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Adsorption of Bisphenol A onto β-Cyclodextrin-Based Nanosponges and Innovative Supercritical Green Regeneration of the Sustainable Adsorbent
(MDPI, 2025) Salgin, Ugur; Alomari, Ismail; Soyer, Nagihan; Salgin, Sema
Bisphenol A is a widely recognized endocrine disruptor that persists in ecosystems, harms aquatic organisms, and contributes to ecological degradation, raising global environmental concerns. Numerous studies have explored beta-cyclodextrin-based adsorbents for Bisphenol A removal; however, their regeneration remains a major challenge, often relying on energy-intensive processes and excessive use of organic solvents. In this study, Bisphenol A was selected as a model pollutant, and its adsorption onto beta-cyclodextrin nanosponges was investigated. After adsorption, Bisphenol A was efficiently recovered from the saturated beta-cyclodextrin nanosponges using an innovative and sustainable supercritical CO2-based green process, which simultaneously regenerated the adsorbent. The adsorption process achieved an efficiency of 95.51 +/- 0.82% under optimized conditions (C-0 = 150 mg/L, m(beta-CDNS) = 0.15 g, T = 25 degrees C, and N = 200 rpm), with a maximum adsorption capacity of 47.75 +/- 0.28 mg/g. The regeneration process achieved over 99% efficiency at 60 degrees C and 300 bar, with 10% (v/v) ethanol as a co-solvent, nearly fully restoring the adsorbent's performance. Unlike conventional regeneration techniques, this green approach eliminates the need for environmentally harmful organic solvents while preserving the adsorbent's structural integrity, making it a highly efficient and sustainable alternative. This study is the first to demonstrate the effective application of supercritical CO2-based regeneration for beta-cyclodextrin nanosponges in Bisphenol A removal, providing a scalable and environmentally sustainable solution for wastewater treatment. Furthermore, characterization analyses confirmed that the adsorbent retained its chemical and morphological stability after adsorption and regeneration.
Adsorption of o-, m- and p-nitrophenols onto organically modified bentonites
(ELSEVIER SCIENCE BV, 2011) Koyuncu, Hulya; Yildiz, Nuray; Salgin, Ugur; Koroglu, Fatmanur; Calimli, Ayla
Experiments were conducted on the adsorption characteristics of o-, m- and p-nitrophenols by organically modified bentonites at different temperatures. Two organobentonites (HDTMA-B and PEG-B) were synthesized using hexadecyltrimethylammonium bromide (HDTMABr) and poly(ethylene glycol) butyl ether (PEG). Synthesized HDTMA-B and PEG-B were characterized by XRD, FTIR and DTA-TG analyses and their specific surface area, particle size and pore size distributions were determined. BET surface areas and basal spacings (d(001)) of the HDTMA-B and PEG-B were found to be 38.71 m(2) g(-1), 69.04 m(2) g(-1) and 21.96 angstrom, 15.17 angstrom, respectively. Increased adsorption with temperature indicates that the process is endothermic for o-nitrophenol. On the other hand m- and p-nitrophenols exhibited lower rates of adsorption at higher temperatures suggesting a regular exothermic process taking place. Results were analyzed according to the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations using linearized correlation coefficient at different temperatures. R-L separation factors for Langmuir and the n values for Freundlich isotherms showed that m- and p-nitrophenols are favorably adsorbed by HDTMA-B and, p-nitrophenol is favored by PEG-B. Adsorption of o-, m- and p-nitrophenols as single components or from their binary mixtures on HDTMA-B and, p-nitrophenol on PEG-B are all defined to be physical in nature. (C) 2010 Elsevier B.V. All rights reserved.
