Browsing by Author "Kivanc, Mehmet Riza"

Now showing 1 - 14 of 14

Adsorption of Malachite Green From Aqueous Solution Using Hydroxyethyl Starch Hydrogel Improved by Graphene Oxide
(Springer, 2022) Onder, Alper; Kivanc, Mehmet Riza; Durmus, Secil; Ilgin, Pinar; Ozay, Hava; Ozay, Ozgur
This study is the first report of the preparation of hydroxyethyl starch (HES) hydrogels rapidly crosslinked with divinyl sulfone in a single step and single pot. To develop the physical and chemical features of hydrogels, Graphene oxide (GO) nanoparticles were combined with the crosslinked HES. In addition to swelling studies, structural characterization of the samples was conducted with a scanning electron microscope (SEM) and transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). For the removal of malachite green model dye by GO-HES, the effects of GO content, solution concentration, temperature, contact duration, dosage and pH on varying adsorption features were researched. Additionally, adsorption isotherms, kinetic and thermodynamic systematics were analyzed. The maximum adsorption capacity of GO-HES composite hydrogel was found to be 89.3 mg/g for Langmuir isotherm. The possible adsorption mechanism of the composite hydrogels for malachite green dye involved electrostatic, hydrogen bonding, and pi-pi interactions. In addition to reasonable cost and simple synthesis method, the prepared composite materials have potential use in wastewater treatment as adsorbents for the removal of dye from aqueous solutions due to efficient adsorption capacity.
Adsorption of Methylene Blue From Aqueous Solution Using Poly(2-Acrylamido Acid-Co Methacrylate) Hydrogel Crosslinked by Activated Carbon
(Taylor & Francis inc, 2023) Ilgin, Pinar; Onder, Alper; Kivanc, Mehmet Riza; Ozay, Hava; Ozay, Ozgur
This study aimed to develop an environmentally friendly, inexpensive, and efficient adsorbent for removing methylene blue (MB) dye from wastewater using a three-dimensional porous poly(2-Acrylamido-2-methyl-1-propanesulfonic acid-co-2-Hydroxyethyl Methacrylate), p(AMPS-co-HEMA) composite hydrogel crosslinked with vinyl-functionalized activated carbon (VAC). The surface morphology and chemical structure of the crosslinker were characterized using transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray spectroscopy (XRD) and Fourier transform-infrared spectroscopy (FT-IR) instruments. The surface morphology, chemical structure and thermal properties of the hydrogel were also characterized using scanning electron microscopy (SEM), FT-IR and thermogravimetric analyzers (TGA). Experimental parameters affecting the adsorption behavior, such as initial dye concentration, time, dosage, pH, and temperature, were systematically investigated. Hydrogel achieved optimal MB removal efficiency (69.53%) at an initial MB concentration of 250 mg/L (1 mg/mL, pH not adjusted) over 24 h. Adsorption kinetics, isotherm, thermodynamic studies, and reusability were investigated. Experimental adsorption isotherm and kinetic data followed the Langmuir model and pseudo-second-order kinetics with a maximum adsorption capacity of 284.90 mg/g hydrogel at 293 K. Thermodynamic findings proved the spontaneity and endothermic behavior of the adsorption process. After 5 adsorption-desorption cycles, the adsorption capacity of the composite hydrogel decreased by only 7.51 mg/g compared to the initial adsorption capacity.
Evaluating Sustainable Colored Mortars Reinforced With Fly Ash: a Comprehensive Study on Physical and Mechanical Properties Under High-Temperature Exposure
(Mdpi, 2024) Akbulut, Zehra Funda; Guler, Soner; Osmanoglu, Faruk; Kivanc, Mehmet Riza; Khan, Mehran
This research primarily delves into a comprehensive investigation concerning the synergistic effects of fly ash (FA) with yellow pigment (YP) and red pigment (RP) in the workability, physical characteristics, and mechanical properties of colored mortars, both pre-and post-exposure to high temperatures. Within the experimental design, FA was employed as a 20% substitute for cement, while YP and RP were systematically incorporated into the cement mixtures at varying concentrations (1%, 3%, and 5% by weight). The specimens underwent controlled exposure to high temperatures, ranging from 300 degrees C to 800 degrees C. This study's outcomes unveiled that while the introduction of FA positively influenced mortar workability, including YP and RP adversely impacted spreading diameters (SD), resulting in a discernible reduction in overall workability. Despite these effects, FA emerged as a pivotal factor to enhancing the residual compressive strength (RCS) and residual flexural strength (RFS) of the colored mortars. For instance, after 90 days at 800 degrees C, the control concrete (R0) exhibited a notable 66.13% decrease in RCS, and the sample solely incorporating FA (R1) demonstrated a reduced reduction of 55.39%. Similarly, mortars with YP additives (R2-R4) and RP additives (R5-R7) showcased RCS reductions within the range of 53.32% to 55.12% and 54.51% to 56.04%, respectively.
