Mithat Yüksel

Removal of bisphenol A (BPA) from water by various nanofiltration (NF) and reverse osmosis (RO) membranes

The removal of an endocrine disrupting compound, bisphenol A (BPA), from model solutions by selected nanofiltration (NF) and reverse osmosis (RO) membranes was studied. The commercially available membranes NF 90, NF 270, XLE BWRO, BW 30 (Dow FilmTech), CE BWRO and AD SWRO (GE Osmonics) were used to compare their performances for BPA removal. The water permeability coefficients, rejection of BPA and permeate flux values were calculated for all membranes used. No significant changes in their BPA removal were observed for all tight polyamide based NF and RO membranes tested except for loose NF 270 membrane. The polyamide based membranes exhibited much better performance than cellulose acetate membrane for BPA removal. Almost a complete rejection (≥ 98%) for BPA was obtained with three polyamide based RO membranes (BW 30, XLE BWRO and AD SWRO). But cellulose acetate based CE BWRO membrane offered a low and variable (10-40%) rejection for BPA.

Removal of Fluoride from Water by Metal Ions (Al3+, La3+ and ZrO2+) Loaded Natural Zeolite

Abstract In this study, the ion exchange of metal ions (Al3+, La3+ and ZrO2+) on modified zeolites was carried out using batch method. Fluoride removal from water using Al3+‐, La3+‐ and ZrO2+‐ exchanged zeolite was subsequently investigated to evaluate the fluoride sorption characteristics of the sorbents. Natural zeolite samples (<45 µm) were pre‐conditioned with HNO3 solution (ZEO‐1), NaNO3 solution (ZEO‐2), and deionized water (ZEO‐3) before loading Al3+, La3+, and ZrO2+ on zeolite. ZEO‐1 type zeolite had a higher capacity than ZEO‐2 and ZEO‐3 type zeolites. Metal exchange capacities are 0.233, 0.089, 0.090 mmol/g for ZrO2+‐, La3+‐, and Al3+‐ exchanged zeolite (ZEO‐1), respectively. Equilibrium isotherms fitted well to Langmuir and Freundlich models. Percent removal of fluoride from aqueous solution containing 2.5 mg F/L was 94% using metal loaded zeolite (ZEO‐1 type) at an adsorbent concentration of 6.00 g/L.

Extraction of Cd(II) and Cu(II) from phosphoric acid solutions by solvent-impregnated resins (SIR) containing cyanex 302

Solvent-impregnated resins (SIR) containing Cyanex 302 (bis [2,4,4-trimethylpentyl] monothiophosphinic acid) have been prepared using Amberlite XAD-2, XAD-4, XAD-7 and XAD-8 as polymeric support. These prepared SIR have been used for the extraction of Cd(II) and Cu(II) from phosphoric acid solutions. The effect of phosphoric acid concentration on Cd(II) uptake has been investigated by batch extraction method. Columnar extractions of Cd(II) and Cu(II) from 40% H3PO4 have been performed using XAD-7 resin impregnated with Cyanex 302. The resin exhibited similar column sorption behaviour for both Cd(II) and Cu(II). The elution of both Cd(II) and Cu(II) from SIR has been achieved with 4 M HCl solution. The elution of Cd(II) occurred sharply but with a long tail-off and furthermore the elution of Cu(II) was slow.

Effect of feed characteristics on the separation performances of monovalent and divalent salts by electrodialysis

Abstract In this study, separation performance for monovalent salts (NaCl, KCI) and divalent salts (CaCl2 MgCl2) was investigated by electrodialysis at pH 6.0–6.5, 4.0 and 2.0 using constant voltage mode of operation. TS-1–10 electrodialysis equipment (Tokuyama) modified with rotameters was employed in experimental studies. The effect of electrical potential, pH and ion valency on separation performance was studied at room temperature using a constant flow rate. The efficiencies of each run were evaluated as specific power consumption with the electrical energy consumed only in stack.

Application of infrared spectroscopy to the classification of kerogen types and the thermogravimetrically derived pyrolysis kinetics of oil shales

In this study, the kerogen types of Goynuk, Beypazari oil shale from Turkey and Timahdit oil shale from Morocco were defined by infrared spectroscopy. Aliphatic, carboxyl/carbonyl and aromatic compounds were considered in order to classify the kerogen types. The IR-analysis result shows that the samples can be classified in kerogen evaluation path I for Goynuk, Timahdit oil shales and path II for Beypazari oil shale. The kinetics of thermal decomposition of Goynuk, Beypazari and Timahdit oil shales have been studied by non-isothermal thermogravimetry (TG). The weight loss data have been analyzed by Coats-Redfern and Chen-Nuttall combinations. The kinetic parameters for the decomposition of the samples were determined and discussed.