Bioconjugation of Magnetic Iron Oxide Nanoparticles and Cross-Linked Enzyme Aggregates: Characterization and Comparison of CLEAs and Magnetic CLEAs
(BENTHAM SCIENCE PUBL LTD, 2017) Salgin, Sema; Salgin, Ugur
Background: The separation of enzymes from the bio-product medium constitutes a significant part of total process cost. Therefore, it is of crucial importance that the separation processes for enzymes be specially developed. In this study, the advantages of cross-linked enzyme aggregates (CLEAs) and magnetic iron oxide nanoparticles (MIONPs) have been combined in magnetic CLEAs matrix. Methods: MIONPs were produced by co-precipitation methods. The synthesized MIONPs and CLEAs were characterized by scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), dynamic light scattering (DLS), phase analysis light scattering (PALS), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) analyses. Results: Optimal pH and temperature values of magnetic and non-magnetic CLEAs have been determined to be pH= 7.5 and T= 45 degrees C. It has been observed that there are differences in apparent KM and V-max values of magnetic and non-magnetic biocatalysts. Moreover, the high activity of nonmagnetic CLEAs is a result of low alpha-helix and beta-sheet contents. Compared with non-magnetic CLEAs, magnetic CLEAs showed high storage stability and good reusability. Due to the different the protein content, the weight loss of the non-magnetic and magnetic CLEAs determined by TGA was about 65% and 53%, respectively. From DSC analysis, the denaturation temperatures of nonmagnetic and magnetic CLEAs were 97 +/- 0.8 degrees C and 108 +/- 0.8 degrees C, respectively. Conclusion: The present work provided important information on production, comparison and characterization of non-magnetic and magnetic CLEAs from Candida rugosa lipase (CRL) enzyme. The magnetic CLEAs had significant enhancement on the storage stability, thermal stability, reusability comparing with that of non-magnetic CLEAs. These improved properties of magnetic CLEAs could be an attractive feature towards more stable CLEAs preparation. The high cost of complex separation processes could be eliminated with magnetic CLEAs.
Crossflow ultraflitration of binary biomolecule mixture: Analysis of permeate flux, cake resistance and sieving coefficient
(WILEY-V C H VERLAG GMBH, 2007) Salgin, Ugur; Salgin, Sema
The aim of this paper is to demonstrate the effects of hydrodynamic conditions on the permeate flux, cake resistance and sieving coefficient in a crossflow ultrafiltration process separating biomolecules of different molecular weights. A binary mixture of L-phenylalanine (L-phe) and lipase was ultrafiltered through a hydrophobic polyether sulphone (PES) membrane with 10 kDa molecular weight cut-off. The changes in permeate flux, cake layer resistance and observed sieving coefficient with different transmembrane pressures (TMP) and crossflow velocities were evaluated. The effect of TMP was examined at two different velocities (0.114 m s(-1) and 0.176 in s(-1)) and the effect of velocity was examined at two different TMP (20 kPa and 115 kPa) for the experimental system designed. In the initial stage of the crossflow filtration, it was determined that the TMP was more effective than the velocity. The cake layer resistance increased with increasing TMP and it decreased with increasing velocity for the high TMP value of 115 kPa. A maximum of the observed sieving coefficient was achieved with increasing velocity. An increase in TMP at low inlet velocity (0.114 in s(-1)) affected the observed sieving coefficient positively.
Determination of correct zeta potential of polyether sulfone membranes using CLC and AGC: ionic environment effect
(TAYLOR & FRANCIS INC, 2016) Salgin, Sema; Salgin, Ugur; Tuzlali, Nagihan
In this study, the correct and apparent zeta potential of polyether sulfone (PES) ultrafiltration membranes at different ionic environments were determined using streaming potential measurements. The apparent zeta potential was found by calculation with classic Helmholtz-Smoluchowski (HS) and Fairbrother-Mastin (FM) equations of results obtained from clamping cell (CLC) and adjustable gap cell (AGC). Correct zeta potential was determined by calculation with a modified HS equation of obtained results from AGC. Obtained apparent zeta potential results from CLC and AGC differ from each other, and the reproducibilityof results was found to be higher for measurements of AGC. Except for low pH values, apparent zeta potential that was obtained from classic HS equation with AGC could be accepted as correct zeta potential. In CLC measurements, underestimated or overestimated zeta potential values were determined in comparison with the correct zeta potential. The effect of membrane surface conductance on zeta potential decreased with increasing KCl concentration. In CLC, the deviation was observed from electrical double layer theory when KCl concentration was 0.1M, therefore streaming potential measurements did not produce correct results at higher salt concentration. 0.001M KCl concentration was the value at which surface conductance became crucial.