Exploring the Flowability, Physical, and Mechanical Properties of Eco-Friendly Colored Cement Mortars With Metakaolin Under Sulfuric (H 2 So 4 ) and Nitric Acid (Hno 3 ) Attacks
(Elsevier, 2024) Akbulut, Zehra Funda; Guler, Soner; Osmanoglu, Faruk; Kivanc, Mehmet Riza; Ashour, Ashraf
This article aims to investigate the flowability, physical, mechanical, and durability properties of metakaolin (MK) -added colored cement mortars exposed to the effects of H 2 SO 4 sulfuric acid (SA) and HNO 3 nitric acid (NA). MK was used in 20 % replacement with cement, and yellow (YP) and red pigments (RP) were added to the mixtures at 1 % and 3 % of the cement by weight. According to the results, although MK reduced the workability and, therefore, the flow diameter (FD) of mortars, thanks to the void -filling feature of MK, filling the voids in the microstructure caused the samples ' apparent porosity (AP) and relative dynamic modulus of elasticity (RDME) to decrease. Additionally, MK significantly improved the residual compressive (RCS) and residual flexural strengths (RFS) of the samples thanks to the calcium -silicate -hydrate ( C - S - H) bonds it formed in the interior structure, owing to its high pozzolanic efficiency. Moreover, this improvement of MK is more remarkable in samples that remain subject to SA and NA attacks for more time. Furthermore, while YP reduces the workability of mortars and, therefore, the FD value due to its needle -tipped grain structure, RP increases the FD value of the mortars with its spherical grain structure. However, YP and RP contributed to reducing the AP of the samples and increasing RCS and RFS capacities at a meager rate by showing a micro -filling effect. In addition, there were significant increases in the total color changes ( Delta E) of YP and RP -added colored mortar samples, especially after longer SA and NA attacks.
A Green Approach To Synthesize Silver Nanoparticles in Gelatin/Poly(2-hydroxyethylmethacrylate-co-2-acrylamido-2-methyl-1-propanesulfonic Acid) Hydrogels With Verbascum Longipedicellatum Extract and Their Antibacterial Activity
(Taylor & Francis inc, 2022) Kivanc, Mehmet Riza
This study aimed to explain the production and the characterization of gelatin/poly(2-hydroxyethylmethacrylate-co-2-Acrylamido-2-methyl-1-propanesulfonic acid), Gel/p(HEMA-co-AMPS), hydrogels including silver nanoparticles (AgNP) that were developed with a simple, cost-effective and environmentally-friendly process. Silver ions were added to the Gel/p(HEMA-co-AMPS) hydrogel matrix synthesized via free radical polymerization, and silver nanoparticles were developed by in-situ reduction of silver ions (Ag+) in the swollen hydrogel using Verbascum Longipedicellatum plant extract. The structure and morphology of the prepared nanocomposite hydrogel were confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDX), X-ray diffraction analysis (XRD) and thermogravimetric analysis (TGA). In addition, the swelling properties of hydrogels were investigated and AgNPs embedded in the hydrogel network were found to absorb more water, improving the swelling properties of hydrogels. Finally, the antibacterial activity of silver nanocomposites against S. aureus, E. faecalis, B. Subtilis, B. cereus, E. coli, P. aeruginosa as bacterial agents and C. albicans as fungal agent was examined. Therefore, the present study offers a multi-component hydrogel containing AgNPs with low-cost and environmentally-friendly fabrication process for application as bactericidal materials in biotechnology and biomedical fields.
