Bayram Kizilkaya

Amperometric determination of sulfide based on its electrocatalytic oxidation at a pencil graphite electrode modified with quercetin

This study describes a new approach for the investigation of electrocatalytic oxidation of sulfide using a pencil graphite electrode modified with quercetin (PGE/QH(2)). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/QH(2) showed a significant electrocatalytic activity toward sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifts from +450 mV at bare PGE to +280 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag/AgCl/KCl(sat) and at pH 8.0 BR buffer solution containing 0.1M NH(4)Cl were linearly related to the concentration of sulfide. The calibration graph consisted of two linear segments of 1-20 μM and 20-800 μM with a detection limit of 0.3 μM (based on 3s(b)). The proposed method was successfully applied to the determination of sulfide in waste waters and was compared with the spectrophotometric method.

Electrocatalytic oxidation of NADH using a pencil graphite electrode modified with quercetin

In the present study, the electrocatalytic oxidation of reduced β nicotinamide adenine dinucleotide (NADH) was investigated using a pencil graphite electrode modified with quercetin (PGE/QH(2)). The PGE/QH(2) was prepared through two steps: (i) the pre-treatment of PGE at 1.40 V vs. Ag|AgCl|KCl((sat.)) in pH 7.0 phosphate buffer containing 0.1 M KCl for 60s and (ii) adsorption of QH(2) on the PGE via immersion of PGE into a 1.0mM QH(2) solution (in ethanol) for 60s. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +500 mV at bare PGE to +300 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag|AgCl|KCl((sat.)) and in phosphate buffer solution at pH 7.0 containing 0.1M KCl were linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 0.5 μM to 100 μM. The limit of detection was found to be 0.15 μM.

Biosensing of glucose in flow injection analysis system based on glucose oxidase-quantum dot modified pencil graphite electrode

A novel amperometric glucose biosensor was proposed in flow injection analysis (FIA) system using glucose oxidase (GOD) and Quantum dot (ZnS-CdS) modified Pencil Graphite Electrode (PGE). After ZnS-CdS film was electrochemically deposited onto PGE surface, GOD was immobilized on the surface of ZnS-CdS/PGE through crosslinking with chitosan (CT). A pair of well-defined reversible redox peak of GOD was observed at GOD/CT/ZnS-CdS/PGE based on enzyme electrode by direct electron transfer between the protein and electrode. Further, obtained GOD/CT/ZnS-CdS/PGE offers a disposable, low cost, selective and sensitive electrochemical biosensing of glucose in FIA system based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. Under optimum conditions (flow rate, 1.3mL min(-1); transmission tubing length, 10cm; injection volume, 100μL; and constant applied potential, -500mV vs. Ag/AgCl), the proposed method displayed a linear response to glucose in the range of 0.01-1.0mM with detection limit of 3.0µM. The results obtained from this study would provide the basis for further development of the biosensing using PGE based FIA systems.

Usage of Biogenic Apatite (Fish Bones) on Removal of Basic Fuchsin Dye from Aqueous Solution

The contamination with toxic dyes is the most important problem facing all over the world for water sources, environment and living beings. Therefore, in present study, the removal of fuchsin dye from aqueous environment was investigated using fish bones as source of biogenic apatite to the best removal efficiency. The removal efficiency of the adsorbent was investigated as a function of contact time and initial dye concentration. The highest removal capacity was found to 14.75 mg/g. The experimental data generally exhibit a good compliance with the pseudo-second-order equation. Langmuir and Freundlich models were also applied to experimental equilibrium data to find the best adsorption isotherm. Weber-Morris and Urano-Tachikawa models were used to calculate diffusion constants. The results were showed that fish bones can be effectively used as a sorbent for the removal of basic dyes from aqueous solutions.

Utilization to Remove Pb (II) Ions from Aqueous Environments Using Waste Fish Bones by Ion Exchange

Removal of lead (II) from aqueous solutions was studied by using pretreated fish bones as natural, cost-effective, waste sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacities of the adsorbent was investigated. The maximum adsorption capacity for Pb (II) was found to be 323 mg/g at optimum conditions. The experiments showed that when pH increased, an increase in the adsorbed amount of metal of the fish bones was observed. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of Pb (II) adsorption and the value of for Pb (II) was found to be 0.906. The thermodynamic parameters related to the adsorption process such as , °, °, and ° were calculated and , °, and ° were found to be 7.06, 46.01 kJ mol−1, and 0.141 kJ mol−1K−1 for Pb (III), respectively. ° values (46.01 kJmol−1) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to the experimental equilibrium data. The fish bones were effectively used as sorbent for the removal of Pb (II) ions from aqueous solutions.

Biosorption of Co(II), Cr(III), Cd(II), and Pb(II) Ions from Aqueous Solution Using Nonliving Neochloris Pseudoalveolaris Deason & Bold: Equilibrium, Thermodynamic, and Kinetic Study

In this study, biosorption of cobalt(II), chromium(III), cadmium(II), and lead(II) ions from aqueous solution was studied using the algae nonliving biomass (Neochloris pseudoalveolaris, Np) as natural and biological sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacity of metal ions was investigated. The maximum adsorption capacities for Co(II), Cr(II), Cd(II), and Pb(II) were found to be 20.1, 9.73, 51.4 and 96.2 mg/g at the optimum conditions, respectively. The experiments showed that when pH increased, an increase in the adsorption capacity of the biomass was observed too. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of metal ions adsorption and the value of R L for Pb(II), Cb,(II), Co(II), and Cr(III) was found to be 0.376, 0271, 0872, and 096, respectively. The thermodynamic parameters related to the adsorption process such as E a , ΔG 0, ΔH 0, and ΔS 0 were calculated. ΔH 0 values (positive) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to experimental equilibrium data. The algae biomass was effectively used as a sorbent for the removal of metal ions from aqueous solutions.

