Mustafa Ersoz

Removal of fluoride from aqueous solution by using red mud

The removal of fluoride from aqueous solution by using the original and activated red mud forms was studied in batch equilibration technique. Influence of pH, adsorbent dose and contact time on the adsorption were investigated. The fluoride adsorption capacity of activated form was found to be higher than that of the original form. The maximum removal of fluoride ion was obtained at pH 5.5. The removal of fluoride was expressed with Langmuir and Freundlich isotherms. Langmuir adsorption isotherm curve was found to be significant. It was found that the sufficient time for adsorption equilibrium of fluoride ions is 2 h. The possibility of removal of fluoride ion by using red mud is explained on the basis of the chemical nature and specific interaction with metal oxide surfaces and the results are interpreted in terms of pH variations.

Immobilization of albumin on aminosilane modified superparamagnetic magnetite nanoparticles and its characterization

Magnetite nanoparticles (NPs) were synthesized by co-precipitating Fe(2+) and Fe(3+) in an ammonia solution. Magnetite NPs coated with 3-aminopropyltriethoxysilane (APTES) were prepared by silanization reaction. After activated with glutaraldehyde (GA), human serum albumin was covalently immobilized on these magnetic NPs. The influence of three different buffer solutions on covalent immobilization was studied. phosphate buffer saline solution (PBS) was shown the highest binding ability for immobilization process compared to other buffer solutions. The morphology and properties of these magnetic NPs were examined by transmission electron eicroscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and magnetization measurement.

Proton-Coupled Oxygen Reduction at Liquid−Liquid Interfaces Catalyzed by Cobalt Porphine

Cobalt porphine (CoP) dissolved in the organic phase of a biphasic system is used to catalyze O(2) reduction by an electron donor, ferrocene (Fc). Using voltammetry at the interface between two immiscible electrolyte solutions (ITIES), it is possible to drive this catalytic reduction at the interface as a function of the applied potential difference, where aqueous protons and organic electron donors combine to reduce O(2). The current signal observed corresponds to a proton-coupled electron transfer (PCET) reaction, as no current and no reaction can be observed in the absence of either the aqueous acid, CoP, Fc, or O(2).

Arsenic(V) removal from underground water by magnetic nanoparticles synthesized from waste red mud.

In this study waste red mud (bauxite residue) sample obtained from Seydişehir (Konya, Turkey) was evaluated for the synthesis of Fe(3)O(4) nanoparticles (NPs) in ammonia solution that can be used to remove As(V) from both synthetic and natural underground water samples. The synthesized Fe(3)O(4)-NPs were characterized by using TEM, VSM, XRD, SAXS, TGA and FT-IR spectroscopy. The Fe(3)O(4)-NPs assumed a near-sphere shape with an average size of 9 nm. The results showed that synthesized Fe(3)O(4)-NPs from waste red mud have satisfactory magnetic properties and As(V) sorption capacity, especially at low equilibrium arsenate concentrations.

An electrochemical biosensor based on human serum albumin/graphene oxide/3-aminopropyltriethoxysilane modified ITO electrode for the enantioselective discrimination of D- and L-tryptophan.

A new electrochemical biosensor based on the human serum albumin/graphene oxide/3-aminopropyl-triethoxysilane modified indium tin oxide electrode (ITO/APTES/GO/HSA) has been developed for the discrimination of tryptophan (Trp) enantiomers.The electrode has been characterized by scanning electron microscopy (SEM) and electrochemical techniques. The electrochemical behaviors of the enantiomeric pairs (D- and L-Trp) at the ITO/APTES/GO/HSA electrode have been investigated by cyclic voltammetry in the concentration range of 0.10-1.0 mM. A clear separation between the oxidation peak potentials of D- and L-Trp, at 0.86 and 1.26 V, respectively, has suggested that the ITO/APTES/GO/HSA electrode can be used as an electrochemical biosensor for the discrimination of Trp enantiomers. In order to find the percentage of an enantiomeric form of tryptophan in a mixture, the ITO/APTES/GO/HSA electrode is used for the simultaneous detection of D- and L-Trp which showed that the percentage of one enantiomeric form can be easily measured in the presence of the other.

Oxygen Reduction Catalyzed by a Fluorinated Tetraphenylporphyrin Free Base at Liquid/Liquid Interfaces

The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB(-)) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen.

Transport of hexavalent chromium through anion-exchange membranes

This papers deals with the transport of hexavalent chromium through SB-6407, AFN and ACM anion-exchange membranes in contact with different salt solutions. The effect of salt solutions on the transport of chromium(VI) was investigated. The effect of salt solutions was observed at different sequences and the transport efficiencies of the membranes was found to be in the order SB-6407>AFN>ACM. The transport was found to be highest in a single state.

Fabrication of novel anisotropic magnetic microparticles

We report a novel technique for fabrication of magnetically anisotropic microparticles based on “arresting” of the alignment of oleic acid coated magnetite nanoparticles (OCMNs) dispersed within the oil drops of a polymerisable oil-in-water emulsion. This was achieved by polymerising the oil drops after gelling the continuous aqueous phase in the presence of an external magnetic field. This approach allowed us to produce magnetic Janus particles with anisotropic optical and magnetic properties which form unusual zig-zag chains and structures when exposed to an external magnetic field. We studied the magnetic properties of these novel microparticles and showed that they retained remanence magnetisation with high coercivity values indicative of ferromagnetic behaviour. This indicates that the composite polymeric Janus microparticles posses a net magnetic dipole and behave like micromagnets due to the “arrested” orientation of the OCMNs in their polymeric matrix. Utilizing the same technique, magnetic Janus microparticles have been prepared based on emulsions stabilised only by OCMNs without the use of surfactants, and the effect of pH of continuous aqueous phase on the morphology of these microparticles has been investigated.

Recovery and concentration of metals from red mud by Donnan dialysis

The transport fluxes of Al(III), Fe(III), Ti(IV) and Na(I) ions from red mud through charged heterogeneous and Neosepta CMB and CMX cation exchange membranes has been studied as a function of H+ ion concentration in stripping phase. In this process, the feed solutions is initially red mud aqueous solution or half-diluted solution which contains Al(III), Fe(III), Ti(IV) and Na(I) ions and other side is HCl solutions at different concentrations (0.05, 1.0 M). It was shown that the fluxes and recovery factor value of metal ions were enhanced with increasing concentration in feed phase and H+ ion concentration in stripping phase.

Microcontact printing of DNA-surfactant arrays on solid substrates

We have designed a novel method for fabrication of DNA arrays based on microcontact printing of DNA-surfactants on solid substrates. DNA-surfactants were prepared by covalent attachment of a hydrophobic anchoring group to the (3′- or 5′-) end of DNA oligonucleotides. This anchoring group allows DNA-strands to be immobilised on hydrophobic surfaces by hydrophobic interactions. The microcontact printing method was adapted for aqueous “inks” containing DNA-surfactants. Special attention was paid to the wetting properties of the ink with respect to the stamp and the solid substrates. The method allows for efficient attachment of DNA strands to solid surfaces and hybridisation with complementary DNA strands. This new technology could be utilised for rapid preparation of DNA-assays and genetic biochips.