Effect of main process parameters on extraction of pine kernel lipid using supercritical green solvents: Solubility models and lipid profiles
(ELSEVIER SCIENCE BV, 2013) Salgin, Ugur; Salgin, Sema
Supercritical fluid extraction of pine kernel lipids from Pinus pinea L using green solvents (only CO2 or mixed with ethanol) was performed in a laboratory scale extraction system. For the first time in this study the effect of main operating parameters [i.e. pressure (20-50 MPa), temperature (40-60 degrees C), CO2 flow rate (0.061-0.259 kg h(-1)), entrainer concentration (2.5 and 5 vol.%) and average particle size (362.5 and 725 mu m)] on extraction yield, initial extraction rate and the solved contents of pine kernel lipid in CO2 or its solubility was investigated systematically. Experimental results showed that extraction yields (from 0.477 to 0.488 g PKLg(-1) dry PK) obtained from supercritical CO2 extraction over 30 MPa of operating pressure was better than extraction yield (0.472g PKLg(-1) dry PK) obtained from organic solvent extraction. It should be noted that the extraction yield obtained using 5 vol.% of ethanol reached to 0.487 g PKLg(-1) dry PK in 90 min under a suitable operating condition such as 30 MPa, 40 degrees C and 0.194 kg h(-1) of green solvent flow rate. The crossover effect of pine kernel lipid was determined approximately at 23 MPa of operating pressure. The experimental solubility data, determined by the dynamic method, of pine kernel oil in supercritical CO2 were correlated by some empirical models such as Chrastil, del Valle-Aguilera, Adachi-Lu, and Sparks models. Adachi-Lu and Sparks models made a lower error in the prediction of solubility. Lipids extracted by supercritical green solvents extraction contain more unsaturated fatty acids than those extracted by Soxhlet with in the n-hexane extracts. (C) 2012 Elsevier B.V. All rights reserved.
Effect of Reaction Parameters on the Synthesis of Cyclodextrin-Based Nanostructured Polymers for Drug Delivery
(MDPI, 2025) Salgin, Sema; Eke, Hasan Huseyin; Soyer, Nagihan; Salgin, Ugur
In this study, cyclodextrin-based nanostructures (CDNSs) were synthesized through the cross-linking of cyclodextrin (CD) with epichlorohydrin (ECH) as a cross-linker. Two types of CDNSs, alpha-CDNS and beta-CDNS, were prepared to systematically investigate the influence of reaction parameters-such as the solubilization time of alpha-CD and beta-CD, the molar ratio of ECH to CD, and NaOH concentration-on the physicochemical properties of the final product. Naproxen (NAP), a poorly water-soluble drug, was selected as a model compound to assess the drug-loading capacity of the synthesized CDNSs. The effect of each reaction parameter on NAP integration into the CDNSs was examined at varying weight ratios. The optimal reaction conditions were determined to be a solubilization time of 6 h, an ECH/CD molar ratio of 8/1, and an NaOH concentration of 33%. Under these conditions, the NAP loading efficiency of alpha-CDNSs was calculated as 67.12%. Comparative analysis revealed that alpha-CDNSs outperformed beta-CDNSs in terms of drug-loading capacity. Additionally, the synthesized CDNSs and NAP-loaded CDNSs were characterized using FTIR, DSC, XRD, SEM, and Zetasizer analyses, while the NAP concentration was determined by HPLC.