Investigation of the Effects of Natural Compounds Isolated From Arum Rupicola Var. Rupicola on Glutathione Reductase Enzyme Purified From Bovine Liver
(Wiley, 2019) Kivanc, Mehmet Riza; Turkoglu, Vedat
Glutathione reductase (GR, E.C. 1.8.1.7), a flavoenzyme, is responsible for recycling of oxidized glutathione disulfide. This study was performed in two main sections. In the first GR was purified from bovine liver by affinity column chromatography and the purification rate and specific activity of the enzyme were calculated as 1832-fold and 141 EU/mg protein, respectively. The subunit molecular weight of the enzyme was determined as 55 kDa by means of SDS-PAGE. The second section isolated natural components of Arum rupicola Boiss. var. rupicola using column chromatography. The isolation protocol for this plant was performed with a series of different-sized columns with hexane-ethyl acetate. According to the thin-layer chromatography plate, seven substances (R1-R7) were isolated. Our study's aim was to find new activators or inhibitors for GR activity. With this aim, all isolated substances were tested for GR activity. R6 showed competitive inhibition, while R4 had noncompetitive inhibition of GR activity. R1 played a role as an activator of GR activity. The inhibitory activity percentage vs. concentration graph was plotted. Values of IC50 for R4 and R6 were calculated as 0.193 mg/mL and 3.98 mu g/mL, respectively, from the equation of this graph.
Investigation of the Effects of Some Water-Soluble Vitamins on Glutathione Reductase Enzyme Purified From Bovine Liver
(Tubitak Scientific & Technological Research Council Turkey, 2019) Kivanc, Mehmet Riza; Turkoglu, Vedat
Glutathione reductase (GR, EC 1.8.1.7) is an antioxidant enzyme and is involved in the reducing reaction of oxidized glutathione. Glutathione and reduced glutathione are very crucial for micro- and macroorganisms because of their barrier function against radicals. Therefore, the aim of this article was to purify GR and evaluate the relationship between purified GR and vitamins. GR was purified from bovine liver using 2',5'-ADP Sepharose 4B column materials. To check the purity of each subunit of the enzyme, SDS-PAGE electrophoresis was performed and each one was 55 kDa. Afterwards, specific activity and purified ratio for the enzyme were calculated as 54 EU/mg x protein and 2700 times, respectively. Vitamins have a regulatory role in organisms and also some, like vitamin B, are coenzymes due to having cofactor effects. In this project, variable concentrations of some water-soluble vitamins, riboflavin, ascorbic acid, nicotinamide, folic acid, and thiamine, were tested. As a result of these kinetic findings, nicotinamide and folic acid increased the activity of glutathione reductase, while thiamine decreased it. Riboflavin and ascorbic acid did not show a stable effect on enzyme activity. Ki and IC50 constants were found as 50.16 +/- 5.63 mM and 21.04 mM, respectively, when Lineweaver-Burk and activity % vs. inhibitor concentration graphs were drawn for thiamine. The results of this article illustrate that the behaviors of vitamins could be complicated and vary from one living organism to other; in other words, they are unpredictable.
A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3-Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide
(Wiley-v C H verlag Gmbh, 2017) Guler, Muhammet; Turkoglu, Vedat; Kivanc, Mehmet Riza
In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3-aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO-APTES) and hydrogen peroxide sensor based on rGO-APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO-APTES/GOx/GC and Nf/rGO-APTES/GC composites showed good electrocatalytical activity toward glucose and H2O2, respectively. The Nf/rGO-APTES/GC electrode exhibited a linear range of H2O2 concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 mu A mM(-1)cm(-2). The Nf/rGO-APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 mu M and sensitivity of 75.26 mu A mM(-1)cm(-2). Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.
Properties and Some in Vitro Studies of 6-Phosphogluconate Dehydrogenase Purified From the Liver of Chalcalburnus Tarichi, the Only Fish Living in Lake Van's Highly Alkaline Water (Ph 9.8)
(Tubitak Scientific & Technological Research Council Turkey, 2015) Guler, Muhammet; Turkoglu, Vedat; Kivanc, Mehmet Riza
In this study, some enzymology parameters and some antibiotics affecting the enzyme activity of 6phosphogluconate dehydrogenase (6PGD) extracted from t the livers of fish from Lake Van (Chalcalburmas tarichi) were investigated because it is an important enzyme-producing NADPH, a reductive power, protecting the cell against the oxidative agents by producing reduced glutathione. The crude enzyme solution was obtained by using the affinity chromatography method. The native molecular weight of the enzyme is similar to 90,000 +/- 3000 Da and it is composed of two subunits with identical molecular weights of similar to 46,000 Da as exhibited on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pH and temperature for optimal conditions of 6PGD were about 8.5 and 40 degrees C, respectively, and the enzyme showed optimal activity in 40 mM ammonium sulfate solution. In addition, in vitro effects of clindamycin phosphate, streptomycin sulfate, and lincomycin antibiotics on the enzyme activity were investigated.