Comparative Study of Biosorption of Heavy Metals Using Living Green Algae Scenedesmus quadricauda and Neochloris pseudoalveolaris: Equilibrium and Kinetics

The biosorption of several heavy metals such as cobalt(II), chromium(III), lead(II), cadmium(II), nickel(II), and manganese(II) from aqueous systems on living microalgae cultures, Scenedesmus quadricauda and Neochloris pseudoalveolaris were studied under laboratories conditions. The kinetic and statistical parameters were calculated by using the data obtained from batch cultivation and well fitted a pseudo-first-order rate equation. The initial metal concentrations in solution were about 5–40 mg · L−1. According to the pseudo-second-order model, the biosorption capacities of Scenedesmus quadricauda for Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions were found in the ranges of 2.14–52.48, 1.98–81.98, 8.05–4.26, 7.81–24.96, 2.17–55.71, and 3.54–75.20 mg g−1, respectively. Kinetic studies revealed that the metal uptake capacity of each living green algae was rather fast. It was also observed that the biosorption kinetic rate decreased with increasing concentration for both microalgae. The application of diffusion-controlled models to the experimental results indicated that the contribution of intraparticle diffusion to the overall sorption kinetics was not very important. Results showed that Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions could effectively be absorbed by using living microalga cultures from aqueous solutions.

Removal of Azure A Dye from Aqueous Environment Using Different Pretreated Fish Bones: Equilibrium, Kinetic, and Diffusion Study

In this study, the removal of azure A dye from aqueous environment was investigated using different pretreated fish bones for the best removal efficiency. The removal efficiency of the adsorbent was investigated as a function of contact time, initial dye concentration, and pretreatment process. Five different pretreatment processes were carried out on the fish bones to obtain the best removal procedure for the removal studies. The highest removal capacity was found to be 9.28 mg/g. The experimental data generally exhibit a good compliance with the pseudo second-order equation for all pretreated bones. Langmuir and Freundlich models were also applied to experimental equilibrium data to find the best adsorption isotherm. Weber-Morris and Urano-Tachikawa models were used to calculate diffusion constants. The results showed that pretreated fish bones can be effectively used as a sorbent for the removal of cationic dyes from aqueous environments.

Utilization on the Removal Cd(II) and Pb(II) Ions from Aqueous Solution Using Nonliving Rivularia bulata Algae

In present study, biosorption and elimination of cadmium(II) and lead(II) ions from aqueous solution was evaluated using the algae nonliving biomass (Rivularia bulata) as easy availability, natural origin and biological sorbents. The effect of contact time and metal concentration on the adsorption capacity of metal ions was investigated. The maximum adsorption capacities for Cd(II) and Pb(II) were found to be 26.36 and 34.30 mg/g at the optimum conditions, respectively. The experimental data exhibit a good compliance with the pseudo second-order equation for Cd(II) and Pb(II) ions. Langmuir and Freundlich models were also applied to experimental equilibrium data to find the best adsorption isotherm and the values of R L for Cd(II) and Pb(II) were found to be 0.735 and 0.926, respectively. Weber-Morris and Urano-Tachikawa diffusion models were also applied to experimental equilibrium data. The results are showed that the algae biomass was effectively used as a sorbent for the removal of toxic metal ions from aqueous solutions.

Bioaccumulation of trace metals in Mediterranean mussels (Mytilus galloprovincialis) from a fish farm with copper-alloy mesh pens and potential risk assessment

ABSTRACT Concentrations of trace metals were determined in the muscle tissue, digestive gland and gills of Mediterranean mussels (Mytilus galloprovincialis) collected from different locations around an offshore copper alloy fish farm. Levels of copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) as mg/kg wet weight in the edible part of the mussels collected from distant zone (upstream Zn7.33 > Fe2.8 > Cu0.13 > Mn0.07 and downstream Zn9.9 > Fe5.67 > Cu0.18 > Mn0.17) were significantly lower (p < 0.05) than those sampled from the cage zone (bottom panel Zn22.25 > Fe13.75 > Cu2.39 > Mn0.85 and cage frame Zn17.1 > Fe8.74 > Cu1.39 > Mn0.26). Trace metal concentrations in mussels were significantly higher (p < 0.05) in the samples from the frame and bottom panel of the copper alloy mesh pen, compared to those from distant areas, namely the farm affected downstream -and non-affected upstream locations. However, the rates of target hazard quotients (THQ) for all tested trace metals from all locations in the present study were smaller than “one” (THQ < 1), indicating that the consumption of mussels grown around a cage farm with copper alloy mesh pens were within safe limits and did not exceed maximum levels suggested by the US Food and Drug Administration (USFDA) and European Union (EU) regulations for seafood consumption.