Enantiomeric separation of antidepressant drug fluoxetine based on chiral membranes
(DESALINATION PUBL, 2018) Salgin, Sema; Salgin, Ugur; Tuzlali, Nagihan
In this study, the enantiomeric separation of antidepressant drug fluoxetine (FLX) was carried out using chiral selector-immobilized polyethersulfone (PES) membranes. For this purpose, the chiral selectors BSA, Candida rugosa lipase (CRL) and alpha-cyclodextrine (alpha-CD) were adsorbed on PES membranes by the static adsorption at different pH values. Chemical and electrokinetic characterizations of modified membranes were done by Fourier transforms infrared (FTIR) spectroscopy and by an electrokinetic analyzer (EKA), respectively. FTIR and EKA analysis were particularly employed in order to evaluate the immobilization efficiency. Racemic FLX was ultrafiltrated with the chiral selective membranes using the stirred ultra filtration cell. The effectiveness of chiral separation was characterized in terms of the values of enantiomeric excess (ee%) in permeate. During the ultra filtration, the samples taken from permeate were analyzed with liquid chromatography system using Chiral-pak AD-H column for the determination of R-FLX and S-FLX enantiomers. The ee(s) values of BSA and CRL in the permeate were approximately equal.
Enantiomeric separation of fluoxetine in ultrafiltration through chiral selector-immobilized polyethersulfone membranes
(ELSEVIER SCIENCE BV, 2012) Soyer, Nagihan; Salgin, Sema; Salgin, Ugur
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The enantioselective hydrolysis of racemic naproxen methyl ester in supercritical CO2 using Candida rugosa lipase
(ELSEVIER SCIENCE BV, 2007) Salgin, Ugur; Salgin, Sema; Takac, Serpil
The enantioselective hydrolysis of racemic naproxen methyl ester by Candida rugosa lipase (CRL) was studied in aqueous buffer solution/isooctane reaction system in the presence of supercritical CO2. The effects pressure (75-160 bar), temperature (32-42 degrees C ) and reaction time (0.5-12 h) on the enantiomeric excesses of the product (ee(p)) and the substrate (ee(s)), enantiomeric ratio (E), conversion (x) and enzyme activity were investigated in a batch reactor system. The highest enantiomeric ratio achieved at 120 bar of pressure, 37 C of temperature and 2 h of reaction time was E= 193 with x=41.3%, ee(p)=97.9% and ee(s)=68.8%. CRL remained active at least for 12h at 37 degrees C and 120 bar in supercritical CO2 medium. Furthermore. enantiomeric ratio increased with increasing reaction time and reached the value of E=236 with ee(p) =98.2%, ee(s) =70.0% and x=41.6% after 12 h of hydrolysis. (C) 2007 Elsevier B.V. All rights reserved.
Extraction of jojoba seed oil using supercritical CO2+ethanol mixture in green and high-tech separation process
(ELSEVIER SCIENCE BV, 2007) Salgin, Ugur
In this study, the extraction of jojoba seed oil obtained from jojoba seed using both supercritical CO2 and supercritical CO2+ethanol mixtures was investigated. The recovery of jojoba seed oil was performed in a green and high-tech separation process. The extraction operating was carried out at operating pressures of 25, 35 and 45 MPa, operating temperatures of 343 and 363 K, supercritical fluid flow rates of 3.33 x 10(-8), 6.67 x 10(-8) and 13.33 x 10(-8) m(3) s(-1), entrainer concentrations of 2, 4 and 8 vol.%, and average particle diameters of 4,1 X 10(-4) 6.1 X 10(-4), 8.6 x 10(-4) and 1.2 x 10(-3) M. It was found that a green chemical modifier such as ethanol could enhance the solubilities, initial extraction rate and extraction yield of jojoba seed oil from the seed matrix as compared to supercritical CO2. In addition, it was found that the solubility, the initial extraction rate and the extraction yield depended on operating pressure and operating temperature, entrainer concentration, average particle size and supercritical solvent flow rate. The solubility of jojoba seed oil and initial extraction rate increased with temperature at the operating pressures of 35 and 45 MPa and decreased with increasing temperature at the operating pressure of 25 MPa. Furthermore, supercritical fluid extraction involved short extraction time and minimal usage of small amounts entrainer to the CO2. About 80% of the total jojoba seed oil was extracted during the constant rate period at the pressure of 35 and 45 MPa. (C) 2006 Elsevier B.V. All rights reserved.
