Osman Duman

Synthesis of magnetic oxidized multiwalled carbon nanotube-κ-carrageenan-Fe3O4 nanocomposite adsorbent and its application in cationic Methylene Blue dye adsorption

In this study, magnetic oxidized multiwalled carbon nanotube (OMWCNT)-Fe3O4 and OMWCNT-κ-carrageenan-Fe3O4 nanocomposites were synthesized and used as adsorbent for the removal of Methylene Blue (MB) from aqueous solution. Magnetic nanocomposites were characterized by using of specific surface area, Fourier transform infrared, X-ray diffraction, vibrating sample magnetometry, thermal gravimetric analysis, scanning electron microscope and transmission electron microscope measurements. The results of characterization analyses exhibited that OMWCNT was successfully modified with κ-carrageenan. Furthermore, OMWCNT-Fe3O4 and OMWCNT-κ-carrageenan-Fe3O4 nanocomposites were of a super-paramagnetic property. Adsorption studies revealed that the data of adsorption kinetics and isotherm were well fitted by the pseudo second-order kinetic model and Langmuir isotherm model, respectively. The adsorption amounts of magnetic adsorbents increased with contact time and initial dye concentration. Compared with magnetic OMWCNT-Fe3O4 nanocomposite, magnetic OMWCNT-κ-carrageenan-Fe3O4 nanocomposite showed a better adsorption performance for the removal of MB from aqueous solution. Therefore, OMWCNT-κ-carrageenan-Fe3O4 nanocomposite may be used as a magnetic adsorbent to remove the cationic dyes from wastewaters.

Attachment of benzo-crown ethers onto activated carbon cloth to enhance the removal of chromium, cobalt and nickel ions from aqueous solutions by adsorption.

This work consists of two stages. In the first stage, the adsorption of some monobenzo- and dibenzo-crown ethers onto activated carbon cloth (ACC) was investigated. Adsorption isotherm data were derived at 30 degrees C. Then the ACC surface was modified by saturating it with crown ethers. In the second stage, the adsorption of three metal ions, Cr(III), Co(II) and Ni(II), onto both the ACC and the ACC modified with crown ethers was investigated. The enhancement of adsorption of the ACC upon modification with crown ethers was examined for the three ions. The effects of the type and cavity size of crown ethers, the size and form of the ions on the extent of adsorption were discussed in terms of interactions of adsorbate species with the ACC surface. All the isotherm data were treated according to Langmuir and Freundlich models. Generally, Freundlich model was found to represent the experimental isotherm data better than Langmuir model.

Spectroscopic investigations of the interactions of tramadol hydrochloride and 5-azacytidine drugs with human serum albumin and human hemoglobin proteins.

The interactions of tramadol hydrochloride (THC) and 5-azacytidine (AZA) drugs with human serum albumin (HSA) and human hemoglobin (HMG) proteins were investigated by fluorescence, UV absorption and circular dichroism (CD) spectroscopy at pH 7.4 and different temperatures. The UV absorption spectra and the fluorescence quenching of HSA and HMG proteins indicated the formation of HSA-THC and HMG-THC complexes via static quenching mechanism. AZA did not interact with HSA and HMG proteins. It was found that the formation of HMG-THC complex was stronger than that of HSA-THC complex. The stability of HSA-THC and HMG-THC complexes decreased with increasing temperature. The number of binding site was found as one for HSA-THC and HMG-THC systems. Negative enthalpy change (ΔH) and Gibbs free energy change (ΔG) and positive entropy change (ΔS) values were obtained for these systems. The binding of THC-HSA and HMG proteins was spontaneous and exothermic. In addition, electrostatic interactions between protein and drug molecules played an important role in the binding processes. The results of CD analysis revealed that the addition of THC led to a significant conformational change in the secondary structure of HSA protein, on the contrary to HMG protein.

In-Situ UV-Visible Spectroscopic Study on the Adsorption of some Dyes onto Activated Carbon Cloth

Abstract Adsorptive removal of the dyes C.I. Basic Blue 9, C.I. Basic Red 2, and C.I. Acid Blue 74 from aqueous solution onto the activated carbon cloth (ACC) has been investigated. The removal of each dye has been followed by in-situ UV-visible spectroscopic method using the so-called scanning kinetics technique. Kinetic data obtained in this way were tested according to pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion models. Pseudo-second order model was found to be the best in representing the experimental kinetic data. Adsorption isotherms at 30°C were derived for each dye. Isotherm data were found to fit best to Freundlich isotherm model among the three isotherm models tested; Langmuir, Freundlich, and Redlich-Peterson. High specific surface area of the ACC allowed almost complete removal of each dye under the experimental conditions applied. Adsorption capacity of the ACC for the three dyes was correlated with the dimensions of dye molecules and pore sizes of the ACC.

Study on the bindings of dichlorprop and diquat dibromide herbicides to human serum albumin by spectroscopic methods

The interactions of dichlorprop (DCP) and diquat dibromide (DQ) herbicides with human serum albumin (HSA) protein were studied by UV absorption, fluorescence, synchronous fluorescence and circular dichroism (CD) spectroscopy. Both DCP and DQ quenched the fluorescence emission spectrum of HSA through the static quenching mechanism. The Stern-Volmer quenching constant, binding constant, the number of binding sites and thermodynamic parameters were determined at 288K, 298K, 310K and 318K. In HSA-DCP and HSA-DQ systems, an increase in temperature led to a decrease in the Stern-Volmer quenching constant and binding constant. One binding site was obtained for DCP and DQ on HSA. It was found that DCP can bind to HSA with higher affinity than DQ. Negative ΔH and positive ΔS values were obtained for the binding processes between protein and herbicide molecules. This result displayed that electrostatic interactions play a major role in the formation of HSA-DCP and HSA-DQ complexes. The binding processes were exothermic reactions and spontaneous. In addition, synchronous fluorescence and CD spectra of HSA revealed that the binding of DCP to HSA did not cause a significant conformational change in protein, but the interaction of DQ with HSA led to an alteration in the protein structure.

