Ilker Akin

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.

Green synthesis of reduced graphene oxide/polyaniline composite and its application for salt rejection by polysulfone-based composite membranes.

In this study, a novel, simple, and eco-friendly enzymatic-reaction-based approach to produce reduced graphene oxide/polyaniline (rGO/PANI) composite material was proposed. Glucose oxidase (GOx) was used as an effective catalyst producing hydrogen peroxide, in the presence of glucose, for the oxidative polymerization of aniline under ambient conditions. The prepared rGO/PANI composite was dispersed in polysulfone (PSf), and the mixed membranes were prepared by the phase inversion polymerization method. The morphology of membranes was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) techniques. The performance of membranes was studied in terms of salt rejection and pure water flux. The incorporation of rGO into the membrane matrix led to hydrophobic membrane surface with the enhanced macro-voids. On the contrary, the contact angle data revealed that the rGO/PANI-incorporated membrane surface is partly hydrophilic due to the PANI fibers in membrane, whereas SEM images showed the enhanced macro-voids. Membranes exhibited an improved salt rejection after rGO/PANI doping. The rGO/PANI-modified membrane loading exhibited a maximum of 82% NaCl rejection at an applied pressure of 10 bar. In addition, the results showed that the PSf-rGO/PANI composite membrane had the highest mean porosity and water flux.

Surface modification of glass beads with glutaraldehyde: Characterization and their adsorption property for metal ions

In this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles.

Highly Active Cobalt Sulfide/Carbon Nanotube Catalyst for Hydrogen Evolution at Soft Interfaces.

Hydrogen evolution at polarized liquid-liquid interfaces [water/1,2-dichloroethane (DCE)] by the electron donor decamethylferrocene (DMFc) is catalyzed efficiently by the fabricated cobalt sulfide (CoS) nanoparticles and nanocomposites of CoS nanoparticles formed on multi-walled carbon nanotubes (CoS/CNT). The suspended CoS/CNT nanocomposite catalysts at the interface show a higher catalytic activity for the hydrogen evolution reaction (HER) than the CoS nanoparticles due to the high dispersity and conductivity of the CNT materials, which can serve as the main charge transport pathways for the injection of electrons to attain the catalytic sites of the nanoparticles. The reaction rate increased more than 1000-fold and 300-fold by using CoS/CNT and CoS catalysts, respectively, when compared to a non-catalyzed reaction.

Calix[4]arene derivative bearing imidazole groups as carrier for the transport of palladium by using bulk liquid membrane.

The carrier activity of calix[4]arene containing imidazole groups towards the facilitated transport of palladium(II) through dichloromethane bulk liquid membrane has been studied. The optimum transport conditions were established by the studies on the effect of pH, feed concentration, carrier concentration, receiver phase concentration and transport time. A solution of 1M hydrochloric acid (HCl) served as receiving phase for maximum transport of the metal ion. Maximum transport efficiency was observed for Pd(II) ion when it was present in the concentration of 10(-3)M and the transport efficiency after 24h was found as 95%.

Green synthesis of reduced graphene oxide/nanopolypyrrole composite: characterization and H2O2 determination in urine

Here we report on a novel, simple and eco-friendly approach for the fabrication of a reduced Graphene Oxide/nanopolypyrrole (rGO/nPPy) composite material and its electrochemical performance for detection of hydrogen peroxide on a glassy carbon electrode. The characterization of the as-prepared rGO/nPPy composite was investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, scanning electron microscopy, contact angle measurement, cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammetry, differential pulse voltammetry and chronoamperometry techniques were used to investigate and optimize the performance of the developed electrochemical biosensor. The proposed biosensor showed excellent analytical response towards the quantification of H2O2 at pH 7.40. Under the optimized conditions, the biosensor shows a linear response range from 1.0 × 10−7 to 4.0 × 10−6 M concentrations of H2O2. The limit of detection was determined to be 34 nM. Reproducibility, sensitivity, stability and anti-interference capability of the fabricated biosensor for the detection of H2O2 were examined. The biological relevance of the developed electrochemical biosensor was further studied by the determination of H2O2 in urine samples. The real sample analysis of H2O2 was achieved before and after drinking coffee in urine samples. The successful and sensitive determination of H2O2 urine samples indicates that the proposed electrochemical biosensor can be applied to the quantification analysis of H2O2 in real samples.

Enhanced Hydrogen Evolution Catalysis Based on Cu Nanoparticles Deposited on Carbon Nanotubes at the Liquid/Liquid Interface

Copper nanoparticles were electrodeposited in situ on a conductive multi‐walled carbon nanotubes (MWCNT) support at a free‐standing water/1,2‐dichloroethane interface. The Cu/MWCNT nanocomposites act as highly active hydrogen evolution catalysts at the interface in the presence of lipophilic decamethylferrocene as the reducing agent.

Photocatalytic Hydrogen Evolution by Oleic Acid‐Capped CdS, CdSe, and CdS0.75Se0.25 Alloy Nanocrystals

Photocatalytic generation of hydrogen by using oleic acid-capped CdS, CdSe, and CdS(0.75)Se(0.25) alloy nanocrystals (quantum dots) has been investigated under visible-light irradiation by employing Na(2)S and Na(2)SO(3) as hole scavengers. Highly photostable CdS(0.75)Se(0.25) alloy nanocrystals gave the highest hydrogen evolution rate (1466 μmol h(-1) g(-1)), which was about three times higher than that of CdS and seven times higher than that of CdSe.

Microwave Assisted Synthesis of Chitosan Nanoparticles

Chitosan nanoparticles (CHN) were prepared based on ionotropic gelation between low moleculer weight chitosan and sodium tripolyphosphate (TPP) under microwave irradiation. Particle size, zeta potential, and FT-IR techniques were used for characterization of CHN. The influence of reaction time on the nanoparticle size distribution was investigated, and the results showed that the microwave irradiation method evidently decreases the reaction times and particle size over the conventional method. It was determined by the results of the zeta potential measurements that synthesized CHN under microwave irradiation clearly exhibits more homogeneous and stable dispersion.

Preparation of a novel PSf membrane containing rGO/PTh and its physical properties and membrane performance

Recent advances in the fabrication of nanostructures such as graphene-related materials have received a lot of attention in membrane technology for the future of water supplies. Herein, we report the synthesis of a reduced graphene oxide/polythiophene (rGO/PTh) composite material using an in situ enzymatic polymerization reaction, which is an eco-friendly and a simple way to construct a nanocomposite material. Polysulfone (PSf) mixed matrix composite membranes containing rGO and rGO/PTh were prepared via a phase inversion method. The morphology of the membranes was evaluated by various characterization methods, including SEM, AFM, contact angle and porosity measurements. The performance and antifouling properties of the membranes were examined in detail. The PSf-rGO/PTh membrane showed a significant improvement in water flux permeability due to the enhancement of hydrophilicity and porosity. Moreover, the PSf-rGO/PTh membrane exhibited an approximately 10 times higher improved water flux than that of the rGO membrane as the pressure was increased. The fouling resistance ratio (FRR) and antifouling properties of the membranes were tested using two different protein solutions: bovine serum albumin (BSA) and cytochrome c (Ctc). The antifouling and FRR properties of the PSf-rGO/PTh membrane decreased due to not only the interactions between the functional groups on the membrane surface and fouling materials, but also the morphological properties of the membrane.