Extraction of sesame seed oil using supercritical CO2 and mathematical modeling
(ELSEVIER SCI LTD, 2010) Doker, Onur; Salgin, Ugur; Yildiz, Nuray; Aydogmus, Mihrican; Calimli, Ayla
In this work, extraction of sesame oil from sesame seeds using supercritical CO2 was carried out. The effect of operating parameters such as pressure, temperature, and supercritical CO2 flow rate and particle size on extraction yield were investigated. An increase in the pressure and the supercritical CO2 flow rate improved the extraction yield and also shortened the extraction time. The extraction yield increased as the particle size decreased depending on decreasing intraparticle diffusion resistance. The maximum extraction yield obtained was about 85% (relative to Soxhlet extraction by hexane) at 50 degrees C, 350 bar, 2 mL CO2/Min, 300-600 mu m of particle size. Some extraction curves were modeled with two mathematical approaches as shrinking core model and broken and intact core model. The evaluation of model parameters showed that shrinking core model, however, is better than broken and intact cell model. (C) 2009 Elsevier Ltd. All rights reserved.
Extraction of sunflower oil with supercritical CO2: Experiments and modeling
(ELSEVIER SCIENCE BV, 2006) Salgin, Ugur; Doker, Onur; Calimli, Ayla
Extraction of sunflower oil from sunflower seeds (Heliantus annuus L.) using supercritical CO2 was studied. The shrinking core model was applied to the modeling of the packed-bed extraction process. The experimental data were obtained for extraction conducted at the pressures of 20, 30, 40, 50 and 60 MPa; the temperatures of 313, 333 and 353 K, the CO2 flow rates of 1-4, and 6 cm(3) CO2 min(-1); the mean particle diameters of 0.23, 0.55, 1.09, 2.18 mm. The supercritical CO2 extraction process was modeled by a quasi steady state model as a function of extraction time, pressure, temperature, CO2 flow rate, and particle diameter. The supercritical CO2 extraction process. The intraparticle diffusion coefficient (effective diffusivity) D, was used as adjustable parameter. The model using the best fit of D. was correlated the data satisfactorily. (c) 2005 Elsevier B.V. All rights reserved.
A green separation process for recovery of healthy oil from pumpkin seed
(ELSEVIER SCIENCE BV, 2011) Salgin, Ugur; Korkmaz, Hasan
In this study, pumpkin seeds, called as "Urgup Sivrisi" and grown in Cappadocia region, were used as plant materials because of high aroma contents. In the supercritical fluid extraction of pumpkin seed oil, the effect of main process parameters as the particle size (250-2360 mu m), the volumetric flow rate of supercritical solvent (0.06-0.30 L/h), the operating pressure (20-50 MPa), the operating temperature (40-70 degrees C), the type of entrainer (ethanol and n-hexane) and those concentrations (0-10 vol.%) on the extraction yield, the oil solubility and the initial extraction rate were investigated. A cross-over effect for the extraction of pumpkin seed oil using supercritical CO(2) was determined at the operating pressure of 20-30 MPa. The maximum extraction yield obtained with entrainer free was reached 0.50 g oil/g dry seed at 600-1180 mu m. 0.12 L/h, 50 MPa and 70 degrees C for the operation time of 5 h. The maximum extraction yield obtained with ethanol as an entrainer in the experiments was reached 0.54 g oil/g dry seed at the conditions of 600-1180 mu m. 0.12 L/h, 30 MPa, 40 degrees C and 8 vol.% for the operating time of 2 h. The oil compositions were determined by gas chromatography analysis and the results showed that the compositions of pumpkin seed oil which were obtained by means of organic solvent extraction and supercritical fluid extraction were similar. The average oil compositions determined as 9.3 (+/- 0.43)% palmitic acid, 7.5 (+/- 0.6)% stearic acid, 32.3 (+/- 0.6)% oleic acid, 48.1 (+/- 0.6)% linoleic acid and 0.7 (+/- 0.3)% linolenic acid. The morphological changes in the seeds were determined by the scanning electron microscopy analysis. (C) 2011 Elsevier B.V. All rights reserved.
