g(-1). Moreover such parameters as the adsorption kinetics, the adsorption isotherm, desorption time and the selectivity of the reactive fiber were studied. The adsorption kinetics is in better agreement with pseudo-first order kinetics, and the adsorption data are good fit with Freundlich isotherms. The grafted fiber is more selective for Hg(II) ions in the mixed solution of Hg(II)-Ni(II), Hg(II)-Zn(II), and Hg(II)-Ni(II)-Zn(II) at pH 3. Adsorbed Hg(II) ions were easily desorbed by treating with 1M HNO3 at room temperature. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Microwave-assisted synthesis of alginate-g-polyvinylpyrrolidone copolymer and its application in controlled drug release
(Springer, 2014) Yigitoglu, Mustafa; Aydin, Gulden; Isiklan, Nuran
The aim of this study is to synthesize graft copolymer (NaAlg-g-PVP) in microwave oven and prepare pH-responsive beads with high entrapment efficiency. For this purpose, PVP was grafted onto sodium alginate using microwave radiation. The copolymer obtained was characterized using FTIR, H-1-NMR, elemental analysis and thermogravimetric analysis. A series of NaAlg-g-PVP beads were prepared as drug delivery matrices for ibuprofen (IB) by cross-linking into beads via glutaraldehyde. The chemical stability of IB after encapsulation into beads was confirmed by FTIR, DSC, and X-RD analysis. Synthesis conditions of beads were optimized by considering entrapment efficiency, particle size, swelling capacity and their release data. Effects of such variables as graft yield and drug/polymer ratio were investigated at 1.2 and 7.4 pH values. Increasing the drug/polymer ratio and extent of cross-linking caused decrease in the IB release. On the other hand, increase in the graft yield led to increase in the IB release as well. The results also showed that NaAlg-g-PVP beads were positive pH-responsive.
One-pot facile synthesis of silk sericin-capped gold nanoparticles by UVC radiation: Investigation of stability, biocompatibility, and antibacterial activity
(Wiley, 2019) Akturk, Omer; Gok, Zehra Gun; Erdemli, Ozge; Yigitoglu, Mustafa
Herein, an easy one-pot synthesis method for gold nanoparticles (AuNPs), involving only gold salt and sericin extracted from silkworm cocoon in the presence of ultraviolet C (UVC) radiation, was developed. Nanoparticle formation was confirmed by characteristic surface plasmon resonance peaks at 520-540 nm wavelengths, and the influence of silk sericin on enhancing the colloidal stability of AuNPs was confirmed. Transmission electron microscopy examination showed the average size (<10 nm) and size distribution decreased significantly with higher sericin concentration. No antibacterial activity was observed on Gram-positive Bacillus subtilis or Gram-negative Escherichia coli for sole AuNPs (0.065-0.26 mg/ml), but the conjugation of AuNPs with streptomycin antibiotic decreased significantly the required minimum inhibitory concentration doses, as also confirmed with agar plating, Scanning Electron Microscopy and Atomic Force Microscopy analyses. Furthermore, sericin-capped AuNPs showed high cell viabilities (>100%) and no sign of any detectable apoptosis or necrosis in 1-day incubation. Also, high real-time cell proliferation results of AuNPs competitive with positive control groups implied excellent in vitro biocompatibility. These results evidenced that sericin enhanced the colloidal stability of AuNPs and the biological activities of sericin-capped AuNPs reported here could render them suitable nanoscale vehicles for biomedical applications.
