Esengul Kir

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.

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.

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.

Voltammetric behavior and determination of doxycycline in pharmaceuticals at molecularly imprinted and non-imprinted overoxidized polypyrrole electrodes

In this paper, electrochemical behavior of a member of tetracycline group compounds doxycyline (DC) was investigated in 20, 30, 40% (v/v) acetonitrile (ACN)-water binary mixture at the pH of 2.0-4.0 prepared Britton-Robinson (BR) buffers, by the differential pulse voltammetric method (DPV). Voltammetric determination of DC was carried out using molecularly imprinted (MIP) and non-imprinted polypyrrole (NIP) modified electrodes. Both types of electrode were prepared by the cyclic voltammetric method. The effect of the ACN-water ratio and pH, on the performance of the MIP electrode was investigated and optimized. The highest anodic signal of DC with MIP electrode was obtained in BR buffer solution was prepared in 30% (v/v) ACN-water at pH 2.0. The detection limit was determined as 4.35×10(-5)M (S/N=3). The method was also applied for electrochemical determination of DC in pharmaceutical samples. The recovery factors for Tetradox(®) and Monodox(®) were found 96.30%, 61.18% respectively with the relative standard deviations 0.46 and 0.54. The results of experiments using two commercial drugs showed that the MIP electrode can be used as a sensor to determine DC in pharmaceuticals.

Preparation and analytical application of the novel Hg(II)-selective membrane electrodes based on oxime compounds.

Novel Hg(II)-selective poly(vinyl) chloride (PVC) membrane electrodes based on oxime compounds of (4-(4-methylphenylaminoisonitrosoacetyl)biphenyl, I1; 4-(4-clorophenylaminoisonitrosoacetyl)biphenyl, I2; N,N-bis[1-(4-phenylphenyl)-2-hydroxyimino-2-(4-chloroaniline)-1-ethylidene]-diethylenetriamine, I3 and N,N-bis[1-(4-phenylphenyl)-2-hydroxyimino-2-(4-chloroaniline)-1-ethylidene]- 1,3-propanediamine), I4 were developed. Effects of the species and ratios of ionophore, plasticizer, PVC and lipophilic additive on the potentiometric response of electrodes were investigated in order to determine the electrode specifications. Overall results revealed that the optimum membrane composition was: 4% ionophore, 64% plasticizer (o-NPOE), 31% PVC, and 1% lipophilic additive (NaTPB). Obtained results showed that the electrodes have detection limit of 1.76×10(-6), 1.68×10(-6), 2.35×10(-6) and 2.44×10(-6) and have linear responses of 34.2, 33.4, 35.9 and 37.6 mV/pHg(2+) for a wide concentration range of Hg(II) ions. According to durability studies, the electrodes can be used for approximately 1 month without any considerable divergence in potential values. Analytical applications of the electrodes were performed and it was found that developed electrodes can successfully be used as indicator electrodes for the potentiometric titration of Hg(II) ion with EDTA solution.

Influence of Chelating Agents on the Recovery of Al(III), Fe(III), Ti(IV) and Na(I) from Red Mud by Cation Exchange Membranes

Abstract The metal recovery from red mud solution containing chelating agents such as nitriloacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), citric acid, and phosphoric acid were studied by using the Neosepta CMX and CMB cation exchange membranes in Donnan dialysis process. The stripping solution was 1.0 M HCl solution and no external potential field is applied. The efficiency of chelating agents on the recovery of metal ions through membranes was correlated with the flux data. It was observed that the removal and fluxes of metals were enhanced with citrate, EDTA and NTA chelating agents in contrast were decreased with phosphate complexing agent.