Kinetic resolution of racemic naproxen methyl ester by magnetic and non-magnetic cross-linked lipase aggregates
(Taylor & Francis Inc, 2020) Salgin, Sema; Cakal, Mustafa; Salgin, Ugur
In this study, the non-magnetic and the magnetic cross-linked enzyme aggregates (CLEAs) from Candida rugosa lipase were synthesized to catalyze the kinetic resolution reaction of naproxen methyl ester (NME). Magnetic iron oxide nanoparticles (MIONPs) were produced through co-precipitation method and their surfaces were modified by silanization reaction. The MIONPs were used as a platform to synthesize the magnetic CLEAs (M-CLEAs). The biocatalysts and MIONPs synthesized were characterized by FTIR spectroscopy and SEM analysis. The kinetic resolution of racemic NME was studied in aqueous buffer solution/isooctane biphasic system to compare the performance of M-CLEAs and CLEAs. The effects of reaction parameters such as temperature, pH, stirring rate on the enantiomeric excess of the substrate (ee(s)%) were investigated in a batch reactor system. The activity recovery of CRL enzyme in CLEAs was higher than M-CLEAs. Compared with M-CLEAs, CLEAs biocatalysts had previously reached ee(s)% values. Although both biocatalysts showed similar cavity structure from SEM analysis, the lower performance of M-CLEAs may be due to the different microenvironments of M-CLEAs from CLEAs. However, the reusability performance of M-CLEAs was higher than that of CLEAs. The optimal reaction conditions for M-CLEAs and CLEAs were found to be 37 degrees C, pH 7.5, and 300 rpm.
A new application of supercritical CO2 technology for cross linked enzyme aggregates
(ELSEVIER SCIENCE BV, 2012) Dincyurek, Derya; Aptis, Hasan; Salgin, Sema; Salgin, Ugur
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Oil recovery in rosehip seeds from food plant waste products using supercritical CO2 extraction
(ELSEVIER SCIENCE BV, 2016) Salgin, Ugur; Salgin, Sema; Ekici, Derya Dincyurek; Uludag, Gamze
Valuable oils in rosehip seeds produced as the solid waste during the process of marmalade production using seed-containing fruits were recovered by supercritical CO2 extraction method. The influence of the particle size (125 <= Dp > 1000 mu m), volumetric flow rate of supercritical solvent (0.75-3.5 mL/min), pressure (20-40 MPa), temperature (40-60 degrees C) and entrainer concentration (2.5-7.5%vol. ethanol) on the extraction yield in the recovery process was examined. The highest extraction yield determined as 16.5 g oil/100 g dry solid was reached in approximately 150 min by using supercritical CO2 extraction (30 MPa, 40 degrees C, 0.75 mL/min, 355 < Dp < 500 mu m) and in the case where 5%vol. ethanol is used as entrainer, it was reached in about 90 min. In similar oil profiles obtained through Soxhlet and supercritical fluid extractions, the ratio of unsaturated fatty acids to saturated fatty acids is about 17. Significant changes were determined in morphological structures of waste seeds compared to unprocessed seeds in marmalade production, by using scanning electron microscope. Apparent solubility values of rosehip oil in supercritical CO2 did exhibit a significant consistency with Chrastil, del Valle-Aguilera, Adachi-Lu and Sparks solubility models. (C) 2016 Elsevier B.V. All rights reserved.