Production and characterization of hybrid nanofiber wound dressing containing Centella asiatica coated silver nanoparticles by mutual electrospinning method
(Pergamon-Elsevier Science Ltd, 2022) Bozkaya, Ogun; Arat, Esra; Gok, Zehra Gun; Yigitoglu, Mustafa; Vargel, Ibrahim
The aim of this work is to produce a therapeutic and antimicrobial nanofiber wound dressing material with suitable air permeability, water vapor transmission, water absorption, porosity, thermal and mechanical strength. For this purpose, first of all, Centella asiatica (CA) coated silver nanoparticles (CA-AgNPs) are synthesized with using CA extract as reducing and stabilizing agent. The green synthesized CA-AgNPs are characterized by UV-Vis spectroscopy, transmission electron microscope (TEM), zeta potential and fourier transform infrared (FTIR) spectroscopy measurements. The obtained CA-AgNPs give a single peak in the 420-430 nm range between 200 and 700 nm due to surface plasmon resonance (SPR). The average zeta potential and size of CA-AgNPs is found to be-30.4 mV and 14.8 +/- 7.3 nm, respectively. Then, poly caprolactone (PCL) and polyethylene oxide (PEO) nanofibers composition containing CA-AgNPs is synthesized by mutual electrospinning method. Before electrospinning, the PCL solution (12% w/v in chloroform/methanol (70%/30%, v/v)), PEO solution (3.5%, w/v in water) and PEO solutions containing 1%, 5% and 10% (v:v) of CA-AgNPs are prepared. In electrospinning experiments, to synthesis the PCL/PEO nanofibers containing CA-AgNPs, an electrospinning set-up consisting of two high voltage sources, an aluminum rotary roller collector and two syringe pumps (one with a double syringe and the other with a single syringe) is used. To produce the wound dressing materials, PEO solutions containing CA-AgNPs are placed on the double syringe pump and PCL solution is placed on the single syringe pump. The surface and physico-chemical properties of the produced hybrid nanofibers are characterized by field emission scanning electron microscopy (FESEM), energy dispersion spectrometry (EDS), FTIR, X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET) surface area and porosity analyzer. Also, the thermal and mechanical properties of the obtained materials are investigated. In addition, the air permeability, water uptake capacity, water contact angle, water vapor transmission, in vitro degradation and silver release behavior of the samples are investigated. The results show that mutual dual-spinneret electrospinning technique combines the features of dissimilar components without corruption. Moreover, the in vitro degradation profile and silver release results show that these nanofibers could be used in wound dressing applications in the long term. With antimicrobial studies, PEO/ PCL nanofibers containing 5% and 10% CA-AgNPs are found to be effective against Staphylococcus aureus, Escherichia coli and Candida albicans. Also, the cytotoxic properties of nanofibers are investigated by MTT (3-[4,5dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay and results show the good biocompatibility for L929 fibroblast cells. Results reveal that CA-AgNPs loaded PCL/PEO hybrid nanofibers materials synthesized in this study has a promising potential for wound healing applications.
Production of 2-hydroxyethyl methacrylate-g-poly(ethylene terephthalate) nanofibers by electrospinning and evaluation of the properties of the obtained nanofibers
(WILEY, 2020) Gok, Zehra Gun; Inal, Murat; Bozkaya, Ogun; Yigitoglu, Mustafa; Vargel, Ibrahim
Nanofiber production was investigated from poly(ethylene terephthalate) (PET) polymers functionalized with hydroxyethyl methacrylate (HEMA) by grafting of HEMA monomers onto the PET fibers. HEMA grafted PET (PET-g-HEMA) copolymers were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy. PET and PET-g-HEMA were dissolved in trifluoroacetic acid and nanofibers were obtained by electrospinning. It was found that the PET and PET-g-HEMA polymers having grafting yield 20 and 55% could be converted to continuous, smooth, and beadles nanofibers. For characterization of the nanofiber membranes, thermogravimetric analysis, differential scanning calorimeter analysis, surface contact angle measurement, porosity analysis, and mechanical tests were applied. When compared with the original PET nanofibers, the thermal properties and degradation process of PET-g-HEMA nanofibers changed according to the amount of HEMA present in the structure of nanofibers. The contact angles of the nanofibers obtained from PET-g-HEMA polymers decreased whereas the water retention ability of the nanofibers increased compared to original PET nanofibers. The porosity of PET-g-HEMA nanofibers was found be high compared to PET nanofibers and whereas the mechanical properties of PET was higher than PET-g-HEMA nanofibers. The obtained nanofibers can be used in many fields such as biomaterial applications.
Production of bioethanol by immobilized Saccharomyces Cerevisiae onto modified sodium alginate gel
(Wiley-Blackwell, 2011) Inal, Murat; Yigitoglu, Mustafa
BACKGROUND: Microbial bioethanol production is an important option in view of the finite global oil reserves. Bioethanol fermentation was carried out using immobilized microorganisms (Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, etc.), which has many advantages compared with the use of free cells. Various support materials have been used for bioethanol fermentation, and alginate gels have been one of the most widely used matrices for cell entrapment. The aim of this study was increased bioethanol production by Saccharomyces cerevisiae immobilized on alginate gels. First, N-vinyl-2-pyrrolidone was grafted onto sodium alginate. Then, the properties of ethanol production were investigated using the matrix obtained. RESULTS: The performance of ethanol fermentation was affected by calcium chloride concentration, N-vinyl-2-pyrrolidone grafted onto the sodium alginate, sugar concentration and the percentage of immobilized cell beads. These effects were optimized to give maximum ethanol production. Ethanol production was accelerated when sodium alginate polymer was modified with N-vinyl-2-pyrrolidone. The maximum concentration, productivity and yield of ethanol were 69.68 g L(-1), 8.71 g L(-1) h(-1) and 0.697 g g(-1), respectively. CONCLUSION: The new polymeric matrix, when compared with sodium alginate, showed better ethanol production due to the hydrophilic property of N-vinyl-2-pyrrolidone. The results suggest that the proposed method for immobilization of Saccharomyces cerevisiae has potential in industrial applications of the ethanol production process. (C) 2011 Society of Chemical Industry
Removal of chromium(VI) from aqueous solutions using poly(4-vinyl pyridine) beads
(Wiley, 2006) Arslan, Metin; Yigitoglu, Mustafa; Soysal, Arif
Sorption of hexavalent chromium ions from aqueous solution by poly 4-vinyl pyridine [Poly(4-VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g-' using 500 mg L-1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. (c) 2006 Wiley Periodicals, Inc.