The Effect of Accompanying Anion and the Competitive Transport of Ni(II) and Fe(III) Through Polysulfone Membranes

The effect of accompanying anion on the transport of Ni2+ and competitive transport of Ni2+ and Fe3+ ions through charged polysulfone or polysulfone polyester-supported cation exchange membranes was studied under Donnan dialysis conditions. In the Donnan dialysis process, two electrolyte solutions were separated by ion permeable membrane, the one side (feed solution) initially containing metal salts or their mixtures, the other is HCl and no external potential field is applied. The transport of metal ions through membranes was correlated with the efficiency factor (EF) values as well as with fluxes and depended on the interaction between the fixed groups in the membrane and the metal ions. The EF value of Ni2+ as a single as well as mixture state was higher than that of Fe3+ for both types of membranes. The effect of accompanying anion on the transport of Ni2+ was found to be in the following order of and the results were correlated with the EF values, as well as with the membrane structure.

Recovery of nutrients from digested sludge as struvite with a combination process of acid hydrolysis and Donnan dialysis

In this study, the effects of the combination of acid hydrolysis and Donnan dialysis on the high-quality struvite production from digested sewage sludge were examined. The Box-Behnken design was applied in the hydrolysis using oxalic acid for the optimization of the conditions that affect the nutrients and metal release from digested sludge. An optimal condition was obtained at oxalic acid 0.5 M, acid/sludge ratio (mL/g) 10/1, and reaction time 60 min. The separation of the metals from hydrolyzed sludge liquid was carried out with the Donnan dialysis using a Nafion 117 cation exchange membrane. At the end of the 4 hours of operating time, the recovery values for Zn, K, Na, Mg, Fe, and Al were obtained as 67.9%, 62.1%, 57.6%, 39.4%, 5.3%, and 2.5%, respectively. The produced struvite meets the legal limits for fertilizer use in terms of Cd, Cu, Ni, Pb, Zn, Hg, and Cr content specified by Turkish regulations. A high Ca/Mg molar ratio and the presence of K, Na, and Al affected the efficiency of struvite crystallization. The use of oxalic acid resulted in low Ca release, and the metal ions that affect struvite purity were eliminated using Donnan dialysis.

Removal of Cr(III) from aqueous solutions using P-EAn and P-MAn/PVDF composite membranes

Abstract In this work, composite membranes were prepared by chemical polymerization of a thin layer of substitute anilines (methylaniline and ethylaniline) in the presence of an oxidant on the surface polyvinylidenefluoride (PVDF) membrane support sheet. Poly-N-ethylaniline (P-EAn) and poly-N-methylaniline (P-MAn)/PVDF composite membranes were obtained from this polymerization. Scanning electron microscopy, Fourier transform infrared spectroscopy, and atomic force microscopy studies for composite membranes confirmed substitute anilines loading on the PVDF membrane. The membrane thickness and their ion-exchange capacities were also measured. Donnan dialysis experiments were performed using P-EAn and P-MAn/PVDF composite membranes for the removal of chromium (III) from aqueous solution. The flux values (J) of Cr(III) were obtained at 25°C. The flux value of Cr(III) for P-EAn/PVDF composite membranes was higher than the other membrane because of the high ion-exchange capacity.

Preparation and characterization of magnetic polysulfone/thiourea microcapsules and their application for Cr(III) removal

In this study, novel magnetic polysulfone microcapsules based on N-Benzoyl-N’-(4-methylphenyl) thiourea (TTU) were prepared with the phase inversion method. Characterization of the microcapsules was performed by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA) techniques. The investigation of the adsorption properties of prepared microcapsules for the Cr(III) ion in the aqueous solution were evaluated. The parameters affecting the adsorption such as pH, contact time, amount of adsorbents (microcapsules), temperature and concentration were examined. Langmuir and Freundlich adsorption isotherms were studied to investigate the suitability of adsorption mechanism. The adsorption behavior of Cr(III) ions was found to be appropriate for the Langmuir isotherm. Cr(III) ion adsorption is spontaneous and exothermic and the adsorption process is more suitable to pseudo second order kinetic model according to the thermodynamic and kinetic analysis of the experimental data. Besides, real wastewater sample was used in order to highlight the effects of background water chemistry. Tannery wastewater was used for the removal of Cr(III) ions. Cr(III) ions were effectively removed by 87.54%.