A parametric study of phenolic compounds desorption performance from organobentonite by supercritical fluids
(ELSEVIER SCIENCE BV, 2007) Salgin, Ugur; Yildiz, Nuray; Koeroglu, Fatmanur; Calimli, Ayla
Supercritical fluid desorption has been carried out in a fixed bed column to desorp nitrophenolic compounds from organically modified bentonite. The experiments were carried out in the sequence of synthesis of organobentonite (HDTMA-B) and then adsorption of phenolic compounds to organobentonite in aqueous solutions, desorption of phenolic compounds from organobentonite using supercritical fluids (SCFs) and adsorption of nitrophenols to regenerated organobentonite. The desorption parameters such as pressure (20-40 MPa), temperature (40-100 degrees C) and co-solvent concentration (2.5-20 vol.%) were investigated at 2 ml/min flow rate. While the desorption yield of o-nitrophenol (oNP) was 93 wt.% using supercritical CO2 (SC CO2) by operating at 20 MPa, 40 degrees C, 2 ml CO2/min in 2 h of desorption, the desorption yields of M-nitrophenol (mNP) and p-nitrophenol (pNP) reached up to 71.8 wt.% (at 20 MPa, 60 degrees C using 7.5 vol.% ethanol) and 50 wt.% (at 40 MPa, 60 degrees C, 10 vol.% ethanol), respectively. In addition, the results showed that the regenerated HDTMA-bentonite toward nitrophenols exhibited changing adsorption capacity after several regeneration cycles. It was therefore concluded that exhausted/used organobentonites might be regenerated via processes involving supercritical fluid extraction. (C) 2006 Elsevier B.V. All rights reserved.
Streaming Potential Measurements of Polyethersulfone Ultrafiltration Membranes to Determine Salt Effects on Membrane Zeta Potential
(ESG, 2013) Salgin, Sema; Salgin, Ugur; Soyer, Nagihan
A systematic study on the zeta potential of polyethersulfone membranes determined by streaming potential measurements was made to examine various salt effects. Chloride salts; KCl, NaCl, CaCl2 and MgCl2 and potassium salts; KCl, KNO3, KClO3, K2CO3, K2SO4 and K2Cr2O7 were used to investigate the effects of cations and anions on the zeta potential of membranes, respectively. The zeta potential was obtained in 0.001 M salt solutions at the range of pH=4.0-8.0. The effect of ionic strength on membrane zeta potential was also investigated in the solution of KC1 and Na2HPO4 with 0.001 M-0.1 M salt concentrations. At high pH values, anion adsorption on membrane surface had a more potent effect on zeta potential, while at low pH values, cation adsorption to membrane surface also possessed more potent effect on zeta potential. In general, zeta potential decreased with increasing ionic strength due to the compression of electrical double layer. However, preferential adsorption of ions on the membrane surface is another important parameter affecting zeta potential beside the ionic strength. The influence of ionic strength on the membrane zeta potential can be observed by performing FTIR-ATR analysis.
Supercritical fluid extraction of walnut kernel oil
(WILEY-V C H VERLAG GMBH, 2006) Salgin, Sema; Salgin, Ugur
The objective of this study was to investigate the effects of the main process parameters on supercritical fluid extraction of walnut (Juglans regia L.) kernel oil. The recovery of walnut kernel oil was performed in a green and high-tech separation process. CO2 and CO2 + ethanol mixtures were used as the supercritical solvent. The extraction was carried out at operating pressures of 30, 40 and 50 MPa, operating temperatures of 313, 323 and 333 K, mean particle sizes of 1.78 x 10(-4), 3.03 x 10(-4), 4.78 x 10(-4), 7.00 x 10(-4) and 9.00 x 10(-4) m, supercritical CO2 (SC CO2) flow rates of 1.67 x 10(-8), 3.33 x 10(-8), 6.67 x 10(-8) and 13.33 x 10(-1) m(3)/s and entrainer (ethanol) concentrations of 2, 4, 8 and 12 vol-%. Maximum extraction yield and oil solubility in SC CO2 obtained at 50 MPa, 333 K, 9.00 x 10(-4) m, 3.33 x 10(-4) m(3)/h were 0.65 kg oil/kg of dry sample and 37.16 g oil/kg CO2, respectively. The results obtained in this study showed that the crossover pressure effect of walnut kernel oil was at 30 MPa. At 30 MPa and 313 K, the obtained extraction yields above 4 vol-% ethanol reached the organic solvent extraction yield of 68.5 kg oil/kg dry sample. Extraction time was decreased significantly because of the higher solubility of walnut kernel oil in SC CO2 + ethanol mixtures.

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