Removing of Congo red from aqueous solution by 2-hydroxyethyl methacrylate-g-poly(ethylene terephthalate) fibers
(Springer, 2019) Gok, Zehra Gun; Gunay, Kubra; Arslan, Metin; Yigitoglu, Mustafa
Grafting of 2-hydroxyethyl methacrylate (HEMA) on poly(ethylene terephthalate) (PET) fibers was carried out via free-radical polymerization technique using benzoyl peroxide as initiator. The obtained copolymers were examined by scanning electron microscope and Fourier-transform infrared spectroscopy analysis, and it was proved that HEMA was successfully grafted onto the PET structure. The synthesized fibrous adsorbents were used to remove Congo red (CR) from aqueous solutions by batch adsorption method. The effects of pH, grafting yield, operation time and dye concentration were studied to find optimal conditions for adsorption of CR by the HEMA-grafted PET (PET-g-HEMA). The obtained results showed that the amounts of adsorbed dye on the PET-g-HEMA lowered with increasing pH. At pH 2, the dye amount adsorbed by the fibers increased with increasing dye concentration up to 70 ppm and grafting yield up to 110%. It was also seen that the adsorption had considerably rapid kinetic and achieved equilibrium within 60 min. The maximum removing abilities of the grafted fibers was found to be 16 mg/g when the beginning concentration of CR was 70 ppm at pH 2. The dye was desorbed from the loaded fibers with 1 M NaOH solution, and it was found that 83% of the adsorbed dye was recovered. The investigations on reusability of the PET-g-HEMA fibers showed that the constructed fibers can be used at least five times without losing adsorption capacities for CR. All these results indicate that the grafting can be used to remove the anionic dyes from the aqueous solution.
Synthesis and characterization of poly(ethylene terephthalate) fibers grafted with N-(hydroxymethyl) acrylamide by free radical: its application in elimination of Congo red
(SPRINGER, 2020) Arslan, Metin; Gunay, Kubra; Gok, Zehra; Yigitoglu, Mustafa
In this study, firstly, N-(hydroxymethyl) acrylamide (HMAAm) was grafted on poly(ethylene terephthalate) fibers (PET) by utilizing benzoyl peroxide (Bz(2)O(2)) as an initiator. The alteration in graft percentage with the polymerization time, temperature, concentration of initiator and monomers were investigated. For grafting experiments, the optimum temperature, duration for grafting and initiator concentration were found be 85 degrees C, 4 h and 0.008 M, respectively, and the maximum grafting yield was determined to be 25% at these conditions. After grafting, the morphological and chemical changes on the grafted fibers were examined scanning electron microscopy and Fourier-transform infrared spectroscopy. The thermal properties of the obtained PET fibers were examined with differential scanning calorimeter analysis. In addition, the water absorption capacities of the grafted fibers obtained at optimal conditions were investigated and it was found the maximum percentage of water retention reached 56%. Removal of Congo red (CR) with the grafted fibers was performed using a batch process. The effects of different parameters such as pH, grafting yield of HMAAm, adsorption time and CR concentration on the sorption capacity of the grafted fibers were investigated. The optimal pH for adsorption of CR was found to be 2, and the adsorption process reached equilibrium in 4 h. The amount of adsorbed CR molecules increased with the increment in the grafting yield up to 17%, and the graft copolymers adsorbed CR with 5.62 mg/g efficiency when the initial CR concentration was 80 ppm. The PET-g-HMAAm fibers synthesized in this study can be obtained easily and inexpensively, and the constructed fibers could be used to remove ionic substance from aqueous solution.
Synthesis and characterization of poly(N-Vinyl-2-pyrrolidone) grafted sodium alginate hydrogel beads for the controlled release of indomethacin
(Wiley, 2008) Işıklan, Nuran; İnal, Murat; Yigitoglu, Mustafa
Graft copolymers of sodium alginate (NaAlg) with N-vinyl-2-pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg-g-PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg-g-PVP were prepared by crosslinking method Using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti-inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg-g-PVP beads,ere optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release Studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polyrner (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing till) ratio and HCI concentration. The highest IM release was obtained to be 77%, for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. (c) 2008 Wiley Periodicals, Inc.

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