Liquefaction of municipal waste plastics in VGO over acidic and non-acidic catalysts

Co-processing of municipal waste plastics (MWP) with vacuum gas oil (VGO) over HZSM-5, DHC-8 (commercial silica –alumina catalyst) and cobalt loaded active carbon catalyst has been comparatively studied. Co-processing experiments were carried out under hydrogen atmosphere at temperatures between 425 and 450 8C. The composition, sulphur and chlorine amount of liquid products were determined. The product distribution and the composition of liquids were changed depending upon the temperature and the catalyst type. As expected temperature led to increase in cracking activity of catalysts. DHC-8 and HZSM-5 showed substantially different activities in coprocessing due to the difference in their acidity. HZSM-5 gave highest gas yield at all temperatures and highest liquid yield (38.3) at low temperature. Although Co-AC was a neutral catalyst, it showed the cracking activity as well as HZSM-5 and more than DHC-8. No chlorine compound was observed in liquid products. The sulphur amount in liquid products varied with the catalyst type. Although HZSM-5 showed good cracking activity at low temperatures, it gave the liquid product containing highest sulphur amount. By considering both the quantity and quality of liquid fuel obtained from co-processing, it may be concluded that Co-AC gave the best result in the co-processing of the MWP/VGO blend. To observe the effect of metal type loaded on active carbon on catalyst activity, a series of co-processing experiments was also carried out. q 2002 Published by Elsevier Science Ltd.

A new approach in biomimetic synthesis of calcium phosphate coatings using lactic acid–Na lactate buffered body fluid solution

The main objective of this study was to investigate calcium phosphate (CaP) coatings on Ti6Al4V substrates by using the biomimetic technique. To this purpose, a new solution was developed to coat CaP on Ti6Al4V alloy substrates. The newly formulated body fluid (Lac-SBF) contained appropriate amounts of sodium lactate (NaL) and lactic acid (HL), as well as all the other ionic constituents of the human blood plasma. The inorganic ion concentrations of the Lac-SBF solutions were identical with those of human blood plasma. The new Lac-SBF solution of this study eliminated the need for using Tris/HCl or Hepes/NaOH buffers. Prior to coating, Ti6Al4V substrates were chemically treated in NaOH and/or NaOH+H(2)O(2) solutions as an alternative route and then heated at 600 degrees C for 1h in air. In the previous applications, the Cl(-) ion concentration was found to be higher than blood plasma 103mM, which exists in human blood plasma as a result of Tris/HCl which are used to prevent precipitation and to keep the pH level at certain values. In this study, instead of using Tris/HCl, HL/NaL which are generated by human body and do not show any toxic behavior, are used and Cl(-) concentration was kept at 103mM value for the first time. The prepared Lac-SBF was shown to have similar concentration to human blood plasma in terms of all inorganic ions for the first time. Solution properties were evaluated by using turbidimeter, pH meter and rheometer. The coatings were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and a scratch tester. The obtained results are presented and discussed.

Characterization of the oil fractions of shale oil obtained by pyrolysis and supercritical water extraction

Abstract Goynuk oil shale was subjected to slow pyrolysis and flash pyrolysis. It was also subjected to super and subcritical fluid extraction with water. Considerable differences were observed in the yields and compositions of the oils obtained under the four different conditions.

Liquefaction of beypazari oil shale by pyrolysis

Abstract Beypazari oil shale was subjected to conventional and free falling pyrolysis at different temperatures to investigate optimum liquefaction temperatures. The oils obtained were characterized by GC, 1HNMR, IR and size exclusion chromatography to follow the molecular changes induced by the pyrolysis. Free falling pyrolysis gave the maximum degree of conversion of 61.9% at 873 K, whereas conventional pyrolysis gave a degree of conversion of 50.5% at 773 K. Conventional pyrolysis gave less n-alkenes-1 than that obtained from free falling pyrolysis at similar temperature. Polymerization reactions are predominant during conventional pyrolysis due to the longer reaction time. In contrast to conventional pyrolysis, more cracking reactions occurred during the free falling pyrolysis.

REMOVAL OF BORON FROM BALÇOVA-IZMIR GEOTHERMAL WATER BY ION EXCHANGE PROCESS: BATCH AND COLUMN STUDIES

In this study, the efficiency of boron removal from Balçova geothermal water provided by the Izmir Geothermal Energy Company, Turkey, has been investigated using boron selective ion exchange resins Diaion CRB 02 and Dowex (XUS 43594.00) by batch and column methods. The results of the column studies have been evaluated in terms of type of resin and feed flow rate, and the effects of particle size and temperature have been investigated using the results obtained from batch kinetic studies. The data from the kinetic studies have been evaluated using pseudo-first-order and pseudo-second-order kinetics models. In addition, the classical diffusion models have been used to evaluate the kinetic data obtained to understand the rate-controlling mechanisms.