Adsorptive removal of cationic surfactants from aqueous solutions onto high-area activated carbon cloth monitored by in situ UV spectroscopy.

Activated carbon cloth (ACC) was used as adsorbent for the removal of cationic surfactants such as benzyltrimethylammonium chloride (BTMACl), benzyltriethylammonium chloride (BTEACl), benzyltributylammonium chloride (BTBACl), benzyldimethyldecylammonium chloride (BDMDACl), benzyldimethyltetradecyl ammonium chloride (BDMTDACl), benzyldimethylhexadecylammonium chloride (BDMHDACl), N-dodecylpyridinium chloride (N-DPCl) and N-cetylpyridinium chloride (CPCl) from aqueous solutions. The adsorption efficiency of the ACC was evaluated for cationic surfactants. Adsorption process was followed by in situ UV spectroscopic technique. The kinetic data, so obtained, were treated according to the pseudo first-order, the pseudo second-order, the Elovich and the intraparticle diffusion models in order to understand the adsorption mechanism of cationic surfactants onto the ACC. The best fit was found with the pseudo second-order model. The experimental isotherm data were obtained at 30 degrees C and analyzed by the Freundlich and the Langmuir models. The parameters of isotherm equations were determined. The Freundlich model was found to represent the experimental data better than the Langmuir model. The observed adsorption behaviors are discussed in terms of the pH of the solution, the nature of cationic surfactants (e.g. functional groups, size, and hydrophobicity) and the nature of the ACC (e.g. surface charge, pore size). A fair linear correlation was found between some adsorption parameters and apparent molar volumes at infinite dilution for benzyltrialkylammonium chlorides.

Binding of fluoride, bromide and iodide to bovine serum albumin, studied with ion-selective electrodes

The interactions of halide ions, F−, Br− and I−, with bovine serum albumin (BSA) in neutral aqueous solutions (pH=7.1) were investigated by the use of ion selective electrodes. The number of ions bound to BSA was determined from the difference in the amount of ion added to BSA solution and the amount of ion remaining free after equilibration. These data were treated according to the Klotz equation to find the number of binding sites, their equivalency and the binding constants. It was found that BSA has one binding site each for Br− and I−, and two equivalent binding sites for F− in neutral solutions. The rather small number of binding sites for the halides studied was attributed to a net charge of −18 reported in the literature for BSA. The binding constants for Br− and I− and the two stepwise binding constants for F− were also determined.

Binding of lead ion to bovine serum albumin studied by ion selective electrode.

The binding of Pb2+ to bovine serum albumin (BSA) at neutral pH was studied using lead ion selective electrode. The binding data was treated according to Scatchard Equation. The number of binding classes and the number of binding sites, intrinsic dissociation constants and stepwise binding constants for each class were determined. Two binding classes were found. Four binding sites in the first class and five binding sites in the second class were determined. Binding in the first class was stronger than in the second. Similar binding studies were carried out with heat treated BSA. It was found that not only the number of binding sites but also the strength of binding increases upon heat treatment.

Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH, Clay Concentration and Mono- and Multivalent Electrolytes

Abstract In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH4Cl, NaNO3, NaClO4, Na2SO4, Na2CO3, Na3PO4·12H2O, MgCl2·6H2O, CaCl2·2H2O, BaCl2, SrCl2·6H2O, CuCl2·2H2O, CoCl2·6H2O, NiCl2, AlCl3, and CrCl3·6H2O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg2+, Ca2+, Sr2+, and Ba2+), heavy metal ions (Cu2+, Ni2+, and Co2+) and trivalent cations (Al3+ and Cr3+) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na+, K+ and NH4 +), monovalent anions (Cl−, NO3 −, and ClO4 −) and multivalent anions (SO4 2−, CO3 2−, and PO4 3−) acted as indifferent ions for these clay particles.

Adsorption Characteristics of Benzaldehyde, Sulphanilic acid, and p‐Phenolsulfonate from Water, Acid, or Base Solutions onto Activated Carbon Cloth

Abstract Adsorption of benzaldehyde (BA), sulphanilic acid (SA), and sodium salt of p‐phenolsulfonic acid (p‐PhS) from water, acid, or base solutions onto activated carbon cloth (ACC) was studied by in‐situ UV‐spectrophotometric method. Kinetics of adsorption was followed over 90 min and the data were fitted to first order rate law. The order of rate of adsorption was found to be BA>SA≈p‐PhS in water, BA>p‐PhS>SA in 1 M H2SO4 and BA>SA >> p‐PhS in 0.1 M NaOH. Competitive adsorptions of BA and SA from an equimolar mixture in 1 M H2SO4 and of BA and p‐PhS from an equimolar mixture in H2O were studied for exploring the possibilities of separation of binary mixtures. It was found that p‐PhS was not adsorbed at all from 0.1 M NaOH solution. Adsorption isotherms of BA, SA, and p‐PhS at 30°C were derived and the data were fitted to the Langmuir and Freundlich models. The Freundlich model was found to represent the experimental data better than the Langmuir model.