Yunus Cengeloglu

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.

Removal of fluoride from water by using granular red mud: batch and column studies.

This paper describes the removal of fluoride from water using granular red mud (GRM) according to batch and column adsorption techniques. For the batch technique, the experiments demonstrated that maximum fluoride removal was obtained at a pH of 4.7 and it took 6h to attain equilibrium and equilibrium time did not depend upon the initial fluoride concentration. Kinetics data were fitted with pseudo-second-order model. The Redlich-Peterson and Freundlich isotherm models better represented the adsorption data in comparison to the Langmuir model. Column experiments were carried out under a constant influent concentration and bed depth, and different flow rates. The capacities of the breakthrough and exhaustion points decreased with increase of the flow rate. Thomas model was applied to the experimental results. The modelled breakthrough curves were obtained, and they were in agreement with the corresponding experimental data. The column adsorption was reversal and the regeneration operation was accomplished by pumping 0.2M of NaOH through the loaded GRM-column.

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.

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.

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.

Facilitated transport of Cr(III) through activated composite membrane containing di-(2-ethylhexyl)phosphoric acid (DEHPA) as carrier agent

The facilitated transport of chromium(III) through activated composite membrane (ACM) containing di-(2-ethylhexyl) phosphoric acid (DEHPA) was investigated. DEHPA was immobilised by interfacial polymerisation on polysulfone layer which was deposited on non-woven fabric by using spin coater. Then, ACM was characterised by using scanning electron microscopy (SEM), contact angle measurements and atomic force microscopy (AFM). Initially, batch experiments of liquid-liquid distribution of Cr(III) and the extractant (DEHPA) were carried out to determine the appropriate pH of the feed phase and the results showed that maximum extraction of Cr(III) was achieved at a pH of 4. It was also found that Cr(III) and DEHPA reacted in 1/1 molar ratio. The effects of Cr(III) (in feed phase), HCl (in stripping phase) and DEHPA (in ACM) concentrations were investigated. DEHPA concentration varies from 0.1 to 1.0M and it was determined that the transport of Cr(III) increased with the carrier concentration up to 0.8M. It was also observed that the transport of Cr(III) through the ACM tended to increase with Cr(III) and HCl concentrations. The stability of ACM was also confirmed with replicate experiments.

Biocompatible thermoresponsive PEGMA nanoparticles crosslinked with cleavable disulfide-based crosslinker for dual drug release

Smart materials have been attracting much attention because of their stimuli responsive nature. We have synthesized biocompatible thermoresponsive crosslinked poly(ethylene glycol) methyl ether methacrylate (PEGMA)-co-vinyl pyrrolidone nanoparticles (PEGMA NPs) using disulfide-based crosslinker by surfactant-free emulsion polymerization method. Particle characterization studies were carried out by dynamic light scattering, and scanning electron microscopy. Polymerization kinetics, effect of crosslinker and initiator concentrations on both average hydrodynamic diameter and polydispersity index were investigated. Hydrodynamic diameters of thermoresponsive PEGMA NPs were decreased from 210 nm to 90 nm upon heating over the lowest critical solution temperature (LCST). Disulfide crosslinked PEGMA NPs were demonstrated as a dual delivery system. Rhodamine B, a model of small-sized drug molecule, and poly(ethylene glycol) (PEG)-alizarin yellow, a model of large drug molecule, were loaded into PEGMA NPs where LCST of these NPs was tuned to 37°C, the body temperature. The rhodamine B was released from PEGMA NPs upon heating to 39°C. Then, PEG-alizarin content was released by subsequent degradation of nanoparticles using dithiothreitol (DTT), which reduces disulfide bonds to thiols. Furthermore, cytotoxicity studies of PEGMA NPs were carried out in 3T3 cells, which resulted in no toxic effect on the cells.

Sorption of Target Anions by Ligand Exchange

ABSTRACT: The sorption of anionic ligands such as I 0 ,Br 0 , and SCN 0 onto diamino-ethyl–sporopollenin (DAE–sporopollenin) was investigated in both column and batchexperiments at room temperature. The isotherm binding constants suggest that theresin is most efficient at the binding of I 0 compared with Br 0 or SCN 0 . The generalligand sorption affinity series observed was I 0 œBr 0 œSCN 0 . This ligand sorptioncould be described by considering the hydration of ions in the exchanger. The sorptionbehavior of the ligand exchanger and the possibilities of selectively removing and recov-ering ligands are discussed on the basis of their chemical and complexing properties. q 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 771–774, 1998 Key words: ligand exchange; sorption; anionic ligands; chelating polymers INTRODUCTION ficiently, are highly desirable for industrial appli-cations. 8–10 In particular, the sorption of contami-The ligand-exchange technique, which displays a nating inorganic ions such as thiocyanates andhigh selectivity for organic molecules and ions in cyanide is a major removalproblem from the pointan aqueous solution, has found extensive labora- of view of environmental pollution. Ligand-ex-tory and industrial application for removing tar- changeresins differfromthose ofcation andanionget contaminants.

Removal of Rhodamine B from water by using CdTeSe quantum dot-cellulose membrane composites

Facilitated transport of Rhodamine B through a novel polymer inclusion membrane (PIM) containing CdTeSe Quantum Dots (QDs) as a carrier reagent has been investigated. The prepared PIM was characterized with Fourier transform infrared (FT-IR) spectroscopy, Atomic Force Microscopy (AFM), confocal microscopy, X-ray Photoelectron Spectroscopy (XPS) and fluorescence spectroscopy (PL) techniques and contact angle measurements. The transport was observed by the increased absorbance peak of the stripping phase by UV-visible and fluorescence spectrophotometer. The transport efficiency of Rhodamine B was observed to be 60% after 6 h under optimized conditions. When the feed phase contained 0.005% Rhodamine B at pH 12.19, Rhodamine B was transported through the PIM (prepared with 0.1% CdTeSe QDs) by using 1 M HCl as a stripping phase. The results also showed that the transport efficiency of the PIM was reproducible and it could be beneficial in long-term separation processes.