Removal of Anionic Dyes From Aqueous Media by Using a Novel High Positively Charged Hydrogel With High Capacity
(Taylor & Francis inc, 2022) Kivanc, Mehmet Riza; Ozay, Ozgur; Ozay, Hava; Ilgin, Pinar
Poly((methacryloylamino)propyl trimethylammonium chloride-co-vinylimidazole) (p(MAPTAC-co-VI)) hydrogels were synthesized through free radical polymerization of 3-(methacryloylamino)propyl trimethylammonium chloride (MAPTAC) and 1-vinylimidazole (VI) in aqueous solutions with ammonium persulfate (APS) used as initiator and N,N '-methylenebis(acrylamide) (MBA) as the crosslinking agent. By modifying with HCl, the positive charge density on the hydrogel network structure was increased and quaternized hydrogels (p(MAPTAC-co-VI)-q) were obtained. Traditional swelling and spectrophotometric characterization techniques were used to gain a better understanding of the performance of cationic hydrogels for the removal of anionic dyes. FTIR, SEM, and EDX confirmed the structure of the hydrogel before and after the adsorption process. Later, dye adsorption performance of these p(MAPTAC-co-VI)-q hydrogels was investigated under different adsorption conditions, including initial concentration, temperature, pH values of dye solutions, and adsorption contact time, adsorbent dosage and in real water samples. Various isotherm and kinetic models of dye adsorption by the hydrogel were also studied and the experimental adsorption followed a pseudo-second order model and fitted the Langmuir isotherm well. Thanks to the effective use of existing adsorption sites, high adsorption capacity was achieved for eriochrome black T (EBT) and methyl orange (MO) dyes. The values of q(max) are as follows: 1818.2 mg/g and 1449.3 mg/g, respectively. Thermodynamic parameters indicate that the process was spontaneous and endothermic. P(MAPTAC-co-VI)-q hydrogels can be used as a potential adsorbent for removal of anionic dye molecules, one of the industrial pollutants, from wastewater.
A Statistical Optimization of Methylene Blue Removal From Aqueous Solutions by Agaricus Campestris Using Multi-Step Experimental Design With Response Surface Methodology: Isotherm, Kinetic and Thermodynamic Studies
(Elsevier, 2020) Kivanc, Mehmet Riza; Yonten, Vahap
In this study, a multi-step experimental design of Response Surface Methodology (RSM) was applied to optimize the medium conditions for the maximum removal of Methylene Blue (MB) from aqueous solution by a novel fungi A. campestris as a biosorbent. In first step, the effect of factors (initial dye concentration, temperature, contact time, pH, agitation speed and adsorbent dosage) was obtained using Plackett Burman Design (PBD). Then Steepest Ascent (SAD) used to predict the optimum region of effective factors in the second step. Central Composite Design (CCD) was utilized to evaluate the optimum medium conditions of effective parameters for the removal of cationic dye on last step. RSM indicated that optimum conditions of initial dye concentration, agitation speed and medium temperature for maximum removal of MB (95%) were achieved as 130.90 mg L-1, 125 rpm and 41.87 degrees C, respectively. The activation energy (Ea) was determined as 149.1, -178.6, 154.5 and 382.3 kJ/mol for 20, 50, 100 and 200 mgL(-1) respectively. The characterization of adsorption process was confirmed by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Adsorption isotherm was used to describe the adsorption equilibrium studies at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherms. Thermodynamic parameters like the enthalpy 15 kJ/mol (Delta H-o), entropy 66.59 J/molK (Delta S-o) and Gibbs free energy -4.47 kJ/mol (Delta G(o)) were evaluated and also,.Go shows a negative values indicating that the adsorption process was spontaneous and endothermic in nature. The results show that a multi-step statistical optimization designs is successful applied to experiments and novel and endemic biomass of Agaricus Campestris is an appropriate biosorbent and has a specific affinity for removal of Methylene Blue at under optimal conditions.
Synthesis of P(hema-Co Nanocomposite Hydrogel With Vinyl-Function Montmorillonite Nanoparticles and Effective Removal of Methyl Orange From Aqueous Solution
(Taylor & Francis inc, 2023) Onder, Alper; Kivanc, Mehmet Riza; Ilgin, Pinar; Ozay, Hava; Ozay, Ozgur
It has become crucial to develop new adsorbents to remove toxic dye wastes from wastewater to protect our existing aquatic ecosystem. Here, to remove methyl orange azo dye from aqueous solutions, a new p(HEMA-co-AETAC)/VMt nanocomposite hydrogel was prepared by using 2-hydroxyethyl methacrylate and [2-(acryloyloxy)ethyl]trimethylammonium chloride monomers using vinyl-based montmorillonite crosslinker. Obtained new types of crosslinker and nanocomposite hydrogels have been characterized by various analysis methods. In addition, the effects of crosslinker amount, monomer amount and pH on the swelling behavior of nanocomposite hydrogel were investigated. The effects of essential parameters such as contact time, initial dye concentration, pH effect of the solution, adsorbent amount, and temperature on adsorption were evaluated. It was determined that there was no significant change in the adsorption ability of the nanocomposite hydrogel in the pH range of 3-10. Experimental results showed that the Langmuir isotherm model fit better, and the calculated maximum adsorption capacity was 961.54 mg/g. In addition, it was determined that vinyl-based montmorillonite used as a crosslinker supported MO adsorption. p(HEMA-co-AETAC)/VMt nanocomposite hydrogel may be a new type of adsorbent to remove toxic synthetic dye residues from aqueous media.
Synthesis, Characterization, and in Vitro Drug Release Properties of Aunps/P(aetac-co-vi) Nanocomposite Hydrogels
(Springer Heidelberg, 2021) Durmus, Secil; Yilmaz, Betul; Kivanc, Mehmet Riza; Onder, Alper; Ilgin, Pinar; Ozay, Hava; Ozay, Ozgur
In this study, the cationic monomer [2-(acryloyloxy)ethyl]trimethylammonium chloride solution (AETAC) and vinyl imidazole (VI) were used with the free radical polymerization technique, which is a simple and rapid synthesis method, to synthesize p(AETAC-co-VI) hydrogels. To increase the density of cationic charge on the hydrogel, it underwent the protonation process with HCl. The obtained p(AETAC-co-VI)/Q hydrogel was modified with Au nanoparticles to increase bactericidal effect to obtain the AuNPs/p(AETAC-co-VI)/Q nanocomposite hydrogel. The morphology and chemical structure of the hydrogels were characterized with SEM and FTIR. Additionally, the swelling capabilities were tested in different pH media. XRD and TEM confirmed the formation of the nanocomposite hydrogel. The antibacterial activity of the hydrogels was tested against E. coli and S. aureus, and controlled release implementations were completed with sodium diclofenac (NaDc) drug. The NaDc drug release profiles of the hydrogels were researched using the Korsmeyer-Peppas model at 37 degrees C in different simulated buffer (pH 6.0, 7.2, and 8.0) solutions. It was found that both the hydrogel and nanocomposite hydrogel followed non-Fickian diffusion mechanisms as free release mechanism. Here, the maximum drug release efficacy was found to be 97%, and drug release was more rapid in basic media when release media were compared. The AuNPs/p(AETAC-co-VI)/Q nanocomposite hydrogels produced in this study with advanced antibacterial features were suitable for recommendation as good carriers for in vitro release of NaDc drugs in areas like the biomedical and pharmaceutical industries.
A Thermodynamic and Kinetic Approach To Adsorption of Methyl Orange From Aqueous Solution Using a Low Cost Activated Carbon Prepared From Vitis Vinifera L
(Elsevier, 2020) Yonten, Vahap; Sanyurek, Nesrin Karaca; Kivanc, Mehmet Riza
In this paper, thermodynamic and kinetic parameters of the Methyl Orange adsorption process on active carbon prepared from endemic Vitis vinifera L. grape seeds (AC-VVL) grown in the Tunceli-Elazig region and % removal of dye from aqueous solutions were evaluated by using a batch system. Experiments were performed as a function of pH (2, 5, 8 and 11), temperature (15 degrees C, 30 degrees C and 45 degrees C) and initial concentration (100, 150, 300 and 1000 mg L-1). The mechanism and characterization of adsorption of dye was analyzed pre-adsorption (AC-VVL) and post-adsorption (AC-VVL+dye) using FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscope) and Brauner Emmet and Teller (BET) analyzer. The activation energy (Ea) was determined as 24.80, 39.15, -22.40 and 61.73 kJ/mol for 100, 150, 300 and 1000 mg L-1, respectively. The Langmuir, Freundlich, Temkin and Harkins Jura isotherms were used to describe the adsorption equilibrium studies at different temperatures. The Freundlich isotherm shows better fit than other isotherms in the temperature range studied. Maximum adsorption occurred at pH 2 and was approximately 79.7 mg/g. The % Recycling Yield was found to be 20% and 9 mg/g with acetone. Thermodynamic parameters like the change in enthalpy (Delta H-o), entropy (Delta S-o) and Gibbs free energy (Delta G(o)) were evaluated and the adsorption process was found to be endothermic and spontaneous. The results show that this AC-VVL biomass is an appropriate biosorbent and has specific affinity for removal of Methyl Orange from aqueous solutions.